Hector's Airgun Blog

"Blue-Printing" a Walther LGV ©

5/24/2022

In "gun-speak" blueprinting an action is understood as the modifications/alterations that make that action fit the specified dimensions of the design.

In this entry, we will use the verb as meaning that we are returning the rifle, as much as possible, to the "as it SHOULD HAVE BEEN issued" state.

It all started quite some months ago (Pre-CoViD) when I was contacted by a fellow FT shooter asking what was the potential in using a Walther LGV to shoot FT.

Since an LGV is my "back-up" gun for serious FT, I answered that a properly setup rifle could be accurate, precise and consistent enough to place well in a competition.

After that first conversation, there was no more talk and I thought that the whole idea had been forgotten.

BUT, in the last North Carolina Classsic, I met with the friend in question and after the first day of competition, he declared: "I'm done, take the gun and make it what it can be".

So, I came back with more guns than I took! LOL!

I will not go into detail about the tear down and the way the gun works, there are other entries that deal with that:

https://www.ctcustomairguns.com/hectors-airgun-blog/a-yankee-tune-for-the-walther-lgu

https://www.ctcustomairguns.com/hectors-airgun-blog/a-yankee-tune-for-the-walther-lgu-second-version

Since the guns are identical, except for the cocking mechanism, what is said of one gun applies to both.

What was the difference this time as regards those first ventures into the LGU/LGV realm was that on this occasion I had NO IDEA of the provenance of the gun. It was an LGV Master. And I am sure it was bought in the USA, my friend purchased it "from a gentleman in PA", but that still does not justify what happened.

So, let's get into the project.

The Rifle.-
My friend is a good shooter. He is, literally, Championship material, so if he says the gun is inconsistent, I tend to believe him, but inconsistent by how much was still a question, so . . . the first thing was to put the gun through the Chrono.
Testing with JSB's 8.44 grs./ 4.52 mms, gave horrible results, in a 20 shot string the ES was 27 fps for a Low of 735 and a High of 762, for an average of 750 ± 7 fps for 10.6 ft-lbs
CLEARLY something was wrong.

On disassembly, I noticed that the previous owner had applied the "Yankee Tune" principles to the "Tee". But the gun simply refused to yield the energy promised and even some drastic spacing forward and aft, did not provide the desired results.

Vortek unit with added spacers

It was also obvious that some effort had been made to tame the buzz through the liberal application of greases:

Gobs of grease

Complete disassembly showed the rear part of the powerplant train:

Rear Section of Powerplant

And I still had to find the heavily spaced TopHat which was hiding inside the piston.
The seal wasn't either an OEM one, being blue, slimmer and shorter than the original:

Non-OEM seal is slimmer

OEM seal's Bore Diameter

Rear Gap with Blue Seal

Piston with Blue seal is shorter

If the idea was to add a millimeter of stroke to the compression volume, the advantage was lost with the looseness and the gaps.

The Fix.-

Still, the job was cut out and so, I replaced all parts for OEM parts (as wished by the owner):

Full OEM Powerplant

A new piston, a new guide and a new spring were installed, all OEM parts.

Observant readers will note that the OEM trigger has been replaced! Yes that is one of Eric Pianori's triggers:

https://www.ctcustomairguns.com/hectors-airgun-blog/new-super-custom-trigger-for-the-walther-lgulgv

and it is superbly adjustable, consistent and reliable.

I thought that everything had gone "just peachy" till the chrono test:

With the same JSB's, the gun clocked 741 ± 4 fps

WHAAATTT?

Uhh-Ohh! I guess that, by now, I should KNOW that if a gun gets to me, it is because others have not found a way to make it work as the owner/customer wants, or as the gun is expected to perform.

Reading over some of my notes, I remembered that at one point I had refused to change the TP of an LGV, preferring to use a much more complicated solution:

https://www.ctcustomairguns.com/hectors-airgun-blog/the-walther-lgv-pushing-the-power-limits

But the owner, in THIS case wanted to have the gun "blue-printed" and nothing is as non-OEM as a custom piston.
It had also happened that I had HAD to open a TP in some other break-barrels and I had made the tools to do it properly, so this time around, I did have the wherewithal to tackle the TP enlargement.

