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Joined: Thu Feb 24, 2011 2:21 pm
Posts: 263
Location: Mt. Home, Ar

Post Posted: Mon Apr 09, 2012 12:52 pm 
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I thought I’d show those of you who might be interested a spot inside the frame that is often overlooked by manufacturers. This area directly affects the longevity of your barrel. I’ve seen problems here from virtually every maker, but not on a consistent basis. In other words, your particular pistol may - or may not, be set up correctly. This is the frame/barrel impact surface, AKA the vertical impact surface. It stops (or at least SHOULD stop) the barrel’s rearward movement. This is not the job of the link, barrels that stop on the link will soon exhibit a failure of the link and/or pin. ‘Course the fly in the ointment of all this is that we not only want the barrel to stop against this surface, we also want it to do so in a way that does not introduce shearing stresses to the lower barrel lugs. Here’s a shot of the area I’ve been talking about. It shows a typical unrelieved impact surface along with surface of the barrel lugs that stop on it.

Image

In this next shot, if you look closely, you can see where the tips of the lower lugs have been impacting against the frame. Definitely not a good thing. This is the thinnest, weakest area of the lugs and, being so far away from the lug/barrel junction, adds high stress loads to that area. Strong strikes can cause a failure at the junction - shearing the lugs, or can start bending the lug tips. I’ve had pistols in my shop that have had the rear surfaces of the lug tips filed back in an attempt to eliminate the problem. This, of course, serves to further weaken the tips. The correct solution to the problem is to machine clearance in the vertical impact surface. By doing this, we’ll be positive that the barrel will impact in the strongest area.

Image

This photo shows the area after the surface is machined. The red pointer is showing the “bowtie” that results from this work. It should be standing proud of the machined area by several thousandths.

Image

If your pistol is set up correctly, this is what it will look like. You should be able to feel a distinct edge between the “bowtie” and the rest of the impact area. At least one barrel manufacturer plainly states in his literature that failure to provide the proper clearance will void the warranty.

Image



Sorry for the book. :)

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Bob Rodgers
www.rodgerspistolsmithing.com

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Joined: Mon Mar 07, 2011 1:49 pm
Posts: 104

Post Posted: Mon Apr 09, 2012 1:38 pm 
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Don't be sorry Bob.

Thanks the 'splanation. As usual , INFORMATIVE.

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Joined: Fri Feb 25, 2011 5:09 am
Posts: 140

Post Posted: Mon Apr 09, 2012 4:27 pm 
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That's not a book, just necessary info. that needs to be known.

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Joined: Fri Feb 25, 2011 5:09 am
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Post Posted: Tue Apr 10, 2012 5:27 pm 
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What did you use to make the cut?

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Joined: Thu Feb 24, 2011 2:21 pm
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Location: Mt. Home, Ar

Post Posted: Mon Apr 16, 2012 4:12 pm 
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Steve,

EGW sells a frame bridge cutter that can be pressed into service for a VIS relief cut.

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Bob Rodgers
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Joined: Tue Apr 17, 2012 1:35 am
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Location: Rochester ny

Post Posted: Tue Apr 17, 2012 2:25 am 
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Thanks for the info I'm already learning new things and have been on this forum less than an hour

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Joined: Thu Apr 26, 2012 9:00 am
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Post Posted: Fri Apr 27, 2012 1:08 am 
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I CHECKED MY KIMBER THIS AFTERNOON AND IT LOOKS LIKE YOU USED MY GUN FOR YOUR LAST PICTURE, :D

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Joined: Sat Feb 26, 2011 2:48 am
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Location: Northern Virginia

Post Posted: Fri Apr 27, 2012 11:22 pm 
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Welcome. As a favor to the older forum members please turn off the caps lock key. It sounds like you're shouting. :D
Joe

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Joined: Fri Feb 25, 2011 5:09 am
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Post Posted: Mon Apr 30, 2012 4:53 pm 
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Bob, how many thousandths should the cut be?

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Joined: Thu Feb 23, 2012 6:03 pm
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Location: CA

Post Posted: Wed May 23, 2012 12:53 am 
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If the VIS was too far forward, would you first cut the entire area VIS and then put in the relief cut to get the proud bowtie?

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