30-30 Case stretch

[hammer58]

After full length sizing some 30-30 brass and tumbling in corn cob media, I noticed what looked like a bulge near the base of the case. Looking at the case dimension specs, I noticed that the base is supposed to be .422 just after the rim. They measure .4145 at the base and .418 at the point that looks like the bulge.

Does this indicate that the cases are in danger of separating from the rim?

I attached some pics so any advise would be appreciated

 

[Slamfire]

I am going to say that what you have is a huge chamber. My guess is that the case has obtruded to the chamber down to the bulge. Pressures were low enough that the case head did not swell out below the bulge.


You did not say what type of 30-30 you have, but I have a Marlin. I talked to Marlin before they were bought out. They were primarily concerned with making a firearm that went bang each and every time. Accuracy was not a consideration, my recollection was that I was told their rifles were for guys in the woods. My Marlin 336 has a huge chamber and the shoulder to base distance of a fired case is way beyond the NO Go on my Wilson Cartridge Headspace Gages.

 

[hammer58]

Slamfire, my rifle is a Winchester model 94 Buffalo Bill Commemorative. I have been loading fairly light loads consisting of 31.5 grains of IMR 4895 with a 150 grain pill.

My concern is that the base is actually smaller than specs. My case measured .414" and case specs are .422". I don't have any measurements before firing so all of these are after firing and FL sizing.

 

[Slamfire]

Slamfire, my rifle is a Winchester model 94 Buffalo Bill Commemorative. I have been loading fairly light loads consisting of 31.5 grains of IMR 4895 with a 150 grain pill.

My concern is that the base is actually smaller than specs. My case measured .414" and case specs are .422". I don't have any measurements before firing so all of these are after firing and FL sizing.

I remember when those came out in 1968 or 1969. Didn't have the money to buy one then.

Lets go back to basics. The case is a gas seal. As long as it is performing the job of a gas seal, the case is doing its job. It would be bad and dangerous if you were having case sidewall splits, due to a huge chamber that was so large that the case ruptured because it stretched too much. It would also be bad if you had case head separations due to a chamber with excessive base to shoulder distance. But you are having neither of these problems.

So what really is the problem? Until you can determine that you are having a function issue, or a safety related issue, I don't see a problem.

 

[hammer58]

I remember when those came out in 1968 or 1969. Didn't have the money to buy one then.

Lets go back to basics. The case is a gas seal. As long as it is performing the job of a gas seal, the case is doing its job. It would be bad and dangerous if you were having case sidewall splits, due to a huge chamber that was so large that the case ruptured because it stretched too much. It would also be bad if you had case head separations due to a chamber with excessive base to shoulder distance. But you are having neither of these problems.

So what really is the problem? Until you can determine that you are having a function issue, or a safety related issue, I don't see a problem.

Thanks for the info. I just wanted to be sure that I am not about to have a problem. It's a really great rifle and loads of fun to shoot. Sure wouldn't want to damage it.

Thanks for your help!

 

[44 AMP]

My concern is that the base is actually smaller than specs.

You're overthinking things a little. Go check the base of a new factory round.

It's going to be smaller than the spec.
Unless there is a +/- on the spec, or other information, always assume it is the maximum allowed.

Chambers and ammunition specs have tolerances. Ammo makers always try to produce cases on the minimum end of the range, so they will chamber in guns with minimum spec chambers. Its just common sense. Fit in the minimum everyone is happy, and you sell more ammo. Be technically in spec but chamber hard in some guns (min spec chambers), those owners won't buy your ammo, and they will tell their friends, your stuff is no good, as well.

Rimmed cases headspace on the rim. All the chamber has to be is large enough to allow reliable chambering, and not so large as the brass ruptures on firing. Period. Goes Bang every time, is the standard. It's nice when the chamber/case/sizing die fit is close enough to allow repeated reloading of fired brass, but rifle makers are under no compulsion to ensure that, even if they could.

Size your brass to fit your rifle with the least amount of working the case as possible and shoot moderate or light loads and the cases will last as long as possible. A ...generous...chamber and full length resizing usually means a shorter case life.

You can section (cut) a case and see how thick the brass is just above the solid head. (you can find pics on the web) or use the "paper clip" method to feel for the ring that will form as the case thins just before head separation. Find a thin spot, the case is DONE, toss it in the scrap brass recycle and move on.

 

[Unclenick]

44AMP has the key. It's tolerances.

Most folks are familiar with common plus or minus tolerances, but those are not what SAAMI uses. SAAMI uses unilateral tolerances, meaning tolerances that are only in one direction away from a given number. This is a common engineering practice where the number given represents a critical limit and going in its direction away from the mean would prevent functioning altogether, such as a chamber to small for you close the bolt on a maximum size cartridge case, or a case too large for you to be able to close the bolt on it in a minimum chamber. So the case dimensions, with a couple of special exceptions, are all maximum case size with a minus tolerance only, while the chamber dimensions are all minimums with a plus tolerance only.

Thus, in the SAAMI drawing of the .30-30, the case diameter 0.2 inches from the head is the 0.4145" number you referenced. That is the critical maximum. On the SAAMI drawing, right under the title plate for the cartridge is a note that says all diameters have a -0.008" tolerance except where noted otherwise (such as the bullet diameter). So the correct dimension for the location you cite may be written as 0.4065"-0.4145".

