Converting 9mm to 38 super

In some posts, on this forum and others, people have stated that a 9mm 1911 can be converted to 38 super by simply swapping barrel and mags. (e.g. https://www.bullseyeforum.net/t7033-38-super-barrel). However, in Gun Digest Shooter's Guide to the 1911, Robert K. Campbell writes:

Robert K. Campbell wrote:Converting from 9mm to .38 Super is more difficult. The 9mm has a .384" breechface and the .38 Super measures .405". The 9mm breechface must be opened in order to allow the slightly wider .38 Super casehead to function properly.

I was thinking about buying a 9mm Springfield Range Officer and get get a gunsmith to fit a 38 super barrel in it, thinking that it's easier to load down 38 super to bullseye speeds (~700fps) and get good accuracy. The gun would be used for 1800 matches and International Centerfire (max 38 cal); we rarely get a full 2700 around here. But Robert's comments have me worried that it may not be as straightforward as I thought.

Thoughts?

I just did a RO conversion. I had to modify breechface slightly for larger rim.
Jon

Or you could shoot .38 supercomp (basically rimless .38 super).

But why bother?  Why not just work up an accurate 9x19 load?  If folks are able to get their 9x19 Bianchi Cup guns to shoot 1.0 - 1.5" at 50 yards, I would think the caliber wouldn't be holding you back.

mpolans wrote:Or you could shoot .38 supercomp (basically rimless .38 super).

But why bother?  Why not just work up an accurate 9x19 load?  If folks are able to get their 9x19 Bianchi Cup guns to shoot 1.0 - 1.5" at 50 yards, I would think the caliber wouldn't be holding you back.

You need velocity to get 9mm to group st 50yds. 1050-1100 fps. Very snappy.
Jon

That's what I read; 9mm needs to go fast. So what is it about 38 super that makes it easier to get accurate loads at lower velocity? They are using more or less the same bullets. Twist probably is a factor in some cases, but 1-10 barrels are available for 9mm too.

Probably around 800 rds thru my RO 9mm to 38 Super conversion. Never had to do anything to the breech face. I use nothing but the Starline competition brass which is actually consistently larger then the regular brass. I guess not all 9s were created equal.

Len

I get 2 1/4 inch groups at 50 yds with my 9mm 10 twist using 147gr bullets at 700-730 fps.  Nice and soft.  But the 147's take the fast twist.

Jon Eulette wrote:

mpolans wrote:Or you could shoot .38 supercomp (basically rimless .38 super).

But why bother?  Why not just work up an accurate 9x19 load?  If folks are able to get their 9x19 Bianchi Cup guns to shoot 1.0 - 1.5" at 50 yards, I would think the caliber wouldn't be holding you back.

You need velocity to get 9mm to group st 50yds. 1050-1100 fps. Very snappy.
Jon

IIRC, don't most aftermarket 9x19 and .38 super barrels have the same twist rate?  If so, it would seem the same velocities would be required of .38 super.

I'm interested in understanding how .38 super can deliver good 50 yard accuracy at 700fps but 9mm cannot.

Jon?

Our supers run a  1 - 16 twist and shoot outstanding groups with 126 Dardus SWCs.  Around 720 fps with 3.6 of BE. Easily  under 2" at 50 yds 

very soft recoil with a slide mounted dot.

jglenn21 wrote:Our supers run a  1 - 16 twist and shoot outstanding groups with 126 Dardus SWCs.  Around 720 fps with 3.6 of BE. Easily  under 2" at 50 yds 

very soft recoil with a slide mounted dot.

What crimp and COL are you running. I'm having a 38 super built and would like to get a little ahead of the curve.

Bill

will check and let you know

On mine and my nephew's Supers we are running 1.269 OAL with a .379 Crimp ( Remington brass)

one is a Kart and one a KKM barrel.

our recoil springs are 8 lb ISMI with 4 coils cut off.

you can run 3.6-3.8 gr of BE to find what your gun likes. We all pretty much use.356 sized bullets. I have tried some .357 and didn't see anything there in my Kart

jglenn21 wrote:On mine and my nephew's Supers we are running 1.269 OAL with a .379 Crimp ( Remington brass)

one is a Kart and one a KKM barrel.

our recoil springs are 8 lb ISMI with 4 coils cut off.

you can run 3.6-3.8 gr of BE to find what your gun likes. We all pretty much use.356 sized bullets. I have tried some .357 and didn't see anything there in my Kart

Thank you for the information. This will make dialing in my new gun a lot easier. Can't wait to receive it.

