Keyholing with 40 Grains at 100 Yards?

Discussion in 'AR 15 Forum' started by English Bob, Aug 8, 2020.

  1. ral357

    ral357 Well-Known Member

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    What scope are you using. I see x14 but no flavor. Is it fixed or variable? If variable are you adjusting power back and fourth?
    I see you are in Florida there are a couple factors I find here this time of year, sweating and gnats. Can cause a great deal of distraction resulting in pulled shots, canting.....etc. I can only stand the sweat in my eyes and those pesky bugs for so long before it’s really time to call it a day.
     
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  2. English Bob

    English Bob Well-Known Member

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    The scope is a Primary Arms 4-14x SLx. It's Chinese, but other people get good results with them. I guess something could be going on inside it. I haven't adjusted it today, except for one thing. I fiddled with the parallax right before I shot the best group. I got all excited, because I thought I had fixed the gun.

    The weather is not too bad today, and there were no bugs. I felt pretty comfortable.

    I got my only good group after the gun heated up. Figure that out. The group on the bottom-left bullseye of the second target is beautiful. Then things went totally insane.
     
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  3. Pawpaw40

    Pawpaw40 Well-Known Member

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    What I did was remove the barrel nut, remove the barrel, lube, torque the barrel nut to 30 ft/lbs, loosen, torque to 30 for a total of 3 times to 30, then torque to the final 80 ft/lbs. I believe this is if you have a steel barrel nut, not sure about aluminum nuts. Do you have an upper vise block? There is also a new tool that holds the barrel in place, takes all the pressure of the index pin on the barrel.
    https://www.brownells.com/gunsmith-...-barrel-extension-torque-tools-prod27452.aspx

    Then again you might just have a barrel heating issue. Try letting the barrel cool for 10 to 20 minutes between groups. PRR1957's suggestion about the possibility of a burr sounds plausible, except for the fact that your rifle appears to group well with a cold barrel. Another possibility is that if the upper receiver face where the barrel extension mates is not "trued" to the bore of the receiver, temperature increases can cause accuracy issues. They make a tool for that also.

    https://www.brownells.com/gunsmith-...16-upper-receiver-lapping-tool-prod20220.aspx

    Good luck. I have been able to cure most of my accuracy issues with my AR's by handloading or minor tweeks of the platform.
     
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  4. English Bob

    English Bob Well-Known Member

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    Thanks for all the help. I'm thinking I may throw another scope on it to see if the Primary Arms scope's reticle is broken or defective.

    This gun has an eternal warranty, and the manufacturer is 20 minutes from here, so I think I'm going to make it their headache before digging into to it too much. Maybe it's something they can deal with.
     
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  5. Firedog

    Firedog Well-Known Member Supporting Member

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    Question 1 for the moderators where did post 10 go?

    I can just give advice after watching my oldest bro shoot, he would load 5 bullets and take 10 minutes to shoot them.
     
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  6. English Bob

    English Bob Well-Known Member

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    Is it possible for a crap magazine to affect accuracy? I have reasonably good magazines, but I bought two cheap metal magazines for prone shooting. I needed short mags so they would clear the platform. It looks like the ammo has been hitting the front of the magazine. I see something there that looks like brass. Maybe this stupid thing has been shaving metal off my bullets.

    I can fix it with a rotary tool. Man, if this is it, I'm going to be pretty mad. With all the wasted ammo, these would turn out to be the most expensive cheap magazines in history.
     
  7. ral357

    ral357 Well-Known Member

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    Anything that damages the bullet can affect accuracy. How much depends on the degree of damage. Certainly worth looking at.
    If you do replace the scope FYI Nikon scopes that are still in stock with dealers can be found with substantial discounts with a little looking. Great scopes but Nikon is leaving the rifle scope market. A shame as they are great scopes for reasonable money. They will continue making other optics so they will be around and will continue to honor their warranty obligations.
     
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  8. English Bob

    English Bob Well-Known Member

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    I cut away some metal from both of my cheap magazines. I looked at a hex mag that came with the gun, and it has a little recess in front of the bullets so they don't slam into the plastic. Just ordered two 10-round PMags.
     
  9. PRR1957

    PRR1957 Well-Known Member

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    This is a little esoteric, but the AR and any other firearm that feeds from a cartridge stager magazine can influence accuracy. Because the cartridges feed from left to right then back to left to right or visa versus, for each shot, and if the gun is accurate enough, one can have two distinct groups. This is a result of the cartridges being push up two separate feed ramps.

    Now with your run of the mill AR, most will not see a difference, but as an example, when I worked for an AR manufacture company, I built a few AR, for myself while there. These guns were built from selected parts, and Krieger match grade barrels. With one with match prepped cartridges, and if I hand feed the cartridges without running them through the magazine, the groups were about .02” center to center, but if the cartridges were run through a magazine, the groups were about .15” center to center, with a very distinct right and left group.

    Now like I said this was with a match built AR, but I was also repeated in a Remington PSS in 223 that normally would group in the low .01” center to center if hand feed.

    I should add that with most AR”s, the barrel extension feed ramps need to be polished to remove any sharp edges which if left sharp can scratch/ score the bullets when feeding from the magazine.
     
  10. gdmoody

    gdmoody Full Time Moderator Moderator Supporting Member

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    This is the second thread that you seem to be accusing a moderator of deleting a post. What was supposed to be in post #10?

    The only changed made in this thread was two posts made by Bob within a couple of minutes were merged.
     
  11. zant

    zant Well-Known Member

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    The lightest I shoot is 50gr(because someone gave me 12bxs)with a 1/8 barrel that seems to love them...my other with a 1/8 barrel spews them like watermelon seeds,weird but the BFS barrel shoots everything from 50-85gr accurate.
     
  12. Firedog

    Firedog Well-Known Member Supporting Member

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    I dont think I'm accusing any one and if I am.i must apologize I was reading down through I didnt see a post #10 that's my only question and on the other one you explained there were 2 very similar posts made.
     
  13. drymag

    drymag Well-Known Member

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    keyholes are an indication of stability issues.
    Another companies 40gr that uses different powder, etc may exit at a different harmonic that matches the bullet better thusly removing keyholes.
    A reloader might do something to change that harmonic to see if that resolved the issue.
    For now, just shoot at a target closer and use them up then buy some 55grs.
     
  14. English Bob

    English Bob Well-Known Member

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    Thanks, but today I shot 50-grain ammo.
     
  15. ms6852

    ms6852 GUNZILLA Supporting Member

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    Some AR's are moa shooters. Groups of 1.5 to 2 inches is common on AR's unless you spend a little extra on a good barrel and trigger and start making your modifications. Have someone else shoot it to confirm your results.