3 ½ years in the making. LOL!
Yes, just like the "Three Musketeers" had a sequel that came well after the initial book, the original "Chapter 1" took some years to "coalesce".
Now, with some talk about returning to the "Classic DIANA 34" it is essential that we truly get into the differences and rescue what is worthwhile from the EMS.
Just to remind everyone, the EMS took the NTec piston and trigger unit and came out as a steel spring powered version.
We have already explored the conversion of "Old 34's" into NTec systems (and in Chap 1 we detailed how to install an NTec unit into an EMS rifle), so, we won't go there. Rather, we'll use the first part of this entry to explore the intrinsic advantages of the EMS system as well as some of its "caveats" and, in a second part, relate in detail what makes the steel spring version of the NTec triggered airgun such a success and how to go about it.
As usual, the disclaimer is that all the operations performed here were done by a qualified airgunsmith who took all the precautions of the case. No warranties are implied or extended, and no responsibilities will be accepted.
If you decide to do this, you are on your own.
SO, let's get into the first part.
Yes, just like the "Three Musketeers" had a sequel that came well after the initial book, the original "Chapter 1" took some years to "coalesce".
Now, with some talk about returning to the "Classic DIANA 34" it is essential that we truly get into the differences and rescue what is worthwhile from the EMS.
Just to remind everyone, the EMS took the NTec piston and trigger unit and came out as a steel spring powered version.
We have already explored the conversion of "Old 34's" into NTec systems (and in Chap 1 we detailed how to install an NTec unit into an EMS rifle), so, we won't go there. Rather, we'll use the first part of this entry to explore the intrinsic advantages of the EMS system as well as some of its "caveats" and, in a second part, relate in detail what makes the steel spring version of the NTec triggered airgun such a success and how to go about it.
As usual, the disclaimer is that all the operations performed here were done by a qualified airgunsmith who took all the precautions of the case. No warranties are implied or extended, and no responsibilities will be accepted.
If you decide to do this, you are on your own.
SO, let's get into the first part.
What makes the EMS a better airgun?
In this, as in most things in life, there is a lot more to an object than "black and white"; or even "Umpteen shades of grey". Life is colorful and we all have our likes and dislikes. So, to be clear: All the following aspects are my opinion, based on more than 24 years of airgunsmithing, out of which, 12 have been at a professional level.
We'll only make two comments about the stock:
- Apart from the ghastly buttplate that is used in the EMS "Classic" that slips on every smooth surface known to man (floor, shirt, or jacket), the stock is quite traditional and svelte, light and nimble to mount to shoulder.
It also has the cutouts to allow the regulation of the fork's tension across the barrelblock axle:
We'll only make two comments about the stock:
- Apart from the ghastly buttplate that is used in the EMS "Classic" that slips on every smooth surface known to man (floor, shirt, or jacket), the stock is quite traditional and svelte, light and nimble to mount to shoulder.
It also has the cutouts to allow the regulation of the fork's tension across the barrelblock axle:
Anyone that shoots/hunts in diverse temperatures (from the 40°C of summer to the -2°C of Winter, knows that this sometimes needs some "adjustment" to the specific conditions.
Underneath the screw and the "nut" there are loc-washers that make the system very reliable.
So, this, I would keep.
In the attachment of the stock to the mechanisms tube, the EMS uses angled screws:
Underneath the screw and the "nut" there are loc-washers that make the system very reliable.
So, this, I would keep.
In the attachment of the stock to the mechanisms tube, the EMS uses angled screws:
This is a far superior method than the bracket that was used in the "old 34", yes it requires a slightly "beefier" stock in this area, but it it less prone to catastrophic failure.
The Caveat here is that a cross threaded, or broken screw, means serious business and is not as easy to resolve as the changing of the bracket itself. So, yes it is a superior system, that requires superior caution and care when working on one of these guns.
The cocking linkage is next: the EMS uses a compound cocking linkage:
The Caveat here is that a cross threaded, or broken screw, means serious business and is not as easy to resolve as the changing of the bracket itself. So, yes it is a superior system, that requires superior caution and care when working on one of these guns.
The cocking linkage is next: the EMS uses a compound cocking linkage:
This allows the slot in the stock to be far shorter than the slot in the "old 34" stock, it also reduces the peak cocking force.
