Fireformed vs Virgin Brass Accuracy

buckbrush · #1 04-07-2009, 08:19 AM

I've been using new brass for my 7 Rem Mag since I began loading for it. I've now got about 150 rounds of once fired and another 150 of new brass yet. The once fired stuff I have just neck sized, prepped and put away.

Will I notice smaller groups by using the once fired brass? Currently the gun shoots about 3/4 MOA.

Thanks a lot for any insight.

RT2506 · #2 04-07-2009, 09:17 AM

The first AND ONLY 7mm Rem. Mag rifle rifle I ever or will ever own was a Rem-700 SS. I bought 100 new cases and started working up loads. I am a very experienced hand loader and have some friends that are also very experienced loaders of the 7mm mag. They pointed me toward loads that had worked great for them and these loads came to about the same conclusion. All the loads that I worked up were with the new cases only. I could not get this rifle to shoot better than about 2" groups no matter what load I tried. When I got to the end of the new cases I FL sized them and loaded up some of the load that had been the best out of all that I had tried. I was about to get rid of the rifle because it would not shoot up to my expectations. When I fired the first two shots @ 100 yards I looked through the spotting scope and could only find one hole in the target. I thought great, now I can't even hit the paper with this thing. I fired the third round. Looked in the spotting scope and still only one bullet hole. Tried a fourth shot. Looked through the spotting scope and that one bullet hole was still there. BUT! I looked just a little bit bigger for some reason. I fired the fifth shot and upon looking through the spotting scope I could tell that there was about half a bullet worth larger hole at the one o-clock position in that same bullet hole. To make a long story short. When using a case that had been fired and then FL sized it almost did not matter what load you tried in that rife it would shoot under 1 1/2" groups @100 yards. It really liked AA3100 powder. I got rid of that rifle because it really was too much rifle for the whitetail deer that I was shooting. They had a bad habit of taking a perfect shoulder or heart lung shot and would run a 100 yards or more into a very thick cut over before they went down. I traded that 7 mag for a 25-06 just like it and I don't have to trail a deer anymore. It is bang flop with that 25.
It goes to show you that strange things can happen when loading and shooting rifles. That is what I like about it. Going off into the unknown. Good luck I hope your groups shrink.

boomtube · #3 04-07-2009, 11:28 AM

"Will I notice smaller groups by using the once fired brass? Currently the gun shoots about 3/4 MOA"

Not likely.

Michael Eichele · #4 04-07-2009, 12:07 PM

This post is geared mostly towards factory rifles due to the larger chamber dimensions.

Depending on how large your chamber is cut and how much larger your FF cases are versus factory specs, the volume changes a wee bit and does so enough to make pressure differences. This difference is enough to see a difference in accuracy equal powder charge for powder charge. Whether or not the accuracy change is better or worse is another story. Typically FF cases need a bit more powder to replicate the virgin brass. I dont know how much for a 7mm but in my old 308 it was 0.5 grains to duplicate the accuracy AND velocity.

Accuracy potential with out any other factors and just based on a FF case versus virgin brass CAN be noticable. I say CAN because every rifle is different. Some rigs as well as some calibers are more picky than others. When I say noticable I dont meen that it will take a .75 MOA gun and turn her into a .25 MOA gun. You may see between .1 and .2 MOA increase AT BEST in most cases. You can only see an accuracy increase IF your loading tequniques are such to take advantage of the FF case. When a case is FF, it leaves a case with the least amount of runout, provided your chamber is cut concentric. With this minimal run out, accuracy will increase. The key is to find a way to resize your brass without adding any mentionable run out.

Also if not done properly, FF cases can do the opposite. That is hurt accuracy. After each firing, the shoulder should be bumped back less than .001" to .001". If your chamber is oversized a custom die may be the ticket so you can bump the shoulder back a wee bit and not size the rest of the body too much either. A factory die will press everything back even though you can set it to just bump the shoulder.

buckbrush · #5 04-07-2009, 10:29 PM

Well I got a yes, a no and a maybe.

Winchester 69 · #6 04-08-2009, 01:06 AM

That's the way it goes in a democracy, unless you own the voting machine.

KQguy · #7 04-08-2009, 07:05 AM

I bought 1000 winchster 7mmWSM brass cases,and have been shooting all virgin brass with good accuracy (5/8 - 3/8 moa @ 100yds.),.I reloaded some fire formed cases just to see the difference,and there was no diffrence in accuracy.BTW,the fired cases were partially resized(bumped the shoulder back .002'').The only advantage I can see with the fired brass was the necks come out straighter,which will give you better bullet runout.The winchester virgin brass can have some nasty runout.
Read this http://www.scidetroit.com/brass_fired.htm