Comparing two 7x57's cases after firing

[C.W. Richter]

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?

yes. in-fact, you can use any (similar length, large enough inside diam. 7 mm sizing die, so long as the body of the cartridge clears it, and it's not too long (i.e. you couldn't get the neck of the 757 far enough up a 7 STW die to make contact.) I use my 7mm WSM seating dies on the 757 AI. I do it all the time w/ various wildcats. Absolutely NO issues. I also use the 338 WM seating die on my 338-06 A-Sq, for example. It's only engaging the neck area. Nothing else.

 

[cash_tx]

yes. in-fact, you can use any (similar length, large enough inside diam. 7 mm sizing die, so long as the body of the cartridge clears it, and it's not too long (i.e. you couldn't get the neck of the 757 far enough up a 7 STW die to make contact.) I use my 7mm WSM seating dies on the 757 AI. I do it all the time w/ various wildcats. Absolutely NO issues. I also use the 338 WM seating die on my 338-06 A-Sq, for example. It's only engaging the neck area. Nothing else.

Thanks; that is great to know! If I can save the $100 from not having to get a set of custom dies made, that will be a bonus.

 

[fourfive8]

Yes... probably be able to use a Lee neck collet die to resize neck on that "improved" case for a reload or two. But sooner or later you'll have to size the body and "touch" the shoulder, otherwise, loaded cartridges will become harder and harder to chamber, or become impossible to chamber. In the long run you are going to need a custom sizing die made for that 7x57 improved chamber- whatever it is??

 

[C.W. Richter]

Neck sizing-only often proves most accurate (i.e. just neck size those perfectly fireformed in the AI chamber cases) for bolt guns. The full length dies will shrink the cases to a minimal dimension that allow for chambering in any gun. It also affects case life. (Less working, longer life.) I only FL size in pumps, autoloaders, levers (also recommended in singles/doubles), pistols and really long/fat chamberings that have quite a surface contact area brass:steel to ensure proper feed/extract in all weather conditions (i.e. 338-378 Wby, 333 A-Sq-3 in long, big diam cases) and all DG ammo. Never an issue w/ the relatively short, yet blown-out 757 AI. You're fire-forming "new" brass every time you shoot. Simply de-prime/neck size, trim, clean-up, re-prime, reload and you're good to go! I generally have no case stretching issues in anything containing 60ish gr powder or less (and the AI is low 50s), but that's the beauty of the AI designs (the FL resizing die IS your chamber!) Enjoy.

 

[C.W. Richter]

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.

275 Rigby Improved would be correct. You should have AI stamped on there in the future, but it's perfectly fine (part of the design) to fire std factory 757 ammo. I've yet to see 1 box of factory ammo that reads 275 Rigby.

 

[C.W. Richter]

OMT: 757 barrel twist rates have varied widely over the years. You may wish to check yours (push-spin cleaning rod w patch over brush to make tight/pen marks for 1 rotation and mark rod again at bore at 1 rotation/measure length) before jumping right into either heavy or light bullets. My neighbor's old Mauser was close to 1:8 (many more are 1:9) which were made for/favor the heavier 170s slugs, whereas other newer bbls can be 1:10 and only like the smaller (i.e. 130-150 gr) pills. LOL I'm sure someone sells a "gauge" for $15 (much like boresighters-unnecessary; in bolts, use the eyeball method to line up the bore on target and then adj the scope. I have on occasion not had to make any further adjustments after that! It simply works.)

 

[fourfive8]

That type sizing may be OK for bench rest/target ammo/guns/use. Many of those shooters are used to occasionally having a hard-to-chamber round. If shooting at a paper target, no issue. Just try another cartridge. Those tight chambers/cartridge fits are usually a bit more accurate as the case and bullet are kept closer to bore alignment during firing. But sooner or later those neck only sized rounds will become more and more difficult to chamber. That rifle does not look like a bench rest gun to me. It is a hunting rifle. The 275 Rigby or 7x57 label makes no difference... the "problem" round/fired case as pictured is not a standard anything. It is some version of an improved 7mm cartridge. Which one? Who knows. To automatically assume it is a "Standard Ackley Improved" or "Standard 275 Rigby Improved" is a wrong assumption. Many if not most of those improved chambers and the reamers that cut them are unique ventures done by adventuresome gunsmiths. At one time that type wildcatting was very common.

