Need ideas regarding case separation

[Bob C]

Today I fired 19 rounds of 30/30 reloads in my 14" Contender. The brass was all once fired, and from factory ammo. Some R-P, some W/W.

My load was 24.0 IMR 4198 with a 150 Sierra BTSP. I set the sizer by screwing it in a little at a time until the action closed easily on the re-sized case.

The first six rounds were in W/W brass, and did fine. The seventh round was R-P, and I got a complete separation .66" above the base of the rim.

I fired the rest of the rounds without any separations, but most of the empties have a bright line at the same place where the one round separated. It's present on the W/W brass, but less so than on the R/P brass.

I miked the fired brass at the shiny line, and it was all .416". Unfired brass at that same point is .411". At the base the fired brass is .420", and at the base of the shoulder it's .407". I also fired 25 or so factory rounds today, and many of them also show the bright ring at that same place, and they have the same dimensions after firing.

The most likely possibility I can think of are an oversized chamber, Since it's occurring with factory loads, and with brass from two different makers, I doubt if it's a badly adjusted sizer, or bad brass.

Any comments or suggestions will be appreciated.

 

[sensop]

The most likely possibility I can think of are an oversized chamber, Since it's occurring with factory loads, and with brass from two different makers, I doubt if it's a badly adjusted sizer, or bad brass.

Any comments or suggestions will be appreciated.

With the evidence you posted, I'd have to agree ... as a preliminary conclusion. Some cerrosafe to cast the chamber would tell that tale, for sure.

Are you sure your action hinge pin is within tolerance? Are there any rough "rings" inside the chamber? Bend a paper clip straight and make a short 60-70 degree "feeler" to pull down the side wall of the chamber to feel if there are any gross imperfections in the chamber. I'd put the "feeler" tip of the paper clip on a sharpening stone to take off the rough edges first. I've done it with a round toothpick too. This will only detect really gross chamber wall problems, though.

 

[kidcoltoutlaw]

get a wilson case gauge

 

[KP95DAO]

You don't say whether the brass was "once fired" from your TC or in another gun. It doesn't really matter. Once brass is fired in a firearm with excessive headspace it is ruined for extended reloading.

The initial firing creates a weak line and any further firing just adds to it. The best thing to do would be to start with your first firing (virgin brass) with the bullets jammed into the rifling. Of course you will need to back off a little on the load. This will set the shoulder where it needs to be and with minimal sizing it should prevent seperation.

If yours was a bolt gun, another "trick" is to lube the case on the first firing. This helps prevent it gripping the walls. However, it also puts more stress on the action and is not wise in a break-open like a TC.

 

[Bob C]

All of the brass was from factory ammo which was fired in my gun.

Checking the inside of each case for a "fault" line with a bent paper clip showed that none of the once fired brass has a problem, but that three of eighteen of the twice fired do.

I'm going to discard the cases where there seems to be a problem, and then proceed with my loading. I'll check the brass regularly, and make very sure I'm not setting the shoulder back at all.

Thanks for the replies.

 

[Mike Irwin]

I'm not 100% certain about this, but I don't think that setting the shoulder back on a .30-30 round will necessarily cause a case head separation, will it?

In a rimmed round headspace, (headspacing problems is the most common cause of a case separation, I think) should be controlled by the case rim, not the shoulder, shouldn't it?

I'm thinking that if the head space is correct, the shoulder should just move back forward to where it should be.

 

[C.R.Sam]

Mike right.

sam

 

[sensop]

Yes. Truth is, I've fired .30/30s in some chambers with the headspace (rim) cut pretty deep and never had this kind of problem. It sounds like what might happen if a rough spot forward in the chamber grabbed the brass and held it during the firing cycle and the case aft of the rough spot traveled rearward, causing the stretch. Especially with a stout load. If the chamber walls are smooth, the .30/30 is pretty forgiving.

Does the loaded round sit flush with the face of the barrel? Or does it sit deep? Have you determined that the chamber wall is smooth and doesn't have a rough spot?

 

[labgrade]

I've no load data to say whether or not your load is "hot," so can't comment in the least.

A rimmed cartridge does headspace on the rim, but in a Contender, you also headspace on the shoulder (closing the action to allow a goodly primer hit, etc. - it's dual-fold, with added "stuff"). Sounds like you did that all OK. & in all acutality, every Contender case headspaces properly on the shoulder - if done right to maximize case life. Headspacing on the "worst case," (= shoulder) maximaizes case life, extends case life , adds to accuracy & adds to increased velocities).

First off failure analysis thing I'd think of is how far out your bullet was seated (which really should have "set off" a "major-sized" brass thingy - action not closing properly.

Furthering the thought process, it may be that you developed a close-to-max load with the bullet at (say) - (that's MINUS) .050" to the lands & susbsequently set these latest right at the lands.

This latter loading may (not will necessarily, but certainly may) drastically increase pressures.

Looks like your brass sizing is OK. First thing I would look at is seating depth of your bullets.

Too, these actions sometimes seem very twitchy reagrds brass = case volume (= presseure due to internal volume). I'd suggest "playing" with only one variety brass till you isolate the problem. Case separation is not a joke in the least & is a sign of imminent catostropic failure! - at best, your gun breaks, at worst = you lose your eyes.

I suggest extreme caution where you're at.

Too & an aside. I'd ask what type micrometer you're using.

A standard ~.125" diameter rotating micrometer will "walk" & not give reliable enough readings for a specific area of any brass cross secition. For this application, you really do need a non-rotating blade micrometer which doesn't spin on the case/& gives a much less sectional measurement - much more accurate & frankly, I don't think the case measurement is the problem.

Not really relavant to what you're pressures are saying, but something to consider later regards accuartely measuring stuff.

 

[C.R.Sam]

By Lyman 46th....that load is HOT.

Sam

 

[Bob C]

Good points everyone is raising. Thanks!

I've checked the chamber, and didn't find any rough spots.

The micrometer used to check the brass is the standard rotating type. Readings were fairly consistent, +/- .001.

The 24.0 grain load is recommended in the Hodgdon's #26 manual as a moderate load useful for silhuettes. That manual, and also the current Speer and Sierra manuals show starting loads in this range.

As noted by C.R. Sam, the Lyman manual shows the max as 23.5 grains.

The load had noticably less blast and recoil than the factory loads. The extraction and primer appearance both seemed OK also.

 

[Pumpkinheaver]

I feel your pain, I had my first casehead separation about a month ago after 15 years of reloading my own and I still havn't figured out why it happened!

 

[swifter]

Go to:

http://bellmtcs.com

Lots of reading on TCs, headspace problems, and diagnostic tests. Beaucoup info...

Tom

 

[Bob C]

This morning I resized 16 rounds of once fired W/W brass from factory loads with the die adjusted so that there was no contact on the last 1/8" of the neck above the shoulder.

All were fired with the 150 Sierra BTSP and a load of IMR 3031 which was OK in all four manuals I checked.

There were no problems while firing. There is a line at the same place on the outside of the brass, but checking the inside of the cases showed no apparent faults.

 

[cdbeaver]

Recently my friend was shooting his Ruger No. 1 .223 from the bench, using "remanufactured" ammo with various headstamps. I shot it twice and the second time the case completely separated.

When I went up to the target (100 yds.) to see whether the bullet even hit the target, my friend tossed the two pieces into the weeds so I couldn't recover them for further inspection.

I suspect this "remanufactured" stuff may have been fired in automatic weapons and in resizing the headspace got screwed up. I can't recall for certain the brand name, so won't even speculate, but it did come from South Dakota.