Hey Guys, Though I would run this by you all since I trust your opinions and you have been gentlemen in your responses to my posts in the past. I recently slugged my new 1911 Government barrel and it measures .4515". I reload and shoot both LSWC and plated .452" 200 gr bullets. I contacted the manufacturer of the pistol and they said their specs are .4505 +-.0015". That being the case, you can get a barrel with a .452" groove, mine is .0005" off that and it's new. I don't want to get in to loading data and bullet sizes right now but would rather have someone tell me how they would feels if this was your situation and how acceptable is this. The manufacturer is very reputable and the pistol in marketed as a "Match" pistol with "Match" barrel. I know to shoot very serious match you get another "true" match barrel but this issue is bugging me. Your input is greatly appreciated....thanks guys

You need to remember that the bullets are "squeezed" down a bit by the rifling and that material displaced has to go somewhere. Where that displaced material goes into is into the grooves, so a bullet that measures at the groove diameter or even slightly smaller will still Obdurate and fill the grooves. The first symptom you'll see if the bullets don't obdurate is severe leading and with many thousands of rounds of 45 ACP downrange in 3 Rugers and one S&W I have yet to see severe leading in any of them. Bottomline, I wouldn't worry about it.

BTW, like you I'm a bit shocked at that +/- 0.0015 tolerance, that is much larger than I would expect. In fact it's larger by a factor of 3. Don't know who you were talking to but I suspect he may have been making things up. Personally I would expect that if you talked to an actual Engineer instead of a Customer Service Rep he would state the tolerance is a lot less than what you were told.

No.
When you slug a barrel you are measuring the groove diameter. Also, the tolerance is plus .0015, not plus or minus .0015.

You are correct +.0015/-.000 and this came from the Pistol Product Manager. Thanks for the correction

As long as the bullet goes where you aim, don't sweat the small stuff.

Dave, let me clarify things a bit because you have misinterpreted what I intended. The LANDS in the barrel are at a reduced diameter in comparison to the Groove diameter. Hard cast or jacketed ammo is typically produced at the Groove diameter or perhaps 0.001 inch larger. Now, just as there is a Law in Physics about Conservation of Energy there is a correlating aspect that can be stated as Conservation of Mass. What this means is that when you squeeze a solid or liquid it will extrude in any "free" direction. So, when the lands compress the bullet some of the material in that bullet will be extruded into any gaps in the grooves and the remainder will cause the bullet to lengthen. Because of this bullets that measure a bit undersized can still obdurate fully in the barrel. Granted, there is a limit to how much undersize can be tolerated but I wouldn't panic about a 0.4515 groove diameter unless I actually observed leading in the barrel or keyholing in the target.

As for my misreading the stated tolerance if you look at the original post you will see that it was typed as "+-0.0015". That is a plus followed by a minus, so you can understand why I interpreted it as +/-0.0015.

Not enough to worry about. The bullets you're loading aren't exact diameter either, so it's all a wash.

I think what the OP is referring to is the bore being what I would consider oversize for a barrel a manufacturer calls a match barrel. It might be in spec according to them but I would consider .4515 on the outer limits of acceptable from a standard barrel. The rule of thumb has always been when shooting lead use bullets 0.001-0.002 over the bore size. Almost all manufacturers lead bullets are .452 for the .45 acp so you would have to go with a .453 bullet since as far as I know nobody makes a.4525 diameter bullet. Plus you would be limited to certain bullet manufacturers since most only list .452. The OP mentioned plated bullets as well. I can't think of any manufacturer that offers .453 plated bullets. Maybe the extra .0005 wouldn't make a huge difference but I wouldn't like it either on a barrel that was labeled as a match barrel. Plus what about jacketed ammo that is .451 maybe the bullet would expand enough to stop gases from escaping around them but I personally would feel better with a barrel a little tighter if it were my pistol.

Thank you for this, you understand my thoughts. I did not want to mention the bullet and powder weights at first because from experience on these forums everyone takes off in that direction and I did not want to know everyones load data and go in a direction that had nothing to do with my original concern, which is ghroove size. That being said here is in fact what I load and why. I shoot a Missouri Target 200gr 12brinell LSWC. I do have loeading issues and I'm trying to keep the recoil down for plate shooting so I want to load light powder loads, that's why I chose the 12brinell for the expansion to keep the leading down. So with the larger bore and leading I would have to bump up the powder charge to expand thye bullet and seal the groove, and that would defeat my purpose. I could bump the load up but then maybe have to purchase a compensator to keep the flip to a miminum, now I'm into more weight and cost. So I think I do have a legitimate concern. I think I'll just conatact the manufacturer again and run it by another service rep and plead my case.