No matter, neck size only for a few reps and loadings and report back. Poking around the internet or this site looking for easy/slick answers or those you agree with can be a path littered with disappointments.

 

[cash_tx]

OMT: 757 barrel twist rates have varied widely over the years. You may wish to check yours (push-spin cleaning rod w patch over brush to make tight/pen marks for 1 rotation and mark rod again at bore at 1 rotation/measure length) before jumping right into either heavy or light bullets. My neighbor's old Mauser was close to 1:8 (many more are 1:9) which were made for/favor the heavier 170s slugs, whereas other newer bbls can be 1:10 and only like the smaller (i.e. 130-150 gr) pills. LOL I'm sure someone sells a "gauge" for $15 (much like boresighters-unnecessary; in bolts, use the eyeball method to line up the bore on target and then adj the scope. I have on occasion not had to make any further adjustments after that! It simply works.)

I'll have to dig out my notebook, but I actually did measure the twist rates on all three of my 7mm Mausers using the cleaning rod technique; and if memory serves, they all came it at around 1:9". I'll try to find my notes to confirm.

 

[cash_tx]

That type sizing may be OK for bench rest/target ammo/guns/use. Many of those shooters are used to occasionally having a hard-to-chamber round. If shooting at a paper target, no issue. Just try another cartridge. Those tight chambers/cartridge fits are usually a bit more accurate as the case and bullet are kept closer to bore alignment during firing. But sooner or later those neck only sized rounds will become more and more difficult to chamber. That rifle does not look like a bench rest gun to me. It is a hunting rifle. The 275 Rigby or 7x57 label makes no difference... the "problem" round/fired case as pictured is not a standard anything. It is some version of an improved 7mm cartridge. Which one? Who knows. To automatically assume it is a "Standard Ackley Improved" or "Standard 275 Rigby Improved" is a wrong assumption. Many if not most of those improved chambers and the reamers that cut them are unique ventures done by adventuresome gunsmiths. At one time that type wildcatting was very common.

No matter, neck size only for a few reps and loadings and report back. Poking around the internet or this site looking for easy/slick answers or those you agree with can be a path littered with disappointments.

Those are some good points, and I appreciate you making them. I don't foresee shooting this rifle heavily (too many others that occupy my attention), so just a few reloads per case will probably last me the rest of my natural life; but time will tell, and we'll see how much it actually gets hunted. With my low volume on this rifle, it might just be more practical to fire-form new brass every couple of cycles (if I even need that much).

 

[Bert the Turtle]

I agree that it appears to be improved of some sort.
whatever it is, a custom die set will sort you out : https://www.whiddengunworks.com/custom-reloading-dies/
Their dies are very well thought-of.

 

[AZDAVE]

It is a 275AI or 7x57AI based on what was put on the barrel.

Graf and sons has a set of fl dies for the AI in stock.

REDDING 7MMx57 IMP FL 2-DIE SET - Graf & Sons

Redding dies are made of the finest alloy steels obtainable and machined on Hardinge Super- Precision lathes capable of holding the tightest tolerances in the industry. To maintain tolerances and guarantee that your dies will last a lifetime, all Redding dies are heat treated in...

www.grafs.com

and a neck sizing die

7mmx57 Imp - Neck Size Dies by Caliber - Rifle Dies - Metallic Reloading - Graf & Sons

www.grafs.com

 

[C.W. Richter]

It's a 7x57 AI (40deg-look at the shoulder.) Many of Ackley's AIs were later further improved/standardized by RCBS so others (esp. .257x757 AI or Improved had either 28deg or 40deg shoulders. Yours is clearly the only commonly used 757 AI out there. And, if a std round fired into a 40 in that gun, a 28 would as well, but looking at your case, it's clearly 40 (nearly 1/2 way between 2 lines at 90). Measure your case against this info...This is the ONLY 757 AI variant shown in reloading databases, and that gun featuring the SS bbl is clearly much newer than any of the old AI developments.

 

[C.W. Richter]

That type sizing may be OK for bench rest/target ammo/guns/use. Many of those shooters are used to occasionally having a hard-to-chamber round. If shooting at a paper target, no issue. Just try another cartridge. Those tight chambers/cartridge fits are usually a bit more accurate as the case and bullet are kept closer to bore alignment during firing. But sooner or later those neck only sized rounds will become more and more difficult to chamber. That rifle does not look like a bench rest gun to me. It is a hunting rifle. The 275 Rigby or 7x57 label makes no difference... the "problem" round/fired case as pictured is not a standard anything. It is some version of an improved 7mm cartridge. Which one? Who knows. To automatically assume it is a "Standard Ackley Improved" or "Standard 275 Rigby Improved" is a wrong assumption. Many if not most of those improved chambers and the reamers that cut them are unique ventures done by adventuresome gunsmiths. At one time that type wildcatting was very common.