In brief: you need carbide drills to drill out the TP to the dimension you need/want, and also a way to remove the drilling burr from the INSIDE of the compression chamber that results from drilling from the outside in.

Carbide drills will cut a VERY precise and smooth hole in steel at slow speeds with mutton tallow lubrication, and that gives you control of the process, it also produces little burr on the other side of the drill, important when the "other side" is, in reality, the INSIDE of the compression chamber; where another surprise awaited us.

Deep Drilling Setup

Peeking into the Face

As you can see there is a gap between the end and the sidewalls of the compression chamber, where a ring of "gunk" forms. You can also see that the face/end of the compression chamber is not perfectly flat.
This gun will never achieve true "full power" because there is a "lost volume" that we cannot get rid of. A lost volume that even the excellent OEM LGV "power pulse" style seal cannot remediate.
It could be fixed with a custom piston, but then that would not be a "blue-printed" gun.

The other thing you can see in this picture (or better yet, you CANNOT see), is the normal burr from drilling the TP out from the OTHER side.
A larger drill was applied with the extension shown above and the burr removed.
Some have argued that the inside of the TP's should be "venturi'ed", IMHO, that is counterproductive because when air flows at the speed at which it flows inside these machines, a slightly turbulent flow is actually a better "lubricated" flow; a venturi style of entry would tend to reduce turbulences, which is something we do not want.
So, we only removed the burr and made sure that nothing was there to damage the seal in the second (or third) landing of the piston.
Here is a detailed look at the TP and surrounding area:

A detailed look of the Face

So, with the TP drilled out to the MINIMUM required for the 12 ft-lbs requested by the owner, we tested different pellets and finally settled on a combination that seems to give very good results.
The barrel in this rifle is easily one of the best I have seen/slugged in any modern Walther, and it seems to prefer the lighter spectrum of pellets (7.9 grs), shooting them at 827 ± 4 fps for 12 ft-lbs on the dot (and the innards are still in the "running in" phase). Predictably, this rifle will settle in the 835-840 fps average and the extreme spread in MV will be reduced to single digit.
This rifle is destined to shoot AAFTA style Hunter Division, so a little over 12 ft-lbs is no problem at all.

The results.-

To test this gun I installed a SIGHTRON 4-12X40 AO scope that has proven to be VERY reliable in an Accurized ZR mount:

Complete view of the LGV rifle

It was very nice to just mount the scope and to have no need of further regulation to get the rifle sighted in at the optical axis of the scope. And so, after some short range tests to determine if the JSB Xp was the right pellet and confirming that it was, I adjourned to the 25 yards distance and this was the result (target shot from the bottom, up):

25 yds Test

As for the non-OEM part, my friend asked for a light and creepless trigger, so I used Eric's trigger's middle screw (to reduce the back force of the spring) and adjusted to a bit less than 1#, this is the average of 5 trigger pulls:

Trigger pull setting

Overall, a very rewarding project, while the gun will not achieve the 17/23 Joules advertised originally, it is still yielding a good performance for the cocking force, and it is working as a "pop gun" in the "Olde English Air Gonne" parlance, meaning that the lubricants are kept to a minimum and there is no energy contributed to the pellet by moderate dieseling.
As ALL Walthers that are made to work in the "pop gun" region, it is a bit "ringy". If this bothers the user the solution is extremely simple: just add a VERY LIGHT coating of tar to the spring. To ME, the thermal aspects of how tar behaves between a cool 50 ° F morning and a scorching 90 ° F noon are not worth it but, to each his own.