What did you use to slug the bore? You want to use pure lead. Technique and alloy can impact the results.

What did you measure the slug with? Unless you used a 0-1" micrometer with 0.0001" resolution, your measurement may be inaccurate. And even if you did use the micrometer listed, accuracy is technique dependent.

So the barrel is within the manufacturing tolerance, right?

Try measuring some of the .452" bullets you are using. I think the results will shock you.

For a BHN 12 bullet, it needs to be driven fast enough to obturate enough to seal the bore. You can have the right size bullet with the wrong lube and get leading. Not cleaning all the copper out of the bore before shooting lead can also result in leading. Lots of things beside bullet fit can cause leading.

According to SAAMI specifications that is a bit large.

I was at a range one day when a guy I know asked me to shoot his two .45's.

The first one was from a reputable maker, started with a "K" and ended with an "r", and was an "Ultra Match" model. It shot alright but I was not impressed, not at all, and I am a big fan of the 1911.

Then I shot the other one. It was a Glock, model 30. I just stood there and looked at it for a minute or so, and I was very impressed.

I believe their "Match" models are just a parts package and have nothing to do with increased accuracy. Only increased price.

Most commercial boolit casters use a less than optimal lube. The lubes they use are designed to stay in the lube groove while being jostled and shaken around in shipping, not to provide the best accuracy and anti-leading. Also most commercial boolits are too hard for target and mid-range velocities in pistols. A 12 BHN is a lot harder than needed for 45acp velocities. My home cast boolits with a quality lube and cast to an 8-10 BHN never lead in my match grade barrel. 12BHN and above commercial boolits and commercial lube will lead every time. Also mid-range 45 acp loads often don't produce enough pressure to fully obdurate harder cast boolits. Probably the best commercial boolits for a 45acp are Speer, Hornady or Remington 200 gr SWC. They are soft and have a decent dry type lube on them. They are also inexpensive.

Methinks that you placed your decimal point incorrectly. How about 0.001-0.002 over the bore size.

Secondly, when I visited barrel plants, they placed much more emphasis on uniformity of barrel dimensions than actual size. I don't have references at hand as to exactly what the acceptable .45 max/min groove diameters were, but match barrel blanks had less than 0.0001 inch variation over the length of the blank from whatever the bore/groove diameter was.

0.4515 strikes my rusty and not always reliable memory as the nominal diameter for .45 jacketed pistol bullets.

Yes I got my decimal in the wrong place thanks for the correction. Since I am a reloader and I load lead what I mean is I wouldn't be happy with a bore that size on a new pistol. I know manufacturers build them for the masses and most people only run factory jacketed ammo so it would not be an issue unless you shoot lead. I look at it from a reloading stand point. I wouldn't want to have to buy another barrel for a pistol that is supposed to have a match barrel and I wouldn't want to have to buy oversize lead bullets to fit a loose bore.

When a lead bullet gets smacked by the explosion in the chamber the base of the bullet will expand to the chamber size providing the bullet isn't to hard for the charge used . That's why a bullet with a 16 BNH may lead with a target load, it's to hard to expand with a light powder charge and gases can get around the bullet and cause the leading. Useing the correct bullet for the powder charge [BNH] is the trick. If leading or accuracy is a problem it's probably the load, not the barrel. Of course anything is possible but the odds are that the barrel isn't the problem.

Hardness of the bullet definately does matter but bullet to bore fit is much more important. If you have the right hardness bullet but it's loose in the bore it will lead. I experienced it with a revolver. I ordered the same hardness bullet but clicked on the wrong size by accident when I ordered. I normally use .358 but the .357 bullets caused leading when the .358 did not. Bullet to bore fit is more important than hardness.

In a revolver alot of folks want the bullet sized to fit the cylinder bores rather than the barrel. Simple test with bullets is to see if the bullet will fall thru the cylinder chambers or has to be pushed. How hard. Of course if the bullet will pass thru the cylinder bores with very little effort then it is to small. The bores do need to be clean. I'm sure you are right about your gun. I'm useing the word bore when I should be saying chambers, I assume you're talking about barrel size. There are several things that should be checked when looking at a new to you revolver.

Your barrel is fine. If the gun shoots OK and there are no other obvious problems - I'd be happy. If you have accuracy problems, I would look elsewhere.