Loosing zero after several shots? Barrel temperature?
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Thread: Loosing zero after several shots? Barrel temperature?

  1. #1
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    Loosing zero after several shots? Barrel temperature?

    Hello, everybody.
    After reading this forum for a while, this is my first post.

    The reason I'm posting is because I noticed that after several shots (maybe 30 or more?), the bullets tend to start hitting low and right. At 60yards, after zeroing my PA ACSS 6x32 .22lr scope and doing nice groups, the bullets start to hit low and right from where I'm aiming. At 60 yards, the bullets hit maybe 6'' off the target. I ended being so tired of this, that I removed the scope and replaced it with a red dot because trying to do "precision shooting" with this problem was annoying.
    Honestly, I haven't done a good experiment to discover the problem. Of course I did my best zeroing the scope, adjusting the mount and cleaning the rifle.
    I have one hipotesis: After shooting X amount of ammo in a rather short time (maybe 50 shots in 5 minutes), the barrel starts heating up and this is why the rifle looses precision.
    I thought about this after removing the scope and I haven't have an opportunity to test this hypothesis. I'll do it as soon as possible by shooting groups until the bullets start hitting low and right, wait until the barrel cools down and try grouping again without touching the scope to see what happens.

    Any thoughts about this?

    Thanks!

  2. #2
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    What rifle, mounts, rings, etc. are you using? What sort of rest are you using for zeroing, etc.? Is this a cartridge rifle or a pneumatic or CO2 rifle? Have you checked to see that the bedding, action screws, etc. are properly done/tensioned? Sincerely. bruce.

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    Have you cleaned the barrel? Fouling always impacts grouping.
    Daryl......

    'You can fool some of the people all of the time, all of the people some of the time, but you cannot fool mom....

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  5. #4
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    The impact point of all barrels climb as they heat up. To counteract it target shooters use heavy barrels (more metal to heat up), fluted (cool faster), etc. Since your rifle is shooting right & low something on the left upper must be touching the barrel to push it over as it heats up or else something in the scope mounting is doing the opposite. It could be caused by stock, bipod, scope mount, scope, rest or...?
    delcrossv and Thewelshm like this.
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  6. #5
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    Unless the OP explains how may times this happened (more than once?) and under what conditions, clean barrel or not, new rifle or not, new problem after mounting the scope, just a zero shift or does repeatability suffer... on and on... it's really difficult to offer intelligent troubleshooting.

    One of the things I would not consider is barrel heat. One of the first things I would consider is checking the tightness of the barrel nut. Lots of loose barrel nuts have been reported over the years on 15-22s. I would also clean the bore and then leave it be. After bore cleaning, rimfire rifles often settle down after a 50-box of ammo. I rarely clean the bores on my rimfire paper punchers until I notice groups opening up, and that can be many bricks of ammo later.

    I've had a 15-22 since 2009. It's one of the best AR platform plinkers ever made, IMO. But for precision paper punching... not it's strongpoint.

    Good luck.

  7. #6
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    The type of rifle you're shooting may be important, particularly if it isn't a .22LR rifle.

    These low cost scopes (made in China, even if inspected in Texas according to the ad) are not made to the same internal construction standards that scoped designed for higher power rifles are. If you're firing this on a 5.56mm rifle or other higher power cartridge, it's likely that it's internals are being knocked off point by the recoil.

    Barrel heading is certainly possible with a .22LR, but pretty unlikely.

    Barrel resonance interacts with heating on a higher power rifle which is subject to heating from shooting. This can throw things off if you tighten parts inappropriately, or if you mount stuff on the barrel assembly that interacts with the hand shield and other support on the gun. The classic failure here is with M1 Garand rifles when the gas cylinder is tightened against the hand guard with no play. Things heat up, resonance changes, and the barrel flexes. But that's a .30-06 or a .308... Not a .22LR.

    If you're using quality ammunition, it would be unusual for it to foul in just 50 shots. Perhaps after a few hundred.

    So, if it's a .22lr Rifle, look to the mounting, and possibly something internally loose in the scope. Trying an alternate aiming optic would help eliminate the scope or the rifle as the issue.

    If you're using it on a high power rifle, get a more substantially made scope. Internal construction is why you see such a price difference between scopes.

    If you let the rifle sit for an hour, without changing anything about the rifle or the mounting, does the aim come back to center?
    Cheers! Marc


    Check out my Gun Rights BLOG at: http://skilledshot.wordpress.com
    accipere facile, sed sumite! - Take it easy, but take it!
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  8. #7
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    Thanks a lot, everybody.
    The rifle is the M&P 15-22, last model.
    I know that I opened up a lot of possibilities for what could be happening to the rifle. I posted this because I was not sure if it was likely to be the barrel (maybe is a common thing on 15-22s).
    I'll better do some testing as soon as possible to start narrowing down the factors, sticking to the options that are in my possibilities. This is my first gun, I've shot arround 2500 rounds in the last 5 months. I noticed this problem from the beginning.
    I will update when I gather more data so I don't make you loose your time typing down all the possibilities.
    THANKS A LOT, GUYS!
    Injunbro and KZero like this.

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    Welcome to the forum!
    KZero likes this.
    Cum Deo et victricibus armis

  10. #9
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    Good rings pushed to the front of the pic rail ? Blue loc tite ? Have 3 of those scopes which means I like'em..


 

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