Possible scratch in barrel?
Hey guys,
I have been trying to figure out why my gun has been grouping poorly. I figured it was in the valve, because I was having the problem after I messed with it. I crushed the stem and I think the the screws are stripped. Even with that I was getting descent numbers, good enough to not affect accuracy, I think.
I have checked everything I can think of, screws, shroud, mounts and found nothing there that should be doing it. I than looked down the barrel and saw a faint line moving with the rifling, but not at the rate. How much could this be affecting the accuracy, short of buying a new barrel is their anyway to test this? Can they be honed or polished or would that make the bore to big?
At this rate I think my gun may be heading back to Florida for the winter, or sooner if Tony will take it again. If so, the valve will never be touched by me again.
Thanks
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I tried Wok’s idea and couldn’t see any marks on the end cap. I still will try without the shroud for 5-10 shots depending on the neighbors.
Take a shaprie marker
Color the entire exit hole of your shroud
Shoot several rounds
Take magnifiying glass and examine the hole and see if any of the marker has been disturbed.
Tell us how it turned out.
It’ll be the shroud, which should be an easy fix. If its a TT one, I’m sure Tony will sort it.
The prone group was worse. I was much steadier so I don’t know what it is. tomorrow I will try without shroud if no luck there I will look for a wood chipper to throw gun in.
This is a 10 shot at about 25yds. This seems to be much better than what I was getting with scope. This was standing with gun on a grill with 4x ACOG and shroud still on. I need to get a bench or vise it would make things much easier.
I’m gonna go try again prone
left to right is 2.5″
I just shot that for numbers, I didn’t want to sit in the rain, gonna go out now. The numbers are not that bad, but before I messed with it they were far, far better.
Nothing wrong with those numbers (except for the low one) but that happens.
Look elsewhere for the problem and don’t beat yourself up over taking the valve apart. It’s not your biggest concern at the moment IMHO.
Was this a 2″ group?
Regards,
Jim
Sunny now, gonna try a group with the ACOG and shroud on gun.
Different speeds can also change the windage. Not sure why but probably to do with the rate of spin as it leaves the barrel. Shoot a really slow pellet and you can see it ‘corkscrew’ out of the barrel.
But not enough to give you 2 inch groups at 20 yards.
My money is on the shroud 😉
Here are the numbers I got today, not good. Kodiaks 2800psi, if they could affect accuracy I dont know, well I know the one real low one could. This also may be stupid question but shouldn’t the speed just affect the elevation?
1001
1012
987.5
1003
1008
994.4
1004
935.4
992.0
1014
I was unable to shoot from inside and find a proper backstop. So I only did the ten shots over the chrony because everything was getting wet. So I know my valve needs to be fixed because its not nearly as good as it was, but still no further on figuring out accuracy. I think I can shoot without a shroud tomorrow and try for groups, if you think those numbers are good enough.
I want to know why the fuck I couldn’t leave well enough alone
👿
i put a piece of masking tape over the end of my shroud and fire a pellet thru it to check center. my shroud has .270 hole at the end.
Roachcreek is right.
The quest for tight baffles will hurt you if you don’t have anywhere for the air to go.
Jim
Jim,
Actually they do not even have to touch to effect accuracy.
Years ago I found that if the baffles are too tight, lets say .228 for a .224 bore, the percuser wave will bounce back and hit the heel of the projectile and cause wobble.
Or at least that was the theory.
One of my first 22 silencers on a Ruger, had that problem, I got 3 inch groups at 25 yards, I reamed it out and and from then on it was 3/4 inches at 25 yards.
A 3/8 inch drill works good to solve that problem.
Assman have you traded scopes yet?
Roachcreek
Assman,
Couple INCHES at 20 yds!!!???!!!. I firmly believe you are clipping the shroud. That is not a velocity problem, that’s a “pellet is getting bludgeoned to death before it gets to the target” problem. Are your pellet holes circles or is the pellet tumbling?
Marks can be very, very hard to see on the shroud, it doesn’t take much at all to upset the pellet. Besides, the offending baffle may be way inside.
If you have a .22 cal rod you can push it down the barrel (from the breech) into the shroud. Or look for misalignment the same way with your eye. If it’s a barrel mounted shroud you can take the barrel and shroud off the rifle and roll it (together) on a flat surface and look for wobbling.
Do you have a clamp or vice you can use to boresight the rifle on target at 20 yds and compare it with the scope? ie boresite dead center, put scope dead center, shoot, re-boresite and see where the scope is aiming. But honestly, to be off that far you would probably be able to tap the scope (while looking through it) and see something shaking.
I certainly don’t mean to be condescending in my explanations, just thorough. Please don’t take it that way. I am here to help the best I can.
BTW the rain won’t matter at 20 yds when you are starting at 2″. I killed a starling at 64 yds in the rain with a 24ftlb .177 without holdoff.
Hope some of this helps,
Jim
PS. please post velocity numbers.
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Wont necessarily show on the exit hole. I had a silencer that was clipping inside slightly, but was leaving no trace on the exit hole.