View Full Version : How Smooth Should A .45ACP Chamber Be?

February 1, 2012, 08:17 PM
I just bought my second 1911 to turn into an open class gun. I shoot reloaded 230gr lead round nose in my 45's. My old WW1 1911 will eat anything but the commercial 1911 will only chamber 1 out of every 10 or 15 of my reloads due to a slight bulge from the lead bullet while factory ammo will drop right in and headspace. I already ordered a carbide crimping die that will fix the problem. The gun is very accurate but the chamber is not very smooth, like they were in a hurry when it was finish reamed.

If I polish the chamber can it be too smooth?

February 1, 2012, 10:36 PM
Polishing the chamber walls is fine as long as you don't change it dimensionally. Unless it is unusually rough I wouldn't worry about it very much. Most feeding issues are actually caused by magazine issues, extractor finish and tension (very important), breechface roughness (machining ridges left in) or, the number one cause, out of spec ammo (too long or too short). One area of the chamber I always look at critically is the small bevel at the top of the opening (the top rear of the barrel hood). A cartridge feeding from the mag will hit this bevel at an angle and then break over and straighten before it goes in. Some barrels have a nice smooth bevel and some have almost none and the surface is very rough. It WILL cause problems for SWC ammo. But before you start polishing anything have a knowledgeable smith (unless you are one) give the gun a thorough checkout and find any feed problems. The extractor is a big problem on very many production guns. So is the magazine's release point and how high it sits in the gun. If you have a match barrel fitted you may have to have a finishing reamer run into the chamber. Most barrel manufacturers leave the chamber a little short so the smith can custom ream it for the ammo that will be used. Just a few thousandths short can make all the difference. Your handloads should drop all the way in and fall back out under their own weight when you tip the barrel up.

February 2, 2012, 12:12 AM
I found taper crimp to be critical to feeding.

Here is what I would do to try and reduce the number of ammo related issues back when i was shooting action matches.

Take your 1911 apart.
Take a bag of your reloads and , one by one, drop them into the chamber.
If the ammo chambers without hesitation, put it in the "good pile"
If the ammo doesn't chamber, or hangs up, put it in the "bad pile"
What's the issue with the bad rounds? Unsized bullets?

Tell us a little about your reloads. .45 ACP open guns are kind of a rarity these days- why aren't you using 200 grain H&G #68s? What was the base gun that you started with, and what's been done to it so far?

February 2, 2012, 11:45 AM
How Smooth Should A .45ACP Chamber Be?
Same as any chamber, it should be smooth, shiny, and free of visible scratches, galling marks, or gouges. If there are visible rings around the chamber, or if you can see imperfections with thenaked eye, you can either call the manufacturer for help (good luck), or buy an aftermarket barrel.

February 2, 2012, 12:21 PM
...commercial 1911 will only chamber 1 out of every 10 or 15 of my reloads due to a slight bulge from the lead bullet while factory ammo will drop right in and headspace.

Fix this first^^.
I had the same problem with my early 230 LRN reloads. Yes, a Lee FCD fixed it. Double check your OAL as well.

IMHO, the rough spot in the chamber is cosmetic. Unless it's truly horrendous or actually affects function somehow, have it fixed at your leisure.

February 2, 2012, 02:57 PM
The gun is an Auto Ordnance. I know they have had some QC issues, but I plan on upgrading just about everything on it. Right now I just Installed some add-ons,(stuff I already had) like a bushing comp, trigger w/ overtravel stop, commander hammer, full length guide rod, and a red dot sight. At some point it will be getting an extended match barrel with a real comp on it.

Yes I would describe the finish in the chamber to have scoring and galling in it, but the chamber is on the tight side (compared to the G.I. barrels I have) and it is very accurate so I think it will tolerate some polishing. I just did'nt know if a mirror finish would give excessive bolt thrust due to less grip when the case expands.

Thanks for the replies.....John

February 2, 2012, 08:58 PM
Was the A-O made in West Hurley NY, or Worcester MA?

Jim Watson
February 2, 2012, 10:28 PM
Rather than polish which can leave you with a shiny out of round chamber, I would get a real gunsmith to run in a sharp SAAMI spec reamer. That will probably let you use your cast bullet reloads and improve function in general.

At least it did on the aftermarket barrel that shot accurately but unreliably in a gun of mine. "Minimum Match Chamber" you know. Actually undersize.

February 2, 2012, 10:51 PM
My gun was made in N.Y.

I should have the carbide crimp die by Saturday. If it does'nt work I may be getting the new barrel sooner than later.

Also, I suspect a sharp finnish reamer would solve the problem. I wonder if my barrel was reamed with a tool that was used well past its usefullness?