Bulged brass . . . high pressure?

[MGMorden]

I've got a CZ-52 that I've been loading 7.62x25 for.  In the past I've used S&B and Starline brass, all of which worked fine.  I've recently started to form cases from .223 Rem brass though, and I've run into a problem (or what I think is a problem).  Titegroup is the powder I'm using, with 110gr Rainer bullets (made for .30 carbine).  I've been working up the loads, and started at 4.0gr (not enough to cycle the slide).  After I hit 4.4gr though, I ran into something odd.  All the cases formed from .223 have a slight bulge on one side of the case about 8mm infront of the case head.  None of the "real" 7.62x25 cases exhibit this (and the charge with this weight of bullet maxes out a 4.8grs, so I'm not that close yet).  I know that the reformed cases will have a little less volume, but I didn't think I'd run into problems quite so quickly.  

Basically, is the bulge a sign of high pressure (in which case I'll back down the charge), or is it normal?

Thanks.

[John Traveler]

MGM,

Those bulged 7.62x25 cases you have can be from high pressure, but are more likely because you made them from 5.56x45 brass.  I just checked a batch that I made and fired once a couple years ago.  ALL of them have the characteristic bulge near the rim.  There is several thousandths inch difference in diameter between the correct pistol brass and the 5.56.

There is enough dimensional difference between 7.62x25 cases and 5.56x45 cases to give this problem.  It usuall not not a problem because the 5.56 cases are stronger and thicker than most 9mm/.38 Super cases in the head web area.  The CZ52 pistol uses the "Stecke" lock (rollers cammed by the firing pin) and needs fairly high breech pressures to open the action.  I would continue to work loads upwards until they give reliable functioning.

Please be advised, however, that the 5.56 brass IS thicker, giving less volume.  You will have to develope your loads and approach max carefully.

I just re-read you post and note that you are using 110 M1 Carbine bullets!!  Please don't do this.... the heavier bullets WILL give higher pressures in this small case.  Stick with the 88-95 grain bullets made for the .32 ACP.  If you use the Carbine bullets, you must go to a slower burning powder and lower velocities to get safe pressures!

HTH
John

[MGMorden]

I just re-read you post and note that you are using 110 M1 Carbine bullets!!  Please don't do this.... the heavier bullets WILL give higher pressures in this small case.  Stick with the 88-95 grain bullets made for the .32 ACP.  If you use the Carbine bullets, you must go to a slower burning powder and lower velocities to get safe pressures!

110gr carbine bullets are a sanctioned load by the Lee data and the Accurate Arms loading manual.  I was previously using 90gr Hornandy XTP's, but they aren't as accurate as the 110gr's and cost nearly 2x a much.  I will go ahead and go up to a slower burning powder though, as Titegroup seems quite fast.  Accurate #7 or #9 should be a bit slower right?  I do wish that Rainer made some ~85grain .308" bullest though (I'd prefer to avoid the .32ACP bullets unless I get a sizer to take them down to .308").

[John Traveler]

MGM,

It surprises me that 110 M1 carbine bullets are recommended loads in the 7.62x25.

OH, wait a minute!  Are you SURE those loads are for the CZ52??  The browning tilt-lock actions (Tokarev) and Mauser M1896 actions are more tolerant of recoil impulse differences than the CZ52 design.  It operates in a much narrower range of chamber pressures/recoil impulse.

I've never had any good accuracy loading .308" bullets in the 7.62x25 caliber.  0.311-0.312" bullets fit the bores of the several pistols I've loaded for.  Maybe your groove diameter is tighter than mine.

Let us know how your load development works out.

John

[John Traveler]

MGM,

It's relatively easy to resize jacketed .32 ACP bullets to .308" diameter at home.

Get yourself a Lee pan lubricator and hand sizer kit and set up the sizing die UPSIDE DOWN in your 7/8-14 loading press.  Partly screw in an expander die body with the expander plug removed.  Use the Lee sizer punch in your ram and push the bullets through the 0.308" sizer die.

It works really well, and I've sized thousands of jacketed 0.311" bullets to use in .30-06 rifles.

John

[MGMorden]

MGM,

It surprises me that 110 M1 carbine bullets are recommended loads in the 7.62x25.

OH, wait a minute!  Are you SURE those loads are for the CZ52??  The browning tilt-lock actions (Tokarev) and Mauser M1896 actions are more tolerant of recoil impulse differences than the CZ52 design.  It operates in a much narrower range of chamber pressures/recoil impulse.

Actually, the Accurate Arms manual listed the loads as "For CZ-52 ONLY".  From all the reading I've done the CZ-52 action is actually supposed to be a lot stronger than the Tokarev action (I've heard varying reports about strength vs the M1896 action).  Naturally the 110gr charges are reduced compared to the loads for lighter bullets, but they're still in the manual (which I was assuming would keep things on the safe side).  I'm surely no expert though.  

After taking a quick look at Midway's site though , I've noticed that 71grain .32ACP bullets are VERY cheap, and a .308" bullet sizer die is only $10 or so.  I might try sizing down some of those and just using 85gr data.