7mm08 Confusion

[Mulligan]

There is some debate about whether the 275 is a variant of the 7X57 or merely a higher pressure, lower bullet weight loading. It is definitely the latter, utilising a 140gn Spitzer as its primary loading at a time when 173/175gn RN bullets were the norm and loaded for Rigby's Mauser '98 action based rifles to rather higher pressures than the original 1892 level for the previous generation Mauser (small-ring) rifles. I've read a few times it has a marginally different chamber, but 7X57 ammunition can be fired safely in Rigby's 275 rifles.

The 7X57 can be loaded to considerably higher pressures than its forebears in today's rifles with good quality brass making it like the 6.5X55 SE/SKAN in this respect. Whilst SAAMI lists its maximum pressure as 51,000 psi, the European CIP gives it an MAP of 3,900 bar / 56,565 psi using the Piezo transducer measurement method.



Loaded to identical pressures, the 7X57 would produce higher MVs than the 7-08 simply because it would involve a heavier powder charge = more energy sitting in the case. As the larger case / charge reduces overall efficiency however, the increase isn't that great. If you model 7-08 v 7X57 in QuickLOAD, their performance is very close even with heavier bullets like the 'traditional' Hornady 175gn RNSP at their respective modern max pressures. (But lower performance from the 7X57 in US factory loaded ammunition at the very low 51,000 psi SAAMI MAP - and that's if all US manufacturers load up to that value which I'd consider doubtful!)

Conversely, load the 154 Hornady SST with H4350 in both cartridges to the CIP 7X57 maximum of ~56,500 psi, the 7X57 is predicted to produce 2,727 fps against the 7-08's 2,678 in 24-inch barrels. In full-pressure loadings the benefits of the 7-08 to the hunter are 7X57 equivalent performance but from a shorter cartridge that fits what is now the standard action length. The handloader gets equivalent performance from a few grains less powder per cartridge loaded.

The benefit of using a larger case in a given calibre / loading is often in running lower pressures to obtain the desired MV or ME. This distinction is best seen in large calibre African dangerous game cartridges. The classic English big game cartridges of pre WW2 used what were on the face of it overly large cases, low fill-ratios with Cordite type double-based propellants that saw lots of air around the Cordite charge bundles and very modest pressures allied to what many modern shooters see as ridiculously tapered case designs. It was done deliberately to allow cartridges to run at low pressures and thereby cope with extreme temperatures whilst almost guaranteeing easy case extraction. Bruce Wieland in his books on dangerous game rifles and cartridges is very critical of some modern US designs that started with the 450 Winchester Magnum and its straight-wall case that utilises a much smaller volume combustion chamber, 100% plus charge fill-ratios, and much higher pressures than 'traditional' designs all to get a 450 that would fit the Model 70 rifle.

Accord to to most online references it is the same cartridge with a different name.
CW

 

[Laurie]

Accord to to most online references it is the same cartridge with a different name.
CW

Yes, that's true. However both Rigby and gunsmiths who've built them say there are some very small differences in their chambers. Exactly what, and more pertinent WHY?, is another question of course. This may simply have been part of Rigby creating an exclusive image for 'their' cartridge. All nonsense of course, but they did (and do) build fine rifles and if you were wealthy and wanted a 7mm deerstalking rifle for your annual outing to the Scottish Highlands (or were a well off African estate owner, army officer serving abroad etc) back in the 1930s, the Rigby .275 built on a fettled and smoothed Mauser '98 action was probably the best you could get at the time.

Another 'Why?' is why people go to a gunsmith and commission a 'genuine 275 Rigby' chambered rifle today from people other than Rigby? Snobbery, or do they know something we ordinary 7X57mm users don't know?

 

[RustyPin]

Yes, that's true. However both Rigby and gunsmiths who've built them say there are some very small differences in their chambers. Exactly what, and more pertinent WHY?, is another question of course. This may simply have been part of Rigby creating an exclusive image for 'their' cartridge. All nonsense of course, but they did (and do) build fine rifles and if you were wealthy and wanted a 7mm deerstalking rifle for your annual outing to the Scottish Highlands (or were a well off African estate owner, army officer serving abroad etc) back in the 1930s, the Rigby .275 built on a fettled and smoothed Mauser '98 action was probably the best you could get at the time.

