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Posted: 4/7/2009 5:26:06 PM EDT
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A couple weeks ago I started this thread because AR#1 wouldn't shoot for s**t. http://www.ar15.com/forums/topic.html?b=3&f=66&t=435466 I received plenty of ideas on what was wrong. As usual, the suggestions of the collective were right on. I replaced the aluminum barrel nut on the float tube Repaired the float tube Cleaned the crap out of the barrel Recrowned the barrel Retightened the FH 360 degrees instead of the 45 degrees of the previous setup. I took it out to the range today. At first I was discouraged. It still shot like crap. A little better but still not up to my standards. I was using Federal black box XM193. Since this is my Zombie/SHTF ammo for my other AR, I switched to another type of ammo. This was some generic XM193? I bought at Outdoor Marksman a couple years ago. Remember when 500 rounds was $119? That's how long this ammo has been sitting in the garage. Then just for s**ts and giggles I switched lowers. From a standard AR lower to my CavArms MkII with 9MM buffer. That did it. Groups shrank from 3" at 50 yards to just over a nickel at 50 yards. Roughly 2" at 100 yards and 4" at 200 yards. This was with the Bushnell Elite 3200 1.5x4.5 scope. I shot all the targets twice with 10 shot groups just to be sure. I swapped out scopes for a Elite 3200 10X and the 100 and 200 yard groups shrank even more. I swapped out the scopes again to check zero on the 1.5x4.5 and the mount held zero and still shot great, even with a 15+mph wind and a hot barrel. The rifle is now pronounced well. It's ready for Practical Rifle in a couple of weeks. Thanks again to all that responded. Obligatory bad picture  |
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Pardon if I missed it Zeke, but did the switch in ammo occur before or after the lower switch? I'm in agreement that the lower by itself should have made no real difference unless say, it had a nicer trigger which allowed a cleaner break. Cant see how the buffer would have made an accuracy difference either. I realize the reasons for using a heavier buffer ( longer dwell time, etc.. ) but I'd be hesitant to declare even that the improvement on a rifle length system.
Edit for spelling. 
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Quoted:
just wondering how can the lower affect the accuracy on the upper that much, but glad you got it shooting. The bolt unlocking prematurely, or without consistence causes variances in bore pressure through uncontentious lock ups and unlocks. With such variances, and even the ammo not tuned to exit the bore on the ideal end point of the oblong barrel whip, this causes the increased spread down range in group size. Bottom line is had the rifle been chronograph while working up loads, or even testing factory ammo, the avg speed norm would have had a high deviation, telling the op that something was amiss from the start. 
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Quoted: At the same time. I'm dubious if changing lowers did any difference in accuracy. I just prefer the A1 length to A2. The timing was coincidental.Pardon if I missed it Zeke, but did the switch in ammo occur before or after the lower switch? I'm in agreement that the lower by itself should have made no real difference unless say, it had a nicer trigger which allowed a cleaner break. Cant see how the buffer would have made an accuracy difference either. I realize the reasons for using a heavier buffer ( longer dwell time, etc.. ) but I'd be hesitant to declare even that the improvement on a rifle length system. Edit for spelling. Quoted: Quoted: just wondering how can the lower affect the accuracy on the upper that much, but glad you got it shooting. The bolt unlocking prematurely, or without consistence causes variances in bore pressure through uncontentious lock ups and unlocks. With such variances, and even the ammo not tuned to exit the bore on the ideal end point of the oblong barrel whip, this causes the increased spread down range in group size. Bottom line is had the rifle been chronograph while working up loads, or even testing factory ammo, the avg speed norm would have had a high deviation, telling the op that something was amiss from the start. I used to have a chronograph. It now has a nifty .223 size hole in it. Pics available upon request. |
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i have to ask 2 more questions 1- what lower did you have on the upper when it was shooting great? 2- what lower did you have on that same upper when it all went to shit?
in your original post of the problem you stated you already tried differant lowers already with no change? |
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Quoted: i have to ask 2 more questions 1- what lower did you have on the upper when it was shooting great? 2- what lower did you have on that same upper when it all went to shit? in your original post of the problem you stated you already tried differant lowers already with no change? Three lowers Standard A2 CavArms MKII w/ RRA 9MM buffer Stag six position stock w/RRA 9MM buffer I play a lot of musical lowers depending on what I need to do. |
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I debated on even replying to this thread...but felt I had to.
First off congrats on getting it to shoot like you wanted it to. Now that I have said that....the lower has nothing to do with that except for user comfort, provided that they all have the same trigger pull. I can see how the A2 stock would provide a better platform for bench shooting over a 6 position stock...but that's all. All the lower is doing is releasing the hammer and allowing the round to go off...the upper does the rest. I am glad that you have settled on a load, upper, lower combo that you can shoot the way you want to...but rest assured that that upper should do the same thing with the same load on any lower you choose to pin on it. Just my .02 
BTW You have got to post a picture of the chronograph with the hole in it....It must be done.
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Quoted:
...but rest assured that that upper should do the same thing with the same load on any lower you choose to pin on it. Just my .02 I have a couple of guns that have distinct female personalities. They work when they f**king feel like it. This gun might be one of them. The trait will be removed. I haven't ran any heavy 69-77gr bullets through it for a while. It used to like the heavy bullets. All I have is 55gr bullets for now. Quoted:
BTW You have got to post a picture of the chronograph with the hole in it....It must be done.
Ask and ye shall receive. 
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Quoted:
Quoted:
BTW You have got to post a picture of the chronograph with the hole in it....It must be done.
Ask and ye shall receive.
Awesome...thanks. Judging by the pictures the shot was almost dead center left/right and just a tad low. 
On the bright side...the penetration was good. LOL Thanks for sharing, I have always had a fear of that happening. You are good sport for showing us. 
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