Short for chamber ammunition, 45 Schofield in a 45 Colt vs in a Schofield chamber.

["Big Boston"]

Life can be interesting. 

 

Several years ago i bought 100 45 Schofield brass to "experiment" with. Recently I purchased a pair of 71/72 open tops chambered in 45 S&W Schofield. before they arrived i used the opportunity to work up a load so that when they came I'd have something to shoot in them. The cylinders are chambered 45 S&W Schofield. the revolvers are sequential serial numbered Uberti early model 71/72 open tops catalog 11114. They have seen a bit of previous service as cowboy guns and I'm working on them to clean up a few issues. Yes, online purchase and pictures do not tell the whole story. Another learning opportunity paid for by yours truly. 

 

To the point, My load was developed in a 4 5/8" barreled Ruger Vaquero (original version) and as it was with some left over 452AA powder that load was posted in a previous thread. 

 

In that gun, with its 4 5/8 barrel the chronograph results were:

 

Velocity Av

648.7/643.6

Es

26/23.4

Sd

10.63/9.53

Shots

5>/5<

 

A decent load with bullets I had on hand. 

 

Although a sequential pair, my 71/72s were not entirely the same and there were issues. One had some timing and lockup issues so I concentrated on the other first. After a brief inspection and clean/lube I completed a chrono test. 

 

Velocity Av

598.3/588

Es

35.7/15.2

Sd

14.7/6

Shots

5>/5<

 

No what I expected at all, shorter chamber/cylinder and a 5 1/2" barrel, I though there would be a velocity gain. The barrel is a bit on the loose side, groove at app 454, but still not what I expected. 

 

I addressed the timing issue, will have to order parts to correct the timing, but as it was safe to shoot, I ran it over the chrono as well. 

 

Velocity Av

633.4/636.7

Es

19.55/4.16

Sd

8.42/2.0

Shots

5>/5<

 

The groove diameter on this one is 452, and that seems to have restored some of the velocity, but still not equal to the velocity with my 45 Colt. 

 

This is the first time that I have owned firearms where testing of this kind were possible. I've used 38 Spl in my 357s and 44 Spl in my 44 Mag, but don't own a 38 or 44 Special chambered firearm. Is a velocity gain in a longer chamber a phenomenon or are there other factors in play that I've not considered. 

 

BB

 

Reference:

 

Calibre	45 S&W Schofield	Date Loaded	2022-05-04
Powder	452AA (Ontario)	Weight in Grains	3.7 (4S)
Bullet	Cactus 230 gr. 45 ACP - pit run	Weight in Grains	236
Primer	CCI 300 LP	Loaded OAL	1.375
Case	¬ 45 ¬  SCHOFIELD	Weight in Grains	99

 

That is the load, IMO not much different that what you'd get with the same or a bit more Bullseye.

 

[Colorado Coffinmaker]

Yes.  Several Factors.

 

Ruger chambers are notorious for undersize Cylinder throats.  Rugers often have tight Barrel to cylinder gap.  Odd forcing cone. 

 

Uberti chambers are not size matched to Ruger.  Uberti Open Top pattern guns normally have issues with Barrel to Arbor fit which contributes to Barrel to Cylinder gap issues.   Short/Steep forcing cones.

 

Powder the exact same lot??

 

Bullets the exact same lot??

 

All of the above will affect your results.  You also have to hold yer tongue just right 

[Chantry]

Years and years ago (20+ I think) I read in a gun magazine that even in identical calibers and barrel lengths, some makers just had "faster" barrels.  IIRC I remember the article correctly a Ruger GP-100 with a 4" barrel always gave slightly higher velocities than a S&W with a 4" barrel.  I believe the testing was done with factory ammo.

["Big Boston"]

15 hours ago, Colorado Coffinmaker said:

Uberti chambers are not size matched to Ruger.  Uberti Open Top pattern guns normally have issues with Barrel to Arbor fit which contributes to Barrel to Cylinder gap issues.   Short/Steep forcing cones.

 

Powder the exact same lot?? Yes, exactly.

 

Bullets the exact same lot?? and yes, from the same pail of bullets.

 

 

To my way of thinking a shorter chamber should increase velocity. The chambers seem a bit tighter in the open tops as well.

 

The cylinders that is in the open tops have throats all over the map, from 452 to 454, yest ES/Sd doesn't seem to reflect that. 

 

Ruger has uniform 451 throats and the groove. dia also 451, It has always worked well, not an issue IMHO. Of the open tops the one with a 454 groove has lower velocity than the 452 grooved barrel. That would seem to indicate the larger grooved barrel isn't sealing as well. 

 

I think my old friends expression, "It's just FM" seems to apply. (FM, Flipping Magic)

 

BB

[Colorado Coffinmaker]

There is actually a standard set of questions and answers.

 

Question:  Can you hit the target with the load??

 

Answer:  NO.  Then change the load to hit the target.

 

Answer:  YES.  No action required.  Any extraneous information is useless trivia.

 

Fairly simple.

 

Ya ever gonna get a SASS Member Number??