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donwalk · Veteran Member

i have accuracy issues with my .22.

i've corrected issues with the barrel pivot and stock mounting and installed and adjusted the aftermarket trigger.

i've tried numerous varieties of pellets and checked the crown.

still not accurate.

i suspect the shroud as being the culprit. (or at least, a part of the problems)

i suspect when tightened, it generates a 'pulling' stress that is NOT equal.

when i remove the shroud, the POI changes DRAMATICALLY!

i also suspect that the thin barrel (0.513") is subject to harmonics generatd from the violence of the NP that throw off accuracy.

i am going to try a barrel weight of some sort, sans shroud and see what happens.

any ideas? Neutral

AirGunEric · Site Admin

As I recall a couple years ago- seems that the original Crosman "NPSS" rifle had some issues like this- turns out the shroud 'cap' (or whatever we want to call it- the threaded piece for the end of the shroud) had a hole that was too small for the pellets and airflow to move correctly- as I recall, drilling out a bigger hole in this 'cap' solved the problem.

donwalk · Veteran Member

AirGunEric · Site Admin

The shroud is BS- it's cosmetic- there is no baffling, no vents in the barrel and no air stripper- it is completely useless for the most part. Just as a sort-of "proof" of this- in Canada, functional shrouds/suppressors are completely illegal, but the government "approved" the sale of the NP's with shrouds after inspecting them...

donwalk · Veteran Member

i chucked up the muzle cap and bored the 'hex' out to 5/16" round...i'm gonna try it today and see what it did...if anything. Rolling Eyes

mtsheron · Member

Good luck. I had to sell mine because after adding the GRTIII which was a nice piece and then the barrel washer mod and polished/honed/deburred the piston cylinder and cleaned the piston chamber the gun still had fliers! I gave up and bought a Weihrauch and have never been happier. I hate it because the platform for the Trail is nice; just still needs some refinements by the factory to make it workable and most importantly keepable!

donwalk · Veteran Member

the drilling of the muzzlecap did not seem to help.

i am not sure of my next step...but i am going to disassemble and replace the pistons seal, clean and de-burr...etc

like the post above...i like the platform but the Benjamin Trail NP seems to have a "Hit or miss" built into the engineering somewhere...

Crying or Very sad

mtsheron · Member

donwalk · Veteran Member

update:

to date, i have:

drilled the muzzle-cap and enlarged the holes in it to slots
replaced the piston seal
honed and de-burred the cylinder and piston
installed a delrin bushing on the NP for the piston to travel on
re-crowned the barrel and chamber

the biggest improvement came from the bushing.

it now cocks and fires very smoothly and there seems to be some improvement in accuracy.

i chose to forego installation of the brass pivot washers for the time being as i believe the plastic washers work ok...but...i may decide to install the brass ones in the future.

at 15 yards, it is highly accurate...5 shots within 3/4"...longer ranges it's still acceptable for hunting accuracy.

Airhead · Member

I had accuracy problem with my trail as well, I check the usual area for problems and didn't find anything. My classic .22 would shoot wood screws at 10m, while my trail just drove me nuts with its accuracy issues.

bigmoose · New Member

I registered just to post "the" fix to my Benjamin Trail NP in .22 Accuracy was all over the place with flyers 4 inches off center at 20 yards. First shot was almost off paper most of the time. I went over everything, multiple times. I installed a GRT trigger, I opened her up and checked the piston and nitro cylinder. I tightened all pivot points... still marginal and inconsistent to the point this airgun was going to be given to someone.

I finally ordered A New-Gamo Tesla Custom Piston Seals Code: GPSTL (it fits my Benjamin). The factory seal was about 0.008 to 0.010 inches smaller in diameter than the Tesla. Tesla measured around 0.997 in diameter and the factory seal around 0.986 or so. The piston would fall free through the compression space with the factory seal.

Put everything back together, and the airgun has become a tack driver. Nickle sized groups at 20 yards are no problem, with a few going through the same hole. No flyers. First shot is as accurate as the 10th. This was hand holding against a post and not off a bench.

If you are having difficulty and cannot find the problem, break your Benjamin Trail NP down and replace the piston seal with something in the 0.995 to 0.998 inch range.

All the best,
bigMoose

JeJa · New Member

Have to agree with Big Moose. I was having the same probs with accuracy. I did a full tune, new piston seal(telsa) honed the chamber, moly, etc, gold trigger and new washers. WOW is all I can say. .25 inch groups at 15 yards.
Modding and upgrading is part of airgunning. Very Happy

robert w · Senior Member

have you checked the crown? a few had rough crowns too. use a qtip and just put in in the bore and turn it n see if the cotton grabs on any of the rifling

bigmoose · New Member

Robert, I did recrown mine. It was one of the first things I did. It did not provide the accuracy improvement that the new piston did. The factory crown was terrible with epoxy spattered over the crown, apparently their form of "loktite" to secure the shroud threads.