Comparing two 7x57's cases after firing

[cash_tx]

I'm curious to figure out why there is a difference between the fired cases from two of my 7x57 rifles. I inherited both of these rifles from my late father, and don't know the history on either of them. One is a custom build on a surplus Fab. Nat. D'armes De Guerre Herstal M98-style action with a stainless barrel marked "7x57", while the other is built with a commercial FN M98 action and an aftermarket barrel with "275 Rigby" laser-etched on the top. The fired cases from the 7x57 with the stainless barrel (on the left in the picture below) look similar in appearance to unfired factory ammo in terms of case length (2.225") and shoulder angle. However, the fired cases from the "275 Rigby" (on the right in the picture below) have a visibly steeper shoulder angle and it looks like the case shoulder has pushed forward after firing (although, the overall case length is slightly shorter at approx. 2.220"). Both cases in the picture below are from the same box of Hornady ammo, but I see this with other brands that have been run through these rifles. The fired cases from the "275 Rigby" are difficult to pass through my full-length resizing die (even though properly lubricated); much more difficult than the cases from the other rifle, which pass through the die normally. I'm curious to know what this means as it relates to my "275 Rigby"; is this anything I should be concerned about? I do have a Lee Precision collett die in 7x57, so I can still neck-size the cases; and reloading them for that rifle shouldn't be a problem. It's just bugging me to know why the noticeable difference here. I appreciate any insight from the fellow members.

Commercial FN marked "275 Rigby"

Surplus Fab. Nat. D'armes DeGuerre marked "7x57"

 

[Tgood1]

very interesting. cant wait to read some answers

 

[Tundra Tiger]

I saw a post on a Nosler reload forum. The guy had two cases that looked identical to what you have. He was fireforming new cases and the one on the right (in your photo) was actually 7x57 Ackley Improved - it's the cases he was creating. So maybe one of yours is that? An AI?

 

[Huvius]

Looks to me to be a 7X57 AI chamber not necessarily anything to do with Rigby which was simply a renamed 7X57 with lighter bullets.

 

[flatwater bill]

The chambers are certainly different. Probably intentionally "improved" on the right. AI is very common, but there were many other shoulder angles not just 40 degrees that Ackley liked. If they head space correctly, keep shooting 'em. Standard cases fired in an improved chamber are often very accurate......FWB

 

[cash_tx]

I saw a post on a Nosler reload forum. The guy had two cases that looked identical to what you have. He was fireforming new cases and the one on the right (in your photo) was actually 7x57 Ackley Improved - it's the cases he was creating. So maybe one of yours is that? An AI?

That was one possibility that crossed my mind as well - could it be that the "275 Rigby" is actually a 7x57AI? I'm hoping another member who actually has a 7x57AI can chime in and maybe confirm.

If that proves to be the case (no pun intended), I'll just simply neck-size the cases for the AI rifle and make sure to keep them segregated from the cases for my regular 7x57s.

 

[IvW]

It is not a 275 Rigby....if that is a fresh case from chamber it was very badly done

 

[cash_tx]

Looks to me to be a 7X57 AI chamber not necessarily anything to do with Rigby which was simply a renamed 7X57 with lighter bullets.

Thanks, and yeah; I think the "275 Rigby" laser engraving in this case is simply a matter of desired aesthetics on the part of whomever built the rifle.

 

[cash_tx]

It is not a 275 Rigby....if that is a fresh case from chamber it was very badly done

As some of the others have said, I think it might actually be a 7x57 Ackley Improved; although it was not marked that way.

 

[IvW]

Looks lika a AI....but the case is rough.....

 

[cash_tx]

Looks lika a AI....but the case is rough.....

I'll double-check, but I think those scratches are from trying to pass it through the FL sizing die. I pushed pretty firmly on it, but stopped short of deforming the case or getting it stuck in the die. I resized several other cases from the regular 7x57 afterwards, so I know the die is ok.

 

[IvW]

Ok that will explain it then

 

[Rez Exelon]

Looks AI but to be sure a chamber cast and calipers are in order. And if it is 7x57AI then adding some new lettering to the barrel might be advised too. I would just take a wild guess that it was rechambered and then the barrel marking was left off. Or possible marked in an area not visible without removing the action from the stock.

 

[cash_tx]

Looks AI but to be sure a chamber cast and calipers are in order. And if it is 7x57AI then adding some new lettering to the barrel might be advised too. I would just take a wild guess that it was rechambered and then the barrel marking was left off. Or possible marked in an area not visible without removing the action from the stock.

