30BR brass necks keep getting loose

[Markhor]

I am running into this problem of loose 30BR necks that have me stumped. I have a .330 neck 30BR rifle. After fire forming, I begin with using a .327 bushing, any smaller is too tight. After firing a couple of times, I have to go to a .325 bushing since things begin getting loose. After 2-3 more firings I am at .324 bushing. After one more firing it seems much looser then when I first used it. It seems that at this rate I will have to go to a .323 bushing soon.

I neck turn my brass to .0010. My mic measurement of a loaded cartridge is coming out to .330 even after using a .324 bushing.

What am I doing wrong? Should my necks be thinner?
Any help would be greatly appreciated.

Thanks,
Ed

[george in KY]

you useing a MIC or calipers ?
325 and 324 are the most used bushings with a 330 neck

[alinwa]

Your neck clearance is overly generous and the brass is changing character as it work hardens.

Leave your necks thick enough that a loaded round measures .327-.328 and you should be OK
opinionsby
al

[abintx]

I have a .330 neck 30BR rifle. My mic measurement of a loaded cartridge is coming out to .330. Should my necks be thinner? Ed

Yes. Turn until you achieve an OD measurement [at the pressure ring, if your bullet has one] of .328 or less, with the bullet seated. With the 30BR, bushings in the range of .323 to .326 are often used, with the majority being .324 or .325, which is what I use. My 30BR likes .003" to .004" of neck tension on the .328 turned [Lapua brass] neck. What type brass are you using?

[mturner]

What am I missing here? I see a comment that the guys neck clearance is generous, but not sure how this conclusion came about. He states that his chamber is a .330" neck. He also states that a measured round is .330". This would tell me that the only neck clearance he has is from the reamer cutting maybe .0005" oversize, which is not enough neck clearance. Can anyone tell me what I'm not seeing in his comments?

Michael

[ConRich]

What am I missing here? I see a comment that the guys neck clearance is generous, but not sure how this conclusion came about. He states that his chamber is a .330" neck. He also states that a measured round is .330". This would tell me that the only neck clearance he has is from the reamer cutting maybe .0005" oversize, which is not enough neck clearance. Can anyone tell me what I'm not seeing in his comments?

Michael

Michael,
You are spot on, I came up with the same question.

Dick

[Charles E]

Mr. Turner, I doubt you're missing anything, except there are too many BR Central "shoot from the hip answers" going on.

Markor says the chamber is .330, and he turns his necks to 0.010 wall thickness. There are two sides to the neck, that's .020. Add a .308 (nominal) bullet diameter, and you're at .328, only .002 off (reported) chamber size.

Well, the pressure ring will add a bit, and the bullets might be fatties, so a .329 measurement of the loaded round wouldn't surprise me. If he's getting .330 with a mike, I'd say the necks might have a .0105 wall thickness, but surely everything is within spitting distance.

The original post said

After firing a couple of times, I have to go to a .325 bushing since things begin getting loose. After 2-3 more firings I am at .324 bushing. After one more firing it seems much looser then when I first used it. It seems that at this rate I will have to go to a .323 bushing soon.

I suspect that "getting loose" doesn't mean the wall thickness is changing, he's just not getting the bullet pull (neck tension) he got with new cases. And of course the reason is the brass is work hardening, so that when it's sized, it springs back more.

You can get into a small argument (or big fight on the internet) over the right resolution, but the *phenomena* Mr. Markor describes is perfectly normal. He can either anneal the necks after every firing or so, or use smaller bushings as the necks harden & spring back increases.

Mr. Markor -- do a search for posts by Al Nyhus, and you'll find, along with many other useful information, a couple good discussions of this issue, and your options.

Also fun: measure the sized neck (no bullet) on a freshly fireformed case. Now measure a sized neck after it's had 3--5 firings. You'll see the springback differences at play.

[Markhor]

Thanks Gentalmen for some good answers.