No matter, neck size only for a few reps and loadings and report back. Poking around the internet or this site looking for easy/slick answers or those you agree with can be a path littered with disappointments.

Sorry, I should have clarified-As these AI designs are older, every single Improved chamber gun I've had was based upon a CRF-style action, whether M98, Win, Montana, Dakota, et. al. with powerful claw extractors. NEVER any extraction issues even with the relatively high pressures involved in fireformed and Improved cartridges. As I said, if you're not really interested in it, there are a plethora of shooters out there that are! Use of the larger (now SAAMI-approved) 280 Rem Ackley Improved is commonplace now-with today's push feed/weaker extraction system guns/ammo still being manufactured for it, as an example. The efficient designs work well. Many AI designs only provides another 150 fps, and those may not be worth all the extra trouble. But the .257-6.5-7s turned out to be winners (some people use 22-250 AI, but i just say why? when the original will get the job done!)

On another note, most of the AI final (for production/custom re-chambering by PO Ackley) designs were 40 deg shoulders. RCBS later reintroduced the 28 deg shoulder in other chamberings (and it says so on the barrel stamps-Imp or Improved, NOT Ackey Improved or AI, and RCBS of course made dies for 'em that also specified the shoulder degree on the box labels!) There were no other common variants of the 757 AI than the tried-and-true 40 deg shoulder. I'd surmise that the owner of the gun (likely) or a smalltime gunsmith reamed the chamber out by hand and failed to stamp the barrel. A competent gunsmith wouldn't have omitted that step. My .257 Imp is the "newer" 28 deg design (the bbl is stamped correctly and the dies that came with it are labeled correctly as well.) I got the gun from an old-timer that used to belong to the Williamsport 1,000 yd range and just shot for fun. It was given to him as a gift from his past employer for years of great service (it even features the quarry name abbrev. on it TFQ-Ticonderoga Forge Quarries if I recall correctly.)

 

[cash_tx]

It's a 7x57 AI (40deg-look at the shoulder.) Many of Ackley's AIs were later further improved/standardized by RCBS so others (esp. .257x757 AI or Improved had either 28deg or 40deg shoulders. Yours is clearly the only commonly used 757 AI out there. And, if a std round fired into a 40 in that gun, a 28 would as well, but looking at your case, it's clearly 40 (nearly 1/2 way between 2 lines at 90). Measure your case against this info...This is the ONLY 757 AI variant shown in reloading databases, and that gun featuring the SS bbl is clearly much newer than any of the old AI developments.

View attachment 597396

Thank you for sharing this, and my case measurements line up near perfectly with the dimensions of that diagram; save for the Case Length of mine are about 0.010" shorter (probably due to a starting Case Length of 2.225"). More specifically, my case measurements clearly indicate a 40 degree shoulder. That being the case, I think we can comfortably confirm that this is a 7x57 Ackley Improved chambering.

This thread is one of the reasons I love this community and forum so much, and I greatly appreciate everyone's input. I think I'll continue my load workup on this rifle with the Hornady 154 grain spire points and IMR 4350 I was already working with, albeit now I know I can (carefully) go beyond standard 7x57 charges.

 

[cash_tx]

It is a 275AI or 7x57AI based on what was put on the barrel.

Graf and sons has a set of fl dies for the AI in stock.

REDDING 7MMx57 IMP FL 2-DIE SET - Graf & Sons

Redding dies are made of the finest alloy steels obtainable and machined on Hardinge Super- Precision lathes capable of holding the tightest tolerances in the industry. To maintain tolerances and guarantee that your dies will last a lifetime, all Redding dies are heat treated in...

www.grafs.com

and a neck sizing die

7mmx57 Imp - Neck Size Dies by Caliber - Rifle Dies - Metallic Reloading - Graf & Sons

www.grafs.com

Thanks for those links, and I will probably order that neck-sizing die pretty soon. In the meantime, does anyone know if I could use my regular 7x57 seating die for these AI cartridges; or should I just order the 2-die FL set in order to get the proper seating die? Not to mention, I'll probably need that FL resizing die at some point.