Another 'Why?' is why people go to a gunsmith and commission a 'genuine 275 Rigby' chambered rifle today from people other than Rigby? Snobbery, or do they know something we ordinary 7X57mm users don't know?

7x57's were known for Chamber differences over 100 Years ago when it was still new in a Battle Rifle. It was proven however no matter the Rifle all the AMMO would Shoot. Apples & Oranges the 7x57 can't compete with the more modern 7-08 Case unless you "Improve" it. IMO

 

[billbonser]

708 is a great cartridge! As with its parent and brothers,(308, 243, 260, 358), is that poor shoulder angle. Reloading rounds multiple times is required for case life and that is why competition shooters shy away from it, and go to an AI cartridge, or to the 284 type where you have a 35 degree shoulder and an almost 30-06 case capacity and use a short action.

 

[Laurie]

Apples & Oranges the 7x57 can't compete with the more modern 7-08 Case unless you "Improve" it. IMO

Oddly enough, I revisited Ken Bird's old Handloader magazine articles on the 7X57mm earlier today to see what sort of MVs I should be getting from an old BSA Hunter sporter. (!'m 100 fps plus down on what I should be seeing with IMR-4350, 4451, and H4350 maximum loads from Hodgdon's data-set and they're really rather disappointing.)

Ken Bird reviewed MVs he'd obtained at acceptable pressures in his load development from both 7mm-08 and 7X57mm and the 7-08 was a clear winner especially with the lighter bullets. Even with 175s, the 7-08 just managed to produce a little bit more out of 22-inch barrel deerhunting rifles, but was ahead by a large margin with 140s.

The reason is that the 7X57 doesn't actually have that much more case capacity despite its looking a much larger cartridge, and the relatively small increase is more than outweighed by the lower pressures involved. Bird found that he could only load the 7X57 up so far even in strong modern rifles before groups opened up and over-pressure signs appeared. So yes, you're right, the 7X57 really needs 'improvement' to produce any velocity benefits. IIRC, Ackley said that due to its severe taper, the 7X57 was one of the few designs to produce really large MV increases through the AI treatment. (The 6mm Remington and 257 Roberts are in effect factory 'improved' 7X57s necked down for smaller calibres.)

 

[Idaho-Lefty]

My son shoots, a Tikka T3X SS lite, in 7mm-08 with, the Horn 150 grain ELD-X's and RL-17 at 2,850 FPS and shot, a nice 6X6
Bull in Idaho with, great penetration and down quickly !. I shoot, a Tikka T3, SS lite, in .270 WSM W/ 140 grain Accubond's W/ IMR 7828 at 3,140 FPS and I got a smaller Bull Elk in Ariz. a few days ago (our Freezers are, full,.. YIPPEE !!). Ready for a laugh ?? We practiced field positions, over "sticks" and over Packs, to 650 Yards,.. I shot my Bull at 60 Yards, his Bull at 250 yards ! LOL,.. so much for LR shooting BUT,.. we were ready ! You don't need a "Cannon", to kill Elk, IF you are a Hunter, just an accurate Rifle with, "good Bullets" and be able to,.. "shoot" it, well ! YUP,.. the 7mm-08 is, a Killer Cartridge !

 

[shooter74]

This is the one I built for the wife, I will admit I steal it for the occasional hunt myself!!!!

 

[284winner]

Thanks for that info, Laurie! I’ve had a Remington long action sitting in a drawer for six months, waiting for my cartridge decision. It was going to be a 30-06, but I bought a gun in it and the recoil is for a younger me. 7-08 it is. Any suggestion on twist?

9

 

[RustyPin]

Oddly enough, I revisited Ken Bird's old Handloader magazine articles on the 7X57mm earlier today to see what sort of MVs I should be getting from an old BSA Hunter sporter. (!'m 100 fps plus down on what I should be seeing with IMR-4350, 4451, and H4350 maximum loads from Hodgdon's data-set and they're really rather disappointing.)