There is more to read about the LGV's in this blog, some of the entries have been superseded by newer materials and components, but I hope the readers will find them interesting:

https://www.ctcustomairguns.com/hectors-airgun-blog/swapping-the-walther-lgus-trigger

https://www.ctcustomairguns.com/hectors-airgun-blog/the-walther-lgv-a-second-look

https://www.ctcustomairguns.com/hectors-airgun-blog/the-gunsmiths-tune-part-14-full-power-walther-lgv

https://www.ctcustomairguns.com/hectors-airgun-blog/the-gunsmiths-tune-part-24-12-ft-lbs-walther-lgv

In the meantime, take care, keep well and shoot straight!

HM © May 23,2022

11 Comments

An unintended coincidence ©

4/26/2022

4 Comments

PREAMBLE

Some weeks ago, a friend posted in a forum the difficulties he was having with an HW barrel in 0.20" cal.
I really do not know much about those barrels having used only one in my work and finding that the barrel I got had no choke. After the fact, it was noted that barrel blanks sold by HW to the US are unchoked, but it was a surprise for me. Since that experience, more than 20 years ago, I have used only L-W barrels. That particular HW barrel was mated to a PCP and a custom mould and shot those specific cast slugs very well, so the barrel was good, just not ideal for pellets.
Again, this was more than 20 years ago, and things change, all this to point out that I do not have too much experience with HW barrels.

Now, apart from the peculiarities of manufacturers about their rifling characteristics, there ARE things that are necessary in a barrel to be efficient, consistent, and accurate.
If a barrel is not uniform, it will not be efficient.
If a barrel is not uniform, it will not be consistent
If a barrel is not uniform, it cannot be accurate.

So, UNIFORMITY is what all barrels, regardless of maker, need to have in order to be truly good barrels.
You may forgive a bad efficiency if it is a short range barrel that is extremely consistent and uniform for the last couple of inches, but in a long range barrel or a hunting gun barrel, you NEED a certain amount of energy to break skin and penetrate, or simply fly to the target at 55 yards and beyond. THEN the last two inches is not "good enough".

And this was the case with the HW barrel in the discussion above mentioned. It had tight and loose spots, and the choke was overdone.

The maker was contacted and after a exchanging more than a few Emails, the barrel, breechblock, and linkage, are on their way to one of the distributors of the brand in the US. Hopefully, the local technician will accept the diagnosis and advise the maker to exchange the whole assembly.

The coincidence

By some quirk of fate, at the same time Midway put on a sale of a limited edition "Lawrence of Arabia" DIANA 34 EMS rifles. All in 0.177"

At the price offered (just a few bucks over $200), it was indeed a tempting offer and many friends took advantage of that sale.
Most have reported good results but, as in the HW case above, even the best makers put out a lemon now and then.
In this case, the rifle was not making even "F in Pentagon" (5.5 ft-lbs) power, so there were more than a few things wrong there.
The owner wanted anyway to have the powerplant changed to NTec (gas spring), and so we proceeded with the powerplant swap.

Powerplant swap

In the picture above you see on top, the OEM powerplant (two piece guide and spring), at the bottom the single NTec unit.
If you want to attempt the powerplant swap, you will need this kit:

The powerplant swap took all of 20 minutes, deburring the action, cleaning with acetone and then relubing with Ultimox 226, took another 20 minutes, and then testing begun.

Uhh-Ohh, not good, power was still very low, we exchanged NTec units, we changed piston seals and still no progress.

HMMMMMM So, we analyzed the barrel.

Good thing about the EMS is that everything is modular (as its name implies)

Once you remove the barrel hinge bolt (do note that there are Nord-loc washers on each side, so do NOT attempt to loosen the nut by itself).
The barrel assembly can be taken out of the forks.
The cocking linkage can be removed with ONE SCREW (no cheap rivets here), and the side-bearing washers can be extracted with a magnet.
The barrel retaining nut can be extracted using the DIANA tool.
Then the ORing falls and then the barrel can be tapped out.

The block is NOT aluminum, but it is not a "hardened steel", so it marrs easily (previous experience, not this gun). Be careful if you want to work in these guns.

A long list of pellets were put through the barrel and a sad lack of uniformity was found that no lapping could repair. Looseness in the middle of the barrel is not something that is "correctable".

