[Kevin Gibson]

All,

We’ve all heard the story about .38 Supers having lackluster accuracy because the early guns headspaced on the case rim, and that accuracy was improved when Colt’s changed to a barrel that headspaced on the case mouth. Does anyone know when that change was made?

 

[Charlie Petty]

70s....::?:

 

[Kevin Gibson]

The reason I ask is because I have a brand new Colt’s .38 Super and when I drop a round in the barrel, by my eyeball it seems to be headspacing on the rim. And I’ve tried several other rounds and see the same.

 

[Kevin Gibson]

Hey, I just found this post on another forum from a guy called "Superman"
38 Super Headspacing - 1911Forum

Read the 4th one down. I remember Nonte being one of the first to chamber barrels that way, and I also remember the Super Elite. If his description isn't correct, then he's slings a good enough line of bull to fool me.

 

[t-star]

i remember back in 72, one of the first things i was told when i got my brand new government was to replace the barrel with either a bar-sto, or to get a 9mm and "make the chamber longer" - just to circumvent that stupid spacing on the rim thing- making the chamber longer was a 3 drill process as the 9mm uses a tapered case, and the 38 super was a straight- left me kind of you know what considering this was a brand new mk4/series 70-

 

[Charlie Petty]

The thing about series 80 rings a bell

The SAAMI drawing (1983) that I have shows the shoulder and inidcates a headspace dimension of 0.050-0.070 which would be from the back of the hood to the bottom of the shoulder.

It would be a very simple matter to make the case headspace on the mouth by simply cutting the shoulder a little deeper. Don't know what was done and all my expereince with Supers was to fit match barrels for IPSC guns (BarSto) which were alleged to headspace on the mouth or to make .38 Specials out of them.

 

[t-star]

well, the author( it was in guns and ammo at the time ) -one of those do it yourself types used nothing more than a drill press and some "letter" drills- i can't remember the sizes - one to take the taper off the 9mm, one to deepen the chamber and a third ( probably something like a finishing reamer) to re-cut the throat- i do remember he said he could have gotten away with 2, but didn't have the right size
i'm only GUESSING on the third drill

 

[Charlie Petty]

PS:

The case drawing shows a length of 0.900 with a -0.010 tolerance.

That suggests that it does space on the rim... :dunno:

 

[t-star]

however, the premise of the article was that the 38 super is a semi-rim, and that the extractor was slipping off that rim , leaving a no-headspace condition and that was detremental to accuracy- the solution was to make the 38 super headspace on the case mouth and leave the extractor out of it altogether- ie make it the same as the 45 and the 9mm; i can't recall whether the author used a 9mm slide and internals as well or simply re-chambered the barrel- i do remember that the 9mm and the 38 super share the same extractor( so presumably the head size of the 9mm and the 38 super are identical or within tolerances) and frames- ie it's a 9mm or 38 super depending on what colt 's tooling is) for all but the barrel

 

[Charlie Petty]

Kevin let me suggest a simple experiment. :idea:

Carefully measure how far a piece of brass goes into the new chamber and then just file off the rim. Measure again.

If the case goes further into the chamber the rim is an issue... if not it is already hitting the case mouth...

 

[Kevin Gibson]

Darned good idea Charlie; mine definitely headspaces on the case mouth of the Fiocci ammo I have.

 

[Charlie Petty]

Don't you just love it when you're right...

However... much of the time headspace is determined by the extractor and that tells me we shouldn't worry about headspace in 1911 style firearms anyhow.

Bob Day did a series of tests and concluded that headspace is only a problem if the gun won't fire...