Where does the 7.62x25 Tokarev headspace...the case mouth, like the 357SIG, or the shoulder like a bottlenecked rifle case? None of my dozen reloading manuals has the info.

I "thought" it was the mouth but wouldn't put any serious $$ on it.

I thought all bottle-necked cases headspaced on the datum line of the shoulder, or at least should. Which begs the question, why headspace a non-belted bottle-necked cartridge on anything else? As you can see, I have no idea, but I am interested in hearing the replies from those who do know.

Datum is on the shoulder .. NO shoudlered case uses the casemouth .. might use belt, or rim, but not casemouth.

Well as I said glad I didn't put any $$ on it. I was wrong on the Sig as well. Going to be one of those weeks.

Sig headpsce info.
http://www.realguns.com/Commentary/comar25.htm

quote:

Originally posted by jeffeosso:
Datum is on the shoulder .. NO shoudlered (sic) case uses the casemouth .. might use belt, or rim, but not casemouth.

Concerning the 357SIG...Hmmm, who to believe, Jeff, Lyman's 49th edition loading handbook, or Speer's 14th edition?

Quote "The 357SIG is a bottleneck cartridge but headspaces on the case mouth...uniform case length is imperative for proper functioning." Unquote

Speer's #14 says, Quote "This cartridge heaspaces on the case mouth, not the shoulder as so many people think." Unquote

So I'm just wondering if the 7.62x25 Tokarev is the same? I didn't think I'd be getting upwards of 15 reloads with this hot (1600+ fps w/ 85gr bullets) little pistol cartridge and if it indeed headspaces off the shoulder, I wouldn't concern myself with trimming to exact OAL.

Are there no pistolsmiths on this forum other than our moderator?

quote:

Quote "The 357SIG is a bottleneck cartridge but headspaces on the case mouth...uniform case length is imperative for proper functioning." Unquote

So I'm just wondering if the 7.62x25 Tokarev is the same? I didn't think I'd be getting upwards of 15 reloads with this hot (1600+ fps w/ 85gr bullets) little pistol cartridge and if it indeed headspaces off the shoulder, I wouldn't concern myself with trimming to exact OAL.

Onefunzr2

I had thought the 357Sig headspaced on the mouth as well. Then I found the article on Real guns that I posted the link to. It shows headspace guages for the Sig that headspace on the shoulder. So I'm now totally confused.

Here is part of another article in Real Guns on the sig.

357 SIG, rumors and propaganda

The 357 SIG stirred up a good deal of controversy when first announced. The SIG round is based upon a bottleneck case, a form more traditionally aligned with a rifle cartridge and, for some reason, even experienced handloader reacted as though they had never seen such a thing. Secondly, both SIG and industry personalities indicated the 357 SIG challenged the 357 Magnum revolver. Quite frankly, I've never understood this selling point for the 357 SIG. The P229 is a 4" barrel gun. A proper 357 Mag revolver would have a barrel closer to 6". In these configurations I don't believe a 357 SIG could get within 200 - 300 fps of the 357 magnum in almost any bullet weight. The final controversy was caused mostly by an initial shortage of brass and ammo, combined with the print public reference to the cartridge as being based on the 40 S&W - handloaders immediately began fabricating .40 S&W brass into .020" too short for spec 357 SIG cases, which eventually sparked the great SIG headspace debate, or put people to sleep if they actually had a life.

Initially, gun magazines reported the SIG cartridge was designed to headspace on the shoulder, then at the case mouth and shoulder, then finally only at the case mouth. Personally, I think this progression of proper headspace description followed the brass shortage, with SIG not wanting to dampen the momentum of a new pistol launch with a shortage of ammo and temporarily will to ok almost anything that could fill one of their new guns. When correct brass became available, a new sense of technical integrity developed within SIG, and the press, as they began citing the SAAMI published spec, a spec that had been in place all along. Of course, concurrence of opinion is nowhere in sight.

If the 357 SIG case really headspaced on its mouth, use of a short formed 40 S&W case would indeed create a headspace problem, but it does not. Factory brass headspace dimension, case head to case mouth, typically run (picture left) .858", formed from 40 S&W brass .848" and Starline brass .858". The SAAMI case spec is 855"~.865", but the chamber headspace dimension spec is .865"~.877" which means, there would be virtually no time when any 357 brass would make contact at the case mouth. Simply stated, just about every time a 357 SIG cartridge is chambered in a SIG or similar pistol, it is headspacing on the cartridge shoulder and not the case mouth. I've loaded lots of ammo based on reformed .40 S&W before 357 SIG brass was generally available, and I occasionally do it today, mostly because I can.