The full group of pellets tested

Deatiled view of some: PC FTT's, JSB H's, JSB Xact's

JSB's and Olympia

JSB 4.53/8.44

So, I sent the results of the tests to DIANA on April 6th, by April 7th I had the promise of a replacement barrel, by April 12th barrel was shipped.
We had to wait till April 25th to actually get it but, an hour after receiving it, the barrel had been "refined", was in place and shooting.
Fit was MUCH better, as you can see in these pictures:

JSB 4.53/8.44 on the left pushed to JUST BEFORE the choke, on the right pushed all the way through.

Same as above, but with H&N FTT's 4.52/8.66

The process of a barrel swap in the EMS is not complicated, but having done a few, I really have to admit that is not within the realm of the home tinkerer, not even the advanced ones. Things need to fit to each other within 0.0005" ; and keeping cylinders parallel to those tolerances is not easy when doing it with common tools.

While some may think that the "promise" of the EMS is not being followed through, the reality is that the EMS STILL holds substantial advantages for the shooter.
In this instance, a complaint that would take a month or more, was solved in less than 3 weeks. So, service is simplified and expedited.

It also opens the door for better, faster, customizations.

If you buy a LoA EMS at $207, and you want it in 0.22" that can easily be done for $100 more, you want it changed to NTec gas spring? $180 will get you there.

Hopefully, in the future, we will have more variety of barrels (short and long, threaded and not, etc.) and then it will be even more interesting.

In the end , it is all about what happens at the target ¿no? LOL!

Final test target showing part of the running-in and then 10 shot groups from the sitting FT position at 25 yards.

This barrel still needs some "running in" and I did not have time to test with GTO's which have proven surprisingly accurate in the latest DIANA 0.177" barrels.
But very clearly, the barrel shows potential, and at a little about 12 ft-lbs in an NTec config, it is an enjoyable gun to shoot all day, it has little recoils, no vibrations, and allows you to call and spot your shots easily.

As time goes by, the rest of the gun will also settle and all aspects will contribute to the shootability of these guns.

Keep well and shoot straight!

HM

© 04/26/2022

4 Comments

The Peculiar "Crosman Tuning Lab" pistol ©

2/16/2022

2 Comments

In the world of airguns peculiar things happen.
For a while, an enterprising person from Russia sold in EBay components to transform the Crosman 13XX pistols to PCP's.
But suddenly he vanished.
And so, some customers were left with parts but no instructions.
Add to that situation that the customers sometimes buy things "for a later date" and then forget them . . . and we have another peculiar situation.

When someone contacted me about "building" a pistol from parts he had on hand, I became VERY curious.

So, after some communications, it was established that there was precious little of the Crosman left (the Transfer Port, the barrel and the main spring only AAMOF).
There was a sidecocking bolt action repeating mechanism, there was an air tube with an offset valve/TP, there was a frame with a Match trigger that was supposedly adjustable, and there was a "free flight hammer".

Hmmmmmmm, curiosity got the best of me and we agreed on an hourly rate and preliminary "budget" and the parts were shipped.

When they arrived, I was looking, literally, at the proverbial "basket case". Lots of parts from the old gun and parts from the new gun without any labelling, order, or concert.
But, as any 5,000 mile trip, everything starts with the first step, and so I started "presenting" all the parts till I got some semblance of a pistol. A VERY BIG pistol.
In my own terms: a "pifle" or a "ristol", something that cannot be holstered, nor carried on the mid-region of ourselves. Not a "sidearm" as understood in most professional circles.

And, so, I started the"build".

As progress was done, I discovered that some parts needed to be modified, and the suggestions from the original EMails exchanged between purveyor and customer were not really to my liking.

So, back to drawing board and some hard decisions needed to be taken.

Through two days of hard thinking and some work, we decided how to do the final build and so the second thing to do was to test the air tank.
I completely disassembled the air tank and cleaned it very well inside and out, then reassembled and tested.
Luckily, there were no leaks. Good on that front!