That's good advice, and I will remove the barreled action from the stock to check underneath for any additional markings. I had it out of the stock a few months ago, but don't remember noticing anything at the time; but I'll give it another look. Thanks!

 

[IvW]

Just measure a fired case no need to chamber cast

 

[C.W. Richter]

757 AI (you can continue to shoot factory ammo if you like, but the Improved 757 is one of P.O. Ackley's most efficient works-as is the 257 AI (257-757). I have one of each and both are superbly accurate and quite the velocity increases over the std chambering (in the 757 AI you can get 3,150-3,250 fps using 140-130 grain bullets.) That's nearly 7 RM performance. And the accuracy!!! The AI has a big following in the US; you'll have no trouble selling it for a decent price, if desired! Someone may have reamed the chamber themselves (but should've stamped AI or Improved on the bbl.) I've only taken 2 deer with this "safe queen" lol; 1 @ 250 yds, another at 300 (and this past season I missed one at 400 yds on a rushed shot I should't have attempted.) lol I DID bag an overhanging tree limb and tree trunk (the limb i didn't see in the scope, 20' in front of the deer)! I'll have to find the pic of that...friends would not allow me to let it go. lol IF that hickory tree is dead this year, I'll cut that segment out and hang it on the wall next to the other deer!

 

[cash_tx]

757 AI (you can continue to shoot factory ammo if you like, but the Improved 757 is one of P.O. Ackley's most efficient works-as is the 257 AI (257-757). I have one of each and both are superbly accurate and quite the velocity increases over the std chambering (in the 757 AI you can get 3,150-3,250 fps using 140-130 grain bullets.) That's nearly 7 RM performance. And the accuracy!!! The AI has a big following in the US; you'll have no trouble selling it for a decent price, if desired! Someone may have reamed the chamber themselves (but should've stamped AI or Improved on the bbl.) I've only taken 2 deer with this "safe queen" lol; 1 @ 250 yds, another at 300 (and this past season I missed one at 400 yds on a rushed shot I should't have attempted.) lol I DID bag an overhanging tree limb and tree trunk (the limb i didn't see in the scope, 20' in front of the deer)! I'll have to find the pic of that...friends would not allow me to let it go. lol IF that hickory tree is dead this year, I'll cut that segment out and hang it on the wall next to the other deer!

That's very helpful info and great to know; and that picture of your grouping has me excited to keep doing the load work-up for it! . I am swimming in 154-175 grain 7mm bullets and IMR 4350 powder, so hopefully I'll find a good combo that this rifle really likes. BTW - your 7x57 AI is one beautiful rifle!

PS - kind of weird that the builder (whomever it was) chose to do this for the caliber marking, rather than 7x57 AI.

 

[cash_tx]

757 AI (you can continue to shoot factory ammo if you like, but the Improved 757 is one of P.O. Ackley's most efficient works-as is the 257 AI (257-757). I have one of each and both are superbly accurate and quite the velocity increases over the std chambering (in the 757 AI you can get 3,150-3,250 fps using 140-130 grain bullets.) That's nearly 7 RM performance. And the accuracy!!! The AI has a big following in the US; you'll have no trouble selling it for a decent price, if desired! Someone may have reamed the chamber themselves (but should've stamped AI or Improved on the bbl.) I've only taken 2 deer with this "safe queen" lol; 1 @ 250 yds, another at 300 (and this past season I missed one at 400 yds on a rushed shot I should't have attempted.) lol I DID bag an overhanging tree limb and tree trunk (the limb i didn't see in the scope, 20' in front of the deer)! I'll have to find the pic of that...friends would not allow me to let it go. lol IF that hickory tree is dead this year, I'll cut that segment out and hang it on the wall next to the other deer!

So, a follow-up question on this: Can I use my regular Lee Precision 7x57 collett die to neck size the 7x57 AI cases, or do I need to get a neck-sizing die specific to 7x57 AI?

 

[Bush Buck]

I would give Lee Precision a call and talk to them about it. They have been very helpful to me in the past. They might even make you a full length die if you send them some fired brass.

 

[cash_tx]

I would give Lee Precision a call and talk to them about it. They have been very helpful to me in the past. They might even make you a full length die if you send them some fired brass.

Thanks, and good advice. I was looking at their website last night, and it seems that they will make a set of custom dies for about $100 if you provide them some measurements and a few fired cases. I'll probably do that.