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Reaming a .45 ACP Chamber
by Roy Seifert

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Disclaimer:  This article is for entertainment only and is not to be used in lieu of a qualified gunsmith.  Please defer all firearms work to a qualified gunsmith.  Any loads mentioned in this article are my loads for my guns and have been carefully worked up using established guidelines and special tools.  The author assumes no responsibility or liability for use of these loads, or use or misuse of this article.  Please note that I am not a professional gunsmith, just a shooting enthusiast and hobbyist, as well as a tinkerer.  This article explains work that I performed to my guns without the assistance of a qualified gunsmith.  Some procedures described in this article require special tools and cannot/should not be performed without them.

Warning:  Disassembling and tinkering with your firearm may void the warranty.  I claim no responsibility for use or misuse of this article.  Again, this article is for entertainment purposes only!

Tools and firearms are the trademark/service mark or registered trademark of their respective manufacturers.


I recently purchased a Rock Island Armory 1911 .45 for my son which I will give to him for Christmas.  The price was right, but like most things in life, you get what you pay for!  The gun was functional, but quality and attention to detail were poor.  For example, I had to replace the sear and disconnector to get a decent trigger pull, and the feed ramp was milled off-center from the frame.

I took it out to the range to make sure it didnít have any other problems and noticed that the chamber seemed to be very tight because the slide would not go into battery with many rounds.  When I returned home I took it into my shop and began checking headspace.  As you can see from the above photo rounds would not fully seat into the chamber.  For proper headspace, the case head should sit flush, or a little below the rear edge of the barrel hood.  If I tried to press the cartridge deeper into the chamber it would become wedged and difficult to remove.  My guess is that the manufacturer was using a worn-out reamer that was undersized.  The solution was to ream the chamber to proper dimensions.


I purchased a .45 ACP chamber finishing reamer from Brownells #513-051-451.  Although this tool is somewhat expensive, I have used it a number of times to correct the chambers in poor-quality, after-market barrels.

I disassembled the pistol and placed the barrel in a padded vise with the chamber up (vertical).  I coated the reamer with cutting oil and placed it into the chamber.  Using a tap wrench I turned the reamer clockwise (reamers and cutters should never be turned backwards as this could damage the cutting teeth).  I immediately could feel the reamer cutting steel!  I removed the reamer after about 5 turns; it is better to go slow than cut too deeply.  The reamer teeth were filled with chips and steel dust indicating that it was doing its job.  I cleaned the barrel and reamer with brake parts cleaner and checked cartridge fit.


I continued to cut and check cartridge fit until the reamer just touched the lip in front of the chamber.  I didnít want to change the headspace; I just wanted to ream the chamber.  Now cartridges seat fully and to the proper depth in the chamber as you can see from the above photo.  Even rounds that I had set aside that wouldnít chamber during the range session now chambered properly.  This pistol should now feed much more reliably.



   © Copyright 2011 Roy Seifert.