Then came the assembly of the air tank to a "connection tube" that ensured that the action was located in the proper place and that allowed the new frame with the Match trigger to hold the parts together to make one unit.

The end result was not bad, actually quite impressive:

There was no special screw in the kit to attach the connection tube to the action. And the connection tube was thin enough that the OEM Crosman screw was not going to "cut it" if the gun lived to its intended power level, so we borrowed an idea from a scope rail replacement job and used a special super-fine thread metric screw that, for some reason is not as strange as it may sound: M4X0.5
Using a full screw, I turned it down so that it would fit into the cavity of the action but would not protrude into the connecting tube.

Apologies for the bad picture, cameras don't really focus well on shiny stuff. LOL!

And then we tested the gun.
MV's were a complete disappointment.
We could also feel the valve bouncing repeatedly (the gun "burped" at each shot), and there was some serious issue with shot count and efficiency.
It was also sadly evident that the moderator was having problems with too slow pellets that were possibly wobbling. We had to take down the whole thing and re-arrange, re-screw and loc-tite all the parts.
We were using the OEM (Crosman) Transfer Port (TP), and we could feel that the whole thing was not sealing properly, so we dismantled the Pifle and obtained some clear tubing (HDPE) to create a new TP.
BUT, the connection tube had a different diameter than the action. So we made a special TP by putting a section of the tubing in a mandrel and turning it to dimension.

The MV's improved substantially, but there was still some "burping" and so we disassembled the gun again.
Somewhat frustrated I started looking into the internet for "Crosman Tuning Lab" and discovered that they had changed name and abandoned the old website and they are now located at : www.airgunbuy.com

I sent an Email through their contact page and almost immediately received an answer!

Wonderful! It turns out that George (Georgiy, in his native Russian) is still the main driving force for the company and they now have some other interesting stuff, even complete rifles available.
I sent him pictures of the build and a detailed description of the problem, and he said he would consult with his technical guy, so support is there for these kits, which makes it more reasonable to use them.
Perhaps we can test some other of their products in the future.

After a night of consulting it with the pillow, it occurred to me that there was NO serious reason why that connecting tube had to have a different diameter and so I mustered the courage to re-drill that passage to the needed 8 mm's and installed a full length HDPE TP.
And the result was simply amazing!
We went from barely peaking at 10 ft-lbs to exceeding 22 ft-lbs in rather longish strings.
Of course it would be ideal if these kits came in with a regulator and an extended LP plenum, as there is capacity to spare in the tank, but this one didn't and the owner was wanting to use his gun, so that will remain for a later date.

Take a look at Airgunbuy.com as all companies, supply chain problems are causing some items to be out of stock, but their philosophy is interesting and their products are innovative.

Keep well and shoot straight!

HM © 2022/2/16

2 Comments

Noch zwei weitere Großartige Damen .- Part 2 ©

2/8/2022

4 Comments

Gun #2.- An attempt at shooting FT under German rules

Germans enjoy good engineering, but getting a license to operate an airgun at higher than the Olympic Match power level (5.5 ft-lbs / 7.5 J) is a long and complicated process (also somewhat expensive).
But still, there are enough Germans shooting FT in Classes 4 and 5 that there are actually matches held for those.
Class 4 is the "F in Pentagon" (under 7.5 Joules/5.5 Ft-lbs) spring-piston rifles that recoil
Class 5 is the "F in Pentagon" (under 7.5 Joules/5.5 Ft-lbs) spring-piston rifles with recoil-less actions
These two classes are shot at distances between 9 and 25 meters (as opposed to 9 to 50 meters that the 12 ft-lbs limit game is played).

If you have ever tried to shoot a Match airgun at 27 yards (25 meters), you will realize that it is not an easy task. especially in the outdoors.

Here in the US, we do not have those limitations, and so, when someone talks about "indoor FT" (where distances pretty much correspond to Class 4 and 5 airguns in German FT), eyebrows are raised, and some even start gathering green firewood to burn the heretics, LOL!

But, we're moving too fast ahead, let's talk about THE RIFLE.