Bill

Rob Kovach wrote:I'm interested in understanding how .38 super can deliver good 50 yard accuracy at 700fps but 9mm cannot.

I'm wondering the same thing. Especially when they are both using the same bullets, with the same barrel (twist rates). But over and over, you hear the people who know saying that 9mm needs to be run fast.

Dr. Don on this site had a thread about successfully running 9mm at 700fps using 147gr bullets. He used fast twist (1/10 or 1/12). He's the exception it seems.

Use the newer 38 Super Comp brass from Starline.  It drops the semi-rim of the 38 Super and uses the 9x19 shellholder.  That way you don't have to mess with converting the breechface. 

you can also use 9mm Largo cases if you can't find the 38 Super Comp or just turn down the rims of the 38 Super brass.

Bruce

bruce.drake wrote:you can also use 9mm Largo cases if you can't find the 38 Super Comp or just turn down the rims of the 38 Super brass.

Bruce

But isn't the 9mm Largo case tapered?  I would think the 9mm Steyr would be a better fit since it is straight-walled, but the Steyr case is longer than 38 Super and might not fit in all 38 Super chambers.

bruce.drake wrote:Use the newer 38 Super Comp brass from Starline.  It drops the semi-rim of the 38 Super and uses the 9x19 shellholder.  That way you don't have to mess with converting the breechface. 

you can also use 9mm Largo cases if you can't find the 38 Super Comp or just turn down the rims of the 38 Super brass.

Bruce

This whole post confused me so I got out the calipers. I guess I got real lucky. I have posted previously that I never had to do anything to my 9mm RO except barrel and magazines to get it to run flawlessly with 38 Super. That is because the 1200 cases I bought from Midway when I converted were all 38 Super Competition. The rim measures .386 and works great. The other part about being real lucky is that they work so well in the 40 S&W conversion also. There was a little bad luck too. I just bought 200 38 Super+p brass and loaded them hot for the RO. They measure .400. I will have to keep them separated from the other brass or possibly have big problems. I now have 200 hot rounds that will work best in the pistol they were not intended for. Oh well

S148 wrote:

bruce.drake wrote:you can also use 9mm Largo cases if you can't find the 38 Super Comp or just turn down the rims of the 38 Super brass.

Bruce

But isn't the 9mm Largo case tapered?  I would think the 9mm Steyr would be a better fit since it is straight-walled, but the Steyr case is longer than 38 Super and might not fit in all 38 Super chambers.

If you are using 38 Super dies, the taper is removed from the 9mm Largo case when you size the case for the first time.

The biggest thing about a Super shooting well at 50 yards and the 9 not is projectiles.  The super you're shooting a lead bullet.  As has been demonstrated time and time again, lead 9mm just doesn't play well at 50 yards.  If you run a jacketed 9mm you need to bring up the velocity to make the round shoot.  It's apples and oranges on this one.

That being said, I'm going to talk with KKM about a 9mm 1911 barrel to see if something can be done to find a "soft" shooting 9mm load.  Time will tell.

KC,

My 10-twist 9mm (Clark barrel) groups well at 50 with the Magnus 147gr (#403 I think from memory) at 700-730 fps.  That is pretty soft.  Not a 1" gun, but will hold 2-2.5" pretty consistently.

KKM just experimeted with 1:10 twist 9mm barrels. They could not get it to group above 800 fps with any bullet. They are not going to offer that twist in 9mm based on their results. They said it could be because of their rifling process is different from other manufacturers. So in their minds they are dealing with factory ammunition. Might be great barrel for reloads. Thought I'd share what I found out a couple weeks ago.
Jon

good to know they are doing 1 in 10 .355 barrels now.

I think the difference is in the throating.

My .38 spl on 1911 platform with 1:10 twist shoots 1.5" @ 50 yds. My best is 889. It works fine!
Jon