For the gunsmith, however, the main advantage is that you can flip the mid-junction up, as in the photo, and with the barrelblock in the broken open position, the linkage comes out and you can withdraw the piston for any work needed without disassembling the cocking linkage from the barrelblock itself.
This saves a ton of time when you only need to change the piston seal.
The Caveat here is that the stock then becomes an integral part of the mechanism of the gun, as it is the stock what maintains the cocking lever in the right position throughout the cocking cycle.
To ME, that is not a disadvantage at all, but some may not like it.
Now, IF, for any reason, the cocking linkage needs to be worked on, it is a very useful characteristic that the "axle" of the cocking lever is not affixed to the barrel block by a simple pin with an "EClip" lock, as in the "old 34", or using a pinned in pin, that needs to be driven out with a hammer and a punch, as in other brands.
In the EMS, the cocking linkage pin is a shoulder screw with a torx head:
For the gunsmith, however, the main advantage is that you can flip the mid-junction up, as in the photo, and with the barrelblock in the broken open position, the linkage comes out and you can withdraw the piston for any work needed without disassembling the cocking linkage from the barrelblock itself.
This saves a ton of time when you only need to change the piston seal.
The Caveat here is that the stock then becomes an integral part of the mechanism of the gun, as it is the stock what maintains the cocking lever in the right position throughout the cocking cycle.
To ME, that is not a disadvantage at all, but some may not like it.
Now, IF, for any reason, the cocking linkage needs to be worked on, it is a very useful characteristic that the "axle" of the cocking lever is not affixed to the barrel block by a simple pin with an "EClip" lock, as in the "old 34", or using a pinned in pin, that needs to be driven out with a hammer and a punch, as in other brands.
In the EMS, the cocking linkage pin is a shoulder screw with a torx head:
And this is locked in place through a cross-grub screw on the other side:
Is this "over-engineering"?
I don't think so. It makes the gun serviceable in ways that only create problems otherwise.
Perhaps it is a matter of customer education. I've seen more rifles damaged by people that want to hammer out the corresponding pin from the wrong side, than I can tell, and the problem is that customer comes to the gunsmith with the complaint: "I didn't do anything wrong, just punched the pin out, and now it does not want stay in". LOL!
Anyway, this is another of the things I would keep.
Keeping to the barrelblock: the barrelblock was designed with enough space to insert a locking mechanism.
There has not been a strong market reaction to this possibility, so it may never happen, but since the locking mechanism's patents have expired a long time ago, perhaps it is time to use the existing state of the art. We'll see what happens on that one.
The next one is one where I am ambivalent: on one side I dislike it, on the other, not so much and even think it is an advantage; I'm talking about the scope rail:
I don't think so. It makes the gun serviceable in ways that only create problems otherwise.
Perhaps it is a matter of customer education. I've seen more rifles damaged by people that want to hammer out the corresponding pin from the wrong side, than I can tell, and the problem is that customer comes to the gunsmith with the complaint: "I didn't do anything wrong, just punched the pin out, and now it does not want stay in". LOL!
Anyway, this is another of the things I would keep.
Keeping to the barrelblock: the barrelblock was designed with enough space to insert a locking mechanism.
There has not been a strong market reaction to this possibility, so it may never happen, but since the locking mechanism's patents have expired a long time ago, perhaps it is time to use the existing state of the art. We'll see what happens on that one.
The next one is one where I am ambivalent: on one side I dislike it, on the other, not so much and even think it is an advantage; I'm talking about the scope rail:
The scope rail is CNC cut into both sides using a dovetail cutter, that enters, cuts, and then comes out.
It is elegant and clean, excellently executed:
It is elegant and clean, excellently executed:
The other side is the same.
IF you are using a fairly common mount with sideplates that make the dovetail when closed by the tension screws, you're OK. But if you want to use one of the best bases (BKL's), then you run into problems.
Of course, if you use a ZR mount, you're good on all counts, it is high enough to give you clearance for even large objective lenses (not that the 34 has need or use of FT type scopes, but the facility is there), and you can also open the sideplates enough to properly insert and clamp the base.
