308 Brass stretching - Is this normal?

[sappnasty]

I was looking at my brass today. I noticed that starting out with factory ammo, in this case Hornady TAP and FEDERAL Match, the overall case length was 2.005. When I measured the once fired brass I got two different measurements. The FEDERAL brass measured at 2.019 and the TAP at 2.015. Both cartridges were new factory ammo, fired out of my SAI Socom II. Is it normal for the brass to stretch this much? My other question is, based on SAAMI guidelines and the size of all of my factory ammo, as long as I make sure all of my reloads are 2.005 I should be fine right? Here are some pics.

 

[243winxb]

Normal, yes. On firing the case will stretch to fill the chamber(maximum loads). Maximum case length is 2.015" When it gets this long, after full length resizing, you trim it back to 2.005" Even if only neck sizing, trim it when it reaches the maximum of 2.015"

 

[Kentucky Jelly]

Your Springer probably had a tag on it with the chamber length on it no?
Minimum trim is 2.005.

 

[sappnasty]

Yes it did....It was a G.I. headspace measurement of 1.632.

 

[W.E.G.]

Completely normal.

Brass always stretches like that when fired in gas-operated semi-auto rifles.

 

[W.E.G.]

Use a case gage, and adjust your sizing die so that you get a correct reading on your case gage.

Trim the brass after it is re-sized.

 

[MEHavey]

The M1A design is particularly hard on brass upon extraction, so your observation of stretch is "normal" in that weapon. It's also the reason that any measured case headspace dimension is garbage after firing. The sholder has been blown forward several/many thousandths from the actual chamber headspace.

Both are the reasons...

(1) You full-length resize every time (At least 1.630" in your case)
(2) You generally trim after every resizing
(3) You don't take the case past four reloadings -- pitch

See pp 3-4 in the attached:
http://www.zediker.com/downloads/14_loading.pdf

 

[sappnasty]

Harvey, thank you for information. You seem to have the M1A reloading thing down pat. I think that I will just PM you from now on when I have any related questions if thats okay. I'm not planning on reloading anything fancy, I just wanna keep my rounds as close to factory as possible. I simply want a good reliable hunting round. Also, thanks everyone else for your information. It is all well appreciated.

Sappnasty

 

[MEHavey]

There are a lot of much more experienced M14 shooters/reloaders on this board than I, sappnasty, but I ran into the same *** problem as you early on. It was the other shooters who pointed me to Glen Zediker's article, and I merely pass on what Zediker found to be de rigueur if we wanted to stay healthy.

 

[medalguy]

Try trimming to 2.000 after the initial firing. You might get one more cycle before having to trim again. I can usually get at least three cycles before I have to trim again using military brass if I initially trim to 2.000.

 

[hancjamk]

M1A is hell on brass, even military brass... Trimming cases is my least favorate thing to do. I have to trim my cases to 2.05 everytime I resize. I think I'm going to take medalguy advice and trim to 2.00. Since I discard the brass after three, or four loadings anyway, maybe I can get away with trimming once, or twice...

 

[MEHavey]

Think....
http://www.youtube.com/watch?v=SGYLmHvKVd0

It was a real convenience for all my rifles before the M14.
With the M14, it was a lifesaver.

 

[Zane]

Anyone know if the RBCS X-die help fix this problem?

 

[HOWARD J]

I buy once fired military brass-.223 about $8 per 100
I resize & trim 4 times
I get 4 loading out of it & the toss it away---not safe anymore.
I find this more economical than new brass

[/URL][/IMG]

.308 once fired available here:

http://www.mcssl.com/store/2254068/catalog/category/5019315

 

[GPWEAPON]

All of the above is quite true, I have found that with a loose chamber that a
case sizing gauge is the best way to get the most out of your brass.
check the fired case in the gauge then resize so the casse drops in about.003 more. this will minimise streching, I've had once fired brass that I could only
get 2 reloads without some head seperation, loads around the 40.5 with the 4895 powders will help to extend the life of the brass also using the 168's
In compition I would only use once fired brass from a reliable source
Malfunctions suck, It only lasts from a bolt gun