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Posted: 3/29/2015 4:35:07 PM EDT
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Noveske Recon 16", Colt BCG, Geissele Mk2 rail, Smith Vortex FH, Geissele SD-C trigger. 500 total rounds shot.
Scope: Nightforce 2.5-10x32 in an ADM 30 mount No issues until today. Ammo was Hornady 75g Superperformance 5.56 match ammo. First three shots were roughly an inch group. 4th was a flyer 5" high. Loaded up 5 more rounds and was a roughly 5MOA group. WTF? Made sure the scope was torqued and the mount was tight. Shot a group with iron sights. 5MOA again. Out of 5.56 Hornady. Switched to .223 Hornady Supermatch 75g and the groups tightened back down to 1MOA. I only had a box of each so could only troubleshoot so much. Thoughts on the issue? Does my Noveske just hate that ammo? Because the first three shots seem to prove otherwise. I'm leaning toward the barrel nut being loose but I'm going to shoot again before I break down the upper. |
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With 500 round through the rifle, back off on the amount of CLP you are using to lube the upper bearing areas (read dam near dry if you are just bench shooting).
CLP has Teflon in it, and as this gets in the barrel bore from migration to the bullets, it will cause flyers until it burns back out (takes about 14 rounds to burn the Teflon out of the bore). Also, switch over to Sweets copper solvent to clean the barrel bore. Its aggressive and will not take a lot of scrubbing to get all the copper out of the bore in just a few mins. Next, the 69gr bullets have a longer ogives, and they need to feed cleanly out of the mag to chamber. Hence a low feed into the upper receiver extended ramps can cause the bullet to bend off axis in the next, and will cause imbed probelms at igntion. Also to point out, boat tail bullets do not do well on a long jump to the lands on ignition. Ideally, you want the jump to be in the .003 range, and if they are jumping more that say .010", just takes way too long for the rounds to sleep as they are moving down range. So on these notes, double check to make sure that the mag catch threaded tip is flush with the mag release button, the mags are being retained in the lower receiver tightly without a lot of mag rocking in the well, and determine the jump distance to the lands of the ammo being used. In most causes, the barrels are throat-ed for shorter ball type ogive bullets, and when feed longer Ogive bullets and trying to print tight groups, the rounds have to be single sled loaded instead. Note here, you can get a barrel short throated so the jump will be ideal for long ogive bullets, but if you try to shoot ball ammo through the barrel, the bullets on loading will embed every time (going to have over pressure problems with ball ammo in these barrels). Also, you pretty much figured out what ammo the rigs likes, hence the 223 Hornady Supermatch 75g. |
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