[BullitHolz]

Can someone tell me what the typical bore diameter is for guns like the 1911 or any other that shoots 45 ACP ammo?

I slugged the barrel on one of my autos and noted it is dead on .450 inch. The gun shoots pretty poor groups and I'm trying to figure out what might be causing this, perhaps the bartrel is oversized?

Thanks,
Scott

[1911Tuner]

Nominal bore diameter is .451 inch.

[RogersPrecision]

Yup.
And most 45acp projos are sized to .4515".

[1911Tuner]

I be thinkin'... :scrutiny:

Slugging the bore gives you the smallest diameter in the bore. It doesn't mean that the bore is consistently the same from muzzle to leade. If there's a tight place in the bore...anywhere behind the muzzle...and it opens back up to .451 inch...accuracy will suffer.

That may be where your bug is nesting.

[BullitHolz]

Well that must be my problem because the slug fit was tightest in the middle of the bore. I guess it might be prudent to slug both ends and knock the slugs out and measure them and note any differences in diameter.

Thanks guys!

[rcmodel]

If you can feel it is tight in the middle while slugging the bore, it's a bad barrel, and there is nothing you can do about it except replace it.

rcmodel

[Jim Watson]

Bore diameter is in the neighborhood of .445".

Groove diameter is nominal .451", with many smaller and a few larger. You are likely in the range acceptable to the maker.

English lesson over.

What load fails to satisfy on accuracy?
Does it shoot well in other guns?
Have you tried other loads in this gun?

[Sir Aardvark]

If you can feel it is tight in the middle while slugging the bore, it's a bad barrel, and there is nothing you can do about it except replace it.

rcmodel

I realize that this is an auto, so replacing a barrel is no big deal, but I have lapped a revolver barrel that was tight around the threading and it fixed the constriction problem and made it a more accurate shooter.

So why not just lap the barrel?

If it's a bad barrel to begin with, as you say, then the worst thing that can happen to it if you lap it, is that you'll have to replace it anyways.

[BullitHolz]

Well I definately have a barrel with a divergent taper. The slug will drop right in the muzzle end and fall about half way before sticking in the bore and stopping. At this point I can use a dowel to push it back towards the chamber and it gets the tighest right at the beginning of the rifling before it exits into the chamber.

The slug measures right at .450" with a 0-1" mic, which would correspond to the tightest point in the barrel right in front of the chamber. Out at the muzzle it measures .451" so that definately explains the accuracy issue I have.

The gun in question is a Smith 4506 FWIW. Does anyone know a source of barrels for one of these? Or can this one be "lapped" in the tight spot to help out with the problem?

Thanks guys!

[rcmodel]

S&W would be the only source of a barrel for a 4506. I think I'd be talking to them about replacing it if it's a low milage gun.

A new S&W barrel will run you $125 bucks from Brownell's.
http://www.brownells.com/aspx/ns/schematics/schemmfg.aspx?schemid=466&m=15&mn=Smith+&model=4506+

rcmodel

[BullitHolz]

I got this one used at a decent price so I have no idea how much it's been fired. Overall it looks really good though, 90% at least IMO. It's a shame because I had one that I let go about 15 yaers ago that was scary accurate.

It's a shame you can't see these things at the gun counter whan your looking a new purchase over.

Thanks for the link RC but they show them as out of stock which IMO means they are probably sold out for good considering the age of these guns and the dwindling support for them that I have noted through many an internet search.

Interesting moniker, rcmodel, do you fly or drive yours.... I fly Cardens and other Giant scale, or did till I got back into shooting this year, now the Edge is sitting collecting dust out in the garage.