>38 S&W / Colt new Police, information needed

[velocette]

I recently purchased a Colt Police Positive revolver. by its serial # it was made in 1918. Barrel is marked just with Colt Police Positive .38. According to the books The correct lead bullet diameter should be 0.360". When I slugged the barrel (with a 9.356" dia. 9mm bullet) the slug came out shiny on all sides & clearly swaged down a bit, it was also tight all the way through. Clearly contact was made all the way around. The slug diameter was 0.355". . New loaded .38 S&W bullets measure 0.358" & just barely fit into the front of the cylinder. What am I seeing here? or is all this just normal?

Roger

 

[Jim Watson]

Colt revolvers have commonly run smaller in diameter than Smith. After they got over heel bullets, at least.
The swaged bullet in factory .38 NP will squeeze right down.

 

[Johnm1]

the slug came out shiny on all sides & clearly swaged down a bit, it was also tight all the way through. Clearly contact was made all the way around. The slug diameter was 0.355".

It is possible that the. 355" bullet you used to slug the bore was engraved by the rifling but not for its entire depth. I use dead soft round ball of a caliber greater than the bore. For 38 camliber I use a 45 caliber ball. A ring of lead is shaved off as the slug is progressed through the muzzle. That way we are certain the slug reached the bottom of the rifling. If you dont have round ball try to find fishing sinkers of a large enough diameter to accomplish the same effect. Just make sure they are dead soft lead.

I would think that the bore would measure .360 at the bottom of the rifling. But we won't be sure until the bore is slugged.

 

[mcb]

Cerrosafe and a hot-air heat-gun is a really easy way to get accurate measurement of chambers and/or rifling without driving lead through the barrel.

 

[herrwalther]

My wife has the same revolver, made a few years later. I keep a couple boxes on hand for her. I never felt the need to slug the barrel as the bore looked fine when inspected. Fiocchi makes a FMJ 145gr round that works very well in the old Colt. The problem, is finding it in stock.

https://redriverrange.com/product/f...8-sw-145-gr-full-metal-jacket-fmj-50-bx-20-cs

 

[RevolvingGarbage]

Despite the standard bore diameter of .38S&W/C.N.P being .360, it’s been noted in several sources that the Colt revolvers so chambered will have smaller diameter bores, with .355 being the most common I’ve heard of. I wonder about how this effects the ballistics of these guns but I haven’t seen any study or comparison to really know. I suspect with a decently stout .38S&W load it probably boosts the velocity a bit higher still, and because the Colt revolvers are solid framed and well built there is little concern about causing damage with sane .38S&W loads. I would be more worried that the combination of increased friction from the bullet being squeezed down the bore and the very lightly loaded .38S&W factory ammo that all U.S. manufacturers tend to sell might cause a bullet to fail to leave the barrel leaving a bore obstruction in the way for any subsequent shots if the situation goes unnoticed by the shooter.

 

[velocette]

Soon, I will have firing line answers. Will try some Missouri bullets company .38 S&W bullets, brinell 12, .361 diameter 145 grain bullet over a mild dose of Bullseye.
Also have some .358" .38 spl bullets at 125 grain and some 115 gr soft .355 9mm bullets. We shall soon see.

 

[RevolvingGarbage]

Soon, I will have firing line answers. Will try some Missouri bullets company .38 S&W bullets, brinell 12, .361 diameter 145 grain bullet over a mild dose of Bullseye.
Also have some .358" .38 spl bullets at 125 grain and some 115 gr soft .355 9mm bullets. We shall soon see.

I use these same Missouri bullet company bullets for .38S&W with HP38 and have had good results. My safe and sane general load is 2.4-2.5gr. Good effect and accuracy, and won’t harm even the less sturdy American .38S&W top breaks.

I also tried .355 124gr lead 9x19 projectiles with a compressed case full of pyrodex behind them years ago and while absolutely filthy they worked decent.

 

[Sarge7402]

I've got a S&W Regulation Police in .38 S&W and it shoots just fine with reloads using .358 dia cast slugs. Makes a great big bore kit gun for woods loofing

 

[velocette]

Checked again, Slugged barrel with 0.356" soft cast 9mm bullet. Came out the same. 0.355 outside to outside, NOT measuring rifling grooves which are clean and sharp.
So, not having set of .38 S&W loading dies, I set about to improvise. (My Marine son taught me to improvise, adapt and overcome.)
I had 9, .38 S&W brass cases from a display of much older .38 S&Ws, so I used my .38 spl sizing / decapping die, then for the rest, I used my Dillon SQ deal 9mm progressive. The flaring station, seating station and crimping station were all just about perfect for the .38 S&W, using the .38 spl, shellplate. re-capped with a hand priming tool, measured 2.5 gr. bullseye powder with a trickler, then seated and crimped in the Dillon.
The 9 rounds came out just fine, chamber properly and will soon be sent downrange, probably Thursday, if it doesn't rain.

 

[mcb]

How is a .356 diameter bullet going to tell you if you barrel has a bore diameter larger than .356?

I have no doubt 9mm bullets will work safely in a 38 S&W but I also would not be surprised if accuracy is poor or leading is an issue.

When I reload 38 S&W I use a 38 ACP die for sizings (it's technically .001 undersized but works well) I then use 9mm seating and crimping dies though I never actually get to the crimp part of the 9mm die and just use the tapered body to remove the flare in the case. I use proper .361 diameter bullets from Matt's bullets and have had great success in my Webley Mark IV.

 

[velocette]

mcb. please check the post from 'revolving garbage' above for the answer to your question.
My barrel does not have a bore diameter larger than 0.356, it is in fact 0.355". According to revolving garbage above, that is not uncommon.
Lord only knows what Colt was thinking or doing in 1918 when they made my revolver.

 

[mcb]

mcb. please check the post from 'revolving garbage' above for the answer to your question.
My barrel does not have a bore diameter larger than 0.356, it is in fact 0.355". According to revolving garbage above, that is not uncommon.
Lord only knows what Colt was thinking or doing in 1918 when they made my revolver.

You might be correct but my point was simply if you think the bore might be as large as .361 it would make sense to slug it with a bullet equal to or larger than .361. If you stuff a .356 bullet down a .361 grove diameter barrel its still going to measure ~ .356 and not give you an accurate indication of grove diameter.