doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com 9.3mm72r/ chambering dimentions?

I have read ever post on this forum as to 9.3/72R carts. and have learned a lot of valuable info, however, I have become more confused. I have discovered there are 3 different chamber diments. I have not been able to find any info. as to their description. I also cannot get a good chamb. cast to determine case length, could this be due to lead fouling. I have spent 8hrs with every listed cleaner and still do not have what I consider a clean chamber. Pilgrim

That must be some serious crud!

WHAT are you using for your chamber castings?

[pilgram,
To clean your chamber, after trying everything else, use a 45 cal borebrush in a short section of cleaning rod, turned by a "drill motor".Mark the rod to indicate expected chamber depth, so you can tell where to stop.Once you have it clean enough to satisfy you, chamber a sized case( or factory cartridge)that has been smoked/colored with felt tip pen or "Dykem". Try to force it in with only your fingers, and then withdraw it.If it shows interference in the middle of the case, what you have is a "D" chamber.If it shows interference at the end of the neck, it is likely you have something other than a 9.3x72R; such as 9.3x70R, 9.3x 57R,9.3x48R, or 9x58 1/2 R S&S. The amount the case protrudes fron the chamber will indicate the chamber length, but nothing is as good as a "cerrosafe" chambercast. Let us know and we will finally be able to get you shooting.
Mike

Hi [pilgram
As Der Ami stated "cerrosafe" chambercast best. Marked case helps if you have something close in dim. to chamber. If you do not have factory 9.3x72R loaded case and you are a muzzleloader/ reloader check the start of rifling by tapping soft round lead ball approx. .375 dia into chamber with wooden dowel. Mark the dowel when ball engages rifling Then tap back out with dowel from muzzle. Measure dowel and lead ball which gives you dim. from case rim to rifling. Bullet dia. in loaded shell should just be short of rifling. A 3/8 hardwood dowel tappered at end will also give approx. dim's. 9.3x72R dim's taken from factory RWS shell: bullet dia. .366, .384 at neck, .426 at rim., 2.827 long case. Don't let brush on drill engage rifling. After clean-up if you have oversize chamber, you may have to fireform and only neck size.
I think chamber dim's are almost unlimited. Fireforming and neck sizing best. You need to check bore dim's also before reloading or shooting factory. I have 8.6 that turned out to be 8.6x72R (.348 dia hornady bullet worked on deer).

wknito

Hi [pilgram. Sorry about end of last post. Don't want to confuse you. Just wanting to make a point on bore sizes. .348 dia shouldn't be bullet for 8.6 (marked). I mold my own and shoot mainly lead bullets thru it. 8.6=.338 8.8=.346 9.3=.366 I would tap a soft lead bullet thru bore (round balls work good)to check bore size. I don't trust the marking. My 8.6 is .010 over. Was it miss marked, marked poorly, or ???

Sorry about that
wknitro

[pilgrim,wknitro,
I have encountered 9.3x72R rifles with groove dia. as small as .352" and have a cartridge in my "pile" that has an outside lubricated bullet of well over .368"(as I recall-.374-375). one of mine is .358" and it seems that a good many are that dia.My late friend and mentor Gene Enterkin ran a custom ammo business for many years, and he reported that he encountered more with .362"( and used .364" cast bullet)than any other diameter.As a matter of interest, the owner of one of the ones with .352" barrels, used selfmade "pound dies) to bump .348 jacketed bullets up to .352". The other one had a good barrel so the owner used lyman 358318 bullet sized to .355"(smallest sizing die I had).I use .364" cast bullets in my .358"barrel with good results.Each of these rifles is a "law of it's own". If you could go to the "Mall Mart" and buy ammo, it wouldn't be nearly as much fun.
Mike

wknitro;
Have you checked the "Bore" diameter of that bbl that uses the .348" bullet. Realize when the proof house stamped the bbl they stamped the Bore dia, not the groove/bullet size. A .338 bore for a .348 bullet would sound about right to me. My 8x58 Sauer has more difference than that & it was proofed for Stl Jacketed Bullets, not lead ones.

Hi 2-piper. I agree with you on bore dia., but if barrel is marked 9.3 which equals .366 and Factory 9.3x72R ammo with .366 bullet fits chamber someone might think it's OK to shoot and should be accurate.
As Der Ami stated "these rifles is a "law of it's own". If you could go to the "Mall Mart" and buy ammo, it wouldn't be nearly as much fun." When someone see you out in the woods with a drilling, they just got to stop and ask.
For anyone just reading this post, Unless the gun is shooting when you receive it, you need to check bore/groove dia.
I purchased this gun in early 1980's. Only my second drilling, first one was 9.3x72R purchased only one day before. Seller had no clue on rifle cal. I know I didn't cast chamber/bore back then. Don't remember how I did it, but probably used .375 dia. soft lead ball to get bore/groove dia. (I have that mold) along with hardwood dowels to verify 72 rimmed case. Then purchased lead molds. Finally tried .348 200gr. Hornady. They are accurate, but don't open to good on deer at lower vel. (just punch a hole thru). I didn't have "cerrosafe" back then. Got it grouping OK and didn't look back. This year I used T/C contender pistol in 357 Max to harvest 8 pt at 75 yards, Like to rotate and use diff. guns. Don't think I bought a factory loaded rifle shell(to shoot)in my life.
[pilgram, I'm new to this forum, but I already know these guys can get you up and shooting. Rolling your own if need be. You just need to ask them.

wknitro

Factory ammo for 9.3x72R is loaded with a bullet that is useable in barrels of differing diameters, essentially it only has a "driving band" of full dia.This doesn't drive the pressures up to dangerous levels.A barrel marked 9.3, and not marked under the 1939 rules,would have around .375"groove dia.See discussion above about the cartridge with "outside lubricated" bullet. Many of these old rifles have an odd number of grooves.This makes measurement of groove diameter very "iffy".
Lacking a special "V" anvil mic, the best way is with a "V block".If very much care is taken and the slug is rotated against the jaws of calipers, a pretty close measurement can be made.With an odd number of grooves, the "land" on one side of the slug is opposite a "groove" on the other side.
Mike

Hi Der Ami. Thank you for the post. Don't use factory ammo, but good info for someone that would like to.

I'm learning
wknitro

wknitro,
I don't either, as a general rule.I brought back a lifetime supply of the factory bullets, and the samething would apply with handloads using them. I think there are a few Norma bullets still around(mine are RWS) and S&B offers them to handloaders,if we could just get someone to import them.If I didn't have a supply,and usually shoot cast bullets,I think I would look into having Corbin make up a set of swaging dies to make similar bullets from 200 gr,35 Rem.bullets or the 180 gr FlatNose bullet that performs so well in my 357 Herret.My main 9.3x72R will accept .358 bullets as they are anyway, so I don't have a burning need. I would be interested if someone else wants to do it.
Mike