Sizing Question

[Drifter]

Yesterday I made a chamber cast of a 1911 .45 cal. barrel. The throat measures .4535 and the groove dia. is .4535 also and my casting sizes are around .453 to .454. I assume I should size the boolits to .453 is this correct?

Drifter

[44man]

If you used Cerro-Safe, you do not have exact sizes! After an hour or a week, subtract .4% and you will be close but still not exact. DO NOT DEPEND ON IT FOR SIZE! You are much better off expanding a soft lead slug in the bore.

[Dale53]

I agree with 44man. A chamber cast is excellent for determining the SHAPE of a chamber. However, for exact measurements, you are much better off with a soft lead slug properly applied to the barrel (you can impact expand for the exact chamber dimensions).

Dale53

[John Boy]

Drifter, general rule of thumb ... shoot lead bullets 0.002 to 0.003 larger than groove diameter

[Lloyd Smale]

I shoot alot of 1911s and have never seen one shot a lick better with bullets bigger then 452. Some like 451 but there rare too. I just about standardized on 452 for the acp.

[Drifter]

Well I think I'm going to have to go back to the drawing board. A couple of weeks ago I slugged the throat/groove area by driving a egg sinker in it and came up with .452 grove dia. and as I stated above yesterday my cast with Cerro-Safe was 453.5 for both the throat and groove area after one hour. Today I used an unsized boolit and came up with 451.5 groove dia. by pressing it into the bore with a drill press. I now feel that my last measurement (451.5) is the most accurate for the groove dia. but I would like to get a good measurement on the throat.

44 & Dale, explain to me what you're talking about when you say expand or impact expand a soft lead slug. I have plenty of stick on WW for making a soft slug but what would be the easiest way to make it?

Thanks
Drifter

[44man]

Easy, start a pure lead ball or slug into the barrel a short way (Or the throat if you need it.) Put a close fitting brass rod in against it for an anvil. Put another rod against the other side of the slug and tap it with a hammer to expand it into the rifling nice and tight. Then gently tap it out. Be sure to oil the bore lightly first.
Don't use hard lead!
Very easy with a .45 ACP barrel or rifle. Revolvers take a little more work and if you need that info, ask.

[Drifter]

Thanks 44man I'll try that.

[Dale53]

44man is "spot on". In a rifle, you can use a case full of lead (a case fired from you rifle). Then chamber the case, drop a round ball (pure lead) larger than your barrel (at least one caliber larger) then drive the ball in the muzzle with a soft hammer (you do NOT want to damage the muzzle). Drive it down with a strong cleaning rod (brass nearly the size of the barrel is best but you can do it with a wooden dowel) until it contacts the lead in the case, Then, hammer it gently until you feel it expand and "set up". Remove the case from the rifle and CAREFULLY remove the lead slug. It will give you a perfect picture of the throat.

Note: If you have a long throat, you will need a soft lead bullet of the SAME caliber (a solid base wadcutter is nice). The bullet, being longer, will give you more information on the long throat.

Dale53

[Drifter]

Thanks 44man and Dale53

I went to Lowe's this morning and bought a 7/16 wood dowel and then went to a local gun store and bought a box of .440 soft round balls. After cutting the dowel approx. an inch longer than the barrel I inserted it in the barrel from the muzzle end (was almost a perfect fit, snug but not tight) and pushed it to the area that I wanted to measure. Next I dropped a .440 round ball in the chamber end of the barrel and pushed it into the throat/groove area (again an almost perfect fit, snug but not tight) and then adjusted the wood dowel to position the round ball exactly where I wanted to take the measurement, turned the barrel up in vertical position with the dowel against my work bench then took another dowel about 5 " long and from the breach end tapped it against the round ball until the ball flattened out and expanded to the inside of the barrel. You guys are right pretty easy. :-D I don't think I'll be using the Cerro-Safe anymore because the measurements were off by .001 to .002 and I followed the directions to a T but it does make a nice looking casting of your chamber for what it's worth.

My measurements are 452.5 throat and 451.5 groove diameter with a very very short throat. I'm totally satisfied with these measurements so now my question is what should I size to, I'm thinking .452 is this correct?

Drifter