Rifle case prep - misc questions

[Cerdan]

Very new to rifle reloading, a considerably more complicated process than pistol reloading.

I bought some Boxer-primed, brass-cased S&B 7.62x39mm ammo recently with the intention of reloading the cases. I shot 30 so far, and am now prepping the cases.

After resizing and depriming comes the trimming. I've noticed some cases need a lot of trimming, others hardly any. My first question is, simply, how come? What would explain such a variation in the length of once-fired brass cases from the same batch of ammo?

Secondly, as a result of this, I've noticed that my now trimmed, deburred and primed cases aren't uniform. Their overall length is the same, obviously, but the height of the shoulders varies. Is this something to be concerned about? How can I avoid this? Should I size once before trimming, and then a second time afterward?

 

[saskgunowner101]

Did you lube the inside of the case mouth?? I've heard that if you don't, it can actually pull or lengthen the case or monkey with the shoulder. AFAIK once you fire cartridges through your rifle, they are a pretty good match for your chamber. My .02

 

[Grizzlypeg]

If the height of the shoulder varies, something is definately wrong. Are you sure all cases were sized full length? IE, did you set up the die properly and ensure that you sized them all till the shell holder touched the bottom of the sizing die? Any chance you short stroked the press on some of the cases?

 

[ErikT]

I've found that some brass will vary widely in wall thickness, even in the same lot. Some manufacturers are better than others, of course. But I've noticed that thick-walled cartridges will stretch less than thin-walled ones, and the same thing happens with harder brass cases as opposed to softer ones. In the end, especially with the varying hardness, you can have cases that will "spring back" more than others, which might explain the difference in shoulders.

Generally, I will lube the inside of the case neck and the entire outside of the case (minus the shoulder), resize, and then trim once. So far, I haven't had any big troubles.

Erik.

 

[Cerdan]

Thanks for the feedback.

saskgunowner101, I lubed one out of two case mouths, but if that was the cause I would've had to trim one out of two cases, which wasn't the case. On the batch of 30, about five or six needed a lot of trimming. And the unlubed ones weren't any harder to resize than the others... Just in case I'll be sure to lube'em all next time.

Girzzlypeg, yeah, the die's installed correctly and all were sized 'til the bottom of the die hit the shell holder.

Erik, that could explain it I guess... Next time I fire some of those factory rounds I'll weigh the unprimed brass to see if there's a great weight spread.

Meanwhile, I removed the firing pin in my SKS and chambered'em all one by one to see if some prevented the bolt from closing or if they came out marked in any way. Didn't notice anything out of the ordinary...

Here's a pic that shows what I'm talking about. Despite the glare of the flash it's pretty clear some of the necks are shorter and the shoulder angle less acute than the others:

 

[merkelerk]

Too much case lube can have some effect but it usually dents the case.

It may be possible that you had too much lube that was very evenly distributed and caused a greater setback of the case neck.

I never lube the inside of the neck.

If your ammo is intended for only one rifle, you should neck size only. Full length sizing returns the brass to factory spec which is not necessarily ideal for your chamber. You can set up a neck sizing die to set back the shoulder almost any amount you wish, less is better in this case.

If you shoot more than one rifle of the same caliber, keep the brass separate, reload it separately etc. etc.

The bottom line......
What do you want your ammo to do?
-Kill a moose at 75 yards? if it chambers and cycles, its fine.
-One ragged hole at 200 yards? Experiment with every aspect of reloading, one item at a time. If you change more than one aspect of the reload, you won't know which of the changes aided/hindered you.