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Posted: 3/23/2009 5:42:49 AM EDT
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Brand new to the site (been lurking for awhile, great reading) I'm new to AR Rifles too. But have been shooting hunting and self defense guns for 25 years. I have never encountered a problem like this before. I found 1 old thread with a similar problem in an old (5000 round count) rifle with no resolution to the problem. I'll describe the situation the best I can.
I purchased a Smith & Wesson M&P15 from a local gun shop.2/28/09.It has a gas block w/rail same level as top rail.Barrel is 1 in 9. They had added some accessories from their shelf . IE: Mako quad rail, Mako front and rear iron sites, Mako folding forward pistol grip. I returned the sights cause thy looked like they were cheap. I mounted my own Burris Black diamond with 30mm tactical (millet) rings, Just to see how it shot. I did not bore site it. I have a big backstop and figured I could get it on paper. Which I did. I was shooting PMC FMJ 55 grain ammo. Fired three shots off the bench. from about 40 yards. Went downrange to inspect. The group was large 4 inches or better hitting about 18 inches right to POA. All three shots were keyholed??? I switched to Remmington 55 grain sp and the group was the same size further to the right but large ragged holes in target. Not keyholed but not what I would expect to see either. I may be able to attribute the Remmington hole size to my weathered cardboard backstop (targets are not stapled flush to cardboard) The PMC keyholes bother me allot and I did not shoot it anymore after the 6 total rounds. I'm an ass and I left the targets at my hunting camp so I can't post pic's. Sorry for the long post. I wanted to share as much info as I could. Any suggestions? Where do I start? Thanks for any help! |
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Quoted:
Brand new to the site (been lurking for awhile, great reading) I'm new to AR Rifles too. But have been shooting hunting and self defense guns for 25 years. I have never encountered a problem like this before. I found 1 old thread with a similar problem in an old (5000 round count) rifle with no resolution to the problem. I'll describe the situation the best I can. I purchased a Smith & Wesson M&P15 from a local gun shop.2/28/09.It has a gas block w/rail same level as top rail.Barrel is 1 in 9. They had added some accessories from their shelf . IE: Mako quad rail, Mako front and rear iron sites, Mako folding forward pistol grip. I returned the sights cause thy looked like they were cheap. I mounted my own Burris Black diamond with 30mm tactical (millet) rings, Just to see how it shot. I did not bore site it. I have a big backstop and figured I could get it on paper. Which I did. I was shooting PMC FMJ 55 grain ammo. Fired three shots off the bench. from about 40 yards. Went downrange to inspect. The group was large 4 inches or better hitting about 18 inches right to POA. All three shots were keyholed??? I switched to Remmington 55 grain sp and the group was the same size further to the right but large ragged holes in target. Not keyholed but not what I would expect to see either. I may be able to attribute the Remmington hole size to my weathered cardboard backstop (targets are not stapled flush to cardboard) The PMC keyholes bother me allot and I did not shoot it anymore after the 6 total rounds. I'm an ass and I left the targets at my hunting camp so I can't post pic's. Sorry for the long post. I wanted to share as much info as I could. Any suggestions? Where do I start? Thanks for any help! That is what may be the problem. I have seen this happen when the paper is just free floating in the air. |
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I agree that that may be an issue, in all the shooting I've done in my life, I've never shot holes like this, I mean they are almost perfect sideways profile holes. I'll replace the backstop next weekend. Remount the scope and bore sight it and try again. I may have hastily mounted the scope and not have it tight, which may be why the group size sucks. The function of the rifle seems good otherwise.
Any other things I should look for? |
| One of the first things I did when I got it home was to field strip it and clean everything. Everytning looked nice, used a bore light on the barell and chamber. All bright and shiny. Lubed everythig well and put it together. I relly hope it is the backstop. I'll find out soon. My buddy has a nice range at his house may have to head over after work one night this week. |
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Keyholing at 40 yards is bad. Group size should tighten up some during break-in. I think AR ammo milspec requires 2 MOA or better out of test barrels at 100 yds. Chrome plating is very hard and requires removing copper left by the bullet at increasing periods until things smooth out.
Some AR's come out of the gate with rough feed mechanisms and/or magazines that can drastically alter the round condition during feed, ie. setbacks. From the magazine, fire one, then manually eject the succeeding one before firing, to see if there is any appreciable damage. Check the flash hider to see that there is no gilding remnants on one side or other, indicating bullet is touching on the way out. It is difficult to inspect through the flash hider, but try to determine that the barrel crown is symmetric and without imperfections (bright light and magnifier UNLOADED OF COURSE) If problems persist, talk to S&W. They may have some clues. Check the appearance of soot on the fired casings. Factory rounds should seal in the chamber from peak chamber pressures so little to no soot proceeds back on the body of the casing. Sooted up casing bodies indicates low pressure loads. |
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Thanks for the ideas guys. I havent field stripped it since last Saturdays experience yet. I should have time tonight. I'll check the flash hider and crown. Spent casings look good. No visual signs of problems, good primer strikes, no cracks or bulges. Function is good, no jams or missfeeds. I only have a few rounds down it though. I'll try to shoot this weekend again under more controlled conditions. IE: at a real range and not off the porch at camp.
If there are still problems after the next trial, would you go back to the store you bought it from or go directly to S&W? |
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Quoted:
Thanks for the ideas guys. I havent field stripped it since last Saturdays experience yet. I should have time tonight. I'll check the flash hider and crown. Spent casings look good. No visual signs of problems, good primer strikes, no cracks or bulges. Function is good, no jams or missfeeds. I only have a few rounds down it though. I'll try to shoot this weekend again under more controlled conditions. IE: at a real range and not off the porch at camp. If there are still problems after the next trial, would you go back to the store you bought it from or go directly to S&W? Contact S&W Directly. They will take care of you. Had a gun in the shop the had a truly awful trigger and I gave them, not my dictributor a call. S&W sent a call tag and I had the gun back in 10 working days. Asked them at the time if the prefer the shop or the gun owner to call them and was told the owner, as they can explain in greater detail what was going on. |
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