I had posted this before. It is in regards to my wife's rifle (7x57) having a chamber I think is not round. The fired cases of near max loads have a visible swelling around 2/3's of the circumference of the case approximately 0.3" from the base. I mean from the base of the cartridge everything looks good for 0.3" and then this swelling. I do not have any more cartridges with me so I cannot measure them. If memory serves and I am looking at my calipers correctly I think the swelling is around 0.030" or thereabouts.
I have never seen any chamber like this. I am not too concerned with accuracy, this rifle will shoot 2" groups with any bullet over 140gr. I have hardly practiced with it and my wife hasn't had the chance to shoot it much either. Meaning if we had the time I know these groups could shrink.

Euro-Imports has received the barrelled action and took the two cases I sent to two different gunsmiths and also contacted the Brno factory. The 'smiths stated the swelling is "absolutely normal" and the factory stated, "if anything were wrong it would occur at the igniter". I think they mean primer.

Should I be satisfied with this? Or should I demand a new barrelled action to replace this one? There is nothing wrong with the functioning and any case looks great after I pass it through my Redding full-length die. The thought is what bothers me so I wonder if I am just barking at the moon?

Any thoughts on this would be appreciated as I will email George Tripes (owner of Euro) back and either demand a new one or send the existing one back. If he sends one then I will have to pay 10% of the worth to gunshop to transfer so I am looking at ~$60.00. Return mail for existing would be only ~$12.00.
Thanks. Roger

Roger,

I suspect the proper way of sorting this out would have been to take a cast of the chamber. I suspect (from a cost point of view) this should have been your first course of action as it would armed you with
proof of the condition of the chamber. From that you could establish if the chamber is with in specs....have the factory provided
written specs??? the other factor of course
is your confidence...if you keep this action, will this always be nagging at the back on your mind?? If so $60 is cheap for what it will bring you....As an aside, most CZ I have seen will average 1" groups if time is spent in load developemnt.....

Pete,
I would have had to order some cerro-safe to make the cast and I thought with the blown-out case from a strong load would give an indication of what was already there. I thought it was abnormal. Apparently the chamber is within specification for a 7x57 Mauser. The specs must be awfully loose though! Oh well, I have used custom 'smiths for any work done and I guess I am spoiled. When I fireform .375 H&H out to .375 Weatherby you cannot see any marks on the case the chamber was so well done. Same with my .500 A-Sq. As a hunting rifle this is fine. I'll wait 'till tomorrow to call him.

.030 eccentric would be outside anybody's specs.

Don

.American SAAMI standard brass is quite a bit smaller than European at the head. If the extractor forces the case to one side of the chamber you may get an eccentric base, not oval.
.The handloader's cure is to center the case for the initial firing, then take care to avoid sizing back. This will equalize the swelling all around. I use masking tape on the base of the case for the first firing.
.You may be able to find European brass that is better in this regard.
.I hope that your chamber is not indeed oval.
.Regards,
Ross

Roger,

Though I have never done it, you can also make a chamber casting using just Sulfur, available at most large pharmacies for just a couple of dollars. Just a thought.

What is the diameter of the unfired brass? SAMI chamber specs call for a chamber diameter at the datum line (.200 from the base) of .472. I have been measuring some of my 7x57 brass and most is in the .461-.464 range. This will result in the unsightly "bulge" you are refering to. Oh Sami specs for the brass is .471, but the only company I know of that even comes close to Sami specs with their brass is Lapua.

RR, Check your tolerences on new brass or ammo before you fire it. You may have brass that is close to the minimun saami specs. Your chamber may be closer to or at the max saami specs. If this is so you may have to find brass that is closer to your chamber specs. I recently had this problem in a 7mm08 in Win brass,it was close to min saami, I switched to Rem brass which was mid saami specs and eliminated the swelling problem. I think saami allows for a .010" variance at the base ahead of the extractor groove. But if the swelling is .030" you better make a chamber cast.

[This message has been edited by sure-shot (edited 09-12-2001).]

If it was my rifle I wouldn't worry about it.And since I load my own ammo, I would probably just neck size some rounds just for fun to see what the difference in accuracy was. Also., if really worried about it, have it rechambered. This is simple and not too expensive, especially if it doesn't have sights.

[This message has been edited by Bubba John (edited 09-14-2001).]

To me it sounds like your chamber is plain and simple oversize in diameter. Factories have large reamers when they are new, to allow for regrinding, and thus the first chamber cut with a new reamer will be maximum in diameter.
Your problem is very common, because when you fire factory ammo, or ammo reloaded on full lenght sized cases, the case will be significantly smaller in diameter than than your chamber, and it will settle on the bottom of your oversize chamber. When fired, the case will expand in the directions where it is the most room, that is upwards and to the sides. At the bottom it will be little or no expansion visible, thus giving the impression of a out of round chamber. In cases like this, neck sizing will most probably give you better accuracy.