Ken Bird reviewed MVs he'd obtained at acceptable pressures in his load development from both 7mm-08 and 7X57mm and the 7-08 was a clear winner especially with the lighter bullets. Even with 175s, the 7-08 just managed to produce a little bit more out of 22-inch barrel deerhunting rifles, but was ahead by a large margin with 140s.

The reason is that the 7X57 doesn't actually have that much more case capacity despite its looking a much larger cartridge, and the relatively small increase is more than outweighed by the lower pressures involved. Bird found that he could only load the 7X57 up so far even in strong modern rifles before groups opened up and over-pressure signs appeared. So yes, you're right, the 7X57 really needs 'improvement' to produce any velocity benefits. IIRC, Ackley said that due to its severe taper, the 7X57 was one of the few designs to produce really large MV increases through the AI treatment. (The 6mm Remington and 257 Roberts are in effect factory 'improved' 7X57s necked down for smaller calibres.)

All the more reason for me to finish my 7-RPC/280-08. That project has kinda stalled I'm afraid as I'm undecided on which barrel Twist & length along with what Action to purchase? I am leaning towards a Left Gain Twist and wondering how short I can go with Length. The more I learn the more I'm convinced the 162's are the lower end and i'm inclined to pursue the 180's.

 

[Laurie]

That should be Ken Waters' 'Pet Loads' from 'Handloader' magazine BTW - memory gets worse with age. Personally, I like 160/162s for match use 175s tops in a long freebore 7-08. With the small case, the heavier bullets are either run at low MVs, or else you have to pack more energy into a limited space using very hot double-based powders. One of my aims with the cartridge was to combine precision with good barrel life.

 

[284winner]

That should be Ken Waters' 'Pet Loads' from 'Handloader' magazine BTW - memory gets worse with age. Personally, I like 160/162s for match use 175s tops in a long freebore 7-08. With the small case, the heavier bullets are either run at low MVs, or else you have to pack more energy into a limited space using very hot double-based powders. One of my aims with the cartridge was to combine precision with good barrel life.

How's your barrel life pushing those 160/162s close to 2900 ?

 

[Idaho-Lefty]

A Note to, 7mm-08 Tikka shooters, the Horn 162 gr ELD-X did NOT shoot consistantly well, in my son's new 7-08 T3X Tikka,..factory TWIST, 1-9.5 ??
BUT, the 150 ELD-X's shot, sub 1/2 MOA for him like a,.. 2 3/4 inch group at,.. 640 yards ! He was using around, 44.3-44.5 grains of, RL-17 for 2,850 FPS.

 

[tmx199]

My favorite round at one time I had 5 7mm08 in the safe sold them and got a 7mm08AI I love it always wanted one! I shot a doe at 375 yards on Friday she went 50yards it's a great round!!!!

 

[Idaho-Lefty]

My favorite round at one time I had 5 7mm08 in the safe sold them and got a 7mm08AI I love it always wanted one! I shot a doe at 375 yards on Friday she went 50yards it's a great round!!!!

Yup, all of, the .308 based cartridges like the, .243, .260, 7mm-08, etc. would do well with the sharper, 30, 35 or, 40 Degree shoulders and LONGER Necks, IMHO ! The 6 mm SLR will be, my next chambering, using N-160 and N-165 for, longer Barrel life on, Deer, Antelope, Wolves, Coyotes, Steel, etc. The 7mm-08 AI, does almost what, the 7mm Rem Mag does, without the Belt, longer casing and a bit less, recoil ! GOOD, choice !

 

[Hammer500]

I agree if I could only own one rifle it would be 7-08. I switched from a 270 to a 7-08 in 788 10 years ago and have taken many deer, elk and moose. I started shooting it in bench competitions that require a factory barrel about 5 years and got worried I might wear it out so I bought it's twin. I have shot and placed in rifle rodeos shooting 100 gr Hornaday, used successfully hunted with 140 he ballistic tips and placed in top 3 with 162 A maxs for bench. I simple love the 7-08.
Unfortunately I ran out of the 100 gr and on my last box of the A maxs. I guess I will have to start over.