As we said in the first part of this entry, we had procured TWO LGV's directly from Germany:

The First one, we discussed extensively in that entry, and so we will not go into it again here.

Gun Number 2 had lost all historical or collector value because a scope rail had been added.
Here is a picture of the modification made by a German gunsmith, attaching the scope rail where normally the "Walther" brand and Patent statement would have been visible:

To compare, this is the original "unmolested" one from Gun #1:

It might be clear to the advanced airgunner that the rail itself seems to be handmade.

In any case, as I said above, this rail destroyed any collector's value the gun could have had and so, it made for a good test-bench to try a few different things and see where the limits of the little engines lie as far as power with accuracy is concerned. And, do please, remember at all times that power by itself is useless in airguns without accuracy.

The same gooey mass came out of the compression chamber of gun #2, and we used the same method (acetone) to dissolve the slime, and a contoured brass rod to scrape, without scratching, the compression chamber walls.
The same HMO style piston went into this gun with an Urethane ORing because the temperatures and the pressures expected do not warrant the use of HNBR material.
I will not go into all the details of the different things tried (we tried Titan springs #'s 7, 10, and 1; plus the OEM spring and the two counter-wound OEM half-springs), but the end result was very interesting:

Using a Titan # 1 spring, cut to 21 total coils (yes, it was a drastic cut off), we obtained a VERY nice shot cycle, somewhat skewed towards the light pellets normal for these guns:

The Diabolo Basic yielded 678 ± 4 fps
The QYS.- 566 ± 5 fps
The JSB RS's.- 575± 5 fps
And then, just out of curiosity, I tested the Domed GTO's (made out of tin using the JSB Exact 10.34 die) and what a surprise.- 732 ± 4 fps
the "little engine" was doing 8.1 ft-lbs at the muzzle!

I've heard of FWB 300's that using the JM/ARH "Arctic" spring yielded 7½ to 8 ft-lbs, but I have never actually seen, tested, nor shot one. So, to me, that is still "vaporware". But this is reality.

Checking the accuracy, at first was somewhat disheartening. The D-B shot well, but as a wad-cutter, it was not precisely FT material.
The RS's performed very poorly, but that detracts nothing of the JSB quality, it just means that the bore is a little on the large side.
The GTO's were nothing to brag about, and so I started thinking:

Here was a gun that was NEVER intended to reach the 8 ft-lbs, the barrel was pencil-thin, and the weight enhancing "anchor" of a sleeve was not there. Originally, it had borne a medium weight sleeve, but we did not need weight, we needed rigidity.
And then it flashed into my mind some experiments performed way back when (1975-1976), with an ultralight-mountain rifle in a heavy caliber.
And so, I decided to put a tensioning sleeve on the little LGV.

I procured some CF tubes in different sizes and tried various combinations of wall thickness to tensions.

I also tried the Baracuda Green pellets.

In the end, the best result was obtained with a 15X18 CF tube tensioned to 35 in-lbs:

At 10 meters, from the FT position with the OEM peep sights, the performance was quite rewarding.

But, what to do with this gun? apart from shooting Olympic Match, of course, ROFL!

Well, my good friends at Palmyra Sportsman's Association provided the answer:
They hosted an indoor/winter FT session (not really a Match), that had targets between the 10 yards and the 22 yards that their indoor range allowed.

Obviously, the idea was to put some "handicap" into the shoot by not shooting my "formal" competition airgun. It's no fun to clean a course that has been designed for less energy and less ranging capabilities.

So, this little gun came in perfectly for the task. How perfectly? you will have to be patient because first we need to talk a bit more about the gun.

The challenge to shoot indoors and still make it a meaningful event, starts with the optics.

You simply cannot put a monster scope atop a relatively little engine. Yes, you will range perfectly, but that is not a challenge! I started looking over my collection of scopes and although I have some really remarkable specimens, after some testing between eye relief, magnification, weight and mounting options, the only real solution was a Leapers Bug-Buster, set in a pair of old steel RWS adjustable mounts.
Why the need for adjustable mounts?
Consider that the OEM peep sight has about 50 MOA's of elevation capacity. There is NO scope in this size that can match that.
And the rifle's architecture does correspond to that. So: adjustable mounts!