IF you want to use a Peep, then it is a bit more complicated. Williams' do fit well, but the more elaborate Match/peep sights have real issues getting into these slots. Do many people install a $200 peep sight in a $400 rifle? not so many, but it is something to consider.
One possibility is to continue the dovetails all the way to the rear, so that, removing the dust protector at the rear, you can slide in anything that has an appropriate dovetail mounting system.
The other possibility would be to re-instate the DIANA scope rail, but, IMHO, that would raise the LOS too much and would add weight and is a potential failure point. I've seen less than half a dozen failed rails in all my life; and most of them have been user-induced problems, but still we need to be candid about both sides of the issue.
Now, let's get to the internals:
Last, but not least is something that bothers me as a gunsmith, it seems to me to be a "shortcut" something that should not happen because, "really, we know better", and that is the angle of the transfer port.
In the EMS, the transfer port is coaxial to the bore, and is located at the top of the compression chamber which means that it is offset from the compression chamber.
What this means is that we do not have an efficient transfer geometry. Yes it is shorter, it is the shortest distance between compression and expansion possible, but it forgets that the piston seal is on the way:
IF you are using a fairly common mount with sideplates that make the dovetail when closed by the tension screws, you're OK. But if you want to use one of the best bases (BKL's), then you run into problems.
Of course, if you use a ZR mount, you're good on all counts, it is high enough to give you clearance for even large objective lenses (not that the 34 has need or use of FT type scopes, but the facility is there), and you can also open the sideplates enough to properly insert and clamp the base.
IF you want to use a Peep, then it is a bit more complicated. Williams' do fit well, but the more elaborate Match/peep sights have real issues getting into these slots. Do many people install a $200 peep sight in a $400 rifle? not so many, but it is something to consider.
One possibility is to continue the dovetails all the way to the rear, so that, removing the dust protector at the rear, you can slide in anything that has an appropriate dovetail mounting system.
The other possibility would be to re-instate the DIANA scope rail, but, IMHO, that would raise the LOS too much and would add weight and is a potential failure point. I've seen less than half a dozen failed rails in all my life; and most of them have been user-induced problems, but still we need to be candid about both sides of the issue.
Now, let's get to the internals:
Last, but not least is something that bothers me as a gunsmith, it seems to me to be a "shortcut" something that should not happen because, "really, we know better", and that is the angle of the transfer port.
In the EMS, the transfer port is coaxial to the bore, and is located at the top of the compression chamber which means that it is offset from the compression chamber.
What this means is that we do not have an efficient transfer geometry. Yes it is shorter, it is the shortest distance between compression and expansion possible, but it forgets that the piston seal is on the way:
Here's a piston seal that has seen a few dry-fires and/or has been oversprung and so the second hit of the piston against the compression chamber end wall is really strong.
It not only opens the seal to damage, but it also interferes with the flow of very hot air at very high pressures into the transfer port.
There's a famous "birds foot" piston seal from another manufacturer, that has not worked too well either.
Yes, the TP needs to be kept as short as possible, and it does benefit from a certain degree of venturization (in break barrels), but this should not be executed at the cost of disrupting the end of a compression cycle that is almost a detonation.
It not only opens the seal to damage, but it also interferes with the flow of very hot air at very high pressures into the transfer port.
There's a famous "birds foot" piston seal from another manufacturer, that has not worked too well either.
Yes, the TP needs to be kept as short as possible, and it does benefit from a certain degree of venturization (in break barrels), but this should not be executed at the cost of disrupting the end of a compression cycle that is almost a detonation.
The NTec trigger was designed from the ground up to be a piston body/locking trigger, to alllow DIANA to dispense with the stem and insert the gas spring, that, by itself, is a stemmed device. In order to "lock" everything into a unit, DIANA made a special "cup" that holds the piston in place when fully cocked, this cup then receives the body of the gas spring while the stem of the pusher element goes into the piston.
The trigger therefore, needed a nut. So as to screw the body of the gas spring into the trigger block:
The trigger therefore, needed a nut. So as to screw the body of the gas spring into the trigger block:
At the top, you can see the safety carrier plate that also acts as a cocking lever, and in the center you can see the threaded part that acts like a "nut" retaining the gas spring body.
At the bottom is the actual "sear" that is a ramp that interferes by pushing itself into a square hole in the bottom of the piston.
