5/1000 boolit re-sizing, .38 Special?

[hanover67]

I read a couple of threads about resizing, but I'm going to ask for opinions anyway. I have a Colt Officer's Model .38 Spl. with a tight (.353") bore. I've been resizing 148gr wadcutters down from the as-cast diameter of .360" to .354". I recently had boolits slide down into the cases so I miked the expander and it was .355". I called RCBS to see if I could get a .353" expander and they told me to measure the cylinder throats and size boolits to fit the throats. My throats are .358", measured with pin gauges. If I size boolits to .358", that's a 5/1000ths squeeze from the cylinder into the barrel, which seems like a lot. I'm worried about splitting the forcing cone or other pressure problems. I'm using a powder charge of 3.0gr of Bullseye and the boolits are cast from range lead of unknown hardness. The RCBS guy said not to worry because "the gun was designed to shoot .357" or .358" factory ammunition."

Have any of you had this much difference between throat and barrel diameters, and have if so have you had any issues as a result? I've been thinking of getting a .356" sizing die and splitting the difference as a cure.

[theperfessor]

Please don't think I'm questioning your competency, but please tell us how you measured the bore size.

Unless the gun already has something wrong with it I doubt you would have any safety issues with any sensible .38 lead bullet load.

[country gent]

Those colts were also known to have a slight choke or taper to the bore big to small from breech to muzzle. Its harder to check for as you cant push the slug tru the barrel it has to start on one end go in about and inch and come back outOn a recolver this is really hard to accomplish at times.

[SSGOldfart]

Hummm I think I'd try.356 or even a .355 but I'd slug the barrel too

[gray wolf]

Those colts were also known to have a slight choke or taper to the bore big to small from breech to muzzle. Its harder to check for as you cant push the slug tru the barrel it has to start on one end go in about and inch and come back outOn a recolver this is really hard to accomplish at times.

This would be a very good consideration and well worth a look see, cause something doesn't sound correct, if not I made my comments below.

with a tight (.353") bore.
Wow that is a tight groove diameter, what kind of slug did you use to drive down the barrel? Soft lead is the best, no spring back. but in your case spring back sounds doubtful.
Also what did you measure the slug with ? mic, or calipers ? ( important )

I've been resizing 148gr wadcutters down from the as-cast diameter of .360" to .354". I recently had boolits slide down into the cases so
That just ain't right, of course they are going to slide down into the case.
so I miked the expander and it was .355"
You have a standard expander for jacketed bullets, .355 for a 357 J-word. A .354 bullet will have just about NO neck tension and a crimp ain't gonna fix it.

they told me to measure the cylinder throats and size boolits to fit the throats.
That's normally how it's done.

My throats are .358", measured with pin gauges.
.358 sounds about right.

I've been thinking of getting a .356" sizing die and splitting the difference as a cure.
A bran new starline 357 case has an inside diameter of about .355 .356 ain't gonna be a cure, if your correct with the math I would say you have a pretty bad mis match in cylinder throat to groove numbers. .356 sizing die and then you would need some kind of custom expander for the cases, something like a 9MM spud, I still think your neck tension with be all out of whack.
Again if your math is correct and I am just saying, cause it is so far off, I would replace the barrel or swap the gun for another and move on. I think a situation like that will have you chasing a big Rabbit down a lot of holes. But lets see what others have to say, I am just one person with one oppinion.

[dubber123]

I would size to the throats and not worry in the least. Even if it is sizing down that much, it will probably only raise the pressure of a fairly soft lead slug load by a miniscule amount. RCBS is right, factory lead ammo would run right in the .358" range, and I'm sure that old Colt has digested plenty of them without an issue. Unless specially requested, most commercial casters will likely size to .358", so the odds are any lead boolit handloads through it were that diameter too.

[hanover67]

I slugged the barrel with a lead bullet and then measured it with a micrometer at the time, several months ago. I kept the slug, and just re-measured it. The barrel is a 4-groove, and today's diameter is .35435", larger than my initial measurement, but still a lot smaller than .358". I have a .358" sizing die and I'll try some boolits sized to that diameter and see what happens.

[MtGun44]

Size for throats and forget the rest. Undersized helps nothing.

Bill

[3leggedturtle]

I had that problem when using R-P 9mm 147HP's in 357 mag. Used a 222 die to make the 1st 1/3 of the case about .004 smaller than what the 357 dies would do. They shot accurately enough to hit a chuck at 150yards. YMMV 3leg