Colt police positive, puzzling - Page 3

J.E.Walker · March 24, 2015, 10:40 PM

Quote:

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

-TL

James K · March 24, 2015, 11:12 PM

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

tangolima · March 24, 2015, 11:17 PM

Quote:

Originally Posted by James K

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

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

-TL

Gaucho Gringo · March 24, 2015, 11:42 PM

.38 short Colt ammo is available here:

https://www.targetsportsusa.com/remi...sc-p-4108.aspx

James K · March 25, 2015, 07:01 PM

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

**Mike Irwin** · March 26, 2015, 05:39 AM

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.

tangolima · March 28, 2015, 04:33 AM

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

tangolima · April 20, 2015, 11:44 PM

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

Salmoneye · April 21, 2015, 06:32 AM

Thanks for the update!

March 24, 2015, 11:42 PM	#54
Gaucho Gringo Senior Member Join Date: May 17, 2007 Location: Vancouver, WA Posts: 366	.38 short Colt ammo is available here: https://www.targetsportsusa.com/remi...sc-p-4108.aspx __________________ 357 Taurus Gaucho, 22 Heritage RR, 2-Pietta 1858 44 NMA Remingtons, Pietta, Euroarms & ASM 36 1851 Navies, 31 Uberti 1849, 12 ga H&R Topper, 16 Ga Western Field, 43 Spanish Remington Rolling Block, 44 ASM Colt Walker, High Point C9 9mm, Winchester 1906 22, Rossi 62 22 rifle, Uberti 1860, H&A & IJ 32 S&W BreakTop, 36 Euroarms 1858, 32 H&R 04, 22mag NAA SS BP revolver, .44 Rodgers & Spencer, IJ 38 S&W BreakTop, IJ 22 Sealed 8

March 26, 2015, 05:39 AM	#56
Mike Irwin Staff Join Date: April 13, 2000 Location: Northern Virginia Posts: 41,380	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. __________________ "The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza Baby Jesus cries when the fat redneck doesn't have military-grade firepower.

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March 24, 2015, 11:12 PM	#52
James K Member In Memoriam Join Date: March 17, 1999 Posts: 24,383	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

March 25, 2015, 07:01 PM	#55
James K Member In Memoriam Join Date: March 17, 1999 Posts: 24,383	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

March 28, 2015, 04:33 AM	#57
tangolima Senior Member Join Date: September 28, 2013 Posts: 3,813	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

April 20, 2015, 11:44 PM	#58
tangolima Senior Member Join Date: September 28, 2013 Posts: 3,813	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

April 21, 2015, 06:32 AM	#59
Salmoneye Senior Member Join Date: December 31, 2011 Location: Vermont Posts: 2,076	Thanks for the update!