9.3x62 case web expansion

[Jon87]

Anybody ever see expansion at the case web like this with 9.3x62? It’s enough that I can feel and see the transition. It’s a little hard to photograph but you can see diameter change right at the cloudy line ahead of the extractor groove.

I’m new to 9.3x62 but not to reloading. I was going through a charge ladder with a new Tikka and new Lapua brass, Barnes TTSX 250, Varget. I know there’s always expansion with brass, but I’m used to seeing more like 0.003” at the most, this is closer to 0.009”. This is just at the web, the case head itself is not changing. These aren’t hot loads at all, 2200-2400 fps. I was thinking my chamber might be oversized or headspace was off when I saw this and stopped. No other pressure signs whatsoever.

I checked the inside of the brass with a paperclip and bore camera. It doesn’t look like case head separation is about to happen. Case length and everything measures normally, just the case diameter that seems odd.

After digging into the specs a little, this seems like it would be typical but I’m looking for a sanity check. The CIP spec says a max cartridge diameter of 0.476” and a min chamber of 0.478”. The hornady manual says 0.467” for the case diameter, which must be either the min or nominal I guess. The unfired Lapua brass measures 0.468” at the web. Just by those values it seems like my chamber is cut to the minimum CIP dimensions and the 0.009” expansion was inevitable. It just looks like a lot.

I haven’t resized any yet, but my redding die measures 0.473” at the base so this area shouldn’t be worked quite as hard on subsequent firings.

 

[track]

I've witnessed case-bulge on belted cartridges, however not on standard bottlenecks. Once you full length resize it and dosen't fit into the chamber, than you will require the Larry Willis die to return it back to spec's. My son's go-to rifle is a Cooper chambered in the 7mm STW. He has this issue with his rifle/cases and the Larry Willis die is a great tool to fix the problem.

 

[Longwalker]

That is surprising for Lapua brass. It is a known, common issue with Hornady cases in the 9.3x62, since Hornady use standard 30-06 base diameter basic brass for forming their 9.3x62 brass, and 9.3x62 base is supposed to be a few thousands bigger. Maybe Lapua got lazy too. Probably not dangerous to use as - is, but I'd be a little unhappy with that much case expansion if it was my rifle.

 

[Jon87]

Didn't think to check that. I have some new Lapua 30-06 brass here too I just compared. They measure exactly the same so that's for sure what they're doing. I'm also a little surprised. This is the first time I've been disappointed with Lapua brass. Per SAAMI, the 30-06 case can be 0.4618-0.4698" and 9.3x62 can be 0.4674-0.4754" at the 0.200" line. My 9.3x62 Lapua brass at 0.468" is technically in spec I guess but it pretty much guarantees this expansion is going to happen. Lame

 

[Jon87]

So...which brass to use then that won't do this? PRVI? Norma?

 

[Potashminer]

Is possible that no brass will fire in your chamber without showing that - I presume today's makers want to get really close to minimum, but still to be within SAAMI spec - uses least amount of material - versus chamber / barrel makers - probably re-sharpen their reamers until their chambers are almost to maximum size - minimum sized brass into maximum sized chamber likely going to do as you show - on other hand, I do not see that, in my loads - which John Barsness say are at 30-06 level pressure - more than 9.3x62 pressure max - using PPU brass in my Husqvarna made rifle - might be the brass; might be the chamber it was fired in.

 

[65cutlass]

Have you tried the fired case back into the chamber?. I would try that, and again with 1 piece of masking tape on the case head. ( kind of like a go- no go gauge). Your case should be fireformed to your chamber , and it doesn't get any better than that.

 

[Potashminer]

I've witnessed case-bulge on belted cartridges, however not on standard bottlenecks. Once you full length resize it and dosen't fit into the chamber, than you will require the Larry Willis die to return it back to spec's. My son's go-to rifle is a Cooper chambered in the 7mm STW. He has this issue with his rifle/cases and the Larry Willis die is a great tool to fix the problem.

I have a Larry Willis die - seems to work just fine to resize the body right in front of the belt on a belted case - where a Full Length resizing die does not seem to have any effect - perhaps 1/16" or so ahead of the belt. I do not think it does anything on a case with no belt - not sure if that Larry Willis company makes different sizes or not?