Here is the result:

In here I have to say that I wish the original owner could now see the gun. All the expense and trouble to add a rail, in reality was not needed. The RWS steel mount is installed in the same dovetail that the OEM peeps sit.
Here is a view of the OEM peep arrangement:

And here is a view of the Bug-Buster equipped rifle:

Clean, light, unobtrusive.

And, so equipped, I shot some distance targets to try to establish the trajectory:

Measuring the drop and measuring the LOS height, I came up with some reasonable idea of the trajectory, which we will discuss in the entry for the indoor FT event.
Overall the gun is a pleasure to look at, to shoot, and to carry.

The Glossy CF tube adds some texture and bling, while contrasting with the matte of the sighting equipment.

In the old days they knew what they were doing and made no qualms about reinforcing the wrist/pistol grips of Match guns. By the very definition of a Match gun, it is a gun that will travel.
And they didn't use ugly wood either:

So, I packed scoped gun, pellets and all the necessary accessories and headed to Palmyra, where the sighting-in cards offered a rewarding and amusing testimony:

5 shots at 12 yards above and 10 shots at the same distance, but with "1 mil" elevation, below.

At 22 yards with various aiming variations. 5 shot groups. From the knee.

One thing that did became apparent early on is that the gun is temperature dependent. I am not saying sensitive, because 50° F of temperature swing is nothing to sneeze at. The gun had stayed in the trunk of the car overnight, and then brought into the indoors range where we were shooting in long sleeved T Shirts.

After a little while and with a little bit of action, the gun stabilized and I started shooting the course.

4 Comments

2/8/2022

9 Comments

In the DIANA users' world, NOTHING elicits more fear than the idea of the scope rail becoming loose.
Or even worse, falling altogether off the gun!

This may happen for several reasons: Too heavy a scope at too high Muzzle Energy, or trying to "bottom" the stop pins in T06 rails, or a bad fall.

SOME users have detected some "play" in the rail and have tried to fix it themselves tightening the "screws" that hold the rail in place.

The result isn't pretty.

On one hand the screws are riveted from the inside of the mechanisms tubes.

On the other, they are VERY hard screws that are torqued to a ridiculously high level.

So, when a good friend asked me how to tighten the rail, I immediately told him to stop and send me the gun.

Of course, following the advice of a professional is unheard of; LOL!

A few months after the conversation, another call was received and he told me that with the help of a machinist friend, he had tried to remove the screws and re-thread/re-attach the rail. Of course, they were not able to.
Furthermore, in the process of trying, the rail had been destroyed.

So, now the issue was to procure a dovetail rail AND attach it to the action in a way that was functional.

It is too easy to install a crooked rail that will not allow ANY scope nor mount to align with the trajectory

By then, I was too busy and had stopped taking in work, but he was decided to wait whatever it took and so he sent the gun.

I was truly taken aback by what I received. The "rivet" studs were still attached to the action, no rail was present, and the note just said: "Yes I know you will be terrified at our butchering. Please do what you can"

Ah, well . . .

And so the process started.

First a carbide spot drill was used to put a dimple into which a normal but tiny pilot carbide drill would "dig" in each of the studs. I had to locate each hole with a magnifying glass.
Then a tiny pilot hole was drilled through the stud and careful observation proved that indeed, all holes were fairly coaxial.
Then a more robust carbide drill was used to remove the hardened studs and create the hole for a new thread. The best possible thread for attaching things to relatively thin tubes is the superfine metric threads.

Special screws had to be sourced, luckily, the M4x0.5 flathead screws were available OTC.

Locating an 11 mm's dovetail was not direct, and the ones located made the whole project almost lose all sense because they had no curve on the underside. Machining that curve would have meant creating a fixture to affix the blank in the lathe and then using a fly cutter; and then creating the fly cutter itself.