Charles; You are spot on, loose is indeed neck tension, brass thickness does not change. It seems that that the brass just does not spring back as it used to in the earlier firings. My load is a bit stiff at 34.8 grs of 4198, maybe that's taking a toll on the brass.

If this is a common phenomena that all non annealers face, then that makes me feel better. I just want to make sure I am not doing something wrong that is causing this. Maybe it's time to look at annealing.

Thanks,
Ed

[mks]

Thanks Gentalmen for some good answers.

Charles; You are spot on, loose is indeed neck tension, brass thickness does not change. It seems that that the brass just does not spring back as it used to in the earlier firings. My load is a bit stiff at 34.8 grs of 4198, maybe that's taking a toll on the brass.

If this is a common phenomena that all non annealers face, then that makes me feel better. I just want to make sure I am not doing something wrong that is causing this. Maybe it's time to look at annealing.

Thanks,
Ed

Ed,
I shoot the same load, and have 50ish firings on some of my brass without annealing. My neck clearance is fairly tight. On new brass, I could get a couple firings without resizing the neck, just seat the bullet. As the necks work hardened I needed to reduce bushing size a couple of times to keep a grip on the bullets. Brass has a maximum work-hardened strength, so eventually it becomes as strong as its going to get, and you won't have to change bushings again. Or you can just start out with that final bushing size, and hardly notice the change.

It would be a good idea to check the actual size of your chamber. My 0.330 neck is actually over 0.331.

Cheers,
Keith

[Charles E]

Just to wrap this up -- well, from my perspective -- couple points.

The springback of brass & it's effect on neck tension depends on whether you're getting the resizing from a bushing, or a "narrowing plus expander." For a bushing only die, the work-hardened cases will spring back to give a bigger hole -- less neck tension. However, if sized beyond what you need then expanded up (conventional die), the spring-back will give you a smaller hole. So your statement

It seems that that the brass just does not spring back as it used to in the earlier firings. My load is a bit stiff at 34.8 grs of 4198, maybe that's taking a toll on the brass.

is true, (it's not the same springback) but misleading -- it work-hardened brass springs back more, not less.

I'd also listen to Keith (mks). Not that it matters, but if your measurements of your loaded brass are anywhere near close, I'd bet your chamber is over .330. Putting a .330 case in a .330 chamber usually give some indication things are a bit tight.

You can almost always trust mks (Keith) to give you good answers. And Michael Turner. And Al in Washington (alinwa). I think alinwa just responded a bit too quickly here. There are quite a few people on BR Central who won't steer you wrong, and are usually pretty clear about what is their opinion, and what is just plain fact. Sadly, there are also quite a few who just repeat old rumors. Take all our answers with that in mind.

With that caution, I'd also add you might not need to replicate the high bullet pull with fired cases that you use with virgin brass, esp with H4198. Some powders seem to need more neck tension than others. My experience is 4198 is not one of them. YMMV, but that mileage should come from firing several targets, not from what "some guy" has told you.

Good luck to you

[alinwa]

My reply about clearance being "overly generous" did indeed come from losing the clarity offered by the original post.

That said, I still believe the answer to lie in "changing character of the brass," ie work hardening as others have so well explained.
al

[mwezell]

Fwiw, I have never seen that much variation in my brass. Over the coarse of 40-50 firings, I've never seen the need to go down more than .001" in bushing size...say from a .325 to .324 over the life of the brass.

[mks]

Fwiw, I have never seen that much variation in my brass. Over the coarse of 40-50 firings, I've never seen the need to go down more than .001" in bushing size...say from a .325 to .324 over the life of the brass.

Mike,
That makes sense. If you start out with more sizing, you probably wouldn't notice much change. From being able to load without sizing, I changed to 0.327, then to 0.326. My necks may be a bit thicker than yours, too.

Hope you are healing up,
Keith

[SGJennings]

Ed,

Not related to your tension issue, but words of advice given to me by HoFer Bill Forrester: "Cut thin to win".

FWIW,

Greg J.

[Markhor]

Thanks all, your feedback is very informative.

Mike, what thickness are you turning your necks to?

Ed