9mm Supercomp And 38 Super Compatibility

[herky]

After losing about 70% of my 9mm Supercomp brass at Sunday's match, I started thinking about switching the gun to 38 Super. Using Starline brass, by the way 9mm Supercomp is now 9x23 Comp, the price difference is almost $30 per thousand. My Dillon dies are labeled 9mm/38 Super and I decided to case and chamber gauge 9mm Supercomp, 38 Supercomp, and 38 Super to see what the difference was. My understanding is that 9mm is a slightly tapered case. All three examples passed the 9x23 EGW case gauge and all three chambered in my barrel to the same depth. Am I missing somethin here or do I have a unique situation? Any input would be appreciated.

[eerw]

From my understanding and conversations with George (EGW)..9x23 is slightly tapered, same length, smaller caserim than 38 super..the case is slightly bigger than super and slightly smaller than 38 super at the case mouth.

My 9x23 guns will chamber and shoot..9x23, 9SC, 38 SC, 38 super ( if I adjust the extractor ) and 9x21 and 9x19.

My 38 super will shoot 9x23 ( if the brass is new, once it's fired it will not chamber) 38 SC and 38 super.

don't think you are missing anything..they given tolerances..it is possible for them to all interchange..whether that is a good thing or not..that's up to you..

[warpspeed]

eerw nailed it.

The 9x23 will chamber and fire all of the 9mm variants and 38 super variants, but will not function 100 % w/ each and every one w/o tuning.

I know of 2 guys that shoot the Armscorp 38 super rimmless in there 9x23 guns w/o any problems.

[Skywalker]

For dimensional comparison, have a look here.

[rmills]

The 9x23 (9 Super Comp) has a taper running from the mouth to the rear. The rear of the case is approx. .010" larger than the case mouth. This was done for two reasons:

1. Ease of extraction. Being a tapered case, the extractor just needs to move the case rearward a few thousandth's of an inch before if is completely free of the chamber walls (unlike a .38 Super with a straight walled case as it is in contact with the chmaber walls theru the whole process).

2. Pressure. The web at the base of a 9x23 case is VERY thick compared to a .38 Super (.38 Super Comp, etc.) and can handle MUCH larger pressures. The last time I looked it was over 50,000PSI.

If you are shooting .38 Super rounds in a 9x23 chambered pistol, most of the time they will work fine BUT if there is a case that has been weakened over time, note that there is an extra amount of space around the base of the .38 Super case when chambered in a 9x23 barrel and it is not fully supported. Be careful.

[BillL223]

FWIW Starline Supercomp has a greater case capacity then Win 9 x 23 which means it is not as thick in the base area. I found this out by minoring at last years Area 8 using a proven load which was chronoed before the match but I didn't pay attention to the mixed lot of brass.

[eerw]

Ouch..tough way to find out...I have cross sections of WIN 9x23 and the supercomps and super...the Winchester is definitely thicker.

[Flexmoney]

This...from the Starlione website:

9 Super Comp (9x23) New Design-New Head Stamp As of 7-7-03 we have changed the head stamp to read 9x23 comp to allow easier identification because it looked too similar to the 38 Super Comp head stamp. At the same time, we slightly changed the interior design to allow the seating of heavier bullets (i.e. 147 grains) but change will in no way affect performance of case for use with lighter bullets.

herky, I'll try to find my old copy of Front Sight. There is a Guy Neil article in there that gives the info on the various 9/38 rounds.