Accuracy issues, Benjamin Trail NP

Here's hoping you made the right purchases, Windmill01! I have a Nikko Sterling 4x32 that is going back on my Titan NP tomorrow, I hope it continues to perform as before.

I installed a charlie-da-tuner trigger in my XL NP. instant trigger releif-1st stage ok and predictable, second stage crisp at 2.5 lbs. Next I added the Bug Buster scope. Final improvement was to find a heavier pellet that my rifle liked. The rifle shoots better than I can offhand now.

My Benjamin Trail NP XL725 .25cal came with the Centerpoint 3-9x40AO mildot scope that's been real nice so far. Good scope. Crosman also has it in an Illuminated mildot reticle I want to get as soon as they're in stock again. They own Benjamin and Centerpoint, for starters.

http://www.crosman.com/optics/scopes/4-16x40-mm-riflescope
​And the four pellets I've used so far, the H&N FTT's giving the highest numbers @ 858FPS/32.55FPE;

Have you tried the challenge yet with that 6-18x50?

"Windmill01" For those of you who have been following Oldspooks 10 Dime Challenge you would have seen my effort with my 177 Trail. I had been having issues with accuracy/grouping for some time now. This airrifle has had its fair share of fixes from a new breach seal, jam spring, pivot washers, bearing fix for the trigger, galling between the piston and compression chamber, several piston seals and numerous pull downs and regreases with molly etc.

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I take “jam spring” to mean the latch wedge lock up spring (IIRC it's the "alive jam" spring or somesuch on the diagram) but if not, I’ve heard shimming and/or replacing it w/a stronger spring gave a more consistant lock up and improved accuracy and MV. 

I've used one bottle of blue locktite alone on this gun.LOL .......It was once a very accurate airrifle but something has to happen with over 18,000 pellets through it and considering it's price.
Yesterday I took it apart once more and useing my dremel polished the part of the sear that comes in contact with the trigger. This improved the trigger harshness dramatically and my groups closed up slightly. I am thinking of polishing the contact on the trigger side but don't know if this will all of a sudden give me a hair trigger or worse. Has anyone else done this without wrecking the trigger completely.
Thanks

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One thing to watch out for is, the trigger group may not all be made of hardened materials, so any grinding to the mating surfaces will be removing material where it’s difficult to replace. If the sear and etc. ARE hardened, still only take away the bare minimum of material in case the hardening isn’t all the way through the parts.

@cobalt327 sez, "One thing to watch out for is, the trigger group may not all be made of hardened materials, so any grinding to the mating surfaces will be removing material where it’s difficult to replace. If the sear and etc. ARE hardened, still only take away the bare minimum of material in case the hardening isn’t all the way through the parts."

Good advice! I have a Benji Summit NP2 with the Crosman CBT and while it does have a clean, consistent break from the 2nd stage it is still very heavy. I was slowly convincing myself to take the action out of the stock and have a go at grinding/filing down the sear surfaces to improve the break. Then yesterday I watched an old Rick Eutsler review of a Crosman gun in which he talked about using Moly grease on the sear surfaces as an alternative to physically reshaping the sear(s) by grinding. Cobalt's explanation just cements the issue for me - a garage amateur like me should just lube the sears, not grind 'em. I'd rather learn my trigger than do a Wile E Coyote and end up with a metaphorical rocket strapped to my butt.

Cool! I'll have a look!...

NEED HELP....

I'm new to this particular forum, but I was drawn by the amount of collective expertise in high powered air guns. I'm having terrible accuracy issues with my Benjamin Trail NP .22 all the sudden Here's the problem.

The gun worked beautifully with the factory Centerpoint scope for 3 years straight. After spending many hours testing every high performance pellet I could find, I settled on the Crosman Premium Destroyer Pellets. My groups with this gun and these pellets were consistently putting 5 shots in the same hole from a LeadSled at 15 yards. In 18 months, I killed 219 squirrels in my backyard and 201 of them were headshots. Yes, I keep a "tickey mark" score card on the inside of my kitchen cabinet, much to the dismay of my wife.

Recently, the gun all the sudden started shooting 3 to 4" groups and I could not hit anything. The squirrels are laughing. I cleaned the gun, retorqued all three bolts to the stock, and checked all the scope mounting bolts. Still the same 3 to 4" groups. I assumed the Scope must have gone bad, so I replaced it with a new Leapers UTG 4-16x44 scope. This is where it gets weird. I got the scope "on the paper" at 10 yards and it was within 1.5" of being zeroed. I did this with only 3 rounds with the LeadSled. I then put three shots in the same hole and I thought YES, it is back! I made one last adjustment for the final zero on the target, and every shot after that adjustment would only hold a 3 to 4" group at 10 yards!! What the hell?? 

Yes, I still have the original (horrible) trigger, but that is not the reason for a radical change in accuracy when I could stack holes before. Also, I pulled a bore snake through the barrel on EVERY shot just to make sure there was no lead fouling problem. 

These are the only reasons I can think of:
1. My original Centerpoint scope really did go bad AND my new UTG scope went bad after only a half dozen shots (unlikely, but possible)
2. Original scope did go bad and the new UTG scope was bad out of the box, and the three shots in the same hole was just random luck with the new scope (based on the reputation of Leapers, this is unlikely, but possible)
3. There is something else wrong with the gun. 

Since the grouping just got broader and did not droop, I don't suspect anything in the air spring mechanism. Thoughts anyone?

Rich

Hay Rich,
Have you checked the pellet speed?
maybe the piston seal is giving out and velocity is all over the place. 
Or another problem with those Crosman rifles is the shims on the breach block are plastic! Yes plastic and will get sloppy in time if you shoot a lot. Cock the gun and check for side to side movement with it unlatched.

just something to check 
James from Michigan, 

"ChuckHunter"Hay Rich,
Have you checked the pellet speed?
maybe the piston seal is giving out and velocity is all over the place. 
Or another problem with those Crosman rifles is the shims on the breach block are plastic! Yes plastic and will get sloppy in time if you shoot a lot. Cock the gun and check for side to side movement with it unlatched.
just something to check 
James from Michigan,

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James, thanks for the response.

I don't have a way to check pellet speed that I know of. However, there are two reasons that I don't think it is a leaking piston seal causing varying pellet speed. Check my logic and I have added more info that I didn't mention before. 

1. On other air guns I have had in the past that have piston seals starting to fail, they would leak gradually worse and worse until you could actually hear them. I've never seen one get worse and then suddenly better on the next shot (without oiling) and then worse again. 

2. The old scope was zeroed on the bullseye and when suddenly moved from stacking holes to a 4" group, the grouping was still centered around the bullseye. I would expect the whole group to be low when it leaked and on target when it did not leak. I would not expect any of the shots to be 2" above the bullseye from leakage because you can't get better than zero leakage, which is where it was zeroed.

3. I would expect that a lower pellet velocity caused by leakage would only cause a vertical drop and not 3" of variability side to side. 

However, I'm an engineer, but not an expert on pellet physics. I did check for side to side movement with the barrel unlatched and I see none. Does my logic make sense?

Rich