9.3x57 sloppy chamber?

I was testing loads with factory 9.3x57 brass not fire forming
The inconsistency would be due to increasing the powder charge with each load…


Current plan: back off the load to where the case stretching disappears and use that as my fire form load

Or try to trade it for a bigger cartridge
 
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Potashminer said:
There will not be any case body stretching occurring, if the shoulder is within a thou or so of the chamber shoulder, and the case head hard on the bolt face - the idea of sizing new, never fired brass to make that "false shoulder" is so the case body fire forms to the chamber with no stretching going on. Once you have the case matched to the chamber, do not want to re-size it any more than needed to re-chamber - so do not want to push that case shoulder back again, regardless of how the die instructions say to do re-sizing. Can not "undo it" however - I have seen on multiple 303 British - factory fired cartridges - definite ring inside felt with wire. Nothing that you can do to "undo" that - was done on that first firing of a case that was not tight - case head to shoulder - in that chamber. (For rimmed case like 303 British, also requires some "slop" in the headspace dimension for that case rim)

Just inserting a factory cartridge in an over long chamber and fire it, may not be fire forming it without that "incipient case head separation" - under firing pressure, the case is going to expand in every direction to fill the chamber - I think starting by grabbing chamber walls first. If there was "slop", the firing pin moved the case forward in the chamber - hence the case head is going to get blown back tight to the bolt face - stretching that case wall area just in front of the case head, which creates that "ring" - if the distances involved exceed the "spring back" within the brass alloy. I think.
Click to expand...

Exactly.

OP: your chamber is long, this is a headspace issue and common with 9.3x57 rifles. The brass is shorter than the chamber on first firing and will "grow" to fit the chamber in one of two ways:
1. the case can stretch at the rear (bad)or
2. the case reforms at the shoulder/neck (good).

To make the brass reform at the shoulder and neck the cartridge needs to be forced all the way back to the bolt face. In this condition the case will reform at the shoulder and neck and after that you do not want to do FL resizing on that brass, just neck size and may need to bump the shoulder back lightly some times if there is resistance chambering. Also You can neck size with FL dies, you don't need to buy neck sizing die.

People have wrecked a fair bit of factory 9.3x57 brass by not fireforming on the first firing. After that the damage is done, the base is stretched and there is no going back, depending on the individual chamber dimensions it may be ok or it may fail next firing. But if the case is fireformed properly using an oversize expander or long cast bullet method then that brass will be safe to use for many reloadings.
 
OP - something to try - if you have any brand new brass left. I can not find an actual 9.3x57 GO gauge to buy. Looking at 30-06 specs, a FIELD gauge is about .010" longer than GO. So GO is absolute minimum length; FIELD is supposed to be absolute maximum. Your new brass will be somewhere in between - likely closer to GO, but you do not know what you have for your chamber. So, computer printer paper is about .004" thick. Cut a number of .400" circles and set on your bolt face and try to close on your chamber with a new case - might let you discover how much longer is your chamber, than is your new brass. Would not surprise me with an older 9.3x57 that you might get 4 or 5 thickness in there - your chamber could be that much longer than your brass...
 
So on my milder loads where the neck has shortened and only the should has changed is the fire form not complete? Using factory privi bullets and loading to length with a reasonable powder charge will not fireform the case correctly?

I don’t doubt the chamber is long or your expertise on this matter, I’m honestly asking. I believe I had 2 issues here: the long chamber and some of my loads going over pressure resulting in the stretching. Is this correct?

I was planning on backing off the full length die and using it to size the necks? After using a universal decapping die?

Maybe I could also try seating a bullet backwards and getting some idea of the length by where the rifling kicks in?

This might be beyond my capability as a reloaded, I was apprehensive of this cartridge for years because of stuff like this. Maybe someone else will enjoy it more or maybe I should suck it up and get tinkering
 
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conor_90 said:
So on my milder loads where the neck has shortened and only the should has changed is the fire form not complete? Using factory privi bullets and loading to length with a reasonable powder charge will not fireform the case correctly?

I don’t doubt the chamber is long or your expertise on this matter, I’m honestly asking. I believe I had 2 issues here: the king chamber and some of my loads going over pressure resulting in the stretching. Is this correct?

I was planning on backing off the full length die and using it to size the necks? After using a universal decapping die?

Maybe I could also try seating a bullet backwards and getting some idea of the length by where the rifling kicks in?
Click to expand...

With long headspace your load does not need be hot to damage the brass. A chamber that is the correct dimension does not have space for the base to stretch overly at normal pressure, but with a long headspace chamber the brass will stretch and thin at the base if you don't use a method to prevent it.
 
OP - so, you are not dealing with a modern rifle or modern way of doing things - do not know what you have, but could have been made in 1940's or earlier. 9.3x57 was introduced in 1900 - as previously mentioned I can not even find consistent specs for what it is supposed to have been - Norma and CIP publish different numbers - different sizes. So, your rifle is what it is. As described above, you can check how far out of spec it might be - to satisfy your curiosity. Once know to be "out-of-spec", need to shift your re-loading a bit from what works with "modern, in-spec" stuff. In effect, you are going to form cases to correctly fit whatever your chamber wants - as that chamber is today. That is what is getting you into fire forming - to force that case head to sit tight on the bolt face and let the firing pressure blow out the rest of the case to match to your chamber. Will not work if you allow that case head to move forward when fired - that is where the "separation" business originates. As previously mentioned, you can force that case head to sit tight on the bolt face by creating a "false shoulder" on that case, or by using a very long seated cast bullet - but just dropping in a new case into a chamber loaded with standard commercial products is not likely to be correctly "fire forming" that case.
 
