Why Not Blue Dot or ?

[Yondering]

I use muzzleloader round balls for slugging. Generally I just use 50 cal balls, since that's what I have, but of course 45 cal balls would work too. I mount the barrel in a vice, padded with leather, and the muzzle down, resting on another leather pad. I like to put some case sizing wax on the ball, but not completely necessary; oiling the barrel is another option. I set the ball on the chamber mouth and use an aluminum rod and a hammer to pound it in. The soft lead deforms easily and won't hurt the barrel.

I do this twice on every barrel; the first ball gets pushed all the way through, the second gets pushed just into the throat right at the front of the chamber, then back out again, so you can measure the throat diameter and length.

Take note of any tight or loose spots as you push the ball through the bore.

Bummer about the chrony. If/when you replace it, I've found the "Pro Chrono" to be much better than the "Shooting Chrony" models, and about the same price.

[EdMc]

Thanks. Good enough, there's a Bass Pro about a mile from me, I'll go an see what they have in black powder balls.

Sadly, it was a Pro Chrono. The only parts really hurt were the two plastic holders/covers over the infrared, or whatever lights. Also a small part off the rear circuit board. I could solder it back but I'm not sure if it's polarity sensitive. No sure what it is, small metal can like a transistor but only has two leads so that's not what it is. Has some blacking marking on one side so it may be a mark for polarity. Could be a small electrolytic capacitor, but who knows?

Added: Use 0.440 .45 cal balls to slug both barrels. The Glock 0.4010
                                                                       The Smith 0.4001

Didn't notice any tight spots in either barrel other than the initial start. I did go from end down to the chamber.

[Yondering]

Slug the barrel from the chamber end, generally you'll get a better slug that way. Important to slug just the throat too.

So your Glock bore is .001" larger than your jacketed bullets? Shooting cast through that barrel, .402" should be the right diameter, but it depends on the throat dimensions too.

FWIW, my new gen 4 G19 has a large bore too; .357" instead of .355". It shoots a little better with .357 jacketed bullets.

[EdMc]

Yeah, the Glock measured .401. By 'throat' do you mean the area just ahead of the end of the chamber? The 'leade' or whatever it's called in a barrel before the rifling starts?

Perhaps I should slug the bores in my BH 45 Colt and M-24 Smith as I shoot cast in those.

[Yondering]

Yes, that's correct. I think "leade" is a European term for the same thing.

[sqlbullet]

Yeah...You should slug anything you are going to shoot lead in.  Bullet fit is the most common answer to avoiding leading.  Knowing what you have goes a long way towards avoiding issues.

One note on revolvers, you need to know the cylinder mouth diameters for each chamber.  And pray they are larger than the bore of the barrel.

[EdMc]

I know Ruger Blackhawks in 45 are known for having undersize cylinder throats. Measured mine once with a pin gage.....they need to be reamed as I remember. Of course anyone who shoots his own chrono has other 'issues' in accuracy that need to be resolved first.

[The_Shadow]

Some Chrony Protection goes a long way to protect the investment!  Last time out I actually forgot my steel plate that I lay on my chrony to provide protection.  Well it was hot, as the secession worn on and the sweat soaked me, my clothes and running onto my eyes I shot the skewer sticks, knowing I didn't have the steel plate I called it a day before I shot the Chrony!

[Yondering]

I know Ruger Blackhawks in 45 are known for having undersize cylinder throats. Measured mine once with a pin gage.....they need to be reamed as I remember. Of course anyone who shoots his own chrono has other 'issues' in accuracy that need to be resolved first.

Yeah, the 45 Colt Blackhawks are a classic example. I went ahead and bought a reamer for mine, so now it's a pretty easy job. I cut the head off a fired case and slip the body over the reamer to use as an alignment guide. Seems to work really well.

In my experience, throat diameter in a semi-auto is more important than actual bore diameter. I size for a slip fit in the throat, and with a decent throat, that will give a tight fit in the bore, and should work with minimal or no leading. The throat will usually be a taper, not just a straight section, and throat length is an important dimension to measure too, as it determines how far out you can seat a properly sized cast bullet.

[EdMc]

Thanks for the tip on BH reaming. Want to rent the reamer?  Just kidding, sorta.....I remember them being a little pricey for a one time use.

Glad you mentioned the taper on the throat slugging. I tried it earlier today and it measured .402~.403, maybe slightly higher.......hard to tell exactly where the poly rifling began as it isn't as distinct as say the conventional rifling of the Smith barrel.