 

[Jon87]

Have you tried the fired case back into the chamber?. I would try that, and again with 1 piece of masking tape on the case head. ( kind of like a go- no go gauge). Your case should be fireformed to your chamber , and it doesn't get any better than that.

I'll try that tonight

 

[Jon87]

Is possible that no brass will fire in your chamber without showing that - I presume today's makers want to get really close to minimum, but still to be within SAAMI spec - uses least amount of material - versus chamber / barrel makers - probably re-sharpen their reamers until their chambers are almost to maximum size - minimum sized brass into maximum sized chamber likely going to do as you show - on other hand, I do not see that, in my loads - which John Barsness say are at 30-06 level pressure - more than 9.3x62 pressure max - using PPU brass in my Husqvarna made rifle - might be the brass; might be the chamber it was fired in.

That makes sense. The lapua 30-06 brass I have here is close to max and the 9.3x62 brass is close to min though in that narrow bit of overlap in the allowable range between the two cartridges. I'm actually working up a load for a new Tikka 30-06 at the same time as the Tikka 9.3x62. Based on the measurements it sure seems like both chambers are cut to min. Could just be a coincidence

 

[Jon87]

Have you tried the fired case back into the chamber?. I would try that, and again with 1 piece of masking tape on the case head. ( kind of like a go- no go gauge). Your case should be fireformed to your chamber , and it doesn't get any better than that.

The fired case still chambers fine. Fired case with tape does not. Unfired case with tape also chambers fine. The tape adds 0.005". The chamber seems to be as it should and near min spec

 

[4fifty8]

FL resized case 0.471", fired case 0.474" (+/-0.001") for handloads in my 9.3x62 Anschutz 1782 case expansion looks like this no visible/feelable bulge. https://i.imgur.com/FuSYoty.jpg / https://i.imgur.com/tzyXIij.jpg

 

[Jon87]

FL resized case 0.471", fired case 0.474" for handloads in my 9.3x62 Anschutz 1782 case expansion looks like this no visible/feelable bulge.

Thanks. That's more like what I would've expected to see. How many firings do you have on the PPU brass? I've read mixed opinions on it, but there aren't a whole lot of options out there.

 

[4fifty8]

You're welcome resized more than a few times think for next batch I'll just neck size.

 

[track]

I have a Larry Willis die - seems to work just fine to resize the body right in front of the belt on a belted case - where a Full Length resizing die does not seem to have any effect - perhaps 1/16" or so ahead of the belt. I do not think it does anything on a case with no belt - not sure if that Larry Willis company makes different sizes or not?

Maybe Small Base dies would do the trick, if they make them for this cartridge.

 

[4fifty8]

9 thousandths of an inch expansion is excessive sounds like your chamber dimensions are off spec?

 

[Jon87]

9 thousandths of an inch expansion is excessive sounds like your chamber dimensions are off spec?

That's what I thought too at first. The unfired brass is 6 thousands smaller than expected though.

 

[Jon87]

Though it could be either issue. Or both. Or something else entirely haha

 

[4fifty8]

New unfired PPU brass 0.471" dia. rcbs FL sizing die done good.

 

[Longwalker]

This got me curious. So I measured a bunch of the various brands of 9.3x62 brass I have on hand.
A variety of manufacturers and dates. All measured just in front of the extraction groove, on the thickest part of the web.

Lapua - new recently made factory loads: 0.468"
Lapua - old stock new brass: 0.471"

Norma - old 3x fired: 0.475"
Norma - New factory loads 2 lots: 0.473" 0.472"
Norma - old stock new brass: 0.471"

Federal - Premium fact. load: 0.472"

Hornady - fact. load: 0.466"

PPU - Old Fact. load: 0.466
PPU - new recently made brass: 0.471"

S&B - 1x fired: 0.472"

It appears Lapua has recently changed to a "slimmer" base diameter, similar to Hornady.
The rest are all reasonably consistent except PPU, apparently they made some "slim" ones in the past too. I'm glad all 200 of my new PPU brass is the fatter version.