For the chamber at that same location, the diameter dimension is 0.4213", which is the critical minimum, and at the bottom right, under the underlined heading, "CHAMBER", it says the tolerance for all chamber diameters is +0.0020" unless otherwise stated. So your chamber should be 0.4213"-0.4233".

Now, knowing your brass expands under pressure and springs back a thousandth or two, I think you can see where your numbers are coming from.

 

[Pathfinder45]

I read this late last night and went out to the shed to measure some of my cases. A box of factory Winchester Silvertips measured .414". Some recently fired cases also measured the same near the base but swelled slightly above there to .417". I get several loading out of a case, for sure. This in a Winchester 94 carbine, circa 1942. All's well, Hammer58; I think you will be just fine with any sane loads.

 

[F. Guffey]

Does anyone measure before and again and then there is that thing with the shell holder deck height of .125". No one measure the thickness of the case head from the cup above the web to case head. I do, it can be alarming when the case head expands when the case is fired. I have cases with a case head thickness .260". I also have cases with a case head thickness of .200", many reloaders claim it does not matter, it does to me.

Does the case bulge above the case head or does the case head bulge? I have never had a problem with 30/30 and then one day I inherited one from a friend that died. I did not check/test the rifle but if was a Marlin that was made before they had all of their problems. I gave the rifle to a family member with new/store bought ammo. The cases came back for reloading, new ammo/once fired cases should not have looked so ragged, and I wondered if 2 of the cases came from somewhere else or was fired in another rifle.

I know the rim prevented the case from going forward, I used my Winchester 30/30 as a gage, I know, no one wants to know how that is possible but it had to do with a feeler gage. When they came for a visit they did not bring the Marlin so what was I to do, the chamber in the Marlin is longer than the chamber in my Winchester.

Bulge? If the Marlin cases had a bulge ahead of the rim I would insist my grandson not shoot the rifle. I would consider borrowing an Ackley Improved chamber reamer for the 30/30. And then there would be other considerations;
I would consider reaming the chamber with a reamer that did not cut the rim.

F. Guffey

 

[F. Guffey]

Hammer58, I looked at the pictures you posted, there is no bulge ahead of the rim, you have unsupported case head, what I see is normal. What is see is a case body that conformed to the chamber when fired.

For years and years I have said there is something about sizing a case reloaders do not understand, reloaders insist on full length sizing with total disregard for the length of the chamber from the shoulder to the bolt face. I would suggest you reduce the ability of the die and shell holder to size the case to minimum length.

F. Guffey

 

[hammer58]

44AMP

You're overthinking things a little. Go check the base of a new factory round.

It's going to be smaller than the spec.
Unless there is a +/- on the spec, or other information, always assume it is the maximum allowed.

That's good to know. I did measure some new rounds and got the same .4145 measurement just above the base. The new rounds measure the same until a little further up the case then it gets progressively smaller... on the new round. I guess I was expecting the sizer to bring the case back to original dimensions.

 

[hammer58]

For years and years I have said there is something about sizing a case reloaders do not understand, reloaders insist on full length sizing with total disregard for the length of the chamber from the shoulder to the bolt face. I would suggest you reduce the ability of the die and shell holder to size the case to minimum length.

F. Guffey

I guess I don't understand fully. Are you talking about neck sizing only? I read somewhere that you should always full length size when loading for a lever action.

Thanks so much for your advise!

 

[Hawg]

I guess I don't understand fully. Are you talking about neck sizing only? I read somewhere that you should always full length size when loading for a lever action.

You should full length resize for a semi auto. A lever action will handle neck sizing only as long as you use the fired cases in the same rifle they were fired from to start with.

 

[F. Guffey]

I guess I don't understand fully. Are you talking about neck sizing only? I read somewhere that you should always full length size when loading for a lever action.

Thanks so much for your advise!

For most there is full length sizing and there is neck sizing; my dies have threads meaning can size a case to 4 different lengths between full length sizing and neck sizing. I started reloading with a feeler gage in my hand, I had no ideal reloaders and smiths had so much trouble sizing a case until I became a member on a reloading forum. Reloaders and smiths are still having trouble and I am still using a feeler gage.

When the feeler gage fails me I determine how and why.

F. Guffey

 

[mikld]

I didn't see it mentioned above (but sometimes I can't see) but you are taking the measurements after you F/L size. I don't see how that will tell you much except what your sizing die is doing...

 

[F. Guffey]

I didn't see it mentioned above (but sometimes I can't see) but you are taking the measurements after you F/L size. I don't see how that will tell you much except what your sizing die is doing...

I do not know who 'you' is. But if you are referring to something I typed always consider I measure before and again after. The difference between before and after when measured in thousandths are all options when it comes to off setting the length of the chamber from the shoulder to the bolt face.

F. Guffey

 

[Rifletom]

Having just read this thread, I measured the only factory box of 30-30's I have. Un-fired, the base is .414.5. Fired is 415-415.5. My handloads measure 414.5 loaded, 415.5 fired.
I'd say you're good to go. BTW, all of mine thru a Mod 94, about 1982.