Runout of loaded rounds

[Bart B.]

I wore out several Garand barrels shooting on the USN rifle team. Each one lasted about 3500 rounds.

New cases always shot most accurate. None of the military teams reloaded their fired cases. Fired case heads were not square and the barrel whipped different before bullet exit depending on the case orientation in the chamber.

[stagpanther]

I'm kinda interested if anyone has ever gotten truly outstanding results with the hornady a-tips (I assume that is what the OP is talking about); I bought a bunch (expensive) in 6.5 and 6 mm and could never get as good results as I could with hornady's eld's.

[Road_Clam]

My goto 300WM bullet for long range work is the 208 Amax. Unfortunately, NLA. I bought 1500 many years ago and have about 800 left. 76gr of H1000, .020" jump , 2760 fps. my best group was . 68" at 200 yds. Very consistent load. R700 Sondero rifle.

[Bart B.]

Originally Posted by Road_Clam

My goto 300WM bullet for long range work is the 208 Amax. Unfortunately, NLA. I bought 1500 many years ago and have about 800 left. 76gr of H1000, .020" jump , 2760 fps. my best group was . 68" at 200 yds. Very consistent load. R700 Sondero rifle.

What is the biggest group's size?

[akinswi]

Originally Posted by Bart B.

I wore out several Garand barrels shooting on the USN rifle team. Each one lasted about 3500 rounds.

New cases always shot most accurate. None of the military teams reloaded their fired cases. Fired case heads were not square and the barrel whipped different before bullet exit depending on the case orientation in the chamber.

Bart B,

Define wore out? Did you change the barrel after you lost a certain amount of accuracy due to throat erosion ? lets say from shooting half moa and they opened up to 1 moa?

I have found you are 100% correct about fired cases from an M1 are not as accurate as virgin brass. I could never get my groups as good from fired cases as I could from new brass. One experiment I have yet to test is too shoot the fired cases from a bolt gun too see if they square cases back up.

[Unclenick]

When a barrel is shot out, you start getting uncalled fliers that become more and more frequent if you keep shooting it. I had this experience for the first time in an M1A. I was frequently cleaning the slow fire targets at our local 100-yard reduced target matches for which we fired two ten-shot targets to be sure we could find every hole. One day I was shooting the first half of that set, putting in 10s and Xs, when I had an 11:00 nine. Normally, If I screw up I get something around 4:00 or 5:00, but I figured I must have done something wrong and cleaned the rest of that target and the next target. The next time, though, I had the same thing. Then a few matches later I had three. Only when I got to four fliers per match, did I finally say "duhh" and add up my round records and see I was at over 3500 rounds. About time for a chrome-moly steel barrel.

In effect, given the fliers were all in the same place, my gun had developed two group centers. I concluded this was likele due to asymmetric throat erosion that caused some bullets to tip the same direction in the bore, throwing them high and left.

Regarding brass accuracy, this can vary some by gun. The Garand and M14/M1A bolts arc up into final position. It's not a mechanism conducive to having the bolt face land perfectly perpendicular to the bore axis. As a result, it tends to eject cases with a slight tilt on the head. If you fire loads warm or have timing off, the extractor can also bend the rim down a little. Either situation causes one side of the reloaded case's head hits the bolt face first. As Harold Vaughn showed, this can cause an off-axis recoil moment that deflects the point of the muzzle just enough to widen groups.

I got lucky and my M1A ejects cases that are square at the head. So does my Garand after careful, light bolt lug lapping with an alignment tool I made myself. The Garand Gear gas cylinder plug or a vented gas plug lowers initial op-rod acceleration to minimize rim bending. The combination gives me cases dimensionally true enough to reload them without producing a detectable accuracy difference. But it does involve some extra gunsmithing bother to go to.