View Full Version : What is your 45 acp bore diameter

February 27, 2010, 09:38 AM
With all the references to slugging bores, I would be interested in your results after slugging.

February 27, 2010, 10:05 AM
I'm not sure exacticly what saami spec is for a 45 acp but any gun made since the '50s will be within .0005 of that. Most people dont have the equipment to measure that close.

February 27, 2010, 10:24 AM
My calipers [Cheap] will measure to .001 but I can guess if if falls between the thousandths ticks. You may be correct if using digital.

Sammi specs I believe are .451 with +.0005 tolerance. [I am probably wrong about this]

But I am interested in what people actually measure after slugging


February 27, 2010, 10:37 AM
The groove diameter is more important than the bore diameter. They are not one in the same.

February 27, 2010, 03:14 PM
I am not a fan of checking groove diameter with calipers. I prefer a micrometer and urge anyone who wants to get it down to the gnat's a** to do the same. A micrometer is a wise investment I think every boolit caster should own...but this is my opinion, of course. :D

February 27, 2010, 04:21 PM
Is the groove diameter the highest points on the lead slug?
If so ,That is what I meant to ask. According to a earlier posts You tube link, the highest points on the lead slug is what needs to be measured. I almost bought a micrometer the other day because I figured that would be the most accurate.

February 27, 2010, 06:42 PM
Yes, the groove diameter is the highest spot on the slug. In the barrel, it is the low spot. Micrometers are nice, Ed. I have a 1" Lyman micrometer. http://www.midwayusa.com/viewProduct/?productNumber=169644

Measures accurately out to .0001". When using these, make sure that whatever you are measuring is clean and the micrometer does not have any gunk on the part that contacts what you are measuring. If you let stuff build up on there, you will get an innacurate reading (readings will show it being bigger than it really is).

chris in va
March 10, 2010, 01:54 AM
Best I can tell mine checks out at .450...Sig 220. Then again if I apply even the slightest amount of pressure on the caliper it can vary by .002.

That'll Do
April 3, 2010, 05:13 PM
I'd like to say that I've slugged the barrel of my Kimber Custom Target II, but I haven't. However, shooting boolits sized to .452" gives me tight groups (withe the appropriate load; usually a 200gr SWC over 4.2gr of Hodgdon Clays) and no leading, so I feel no need to slug my barrel.