As further reinforcement that the 357 SIG headspaces on the shoulder - 357 SIG "Go" - "No Go" gauges check at the shoulder datum line, not the case mouth, and reloading equipment manufacturers favor headspacing on the shoulder. Hornady, Lee and Redding dies roll crimp rather than taper crimp. Cases that headspace at the case mouth at not roll crimped, they are taper crimped. Redding does offer a taper crimp seating die as an option. RCBS's two die set forms a roll crimp. My set of RCBS dies included a slip sheet that specifically instructs how to produce 357 SIG cases from 40 S&W brass. In addition to the sizing instructions, the slip sheets go on to explain the under spec case length of the resulting formed case, offers a caution regarding potential problems, then puts the caution into context by indicating they never experienced a problem using cartridges made through this process.

Now that I'm really confused and since I own neither I'll go have coffee.

The two reloading manuals I quoted are as up-to-date as you can get, so I would tend to believe their expertise.

Any idea what vintage those realgun articles are?

quote:

Any idea what vintage those realgun articles are?

Sorry no clue

quote:

Are there no pistolsmiths on this forum other than our moderator?

One of our resident gunsmiths should know the answer.

onefunzr2,

The 357 SIG is designed to headspace off of the mouth of the case.

Headache

email dave manson and ask him where the SAAMI datum line is

Jeffeosso I right on...Sometimes the written word is not cast in concrete and you have to use a bit of common sense or go to another source to get the required information. The numbers prove this out I think...minimum of 0.855" to maximum of 0.877" from the SAAMI case specs and the chamber headspace dimensions leaves a range of 0.022"...

I've never delt with ANY weapon with that much range of possible headspace that didn't give all kinds of problems with the brass or reloading process.

It would seem that measuring a fired case shoulder to base length, then resizing it and comparing the two would give a very accurate picture of the ACTUAL numbers involved and stop or address all the other conjectures.

I do this type of measurement with the dies I will use, as a matter of course, with ANY rifle I build...that way I can adjust my chamber length to the dies case sized dimension and NEVER have a problem with brass head separation or excess headspace, or short chamber.

You have to remember that ALL reloading components, dies, reamers, headspace gauges, etc., have a SAAMI spec tolerance...stack those tolerances in the wrong direction and you could have headspace problems with factory dies and chambers, or go the other way and have end up with a chamber that the bolt will hardly lock down on factory ammo.

Plus...as Jeff suggested...email any of the reamer or headspace makers and get their actual numbers.

I would bet the 357 Sig chambers at a datum line somewhere on the shoulder...

I have a couple thousand loaded 357 Sig rounds, but no fired ones, or dies any more and nothing to fire of a round so I could check and include that information.

I need to buy a 40 cal Sig and extra 357 Sig barrel just to use up all the 357 and 40 cal ammo I have aquired over the years.

It would be interesting if those who do have fired, unfired and resized brass would measure them and post that data.

My question of headspace is on the 7.62x25 Tokarev cartridge, NOT the 357SIG.

I only brought up the latter as a matter of comparison between two bottle-necked pistol cartridges.

I thought at least one of the known gunsmiths who frequent this forum would have a knowledgeable answer. I would appreciate that answer from any who's last name isn't Smith.

quote:

Originally posted by jeffeosso:
email dave manson and ask him where the SAAMI datum line is

There's your answer Dave

I just happen to have the print from them, as this is a round i've been piddling around with for decades ...
Dataum for go .856,

funny how that works, aint it?

oh, i was wrong.. its a CIP cart, not saami .. doesn't change the go datum line though. not does it change my surname! LMAO

quote:

Originally posted by jeffeosso:
There's your answer Dave

I found the 'correct' answer by asking a Sierra bullets tech. I felt guilty about calling him when I don't use their bullets in my CZ-52, as they don't make one that fits well in my .3095 barrel. But he was happy to chat nonetheless.

800-223-8799 Missouri time zone

quote:

Originally posted by jeffeosso:
Datum is on the shoulder .. NO shoudlered case uses the casemouth .. might use belt, or rim, but not casemouth.

You mean to dismiss out of hand our resident knows-everything-about-everything mod who made the above statement? Tsk, tsk, tsk!

one more time ..
7.2x25 and/or 30 mauser headspaces off the shoulder, per Dave Manson, per CIP, and per wikipedia
http://en.wikipedia.org/wiki/7.63x25mm_Mauser

357 SIG, per CIP, on the SHOULDER, though lyman once published incorrect data of on the mouth

quote:

According to the official C.I.P. (Commission Internationale Permanente Pour L'Epreuve Des Armes A Feu Portatives) 2007 guidelines the .357 SIG headspaces on the shoulder(P2-H1). Some US sources concur this C.I.P. ruling.[6] US reloading supplier Lyman once published the .357 SIG headspaces on the case mouth(H2

http://en.wikipedia.org/wiki/.357_SIG

just like what the "know it all" said ..