A Yankee Tune for the Walther LGU.- Second version

I noted in my past blog entry, that there were two spring kits that could be used to "tune" the Walther LGU:
The first one was the Vortek Products kit for the HW97-25 mm's.
The second one was to use the Maccari spring for the LGV.

My good friend, the Pennsylvania Yankee was delighted with the Vortek option because there was no bounce, no buzz, no spring noise and no vibrations. All lofty and proper goals in a spring gun tune.

Sadly, for ME, the accuracy of the setup was less than stellar, especially in the 45 to 55 yard regions.

LGU's are accurate out of the box. NO questions about that. In the case of those rifles shipped to the US market, they are overpowered as regards WFTF rules.
And, at least in my hands with my rifle, the piston bounces. You can clearly feel the first strike, then the pellet exit and report, and then the gun jumps forward once more. Annoying, to the point that I could not see myself shooting 3 days, 150 shots, like that.

Herein lies an interesting difference: Some guns are not as accurate as others, but they are more "shootable" for a specific person and, in the end, this brings better results for each one of us. Or viceversa.

So, the guns need a tweak. It would be spectacular if the guns needed no tweaking and no tuning but let's face it, WE are ALL DIFFERENT!

So, having said that, and because for ME, the Vortek kit was not giving the results I wanted or expected at the extreme ranges, I started the process all over to establish the tune for the Maccari kit.

I will not go through the disassembly process, that is the same whatever kit you are using.

Once the gun is apart, you need to compare the springs.

In our case the Maccari spring for the LGV is substantially longer than the one used by Walther in the LGU, so I cut off 2 coils to bring the Maccari spring into the ballpark.

Then I started testing the power output. 14.2 ft-lbs with the Exacts AND with a definite piston bounce! Hmm . . . not good. The OEM setup had produced 13.1 ft-lbs for this same pellet, so we were on a good track, just a little away from what we were actually looking for. Pre compression, as measured from the initial point of contact to the effective closing of the rifle, was 35 mm's. 5 mm's short of the OEM setup.

So I cut 1¼ coils off, added a tight fitting composite top-hat and tested.

How tight? you ask.

Well, if I pull the spring out the piston comes with it. I have to pull SLOWLY and allow air to get in between the TopHat and the piston to allow them to part.

Precompression now was 25 mm's and power output was 13.5 ft-lbs. Interesting! 1¼ coils off was a somewhat brave and drastic measure, how can the rifle STILL be generating this much power? Of course the tophat acted as a spacer and added weight to the piston, but the important thing: No more piston bounce! Snug as a bug!

So, off came 1 3/4 coils more. And then tested:
With JSB 8.44's.- 11.4 ft-lbs.
With AA 8.44's.- 11.2 ft-lbs (interesting because the relationship between AA's and JSB's is usually reversed).
With JSB Express 7.9's.- 11.74 ft-lbs.

That should do it, with extreme spreads of 5 fps the maximum power in a string of 10 shots was 11.80 ft-lbs. So, no worries about the chrony on the lanes.

The amazing part is that precompression now was down to 10 mm's, the gun could be put together and taken apart with simple hand pressure. NO spring compressor required.
Sure four hands are better than two because you need to align the small pin holes and hit on the pins to assemble or on the punch to disassemble, but having a gun that actually needs no spring compressor is an interesting experience in itself.

So, now that we are "legal" even with light pellets, and that we know that the barrel likes somewhat "fatter" pellets, we need to start the search for accuracy all over again.

The shot cycle is very nice. Recoil is straight fore-aft, no more jumping up and kicking like a mule. After the shot, you can see the target and see how off you were on your hold. Still cannot see the pellet travelling nor the impact the moment it occurs, but a lot more steady than any other airgun without a sled system.

Cocking effort was also substantially reduced, not to the 20#, but almost; it is at 25# a great improvement over the 32# of the OEM setup.

Accuracy at short and medium range (32 meters) is as good as with the OEM setup and I think that the "captive" guide has a LOT to do about that. I'll have to wait for longer range testing till next week.

As an aside, I've been informed that AA has ALSO stepped over to the "captive" guide field with the latest TX-200's. Theirs is a pressure fit, not a truly captive guide-in-a-groove kind of thing, but users tell me that it takes quite a lot of fiddling to get that guide out.

I was told Vortek Products already has all the measurements needed to make a kit that will have all the good Vortek characteristics, plus will add the "captive" guide principle. Let's hope we can see that kit soon!

In the meantime, have fun!