30 carbine case length growth and trimming

[albert]

Anyone have any tips for reducing case growth? My loads are standard, but I get some that stretch and need trimming others that don't. I trimmed them all and after shooting about 10% were over max on my drop gage. I tried sorting thru them and then decided just to put the whole lot thru my drill powered forester trimmer. It's tedious work. It's Sellior and Bellot brass.

[psteinmayer]

I think most rifle cartridges with some sort of bottle neck will stretch, and require trimming after each firing. I use Lee Trimmers. They are completely fool-proof, and work perfectly every time.

[Johnny in Texas]

You may be over-resizing the brass. Have you check to see if you sized brass meet specs. Because this case is tapered it gets longer the more the case is opened up so rifle headspace and cartridge headspace . variation in case wall thickness will also affect how much a case lengthens during resizing.

[randy langford]

I think it is just part of owning a M1 Carbine my brass does the same thing I put them all through the trimmer.

[Tuna]

All 30 carbine brass will stretch to some extent with each sizing. Some more then others but it's the sizing die and the brass diameter that allows the case to stretch. Trimming is a pain the neck but it's what has to be done each time it's fired as the case headspaces on the case mouth. Too long a case can cause the rifle to discharge out of battery and you really don't want that to happen.

[joem]

I measure all my cases after sizing and anything over 1.280 are trimmed back to 1.280. Yes I know it's under as some books that state the trim to length is 1.290.

[Art]

Correct case length is absolutely critical in an M1 Carbine. Cases that are too long can result in the weapon firing out of battery. One who knows .

[DaveL]

As others have said, 30 Carb needs to be trimmed each time you load them. They stretch, there's no way around it. 30 carb headspaces on the mouth so they must be correct. Also you can't over crimp them. As a matter of fact, I don't use any crimp on 30 carb and have never had any bullet lengthen in the magazine during firing. As to over-sizing, I guess it's possible. But on the other hand, all semi-auto (especially military semi-auto) rifles need to be full length sized to insure reliability. Also the US M1 30 Cal Carbine will not fire out of battery unless the rifle is VERY worn out. A Universal brand or most other civilian versions WILL fire out of battery. I won't even shoot a Universal carbine for just that reason.
As to why you have cases "growing" differently, I suspect it's one of 3 things. 1) Multiple brands of brass. I have found (after loading hundreds and hundreds of 30 carb) that there is a big difference in case mouth thickness with the different brands of brass. The only thing that helps a little is to sort your brass and find out which brand your dies like. I find the military brass is the most consistent, if you can find it. That brings us to number 2) If you are using Lee dies you will most likely never solve your problem with 30 carb. 3) What I do with Sellior and Bellot brass is throw it in the brass scrap can. I don't say that because of other people’s comments, I say it from personal experience. Over the 40 some years I've been reloading I have never seen any brass that is as crappy as S&B. I've had oversized primer pockets, undersized primer pockets, blown out primers, thin cases, thick cases, cracked necks on the first reload and split cases with S&B brass. The worst was trying to reload S&B cases in 45 long colt. My Lyman dies sized every other brand I had correctly but the S&B cases after resizing, were so thin that the bullet just dropped into the case until it hit the powder.
So, keep trimming your brass to the proper length. I know it's tedious work but a rifle that will go through a full magazine without a stoppage is worth the extra time. 30 carb isn't the easiest cartridge to load and the biggest reason is inconsistent brass as you have discovered.
HTH
Dave

[kcw]

I use standard RCBS dies for the 30 carb. I've found that by adjusting the expander die setup so that the case mouth is only belled to the acceptable bare minimum helps greatly. There's no point in belling the mouth beyond that which is absolutely necessary. I also ever so slightly chamfer the inside of the case mouth after each trim so as to reduce the sharp angle at the mouth. Additionally I have no problem in experiencing a bit of a "bump" when the heel of the bullet is forced into the case mouth.
Additionally I make certain that the case is lubed appropriately so that the expander button doesn't abnormally drag the brass on the way out. In following these practices I can usually get four firings before I need to trim. I sample check after the third. My brass is about 90% LC, the rest is PS.

[joem]

"I have never seen any brass that is as crappy as S&B."

I have and it's AMERC. If I pick it up by mistake it goes in the scrap bucket.