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Posted: 1/24/2012 1:43:26 PM EDT
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Some time back I bought a CMMG complete 5.56 upper - 16", mid-length gas, 1:7 twist, chrome, medium-contour, A3 upper, 'FA' carrier. I have an ACOG-type 4x scope on it and I use it in a lower with an M16A1 stock, standard rifle buffer and spring. I put a Colt carry handle on it to zero at 25, which went well. Then I put the scope on and used a chamber laser to get it on the paper, and tried to zero the scope at 100. I was using M855 at that time for lack of anything better, mostly USGI and Portugese military. I got it lined up pretty well but dispersion was too great to suit me, at about 4" to 6".
This time, I took some hand-loaded 62 gr and some new PRVI 75 gr OTM. Because of my eyesight, I decided I wanted to zero the scope at 50 as tight as I could, and maybe move to 100 next time, where I would expect to be 2" high. I had removed the scope and put it back on in between, so I expected a slight misalignment. Right away, the hand loads were grouping tight enough to make meaningful scope adjustments, and I was only about 2" left and 1" low. I got it roughed-in with the hand loads and switched to the PRVI. Within a few strings of three I was putting them all in the 2" orange sticker I like to put on my targets. I had brought 60 rounds of PRVI and only used 23, plus the 50 hand loads. Some of each was just shooting more holes after the zeroing was done. So, I left the range feeling very good about the rifle and the ammo. The 100 yd range problems I had before apparently were in part the ammo and in part me. Since then, I learned that I need an 8" diameter black ball with a 2" blaze orange sticker in the center whether using irons or a scope. Also, I'm training myself to slow down, control breathing and squeeze them off. I'll find out what I can do on the 100 yard range next time, but I'm expecting no more than 4". I won't zero at 100 but may make minor corrections in windage if needed, and elevation if the trajectory is much higher than 2". The only thing this rifle really needs now is a better trigger. I've never been one for spending money on trigger jobs, but now I can see how this trigger is really getting in the way of better accuracy. I expect I'll spring for a Geissele SAA for this one. My Colt came with an acceptable trigger but I assembled this lower and didn't do anything at all to the trigger. |
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