So, we found a 3/8" dovetail blank plate that had the proper underside curvature and decided it would be preferable to modify extensively the ZR Mount than to create a dovetail to suit the gun's profile.

Same would have been true for the many Picatinny rail blanks available. AND ZR mounts of the Picatinny version are as scarce as hen's teeth.

Once the studs had been removed, the dovetail "plate" was locate and drilled to match the OEM holes.

As parts started to trickle in, it became obvious that the challenge was going to be to get the plate in place roughly aligned to the bore of the gun. We COULD later, do some minor regulating, but we really did not want to have to do too much of it.

So, we sourced a bore-sighter and turned the stem to fit the airgun barrel.

It proved to be a very wise decision, as it turned out that the OEM holes were not precisely "perfectly" aligned to the barrel/bore, it may be that the barrel had been bent out of whack some time previously, or that in the operation of removing the old rail, the barrel had been affected.

In the end, after some relieving and "slack-building" we were able to mount the plate to the gun, and check everything before gluing the plate.

Once everything was dry and everything was re-checked, this was the result:

Just to clarify, I did NOT put that scratch to the left of the action. LOL!

I tested the gun with a 1" scope in an Accurized ZR mount and discovered that there was too much of a difference between the 3/8" and the 11 mm's dovetail, or at least between THIS dovetail plate and the 11 mm's standard dovetail as understood in Europe.

And so the really long part of the project began, because dovetails are fickle beasts! You take off a bit here and all the angles and surfaces change and all goes out of whack.

In the end, we spent more time making sure that the mount sat square and plumb and tightened enough the dovetail than attaching the dovetail rail plate.

A substantial amount had to be milled out of the right side of the base, so that the moveable clamp could tighten well and still keep the proper angle.
Then about 0.5 mm's had to be milled from the bottom of the left side, to ensure that the mount sat level & square.
Since this rail plate has no stops, I re-drilled and re-tapped the holding screws to receive M4 screws and ensure a solid attachment..

Then came another challenge: The customer had decided on an Athlon scope, and those scopes have a rather hefty "saddle" which meant that 0.6 mm's had to be milled off the watertable to allow the scope to move freely in the ZR mounts.
All in all 7 solid hours of serious work were put into this, mostly setting up, measuring and re-measuring, and then re-checking everything once again before even starting the milling.

So, what do we get for all that work?

And

Do note:
- all these are 10 shot groups from a full powered (21 ft-lbs) 0.22" cal D54
- the 10 M groups are single hole
- the 25 M groups (zero) are barely larger than ½"
- the 40 M groups are about ¾"
all this from the knee/FT position.

For the first try some effort was made to compensate for the wind, for the second I tried to get a better feel for long distance (55 M = 60.2 yds) wind drift.
Wind was kicking hard and moving not only the pellet but the shooter also!

The rifle's architecture is a straight hunter, low-sitting scope for more reliable trajectory in the short to medium ranges, quite pleasing to carry and to shoot.

So, from an almost "lost cause" case to a really good shooter.

Marvelous machines these are indeed!

Keep well and shoot straight!

HM
© 10/28/21

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Hector Medina

2012 US National WFTF Spring Piston Champion
2012 WFTF Spring Piston Grand Prix Winner
2013 World's WFTF Spring Piston 7th place
2014 Texas State WFTF Piston Champion
2014 World's WFTF Spring Piston 5th place.
2015 Maine State Champion WFTF Piston
2015 Massachusetts State Champion WFTF Piston
2015 New York State Champion WFTF Piston
2015 US National WFTF Piston 2nd Place
2016 Canadian WFTF Piston Champion
2016 Pyramyd Air Cup WFTF Piston 1st Place
2017 US Nationals Open Piston 3rd Place
2018 WFTC's Member of Team USA Champion Springers
2018 WFTC's 4th place Veteran Springer
2020 Puerto Rico GP Piston First Place
2020 NC State Championships 1st Place Piston
2022 Maryland State Champion WFTF