Headspace issue on 357 92?

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Headspace issue on 357 92?

Postby FrankFisher » 06 May 2018 08

Hi guys, can I pick your brains? Bit of a newbie here. I have a 16 inch 92 in 357. It shoots great, very accurate. However, at the range today a couple of other members noted that my ejected brass has bright marks on the leading edge, as if the tip of the case had been polished after firing. These guys suggested this indicated excess headspace, and that the cartridge was stretching or slopping forward in the bore, impacting the bore, leaving the bright marks, and that this was a problem.

Any thoughts?

These cartridges were both handloaded and factory - I think in both cases the cases are slightly under the .357 max length. The factory ammo is PPU which i find is around 1.280 after firing and my loads were 1.275 or less.

Does this sound like a headspace issue, or anything else significant? I was thinking that obviously this rifle is also chambered for .38, and those are shorter cases, so any case between .38 min and .357 max should be safe to shoot?

I will probably get a Go and NOGO .357 gauges. I'd rather spend a few quid and feel safe, but any advice would be welcome.
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Re: Headspace issue on 357 92?

Postby Ohio3Wheels » 06 May 2018 14

Frank, by all means get it checked but if I understand your description correctly that doesn't sound like head space. The 357 and its cousins head spaces on the rim. With too thin a rim on firing the case mouth will grip the chamber walls and the case will stretch back against the breech face to make up the difference. If this goes on long enough the case will develop a head separation. Early symptom of that is a bright ring on the case ahead of the web. The danger there is the "going on long enough" is an indeterminate variable, first firing or 20th, or when ever and trust me it's less than pleasant when it happens.

Fatter than spec rims can cause difficulty closing the bolt all the way.

I wonder if it's possible that what you're seeing is a bit of cold working of the case mouth as the result of the crimp opening up. I routinely check case mouths for cracks and splits but don't recall seeing bright rings. Next time out I'll have to look.
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Re: Headspace issue on 357 92?

Postby FrankFisher » 06 May 2018 15

Thanks for that. I have been reading up today and it doesn't seem like headspace either. In fact, I saw a trick to use to measure space behind the rim, ie between rim and bolt, which isn't strictly headspace is it? By measuring a cartridge case, part seating a dead primer, measuring, then insert and close the bolt on it - retrieve, measure the case plus now-depressed primer, and with a little subtraction you have the clearance between bold face and rim, once seated. So I did this with some starline brass and the clearance was .010, with PPU brass it was .006. I measure the rims on those and sure enough the PPU is four thou thicker than the starline, so I'm figuring all is good, and if I want tighter tolerance I need to find brass with a slightly thicker rim?

I'm learning as I go, so please shout out if this is all nonsense....
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Re: Headspace issue on 357 92?

Postby Ohio3Wheels » 06 May 2018 19

Neat trick and it puts you in the ball park. Head space shouldn't be a problem as long as the rifle is correctly assembled and the rims are within spec.

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Re: Headspace issue on 357 92?

Postby GasGuzzler » 07 May 2018 06

Post a pic of the brass.
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Re: Headspace issue on 357 92?

Postby FrankFisher » 08 May 2018 13

I think I have figured this out. The attached pic shows two case of length 1.275, both blacked with a dab of blueing. The first I loaded, closed the lever, extracted normally. The second I manually pushed home with bolt open, tapped with a rubber mallet and wooden dowel to ensure was fully seated, then teased out with fingerrnails, not using extractor.

DSC_0155.JPG


The first has the bright fresh brass that concerned the guys at the range, the second does not. Obviously neither has been fired, but after watching closely the extraction of other cases I think the bright marks are simply where the end of the case impacts the breech on extraction. The Rossi fires cases a couple of yards, so there's obviously a fair bit of force.

I have an endoscope knocking around so also took a look in the chamber - it looks fine to me. The "step" up to the rifling seems even and as it should be - would you agree?

WIN_20180508_19_13_21_Pro.jpg

So I'm tempted to think this is a fuss about nothing and all is well?
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Re: Headspace issue on 357 92?

Postby Ohio3Wheels » 08 May 2018 15

I do believe you're right, Frank. The final "proof" if you will would be to mark a couple of cases so you know their orientation in the camber and see where that mark is after firing. It would tell you where they bump. Then again it's probably much ado about nothing.

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Re: Headspace issue on 357 92?

Postby FrankFisher » 09 May 2018 02

I think so Ohio3Wheels, what you can't see is that the two marks are opposite each other, one is about double the width of the other, I'm pretty sure it's just ejection dings. I will also try to remove cases without hard ejection, see if they are clean.

Being very over-cautious but as I say I'm a bit of a newb, and feel it's prudent to listen to more experienced shooters. I think with a necked cartridge that headspaces on the shoulder, their concerns would be more valid, esp if the case isn't whacked with a hammer blow on the way out.
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Re: Headspace issue on 357 92?

Postby GRV01 » 09 May 2018 05

Great thread, lord knows ive come here and posted all kinds of pics with questions of 'is this normal??' like a new parent with their first sick kid

I think youre getting closer to the answer, and i know my 92 in 357 is very sharp at the 'twelve oclock' of the mouth of the breech as if it was relieved by dremmel by some underpaid factory worker so it makes sense. When i get those cases i run the case gauge deburring tool over the case mouth and throw them back in the pile

Also i kinda chuckled at the concern over headspacing from those well intentioned gents at the range -- theyre used to shooting their rimless autoloader cartidges :)
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Re: Headspace issue on 357 92?

Postby FrankFisher » 09 May 2018 05

GRV01 wrote:Also i kinda chuckled at the concern over headspacing from those well intentioned gents at the range -- theyre used to shooting their rimless autoloader cartidges :)


Alas, not in the UK. The only semi-autos we're allowed are rimfire rifles....
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