Here it is with the cocking assist lever installed.
De-stalled.
Oh, good. Fiber optic sights.
Seems you can't get away from them nowadays. The bright dots make it very difficult to achieve a repeatable sight picture--at least on a paper target.
The rear sight is pretty flimsy--lot of play both horizontally as well as vertically.
Along with the sights, the long and heavy trigger pull has been almost universally panned. A longer adjusting screw (It's a 3mm) will take care of most trigger complaints.
While digging through the bolt assortment, I swapped out all the phillips head stock fasteners for allens.
The grip is aggressive and took some getting used to. There's a couple rub points, esp right under the trigger guard.
This has taken so long because I couldn't get the gun to shoot worth a damn. I shot some awful groups, changed pellets a couple times and shot even worse. Couldn't get the pellets in the same neighborhood. I mean I was missing the 8" x 12" backstop at 30 feet. This thing was a complete dog. Crosman owes me a quart of paint to touch up the concrete block wall it was so bad. Since I've got a pile of other guns that are actually, you know, accurate, the Nitro Piston was set aside until my memory faded and I forgot just how bad things were.
Initially, I had hopes that getting rid of the horrible sights would make thing better. Used a heat gun to break the front loose.
Pulled right off after about a minute at low heat.
An angled flat on top of the muzzle. At this point I started digging through my collection of pieces and parts to see if anything looked promising.
This part of my experimentation didn't pan out for me, though it would work with a different rear sight. This is the front sight unit from a AR2078 --it was a snug fit to the 15mm NP barrel.
Removed the globe insert and installed a post.
Used an M5 cross bolt to clamp it to the gun. Note that the proper way to mount this sight is to groove the barrel for a cross pin. This is virtually identical to how break-barrel pistols used to be equipped with front sights. The protective hood shields your hand from the sharp sight edges while cocking. Archer Airguns sells these for about $15 here. After getting this installed, I shot another group and realized that the grouping problems weren't related to poor sights.
Looked at the breech seal next.
Really didn't see a problem.
Removed it and found a steel shim.
Checked my breech seals and found I actually had a new one, so I tried that--with and without the steel shim. The gun leaked slightly without the shim. Looked at the spring plunger and found that the tension was very, very low. I think the barrel lock-up is inconsistent and the cause of the inaccuracy.
Removed the four screws and pulled the action out of the stock.
Removed the e-clip at the rear of the anti-beartrap lever.
Then the return spring and lifted it off. I see that it's already slightly bent. Superb.
Barrel pivot lock screw...
Barrel pivot. The shim washers are plastic. I didn't get to it today, but in my experience, these plastic washers are nothing but trouble for consistent lock-up. Bronze will be a good replacement material.
Knocked out the roll pin and there was zero preload on the plunger. Zip. None. I actually found this encouraging.
Found a longer spring of about the same wire size. It's about 2 coils longer. If I do this again, I'll make it 3.
A small nail made for a fine slave pin. Tapped the roll pin back in.
The bent anti-beartrap lever is humped slightly in the middle.
Put it all back together with a cheap red dot and a muzzle weight from the old TF79 project.
I can live with this. Just one called flier on the right. Fifteen shots with a mix of RWS Super H-Points and Geco wadcutters. Some bronze pivot washers and an even stiffer plunger spring should make this even better. Lot of work. A typical Crosman 2240 or 1377 will outshoot the Nitro Piston pistol all day long with no mechanical effort--or wall painting.
