Colt police positive, puzzling

.38 Short Colt will fit and fire in a .38 S&W chamber; cases might bulge slightly. As for .38 S&W in a .38 Special/.357 or .38 LC chamber, the operative word is "sometimes."

SAAMI .38 S&W (.38 Colt NP) case diameter specs are .380-.386". .38 Special (.38 SC. ,38 LC, .357 Magnum, .357 Maximum) case diameter specs are .373-.379".

As you see, the upper end of the .38 Special spec is close to the lower end of the .38 S&W spec, and if a slight difference in chamber diameter is added in, the "larger" round will fit and fire in the "smaller" chamber. Just for fun, I tried loading .38 S&W into a dozen .38 Special revolvers and found it fit about half. In some guns, it would fit some of the chambers, but not all.

Jim
 
MY Police Positive made in 1925 has the same measurements as your's which is standard for Colt. In fact, colt used the same barrel measurements on thei 38 NP, .38 special and .357 magnum. Smith and Wesson and othes have the large diameter bbbls and work best with .360 +bullets.
attachment.php



attachment.php
 

Attachments

  • 38ppwhite.jpg
    38ppwhite.jpg
    142 KB · Views: 76
  • 38 S&W loadss.JPG
    38 S&W loadss.JPG
    20.1 KB · Views: 73
"In fact, colt used the same barrel measurements on thei 38 NP, .38 special and .357 magnum. Smith and Wesson and othes have the large diameter bbbls and work best with .360 +bullets."

Now that is news to me. Colt .38 DA barrels ran .370+" groove diameter in the 1889 Navy, which used the old .38 Long Colt heel type bullet running up to .378-380". And they kept the large bore and straight chambers for the Army and Navy revolvers into the 20th century in spite of the Army going to inside lubricated bullets of .357" diameter in 1892. Colt finally changed the groove diameter to .357" at the same time they put shoulders in the chamber for .38 Special around 1903. From then on, Colt's barrel dimensions were different for the .38 Special and .38 Colt New Police.

Jim
 
Here is what W.H.B Smith , Book of Pistols and Revolvers, Castle Books, 8th edition p. 391 had to say about the Police Positive in 38 NP/S&W:
Bore diameter- .347--001
Groove Diameter -.354-.001

Smith and Wesson Regulation Police, Smith and Wesson Safety Hammerless Smith and Wesson Perfected Model:
Land Diameter- .350-.351
Groove Diameter- .360=.361
p.398- 402
 
Last edited:
J.E.Walker said:
Here is what W.H.B Smith , Book of Pistols and Revolvers, Castle Books, 8th edition p. 391 had to say about the Police Positive in 38 NP/S&W:
Bore diameter- .347--001
Groove Diameter -.354-.001

Smith and Wesson Regulation Police, Smith and Wesson Safety Hammerless Smith and Wesson Perfected Model:
Land Diameter- .350-.351
Groove Diameter- .360=.361
p.398- 402
Click to expand...
Great! That solves the puzzle. Thanks. Even for 0.357" projectiles, groove diameter of 0.354" is still a bit tight. But it is what it is. I just need to work with what I have. Good news though. I can easily find 0.357" or 0.355" bullets, but they don't sell 0.361" everywhere.

Does the book say anything about enfield #2 in 0.38 s&w? That's the next gun I will be working on. Thanks in advance.

-TL
 
I was hoping to find similar information for the Webley and Enfields. There are large sections on them but no bore measurements. The narrow barrels on the colts are sometimes credited with the fine accuracy of the Pythons. Before I found out about the measurements on the police positive, I found a source for .361" bullets and they work just fine through the tight bore. The speer handbook used to - maybe still does list loads for the .358 hollow based considering it at least usable in all of the barrels.
 
It's quite alright the book doesn't have the numbers. I'm slugging it anyway.

