View Full Version : Screwing up my .45

November 26, 2009, 01:54 PM
OK, so being "handy" I decided to "improve" my Kimber 1911 GM with some nice feed ramp and barrel ramp area polishing. I think I blew it. I probably took off too a little much, so now I have some "how to fix it" questions:

1. Is there a gauge of some sort that would tell me if I moved the barrel ramp area too far forward? Is there a gauge to show feed ramp angles?

2. A round in the chamber now "rattles" around more than in my other .45 chambers. There is probably .002 movement of the round side to side (or up/down depending on how you move it). Is this too much?

3. How much of a safety margin is needed for the unsupported portion of the case head? I increased this unsupported portion by about .001"

I need to know if I should buy a new barrel or if this one can be used.

Harry Bonar
November 26, 2009, 06:21 PM
From your description I don't think you screwed up your Kimber!
With your pistol apart take the barrel on the frame and move it back as far as you can. There should be about 1/32nd of an inch between the bottom edge of your barrel and the top edge of the ramp. If there is, you're O.K.
Chamber rattle: If it's only .002 you did no harm. The 45ACP is a low pressure cartridge and can tolerate this and also the .001 more case exposure means nothing! You did no harm.
I usually take a 3/8 dowel with 240 grit around it and polish out any factory marks there - then I polish with Brownells 555 grey till it is a mirror finish and the same treatment in the chamber.
Does your gun function now? I'll bet it does - I don't think you've done any harm. 1911s are not too sensitive to those small issues you cite.
Harry B.

November 26, 2009, 06:56 PM
I was a bit scared to test fire it -- was planning on getting my welding glove and mask to do so in case the case blew out.

I'll give it a try.

November 26, 2009, 07:21 PM
Harry, as usual, speaks the truth.
However to keep you out of trouble in the future, I suggest that you buy Jerry Kuhnhausens book on the Govt. model pistol. It will tell you what to do and what not to do. Money well spent for sure.
"The Colt .45 Automatic" "A Shop Manual" VSP Publishers.


Harry Bonar
November 26, 2009, 08:45 PM
I agree. Jerrys book is very thorough!
Harry B.

November 26, 2009, 11:28 PM
Hi Harry,
I am sure you have much more experience than I do with the M1911, but I don't believe the suggestion of using 240 grit sandpaper is a good one. I find that 600 grit wet/dry is sufficient in general to remove slight machine marks and sharp edges. Any coarser grit invites actually removing measureable amounts of material rather than just polishing.

The M1911 types are quite tolerant of some messing up in some areas, but I would say that there is a pretty good chance that the frame of the gun has been altered in such a manner as to take it permanently out of spec. It may still function quite well regardless:

There is a maximum distance between the lower edge of the chamber and the breech face. This dimension puts the unsupported area of the chamber over a fairly thick section of the "average" .45 ACP case. If you push it too far forward, the unsupported section goes toward a thinner area of the case. There may still be a margin for safety, but technically it is out of specification.
If the feed ramp on the frame has been altered (and that is what I am guessing happened here), In order to maintain the proper angles of the barrel and frame ramp and still allow the 1/32 inch space between barrel and frame, the lower edge of the chamber may NEED to be put so far forward as to be out of spec. If this is the case, the only way to stay within specifications may be to have a ramped barrel or a frame insert fitted. I am not saying the gun won't continue to function reliably indefinitely if this happened, but it would still be out of specification. BTW, Kuhnhausen's second book on the M1911s describes these measurements better than the first book and the numbers are not quite obvious but can be calculated.

BTW, I have had an apparent double charge from a commercial reload blow out the unsupported part of the case. The result was not pretty, but no serious damage was done:
The case vented into the magazine well.
The gas cut through and set off two other rounds in the magazine.
The magazine (a Chip McCormick) vented gas out the holes.
One medallion (from a very nice set of Colt Medallion grip panels) went out the port side and was never seen again.
The other medallion stung the palm of my right hand
Both grip panels were blown to wood scraps
The pressure compressed the mag spring PAST its solid length
The pressure swelled the magazine so that it was too wide to be extracted.
Brass scraps were blown through the ejector tunnel into my glasses and cut my forehead slightly.
I can't quite remember if the slide locked back on that shot or not but I think it did.

The "No serious damage done" was because only the grip panels and magazine were a total loss. I ended up fitting a new Kart barrel, but only because I thought the barrel looked like it was over ramped from the factory.

- Ivan.

November 30, 2009, 05:49 PM
Well, the gun test fired OK. No problems, and I double checked the fired brass with a micrometer and found the cases expanded the normal amount so I guess the lack of support I noticed is no big deal. Thanks for helping put my mind at ease though.

Harry Bonar
December 1, 2009, 09:10 AM
It sounds like you did a good job on the Kimber - they are probably the best "out of the box" 45s. Most, if not all need the feed ramp polished, the extractor tension checked and the barrel throat polished and sharp edges broken. You did no harm.
Don't try a trigger job yet till you get Kuhnhausens book!
Harry B.