Which Diam. .45 LRN?

[cmort666]

Years ago, I received as a gift from a family friend, a Colt New Service. It's got a .45acp cylinder, but you couldn't hit the Pacific Ocean with it, shooting underwater. It keyholes virtually every shot.

I puzzled over the problem for the better part of a year before possibly hitting on the cause. I was told that it was an M1917. Of course GI M1917s weren't nickeled. Looking at the details of the gun, and the serial number, indicates that it's a post WWI commercial New Service. The gun was taken off of a Mexican criminal in Chicago back in the '60s. I surmise that at some point (possibly in Mexico), a .45 Colt gun was converted to .45acp because the ammunition was easier and cheaper to find. .45 Colt guns of that vintage typically have larger bores than .45acp guns.

My question: Penn Bullets offers a variety of bullet diameters for their 230gr. LRN (and other .45acp bullets), including .454 and .455. I think that if I use a larger diameter bullet, the accuracy problem will be cured. Which diameter would you use?

It's a neat old gun, but pretty much useless for shooting as-is. I was going to replace the cylinder, but nobody had a .45 Colt cylinder for a reasonable price.

If a larger diameter bullet works, it'll solve the problem at minimal cost.

Thanks.

 

[ChuckS1]

I'd slug the barrel to see what the diameter is, first of all. Then I'd measure the cylinder throats to get those diameters and match the bullet diameter to the cylinder throats. Lastly, I wouldn't necessarily limit myself to a 230 grain bullet.

I'm trying to visualize how a .45 ACP cylinder would fit in a .45 Colt frame. Aren't the cylinders different lengths? So unless the barrel was changed/adjusted as well, you'd have a relatively large gap there. You didn't mention that.

Anyways, if it were me, I'd start off with the .454 bullets and see how it shoots.

 

[john traveler]

The commercial Colt New Service barrels were marked with the caliber on the left side near the frame.

If yours is a military barrel, it may be unmarked, but will be .45 ACP.

The Colt barrels are notorious for having shallow rifling. If the rifling rusted and was cleaned off once or twice, it will have a hard time stabilizing any lead bullet. You might try Remington or Winchester 250 grain RNF hollow-based bullets intended for .45 Colt loaded in .45 Auto Rim cases. If the gun won't shoot with those, it won't shoot with any lead bullet, no matter what diameter.

 

[cmort666]

Originally posted by ChuckS1:
I'd slug the barrel to see what the diameter is, first of all. Then I'd measure the cylinder throats to get those diameters and match the bullet diameter to the cylinder throats. Lastly, I wouldn't necessarily limit myself to a 230 grain bullet.

I'm trying to visualize how a .45 ACP cylinder would fit in a .45 Colt frame. Aren't the cylinders different lengths? So unless the barrel was changed/adjusted as well, you'd have a relatively large gap there. You didn't mention that.

Anyways, if it were me, I'd start off with the .454 bullets and see how it shoots.

Frame size is identical for all calibers in the New Service as far as I know. Barrels used to be widely and cheaply available, so it's entirely possible that it was changed or the barrel hood turned down to allow it to be screwed in deeper.

Barrel-cylinder gap isn't excessive. It's been a few years since anyone looked at it. I don't remember what the measurements of the cylinder mouths was, but I don't think they were out of line for a .45acp cylinder.

 

[cmort666]

Originally posted by john traveler:
The commercial Colt New Service barrels were marked with the caliber on the left side near the frame.

If yours is a military barrel, it may be unmarked, but will be .45 ACP.

The Colt barrels are notorious for having shallow rifling. If the rifling rusted and was cleaned off once or twice, it will have a hard time stabilizing any lead bullet. You might try Remington or Winchester 250 grain RNF hollow-based bullets intended for .45 Colt loaded in .45 Auto Rim cases. If the gun won't shoot with those, it won't shoot with any lead bullet, no matter what diameter.

The barrel says, "New Service 45 Colt". I've got the Serven Colt book, but nothing more detailed about the New Service. Now that I think about it, that roll mark just SCREAMS ".45 Long Colt" to me.

 

[john traveler]

Your .45 Colt barrel may be the twin to mine. It was marked .45 Colt and the groove diameter measured some 0.457", same as a .455 Eley marked barrel I had. Nothing would shoot in that thing. I tried several hundred cast bullets in various diameters, RN, SWC, RNF, etc, and nothing would group inside of 6"-7" at 25 yards. It would lead like crazy with both soft and hard bullets, and 230 grain FMJ would tumble into the target. I ended up rebarreling with a surplus .45 ACP barrel to get an acceptable shooter.

 

[cmort666]

Originally posted by john traveler:
Your .45 Colt barrel may be the twin to mine. It was marked .45 Colt and the groove diameter measured some 0.457", same as a .455 Eley marked barrel I had. Nothing would shoot in that thing. I tried several hundred cast bullets in various diameters, RN, SWC, RNF, etc, and nothing would group inside of 6"-7" at 25 yards. It would lead like crazy with both soft and hard bullets, and 230 grain FMJ would tumble into the target. I ended up rebarreling with a surplus .45 ACP barrel to get an acceptable shooter.

You got GROUPS???

I've got a .476 Ely cylinder lying around.

I think I'll try the .455 bullet first. I just did some quick checking and didn't find any .45acp barrels.