38 Super headspace is making my head spin

All of the literature seems to blame the "accuracy" problems early in this cartridges' life, on the fact that chambers were cut to headspace on the semi-rim.  Doesn't the 38 Special, one of the most accurate cartridges we have,  headspace on the rim?  And wouldn't you think that headspacing on the rim actually gives you MORE precise positioning of the bullet relative to the beginning of the rifling, since we no longer have to worry about case length?  Why am I thinking that the Super should be, and have always been, a more accurate cartridge than anything that headspaces on the case mouth?

The semi rim is too small for reliable headspacing so we intentionally cut the chambers to headspace on the mouth. The 32acp is also a semi rimmed case and we do the same thing there. The 38 special rim is huge by comparison.

Im sure all factory supers today headspace off the case mouth. Think it was BarSto that initially made the change

The Super Comp brass which is all I use is pretty much rimless.

We should thank the action pistol community for bringing us the improved barreling of the .38 Super. They wanted more power than 9mm and more capacity than a .45 acp, but more accuracy than the then .38 Supers. I don't know who came up with the idea, but as was mentioned I am pretty sure it was Irving Stone at Bar-Sto who first produced barrels in .38 Super head spacing off the neck, instead of the rim. Early 1980s era.

Does anyone know for sure, if the most accurate .38 Special semi-autos headspace off the neck? Should they? Interesting....

I don’t think it was Irving Stone alone who made the switch.  Like most things it was likely a small set of individuals who came up with the idea.  Irving Stone likely made it more readily available.

As for the 38 match barrels?  I dunno.  They kinda lost favor thru the 80s and the concept likely didn’t get passed tru.  The rim really does give adequate headspace control even with just a partial engagement like a hooded barrel.  

Neither of these cartridges have the headspace dimensions on the case mouth codified in the SAAMI chamber drawings.

Allgoodhits wrote:We should thank the action pistol community for bringing us the improved barreling of the .38 Super. They wanted more power than 9mm and more capacity than a .45 acp, but more accuracy than the then .38 Supers. I don't know who came up with the idea, but as was mentioned I am pretty sure it was Irving Stone at Bar-Sto who first produced barrels in .38 Super head spacing off the neck, instead of the rim. Early 1980s era.

Does anyone know for sure, if the most accurate .38 Special semi-autos headspace off the neck? Should they? Interesting....

I don’t work on or shoot M52 .38 specials, so they are not included. They also in my time as a serious BE competitor did not provide the accuracy to shoot and win matches against our countries best shooters.
All the 1911 .38 special conversions I have seen have always headspaced off the rim and the end of the chamber varies from 0.020-0.030” beyond the case mouth. I think that is excessive but they still shoot well; 1.5” ish at 50 yds.
Jon

The following is from this article:  http://www.shootingtimes.com/editorial/super-accurate-38-super-loads/326242


"The .38 Super is a very accurate cartridge, something not so well known to many shooters just a few decades ago. In fact, many Colt Super 38 1911 pistols had a reputation for poor accuracy. The problem was traced to excessive headspace. The chambers were cut too deep because the round was expected to headspace on the semi-rim. The problem was that the semi-rim could slide past the cutout in the barrel’s hood, allowing the round to slip too far forward and essentially headspace off the extractor. Accuracy suffered.

John Rollins and Richard Shockley identified the problem and sleeved the barrel chamber so the cartridge headspaced off the case mouth. They described this in an article in the June 1961 issue of American Rifleman. Once properly headspaced, accuracy improved."

Reviving this with new interest and a curious observation….
The SAMMI engineering drawing available on-line is from a fairly new specification (2022) yet the chamber is still showing headspacing off of the semi-rim. Shouldn’t the spec have been revised by 2022 to show headspace off the mouth? With no industry spec drawing for a guide, what are barrel and reamer manufacturers using for guidance regarding dimensions? And what are pistolsmiths using when they start with a short-chambered style of barrel?  Most of the dimensions from SAMMI for their rim-headspacing chamber could be reused but there are still some missing dimensions that are unique to a case mouth-headspacing chamber.

inthebeech wrote:Reviving this with new interest and a curious observation….
The SAMMI engineering drawing available on-line is from a fairly new specification (2022) yet the chamber is still showing headspacing off of the semi-rim. Shouldn’t the spec have been revised by 2022 to show headspace off the mouth? With no industry spec drawing for a guide, what are barrel and reamer manufacturers using for guidance regarding dimensions? And what are pistolsmiths using when they start with a short-chambered style of barrel?  Most of the dimensions from SAMMI for their rim-headspacing chamber could be reused but there are still some missing dimensions that are unique to a case mouth-headspacing chamber.

You can order a custom reamer to whatever specification that you want, the wildcat guys do it all the time.

I use a Manson reamer for all the supers I've chambered and they all chamber off the case nose. I generally clearance the hood a bit to insure that the semi rim is not involved. All the supers I've messed with have shot very well with either lead or jacketed. The reamer was their std. Super cut.

Hmmmm ....

Match 45's headspace off the case mouth. So do 9mm's ...

Why should a 38 Super be any different?

Dear Lord people, it isn't that hard.

38super was hatched out of making the 38 auto (acp) meaner and faster.  The 38 auto was designed for the Colt 1900 that headspaced off the semi-rim.  The 38 super has grown over the past 80+ years and most folks now run rimless versions of 38 super (38sc, 38tj, 9x23, etc) for enhanced reliability feeding.  

I had George Smith re-tune a 38 super IPSC pistol for me to run 38sc.  He just re-tuned the extractor for the marginally smaller rim (0.022" smaller diameter). He also fit a new cone comp, Hiett Red Buff mount for the C-More and some trigger work.  That pistol ran thousands of rounds without a hitch.

Headspacing off the case mount works.  It has for over 100 years.  300wm headspaces off the belt on the case, but any good gunsmith will also ensure the distance from bolt face to shoulder is maintained in a tight band.