When the lower lever pushes the upper lever and the sear "breaks" what is happening in reality is that this little ramp "falls" and allows the piston to fly forward.
Now, to make it possible for this mechanism to work reliably, the POSITION of the piston has to register to within 0.010" each time the piston is cocked, and without the support and alignment of the stem and guide, a "cup" needs to be added, like this:
At the bottom is the actual "sear" that is a ramp that interferes by pushing itself into a square hole in the bottom of the piston.
When the lower lever pushes the upper lever and the sear "breaks" what is happening in reality is that this little ramp "falls" and allows the piston to fly forward.
Now, to make it possible for this mechanism to work reliably, the POSITION of the piston has to register to within 0.010" each time the piston is cocked, and without the support and alignment of the stem and guide, a "cup" needs to be added, like this:
In the case of the NTec rifles, the male thread is part of the gas spring, but in a steel spring gun?
We use a very special screw:
We use a very special screw:
Now, in true DIANA tradition, this is an ISO/DIN part. It is a standardized screw. Not common, but it is a standardized screw.
In the US it is obtainable from the better industrial supply houses.
In the US it is obtainable from the better industrial supply houses.
Conversion of an NTec airgun to a steel spring one
So, now that we understand how critical it is to have the piston in exactly the same position every time, we can understand how the EMS uses a steel spring powerplant:
So, there are FIVE parts in this picture of the powerplant, from left to right:
-Screw (almost invisible, you only see part of the thread)
-Cup
-Spring guide
-Spring
-Forward guide
Wait . . . ¿WHAT? a forward guide?
Yup!
It is a forward guide and also a piston weight.
Without this forward guide, there would be a LOT of spring breakages and the power achievable would be cut significantly, especially for mid to heavy pellets.
We need to remember that the 34 and all its variations: EMS, AM03, 340, are break barrel, and that means a long transfer port. Weight in the piston is essential to ensure proper energy transfer through the transfer port.
I have tested different arrangements of forward and rear guide, some of them worked in some guns, some made funny noises during the cocking stroke, some of them worked in some but not all guns, some of them worked with one spring but not another, some of them worked for a while, but did not have the long term reliability that DIANA demands from their products. So, after DOZENS of tests and hundreds of shots, CCA has decided to stay (for the moment) within the OEM design, just use much tighter tolerances:
-Screw (almost invisible, you only see part of the thread)
-Cup
-Spring guide
-Spring
-Forward guide
Wait . . . ¿WHAT? a forward guide?
Yup!
It is a forward guide and also a piston weight.
Without this forward guide, there would be a LOT of spring breakages and the power achievable would be cut significantly, especially for mid to heavy pellets.
We need to remember that the 34 and all its variations: EMS, AM03, 340, are break barrel, and that means a long transfer port. Weight in the piston is essential to ensure proper energy transfer through the transfer port.
I have tested different arrangements of forward and rear guide, some of them worked in some guns, some made funny noises during the cocking stroke, some of them worked in some but not all guns, some of them worked with one spring but not another, some of them worked for a while, but did not have the long term reliability that DIANA demands from their products. So, after DOZENS of tests and hundreds of shots, CCA has decided to stay (for the moment) within the OEM design, just use much tighter tolerances:
At the top is the OEM components, at the bottom is the CCA rear spring guide and front piston guide.
The differences of a some thousandths in each dimension (internal and external) are not visible in the picture, but the quality of the shot cycle is night and day.
The differences of a some thousandths in each dimension (internal and external) are not visible in the picture, but the quality of the shot cycle is night and day.
So, what can we expect from converting an NTec rifle into a steel spring powered rifle?
Taking advantage of a request from Eastern Europe and with infinite thanks to my Serbian friend for his patience and forbearance, I performed a full/organized test of all the methods I had used in the past to get to some conclusions.
Please bear in mind that nearly a thousand shots were made to reach these conclusions, they are not the result of a few groups/strings.
Using a well characterized pellet (the JSB Exact 8.44/4.52) in a recent production EMS in 0.177" cal. and using the Titan XS spring #3, the results are as follows:
With the NTec unit the rifle yielded on average 13.8 ft-lbs (860 ± 3 fps) as measured by a Caldwell chrono with IR screens at a controlled distance.
