7mmRM...how to determine if brass is wearing out?

[imq707s]

I've been reloading rounds for my 7mmRM for a long time now. I full length size every time, and the loads are not close to "max loads". They are a very conservitve loads that gets great accuracy.

One batch of brass I have is on it's 12th reloading. I didn't see any visible signs on the outside of the brass that would indicate that it was getting ready to fail (shiny ring around the outside that indicated thinning)......but during my last trip to the range I has a case split on me. I started thinking "12x's is probably pushing it for the same brass). So I cut the split brass with a bandsaw to look at it. As you can see from the picture, it's thinned out a bunch near the base of the case. It's reading around .014" at the thinnest spot. The piece of once fired brass is reading .037" at the same spot.

Here is my question......at what point should I chuck the brass and start with new. How thin can that ring around the be before the brass is junk?

Any info on this at all would be very helpfull. If you have any questions, please let me know.








Once fired brass




12x's reloaded brass that split on me




Cross section of above brass

[Buckythebrewer]

12x Is way to much under your conditions IMO, and that case is proof enough.When your getting head case seperation(or close to it) it is BAD!!.In a semi-auto That can get you killed .
I think the best investment you could possibly make would be a lee collet neck sizing die and/or also an RCBS precision mic(it will measure shoulder displacement for adjusting FL dies).When you size using a FL die ,it is really easy to OVER size it causing more wear and tear on the brass.The precision mic will tell you how much shoulder displacement your getting before and after firing and that will help reduce your chance of head case seperation as well as make your brass last longer.The other method is the Lee collet (neck sizing )die.That will allow your brass to fire form to your chamber,and then from there neck size only(The only way to go in a bolt action IMO).I have read that you have to be very carefull around the belt of the magnum.I cannot remember what to check or how to measure,but I would do the research If I were you.
Be very carefull,Head case seperation can do alot of damage to your rifle,ESPECIALLY in semi-auto's(usually sending parts back at the shooter ).
Good luck

[Buckythebrewer]

Usually after you have fired your FL brass in your chamber and then start neck sizing,You usually only have to trim your cases.Maybe after a few loads you might have to bump the shoulder with a FL die to enable you to close the bolt without to much effort..
Again,I recommend a rcbs precision mic for you as well as the Lee collet neck sizing die(requires no lube to use).It will make a big difference in your brass life over a regular FL die without measuring the shoulder.

[castnblast]

I'm with you, I like to full length resize my 7mm brass because it is easier to chamber in hunting situations, especially when it gets real cold. 12x is WAY too many times if you are full length resizing. I was wondering why you are on the 12 time...Are you using one or two boxes of once fired factory ammo? If so, bite the bullet, and purchase some inexpensive Winchester or Remington never fired brass. They come in bulk, are fresh, never fired, and are fairly inexpensive. They run 10.49 for a box of 20, or you can get 100 rounds for 40.99 right now at midwayusa.com. You can cycle your brass much better, and cut down your firings per piece better. Personally, I'd toss them after 5 or 6 rounds.

[mrawesome22]

I'm with Bucky. Get a neck die if your using a bolt or single shot. The neck will split as you are seating a bullet, telling you that the brass is no good anymore. At least this has been my experience so far. If you really want to keep FL sizing, you must have correct headspace or the brass really gets worked a lot. That precision mic Bucky was talking about would do the trick for getting correct headspace. If you want a custom FL die, you can either send a fireformed brass, or a chamber cast to any of the die making company's and they will make you a custom FL die. To me, this would be the optimal way to go if you want to keep FL sizing. But if your just going to FL size with production dies and not measure headspace, I'd throw them out after 5 or 6 times like has been said before.

[L Puckett]

As Bucky stated,

You are setting the shoulder back to far when sizing. Get the RCBS precision mic and set your die to bump the shoulder back .002 for a bolt gun, or .003 for a gas gun. Above this you get too much case stretch. I agree with F/L everytime.

Neck splits are due to work hardened brass, I anneal the necks every other reloading for competition rounds and every 3rd reloading for practice rounds. Neck tension consistance starts to drop off after that.

Watch your primer pocket stretching with the softer brass (IE: Federal, etc).

I expect up to 25 reloads on my Lapua brass, in .308 Win.

I would highly recommend you toss this set of brass in the trash and start with new brass and new die setup procedure.

LP

[James A. Mullins]

One way to check brass for head seperation is to bend a small right angle on a paper clip. After sizing run the paperclip from the bottom of case up. If you feel a indention on the inside of the case its starting to seperate. All the tips you've gotten here good advice. One more to set your die's to stop just short of the sholder, use a black felt marker and draw a line from top of case mouth to jest over the sholder. Back your sizing die out 2-3 turns, then slowly trial and error turn the die back in run the case to top of ram stroke. Be patient the die will displace the color of the marker. Lock your die when mark just reaches the sholder. If you use a auto loader rifle toss the brass when you feel the grouves with paperclip. I shoot both 300 and 338 Win. Mags and load to 1 or 2 % below max charges and get 10-15 loads out of each case.
The very best to you.
James

[.45 Vet]

+10 to what J.A.Mullins posted. Check out the "DARK LINE" on your 3rd picture that's perpendicular to the thin area of the brass. The paper-clip trick used to be recommended in most of older re-loading manuals....