I bought 0.361" from Missouri bullet company. They worked. But I will need to seat the bullets deep enough to chamber. Also it doesn't feel right to use the throat to size down the bullet. I plan to use 0.361" on the enfield, and keep feeding the colt with 0.358" or 0.356". So far 0.358" seem working better than 0.361" in the colt.

-TL
 
those are the bullets Ive been using. I did have to pay attention to seating dept in the Colt but not so much in the old Owl head. They really are pretty good bullets and will come into their own if I ever pick up a Regulation Police.
 
With respect to the late Walter Harold Black Smith, I think he got his guns mixed up. There is no way Colt would have made a PP in .38 Colt NP with those barrel dimensions. Just now I slugged a PPS in .38 Special and got .354" groove and .346" land, almost exactly the dimensions Smith gives for the .38 Colt NP barrel.

The SAAMI specs for .38 Special are .355 and .346 respectively.

Jim
 
James K said:
With respect to the late Walter Harold Black Smith, I think he got his guns mixed up. There is no way Colt would have made a PP in .38 Colt NP with those barrel dimensions. Just now I slugged a PPS in .38 Special and got .354" groove and .346" land, almost exactly the dimensions Smith gives for the .38 Colt NP barrel.

The SAAMI specs for .38 Special are .355 and .346 respectively.

Jim
Click to expand...
I am holding one in my hand right now. Colt police positive 0.38 NP. Groove diameter 0.354".

-TL
 
I have to apologize and withdraw my comments. I just slugged a PP chambered for the .38 Colt NP and the barrel dimensions are just as Tangolima (and W.H.B. Smith) say. I find it hard to believe Colt was so far off with its barrel dimensions, but then they were around before SAAMI and maybe either the results worked or they just didn't care. (At the low pressures involved, the latter might not be far from the case.)

Anyway, this whole thread has been a valuable lesson in not taking anything for granted!

Jim
 
James K said:
I have to apologize and withdraw my comments. I just slugged a PP chambered for the .38 Colt NP and the barrel dimensions are just as Tangolima (and W.H.B. Smith) say. I find it hard to believe Colt was so far off with its barrel dimensions, but then they were around before SAAMI and maybe either the results worked or they just didn't care. (At the low pressures involved, the latter might not be far from the case.)

Anyway, this whole thread has been a valuable lesson in not taking anything for granted!

Jim
Click to expand...
It is quite alright. Different pieces complete a big jigsaw puzzle. I thank you, and everyone who has responded, for your input.

-TL
 
When I get a chance, I'll check a Colt Model 1877 and a Model 1892, and see what the groove and land diameters are. I have long thought that when Colt changed the New Army/New Navy to use .38 Special, they changed the barrel dimensions also, but now I wonder if they did and what the dimensions were before the conversion.

Jim
 
As I noted in my post earlier in this thread, I've seen a Colt .38 NP with a groove diameter of .352.

As I also noted, it's not that big a deal, really.

The .38 New Police/.38 S&W is a low pressure round and the bullets were traditionally all lead.

They would easily swage down to the tighter Colt dimensions.

By adopting a common barrel dimension they didn't have to keep a separate set of tooling in stock for .38 NP barrels.
 
Colt 38 revolvers tend to have tight bores, <0.357" groove diameter. I guess this is well established. It doesn't matter much to use as big as 0.361" cast bullets. This is also accepted.

But knowing what I know, it would be silly for me to keep on using 0.361" bullets as there is no advantage to do so. Normal 0.358" bullets work better.

I was about to slug my enfield revolver. That I had this idea. Instead I just pin gauged the throat. It was 0.358". There no point using 0.361" bullets foe this gun either. The throat will just size it down to 0.358". I am going to apply the same principle for all revolvers.

-TL
 
Tried using 0.356" (9mm) cast bullets today. It worked great. It is the best accuracy result I have gotten so far, better than 0.358" (38 spl), and kicking the butt of 0.361" (38 s&w). It will be the bullet of choice in my future loads. Thanks gentlemen for your inputs.

-TL
 
You must log in or register to reply here.
Back
Top