Converting brass

[IMR]

I'm thinking about buying a 7.5 X 55 K-31. Come to find out the brass is high and hard to find at that. How 'bout one of you NASA certified gurus check something out for me.

I went through my books comparing case dimensions of various calibers to the 7.5 X 55 and it looks like the 8MM is real close. As I see it, the 8MM is only.051 longer and the case head is only .012 smaller on the radius. The 8MM case can be trimmed to length and 12 K smaller on the radius, I think, is inconsequential.

Standing by for feedback.

IMR

[Maven]

IMR, The fly in the ointment is the different diameters of the case heads. The 8 x 57mm has a .473" dia. case head (same as .30-06, .308Win., et al.) while that of the 7.5 x 55mm is at least .498". The better way is to search Graf & Son's site for 7.5 Swiss brass, or buy .284Win. brass and FL size it (make sure the 7.5 FL die is in firm contact with the appropriate shellholder). It will chamber and extract smoothly, which the 8 x 57mm may not do.

[IMR]

Maven,
My Hornady manual says the .284 Win. case has a head diameter of .473, same as the 8MM. If that's the case, I should be able to FLR and fireform from 8MM to 7.5. Right?

IMR

[Toney]

cut down surplus 06 is supposed to work good. read just yesterday about rapping masking tape around the head so the will expand evenly all the way around

[StarMetal]

IMR

NO....use either 284 brass or buy 7.5 brass. Like the 284 brass the 7.5 has a fatter body. I believe it's too much to blow out (fireform) any of the 30-06 class of cartridges including the 8mm mauser. Might be unsafe too especially if the case splits and blows gas back. Be safe and use 284 or 7.5 brass.

Joe

[KCSO]

With Graf's brass in abundance and priced at 28.00 a hundred I sure wouldn't mess with converting brass that may or may not last 3 shots. My Graf's brass has done 15 loads in a single case without any problems. Thats at least 1500 shots from a hundred brass and probably more.

[IMR]

OK, teach me something here. I just came from Graf's site and the onliest 7.5 X 55 brass I see is made by Norma and I'd have to take out a second mortgage to buy it. So where on the site is this magic $28/100 brass? I'm pullin' my hair out here!

[KCSO]

Sorry
Last time I talked to them they were going to have Privi brass in in 2 weeks and I didn't check back. The have the loaded ammo for 12.99 a box and Sportsman guide has the new Wolf ammo in stock also. PM me and I will put you in touch with 50 rounds of good brass.

[Maven]

IMR, Graf's IS out of their brand of 7.5 x 55mm brass. As for what you can use in its stead, here are some dimensions for the shoulders and areas above the rim (toward the neck) of the 3 cartridges mentioned:

7.5 x 55mm: Shoulder = .460"; above the rim/head = .491"

.284Win.: Shoulder = .500"; above the rim/head = .478"

8 x 57mm: Shoulder = .434"; above the rim/head = .470"

It would seem that the .284Win. is the better fit than the 8 x 57mm since the shoulder can easily be sized down to fit the 7.5 chamber, but I'd be leery of fire-forming the 8 x 57mm up .026" as the case may split. Ditto for the case heads. Moreover, the K-31's, et al. don't handle high pressure gas (from a ruptured cartridge) very well. The prudent, not to mention safer course, would be to wait until you can get the 7.5 brass, or barring that, reform the .284Win.

[rocklock]

IMR,

Graf's 7.5X55 shows up on eBay quite often.

Not as cheap as buying it direct from Graf's, but still cheaper than Norma. (Then again, what isn't?)

[Buckshot]

...............IMR, I see on another thread you asked me to check the dimensions of the 284 Win against the 8x57. Those given above would be correct.

"..............Maven,
My Hornady manual says the .284 Win. case has a head diameter of .473,"

That would be the RIM diameter. The 284 Win is one of the few cartridges having a rebated rim, where the body ahead of the rim is larger.

Before Graf was bringing in the correctly headstamped and sized 7.5 Swiss, besides FL sizing the 284 Win people were resizing the 6.5 Swede. It has a larger rim and casehead then the 'standard' Mausers. Sticky issue here was opening casenecks from .264" to .308". However it was done.

The tape deal around smaller then desired caseheads is a common practice but usually NOT with potentially high intensity cartridges.

http://www.fototime.com/FB833F810B2C0FE/standard.jpg

These are awaiting final fireforming. For the 11.15x42R Brazilian Comblain. An early 1870's black powder cartridge. Decidedly non high intensity 8)

.................Buckshot

[jh45gun]

The 284 brass works fine and ejects just as well as the 20 rounds of 7.5x55 brass I have I cannot tell no difference in how either performs. If you cannot get 7.5x55 get the 284 brass and run a the sizing die with like was stated before with the die touching the shellholder with a case in the die and you can make great cases.

[IMR]

OK, guys, sure do apreciate all the feedback. By the way, the masking tape trick is a new one for me. Always like learning new tricks.

[26Charlie]

Ditto what jh45gun said. Before any 7.5 brass or ammo was available for many years I used the .284 brass in the older Swiss rifles before the K-31 came on the market, just chamfered a little and then run into the 7.5 x 55mm FL die with no further work. They load and eject fine, the body of the .284 is so close in size and the length is close. The rebated rim was not a problem as far as I could tell, but I haven't had any regular stuff to compare it against. The shell holder for the .284 is the same as for .30-06, but I am told the shell holder for the 7.5x55 brass is the same as for .30-30.

[KCSO]

IMR

I have located for you 40 rounds of Graf's brass new in the box $10.00. Dies 14.00

[IMR]

KCSO,
Thanks, pardner! Sure appreciate you looking after me like that. Got keep my priorities in order, though. I got my W-2s back and now I gotta get down to H&R to file. Soon as I get my money from the gummint, I'll be ready to start on this new venture of owning and feeding a K-31.

IMR (I Make Reloads)

[Bob S]

.284Win.: Shoulder = .500"; above the rim/head = .478"



Maven:

You got the two dimensions flip-flopped here ... the base of the 284 is .500. The CIP dimension (converted to English units) for the base of 7.5 x 55 is .495.

The 284 case as reformed in 7.5 x 55 dies is near-perfect as you can get and is much more robust and higher quality than the stuff Graff's was selling IMHO. The rebated rim of the 284 causes no problem whatever in my modest managerie of 7.5 x 55 rifles, and I have never had a case failure of any kind. Unforunately, 284 brass is not always available ... Winchester (actually, Olin) makes it "seasonally". It is ironic that probably none of the brass they make gets loaded as .284 ... most gets formed into something else ... 7.5, 6.5x284, 30 x 284 ....

Resp'y,
Bob S.