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Thanks for your well thought out responses gentlemen

I guess nothing in this life can ever be easy lol

Is the “beehive” shape of the shoulder on both the low pressure load that shortened and the cases which stretched at the base what suggests to you the fire form is not complete?

Jet hunter is your cast bullet solution to use pistol powder and a long bullet seated far out to fill the chamber?

Edit: seems like this is the way, thanks PM
 
Should be a picture below of a casting of the 9.3x57 that I am still working on - chamber, throat, "ball seat", lands, etc. So those were brand new PPU 8x57 brass. I forced a series of larger expander balls, until I got the brass case almost "straight walled". Then started them into a 9.3x57 FL die - size a bit - try in rifle - bolt won't close. Turn die in a bit more, size again, try in rifle. And repeat multiple times until about 1/16 of die rotation so that I could just barely close the bolt - that tells me that those cases are tight between the bolt face and the chamber shoulder. They will not move back / forward when fired - just going to expand outward and blow out the shoulder to nearly perfectly match that chamber. There should be a bit of "spring back" to that brass, so the case should extract. When reloading it / resizing it - I will not want to push that shoulder back at all.

My dilemma was that I could not reach the lands to know how long to seat the bullets. So I did a cerrosafe cast. Others have commented that this is about as squirrelly as can get - can see that the bullet will be a long way out of the case mouth, before the fat part of the bore rider bullet hits the rifling. That is all for the next part of the project.

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"Long bullet" - yep - I could not reach with a 286 Partition for my 9.3x62, seated backwards - hence why the "false shoulder" was only thing that I could think of, that would work. And, to repeat - others who know more about these than me, have said this is a VERY long "ball seat" - even for a Husqvarna 9.3x57. Your's might be half or less - or similar!!!!

You might notice there is a lot more neck length cut in that chamber, than the length of necks that I got from my cases - and I expect cases to get shorter when I fire form them. Why I mentioned earlier, that "next time", I would probably start with 30-06 brass - and would know the neck length would be "better", but no clue how that will work for case neck thickness - have not tried it yet... Whole objective is to make brass that will fit to this chamber - warts and all!!!
 
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Hey, jethunter - a BIG PLUS 2 for that link that you gave and the mention of that Darryl S guy - was the same reference as given to me some time ago by CGN's WhyNot? guy - Darryl S definitely "knows his stuff" when it comes to playing with 9.3x57, so far as I have learned, by following the advice given!!! To be honest, some of the stuff that you have posted here and elsewhere is not too shabby, either!!! :)
 
I've thought of putting a wrap of teflon thread tape on the bullet ahead of the case neck over the ogive to add about .003" to the bullet diameter. Maybe .002" if you stretch the tape. Just enough to give some resistance for chambering to hold the brass back against the bolt face for proper forming. Probably a good reason why it wouldn't work. Maybe some risk of having it left behind in the barrel? Theoretically to me it shouldn't be much different than paper patching. So what am i missing?
 
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I will be back

I would love one of these in a SAAMI chamber on a small ring 98

I have to say I’m pretty keen on the m96 sporter as well, and I do wonder if these issues will present themselves in 8x57, 30-06 and 9.3x62 models

Also you never know if anyone will buy it lol
 
Issues - I must admit to never having played with chamber casting in the three cartridges mentioned in a M96 based rifle. But, is sometimes an issue that the m96 magazine is shorter than is found in the m98. I have a STIGA rifle - so a conversion from an m96 type that is chambered for 30-06 - has the proof marks - so "strong enough" to pass CIP pressure tests - but can see underneath that the magazine box was lengthened, and that required some material to be milled out of the underside of the receiver, right behind the lower bolt lug recess. Had heard similar "length" issues in m96 based 9.3x62 - do not know if those were a commercial product, or if someone just screwed on a pre-chambered barrel, or if someone just reamed out the original chamber from 9.3x57. What lead me to appreciate the proof testing requirements in Europe - no doubt in my mind that the resulting rifle was "strong enough" for factory ammo. I had been told, but never confirmed, that STIGA rifles also have longer than normal "free bore" area - was a way to relieve some breach pressure - was done for sure in the Weatherby early days "big boomers" that would otherwise have had some pretty scary breech pressure numbers without that relief.
 
Potashminer said:
Had heard similar "length" issues in m96 based 9.3x62 - do not know if those were a commercial product, or if someone just screwed on a pre-chambered barrel, or if someone just reamed out the original chamber from 9.3x57
Click to expand...

Husqvarna made about 220 Model 46AN 9.3x62 using M96 based actions during ww2 when FN98 actions weren't available, Belgium being occupied by the Nazis at the time. These rifles didn't have the thumb cutout on the left side and the barrels were marked "Svenskt Nikelstal Antioxid". The magazine was not stretched.

Most M96 9.3x62 rifles were built by Stiga and Vapenfabriks Falun from milsurp rifles, and likely some gunsmiths did conversions on milsurp rifles too.
 
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Had been a poster here on CGN some time ago - as I recall, could not get his 9.3x62 ammo to go into his "mauser" magazine. I do not remember if factory ammo, or hand loads. After a bit, was discovered he had a Mauser 96 - so likely a 3.2" magazine. Typical Mauser 98 often 3.3" or 3.4". Looking at my Nosler #9 book, they identify COAL at 3.291" as tested with both 250 Accubond and 286 Partition - so would be problematic with a 3.2" internal length magazine if you went solely from that "book".
Checking the others in the Nosler 9 book - 30-06 Springfield is showing as 3.340"; 8mm Mauser (8x57) is showing as 3.250" - both would also be problematic in an unaltered 3.2" magazine.
 
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