 

[C.W. Richter]

Thank you for sharing this, and my case measurements line up near perfectly with the dimensions of that diagram; save for the Case Length of mine are about 0.010" shorter (probably due to a starting Case Length of 2.225"). More specifically, my case measurements clearly indicate a 40 degree shoulder. That being the case, I think we can comfortably confirm that this is a 7x57 Ackley Improved chambering.

This thread is one of the reasons I love this community and forum so much, and I greatly appreciate everyone's input. I think I'll continue my load workup on this rifle with the Hornady 154 grain spire points and IMR 4350 I was already working with, albeit now I know I can (carefully) go beyond standard 7x57 charges.

When a person has reloaded very particular cartridges so many times, it's immediately recognizable! Yes, sidenote...although the std factory ammo will shoot fairly accurately through the improved chambers, the pressure and corresponding V drop off, so for hunting the AI cartridges are recommended. Both AI guns shoot superior 5-shot groups even using cheap factory ammo (for fireforming purposes.) This was 5 federal blue/white box 140 and 5 Aussie 130s my neighbor had given me because his 757 std only liked the heavier pills. And for Africa, I'd go with the 160s-175s on PG! The SDs provide great penetration.

 

[C.W. Richter]

The cartridge case you have may have been trimmed for reloading, or simply shortened a bit during fireforming. poss. explanation for the -0.010" Perfectly fine to be a bit shorter (but trim to make all consistent unless only 1 is short.) It's the longer than Std. case lengths that will cause hangups upon closing the bolt. No issue with slightly shorter.

 

[Bob Nelson 35Whelen]

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.

View attachment 597147

Commercial FN marked "275 Rigby"
View attachment 597148

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

View attachment 597149

@cash_tx
The one in the left is a standard 7x57. The other with the sharper shoulder definitely screams 7x57 Ackerly Improved.
Just the opinion of a mad wildcattr
Bob

 

[Bob Nelson 35Whelen]

Sorry, I should have clarified-As these AI designs are older, every single Improved chamber gun I've had was based upon a CRF-style action, whether M98, Win, Montana, Dakota, et. al. with powerful claw extractors. NEVER any extraction issues even with the relatively high pressures involved in fireformed and Improved cartridges. As I said, if you're not really interested in it, there are a plethora of shooters out there that are! Use of the larger (now SAAMI-approved) 280 Rem Ackley Improved is commonplace now-with today's push feed/weaker extraction system guns/ammo still being manufactured for it, as an example. The efficient designs work well. Many AI designs only provides another 150 fps, and those may not be worth all the extra trouble. But the .257-6.5-7s turned out to be winners (some people use 22-250 AI, but i just say why? when the original will get the job done!)

On another note, most of the AI final (for production/custom re-chambering by PO Ackley) designs were 40 deg shoulders. RCBS later reintroduced the 28 deg shoulder in other chamberings (and it says so on the barrel stamps-Imp or Improved, NOT Ackey Improved or AI, and RCBS of course made dies for 'em that also specified the shoulder degree on the box labels!) There were no other common variants of the 757 AI than the tried-and-true 40 deg shoulder. I'd surmise that the owner of the gun (likely) or a smalltime gunsmith reamed the chamber out by hand and failed to stamp the barrel. A competent gunsmith wouldn't have omitted that step. My .257 Imp is the "newer" 28 deg design (the bbl is stamped correctly and the dies that came with it are labeled correctly as well.) I got the gun from an old-timer that used to belong to the Williamsport 1,000 yd range and just shot for fun. It was given to him as a gift from his past employer for years of great service (it even features the quarry name abbrev. on it TFQ-Ticonderoga Forge Quarries if I recall correctly.)

@C.W. Richter
Good ol P.O said of all the cartridges he developed only a few showed any worthwhile increase in velocity. Some of those were the 25-35, 250 Savage, 257 Roberts, 7mm Mauser, 30-30 the 300 H&H and a couple of others. A lot showed no worthwhile gain in velocity but did improve case life.
His books make great reading
Bob

 

[C.W. Richter]

The 7x57 AI is just Perfect for international travel, including African PG hunting....IF, God forbid, your ammo should go missing (and I know this NEVER happens LOL, Namibia <cough, cough>) you can still fire any available factory stuff which is quite popular outside the US. 7x57 is stocked by my local, high end/specialty outdoor stores (5 within reasonable driving distance), so it's available in the US as well.