With the CCA components and a full size Titan #3, the gun yielded 14.6 ft-lbs (883 ± 2 fps)
Since my friend is going to use this rifle as a practice rifle for UK/HFT, the rifle needed to yield sub-12 ft-lbs.
We had to cut 3½ coils off the spring to achieve this.
Now with the shortened spring, the gun yields 12 ft-lbs (798 ± 2 fps) and with heavy pellets, like the H&N BFT, it yields 11.3 ft-lbs (731 ± 4 fps).
The Titan #3 can be spaced up almost 0.040" / 10 mm's, but while the speeds do go up, the shot cycle becomes less than stellar.
If more power is wished, accepting the cost of a harsher shot cycle, then it would be advisable to use the Titan #4.
I don't have a 340 Ntec, to test, nor a 350 NTec. And, quite frankly, this whole thing has taken far too much time, not a bad investment, but there are other things that also need to be addressed, so this will be the end, for the moment of this development. IF/ WHEN there is a solid interest, we may retake the idea again.
The fact that a properly built steel spring powerplant is superior, not only in power, to a gas spring; but also offers a much better shot cycle for a given power is interesting.
The LIMITS of the above statement is when using heavy for caliber pellets; in that situation, the gas spring does become a better powerplant, limited only by the swept volume, the barrel length, and the transfer port geometry.
For example: my D34 converted into NTec in 0.20" cal and a short barrel, develops 15.2 ft-lbs with JSB's 13.4 (715 ± 3 fps) , and 16.7 ft-lbs with H&N FTT's (811 ± 3 fps) , while in 0.177" cal, even using a longer barrel, it only developed 13.8 ft-lbs
I need to get some heavy 0.20" s from JSB and test, but that will be another story.
Keep well and shoot straight!
HM
Taking advantage of a request from Eastern Europe and with infinite thanks to my Serbian friend for his patience and forbearance, I performed a full/organized test of all the methods I had used in the past to get to some conclusions.
Please bear in mind that nearly a thousand shots were made to reach these conclusions, they are not the result of a few groups/strings.
Using a well characterized pellet (the JSB Exact 8.44/4.52) in a recent production EMS in 0.177" cal. and using the Titan XS spring #3, the results are as follows:
With the NTec unit the rifle yielded on average 13.8 ft-lbs (860 ± 3 fps) as measured by a Caldwell chrono with IR screens at a controlled distance.
With the CCA components and a full size Titan #3, the gun yielded 14.6 ft-lbs (883 ± 2 fps)
Since my friend is going to use this rifle as a practice rifle for UK/HFT, the rifle needed to yield sub-12 ft-lbs.
We had to cut 3½ coils off the spring to achieve this.
Now with the shortened spring, the gun yields 12 ft-lbs (798 ± 2 fps) and with heavy pellets, like the H&N BFT, it yields 11.3 ft-lbs (731 ± 4 fps).
The Titan #3 can be spaced up almost 0.040" / 10 mm's, but while the speeds do go up, the shot cycle becomes less than stellar.
If more power is wished, accepting the cost of a harsher shot cycle, then it would be advisable to use the Titan #4.
I don't have a 340 Ntec, to test, nor a 350 NTec. And, quite frankly, this whole thing has taken far too much time, not a bad investment, but there are other things that also need to be addressed, so this will be the end, for the moment of this development. IF/ WHEN there is a solid interest, we may retake the idea again.
The fact that a properly built steel spring powerplant is superior, not only in power, to a gas spring; but also offers a much better shot cycle for a given power is interesting.
The LIMITS of the above statement is when using heavy for caliber pellets; in that situation, the gas spring does become a better powerplant, limited only by the swept volume, the barrel length, and the transfer port geometry.
For example: my D34 converted into NTec in 0.20" cal and a short barrel, develops 15.2 ft-lbs with JSB's 13.4 (715 ± 3 fps) , and 16.7 ft-lbs with H&N FTT's (811 ± 3 fps) , while in 0.177" cal, even using a longer barrel, it only developed 13.8 ft-lbs
I need to get some heavy 0.20" s from JSB and test, but that will be another story.
Keep well and shoot straight!
HM
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