Short stroke TX200 testing

no avatar
FPoole
Posts: 339
Joined: Mon Feb 16, 2015 2:37 am

Short stroke TX200 testing

Tue Feb 02, 2016 12:47 am

Well, I've got around 500 shots through my new TX set up. LGU piston and seal, rear guide machined into end plug, compression tube nut machined down to shorten transfer port and some tight guides front and rear. My conclusion is that it's a bit disappointing. I used a proven very good TX and I just haven't seen the groups I was getting with factory parts. Shot cycle is smooth, but the gun seems to jump with the quick shot cycle. The pellet on the scope turret screw stays put, but the gun just requires a perfect hold. The whole reason for trying the new set up was to make my part of the shot not as important. This set up is very sensitive to how the gun is held, much more so than the factory set up. I was using a 93 mm FAC MarkII piston with a soft spring to achieve the 12 ft. lb. levels and I have other guns with the factory 84 mm piston to go along with the newer 98 mm stroke guns. I've never shot a 12 ft. lb. 98 mm stroke gun, but the same gun in FAC is less sensitive than my new kit. The old MarkI and MarkII 12 ft. lb. piston is worlds better as well. After 500 more break in shots I will decide which way to go with this. I'm thinking that keeping the comp. tube with the short port is good, but I think the LGU piston and seal may not be so great after all. Perhaps a factory 84 mm piston with the new comp. tube may be good? It could also be that the rear guide is just too tight.

no avatar
gary martin
Posts: 815
Joined: Thu Feb 19, 2015 8:21 pm

Re: Short stroke TX200 testing

Tue Feb 02, 2016 8:12 pm

the lgu piston is a little heavier than the tx one i believe. a short stroke heavy piston gives a heavy feel in the compression stroke i have found. i am using a reduced weight of piston by 24.8% it softened the feel greatly. of course the breaking force of the compressed air slowed the piston down faster, using less of the stroke. adding a little preload rasied the output backup without sacrifcing feel. i use an o ring seal though. i would suspect by shortening the transfer port though you are using quite a lot of the stroke with the reduced bleed off of pressure. this could be giving you a harsh feel at end of stroke. maybe suggest reducing weight of piston a little.
Gary.

no avatar
FPoole
Posts: 339
Joined: Mon Feb 16, 2015 2:37 am

Re: Short stroke TX200 testing

Wed Feb 03, 2016 1:36 am

The piston appears to have been shaved down a bit and I think the stroke is around 81 mm. The LGU piston is big compared to the TX piston. I think I will weigh them and see the difference. I will also see how thick the LGU piston walls are. If there's enough meat, I will thin it down a bit.

no avatar
FPoole
Posts: 339
Joined: Mon Feb 16, 2015 2:37 am

Re: Short stroke TX200 testing

Tue Feb 09, 2016 1:36 am

Update, it's getting better. Maybe 1,000 break in pellets will be the magic number.

no avatar
FPoole
Posts: 339
Joined: Mon Feb 16, 2015 2:37 am

Re: Short stroke TX200 testing

Fri Feb 12, 2016 10:54 pm

Finally put it over the chrono again and it's doing 730 fps. I'm going to try something else because this is simply too slow for a 55 yard target in the wind.

User avatar
Sake-san
Posts: 551
Joined: Mon May 18, 2015 7:28 pm

Re: Short stroke TX200 testing

Sat Feb 13, 2016 8:35 am

Forgive the question but, it is an LGU seal and not the LGV one with the central nipple?. I was getting without problem 775fps (AA Field) with either a Mk2 or shortened Titan no.9 spring when I experimented with this piston set up. But, as we know the efficiency of individual rifles can vary a lot (ref my last PM to you), out of interest what does your piston weigh?.
Not sure how you got on with Nick Gibney but, I have yet to hear or read anything negative about his ally o-ring pistons, the lack of sight picture movement is astonishing, you can even shoot the gun off a rest like a PCP without problem.
All good fun, hope you get it sorted to your satisfaction.
TX200/Gary Cane/Sightron SIII 10-50x60
TX200/Gary Cane/Sightron SIII 10x42
TX200 test / analysis gun

no avatar
FPoole
Posts: 339
Joined: Mon Feb 16, 2015 2:37 am

Re: Short stroke TX200 testing

Sun Feb 14, 2016 3:28 am

Yes it's the LGU seal. I picked up 40 fps by opening up the inner diameter of the rear guide. It was snug on the piston stem, so I opened it until it was a smooth slide with no grabbing. The first few shots were in the dark and it felt a bit twangy. Today I put 20 shots over the chrono and it's up to 770 fps. I did 2 10 shot strings and it was 767 on the first for average with a standard deviation of 3. The next 10 shots had a spread of 8 fps and a standard deviation of 2. The average was up to 769. I'll let it run in a bit more as it was gradually climbing over the 20 shots. Strange thing was that the twang has gone. This same gun usually has a spread of 4 fps and a standard deviation of 1 with the factory style set up of 93 mm stroke. I'm not sure I like the seal material as it seems a bit hard and shows a wear pattern on the seal edge. I always used Maccari's old Blue small Apex seal that was soft and flexible, but would show no sign of wear even after 10,000 shots. I would just change them after a few years to be on the safe side. Might see if he offers an HW style seal in the old blue material.

User avatar
Sake-san
Posts: 551
Joined: Mon May 18, 2015 7:28 pm

Re: Short stroke TX200 testing

Sun Feb 14, 2016 5:49 pm

Good to hear it is all coming together, I recall reading somewhere (but, cannot recall where) that Walther in their testing believe the LGU seal to be good for 70,000 shots!
TX200/Gary Cane/Sightron SIII 10-50x60
TX200/Gary Cane/Sightron SIII 10x42
TX200 test / analysis gun

no avatar
FPoole
Posts: 339
Joined: Mon Feb 16, 2015 2:37 am

Re: Short stroke TX200 testing

Sun Feb 14, 2016 8:51 pm

I hope so and it does look like a thin line around the lip where it's been seating in. I once used an old Maccari blue Apex seal for over 50,000 shots and it looked and felt fine. It had changed a bit in color, but I swapped it out because I had plenty of spares. There was also a Diana blue seal that fit the TX/PS and it was also excellent.

Post Reply

Who is online

Users browsing this forum: No registered users and 16 guests