Titan GP Upgrade with Weaver Rails

[demarisl]

Titan GP Upgrade

Spent a marvelous weekend in Burt, IA with Mike Melick and 3 other air gun enthusiasts.  Not only did I learn more than I'll probably retain about tuning springers but also had my first taste of Jalapeño beer.  All while enjoying good conversation and getting to shoot quite a few of the guns in Mike's collection.  Mary, Mike's wife, fed us way too much good food and their hospitality couldn't have been better. 

Anyway, one of the project guns was my TitanGP which had a bad piston seal.  While waiting for the weekend with Mike to arrive, I ordered the Trail NP compression chamber with the weaver rail from Crosman and the NP - GRS bushing kit from AirGunToys.  It already wore a Summit stock and sported a gold trigger.  The scope is a Centerpoint 3x9x40.  Mike worked his magic and it now looks like this:








The shot cycle is fantastic, just a thump and a little vertical jump.  After 20-30 initial shots, dieseling disappeared.  Ran three ten-shot chrony strings this afternoon to establish a baseline.  The first was with the Peak domed pellets sold by Mike.  These say 13.9 grains on the lid but the average weight of the ten I weighed was 14.15 grains.  These were:

Max 686
Avg 672.1
Min 662
Spread 24
SD 7.062

The next ten were the BSA Storm at 15.43 grains:

Max 685
Avg 672.8
Min 659
Spread 26
SD 9.065

The last ten were Crosman Hps at 14.2 grains:

Max 692
Avg 680.9
Min 660
Spread 32
SD 10.616

I expect to see these numbers climb as the seal wears in.  Will repeat the chrony strings after a couple tins of the Peak pellets.  The Storm and CHPs were sorted by weight while the Peaks were straight out of the tin.  Interesting that they had the smallest spread. 

Sight in at 20 yards proved a challenge.  The rings I was using weren't high enough and pressure on the scope tube prevented any changes in elevation.  Ran to Scheels and picked up a pair of medium profile UTG Weaver rings.  Removed the old rings, optically centered the reticles with a mirror, and mounted the new rings.  Shot one five-shot group with CHPs for the record before having fun rolling a tin can around. 



Peaks are shooting pretty close to the same POI as the CHPs and I intend to shoot at least 500 of them before I do any real accuracy testing.

Larry

[fla45fan]

Nice looking rig - how do you like the CP scope?  And how does the Weaver rail mount?  Great write-up by the way!

[Deane]

That looks great! I'm thinking about modding my .22 Benji NP (identical to the Titan) the same way. If you don't mind me asking, how much did the Trail compression tube run you?

[demarisl]

Thank you.  I like it.

The weaver rail is an integral part of the compression tube.  Part # BT9M22-02.00 for $49.66 plus $4 shipping.

The CP 3x9x40 originally came on my Remington Summit which I relieved of its stock.  The scope developed a rattle in the AO assembly and Center Point replaced it for $10 since it was over a year old.  I find it a decent scope and seems to be about right for this rifle.

Larry

[Deane]

Kewl, thank you! I have a CenterPoint 4-16X40AO illuminated mil-dot reticle and it works great on my Gamo Whisper. It was $70 at Wal-mart.

[kosmickopp]

    demarisl,   Are you certain of the price of your Trail NP compression tube?    I bought one from Crosman about a month ago for $14.99 (plus shipping).    100% certain - just checked the invoice...   Same part number - Weaver rail.

[demarisl]

My invoice says $49.66 so either you got a great deal or I got screwed.

Larry

[Rescue912]

Mine was $14.99 plus shipping - about 2 weeks ago too though. Might call and ask, maybe they went up in price.

[Deane]

You're talking about the complete compression tube with the rail, not just a rail right?

[kosmickopp]

Deane - Yes.    As sold, the Weaver rail on the Trail NP tube is welded on.     

[Deane]

Kosmickopp, I'm sorry, I was replying to Rescue912's $14.xx comment.

[3ants]

did you get just the comprision tube or a piston and gas ram?

[john]

Thanks demarisl for the great write up and pic's. While you had your piston out, did you see wear marks, like where it was rubbing the inner wall of the compression tube? I ask because I just had mine out...long area of rubbing along the bottom of my piston and a couple of spots on top...no galling thank goodness...so i am just curious about what's typical.

[demarisl]

Never looked down the old compression tube as we were replacing it.  No obvious wear on the piston itself, just a badly nicked seal.  Did just shine a light down the old tube and don't see any obvious wear points.  Got about 250 rounds through it tearing up cans while wearing in the new seal so I guess its time to see what it can do in the accuracy department.  Definitely going to call Crosman and check on the price.

Larry

[Deane]

Definitely going to call Crosman and check on the price.

For sure! That's one sweet upgrade for the Crosman or Benji Titan.

[cole5169]

That's a great upgrade!  I've got a Titan GP in a Summit stock, and I love it, but would really appreciate a Weaver rail.
Looks like I've got some tinkering to do...
-joel

[john]

So demarisl, I hate to keep grinding on you for info but you know stuff that is not common knowledge to newbies. Most tuning info is vague, ambiguous, lacking in details, undefined slang terms are used.

Regarding your damaged seal, was it just nicked around the outer lip or was there other damage.

The reason I ask is that mine that I changed out recently had only minimal cosmetic outer edge damage but was missing a large chunk from its face in a spot near the edge which would have been closest to the transfer port as if firing had blown seal material away. Would like to find out if this is a known failure mode. The most likely cause I can think of is that I ignorantly dryfired it once (using one of those fiber cleaning pellets, dumb) and later dryfired accidently twice more over gun’s 5month lifetime. The Maccari piston seal appears to be made of tougher stuff and I suspect it would be much less likely to sustain such damage.

If you can take the time to describe details of the deburring & crosshatching process, how it was done, etc. stuff like that would really help us? Did you get a Crosman piston seal or aftermarket. How did he apply moly to the cylinder?

Word on the yellow forum last year was Mike dissolving his relationship (owner?) with Best Airgun, 208 Walnut St, Burt IA. What’s the scuttlebutt on that?

Edit1: kosmickopp just reminded me that Charlie Da Tuna has good tuning tutorial despite my ranting.
charliedatuna.com/airgun_docs/B19 Super Tune.doc
I'm told the Trail is based on B19.

Edit2: Added the poorly posed pic. The dark spot in the middle of the metal seal seat is nothing - ignore that. The dark port-sized circular discolorations at the edge of the seat indicate that the piston apparently spent its life in 2 different positions - cause of shift unknown. I should have rotated it 180º before taking the pic. A long chunk of seal is missing right where it meets the port. There have been alot of discussions about transfer ports [ https://www.pyramydair.com/blog/2010/02/changeable-air-transfer-ports/ ]. I'm guessing the discoloration is due to combustion. Note that the transfer port is not coaxial with the piston axis. I found alot of piston wear along its side opposite the cocking linkage so I'm guessing the process of cocking forces the piston against the opposit cylinder wall and drags it along...hopefully moly I applied will slow that wear.

[kosmickopp]

John -  Sent you a PM..

[AlwaysLearning]

You've got to love Crosman's product line. Great rifles and easy modifications.

Matt

[roadchoad]

John, could that be from dieseling burning away at the seal? If it was on the edge, check to see if it matched the position and size of the scope stop hole.  My stock seal had nasty scoring that corresponded exactly with the scope stop hole, cocking slot, and trigger group slots.  A deburr cured that ailment.