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Post by inthebeech on 10/27/2020, 8:29 am

[h2][size=32][size=36]"B[/size][size=30]UNKER[/size] [size=36]A[/size][size=30]RMS [/size][size=36]R[/size][size=30]ADIAL [/size][size=36]B[/size][size=30]ORE[/size] [size=36]B[/size][size=30]USHING[/size][/size][/h2]
[size=14][size=14]The Bunker Arms Custom Radial Bore barrel bushing is an exclusive design taking the timeless 1911 barrel bushing and enhancing it with today's technologically advanced machining processes. One of the main challenges faced by custom 1911 builders is achieving a zero tolerance lock-up at the muzzle without any barrel springing. [/size]Instead of a traditional straight bore bushing design which requires a wedge style lock-up, the radial bore bushing has a radiused bearing surface to allow full contact with the barrel in any position, and throughout the entire cycle, improving accuracy and reliability."[/size]


[size=14]I can only evaluate from a mechanical enginering/ kinematics viewpoint so maybe I'm missing something.  Pistolsmiths feel free to sort me out.  But there is no avoiding an oval shape being required if a linked barrel is to be snug at lock up and slip when it rotates down out of battery.  The slight angle between the two conditions requires it.  Unless the spherical shape itself pivots (Briley spherical) in the slide, this concept does not perform as advertised.  I will not be buying one of this guys eight thousand dollar guns. :pirat:
[/size]
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Post by Wobbley on 10/27/2020, 11:58 am

Well, as a mechanical engineer.... unless you have some clearance between the two parts they cannot move relative to each other.  You could spend a ton of time and money lapping them to have clearance measured in millionths of an inch, but I’m not sure what would be gained.  It is also difficult to get two spherical surfaces Like in a Briley to have tight axial clearance.  The geometry doesn’t allow it.  A .001 radial clearance in a Spherical Will give a .003 to .005 clearance axially.  

Just use more or less standard parts, fit them well so they return to the same place.  It ain’t rocket science
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Post by David R on 10/27/2020, 12:03 pm

EGW angle bore bushing.  It is made to your barrel  and slide size.

David
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Post by Jon Eulette on 10/27/2020, 1:02 pm

Either you know how to fit a bushing or not! 1911 barrel locks up into the slide locking lugs which puts approximately 1 degree of rotation for lockup. Most barrels can give you 0.045" of lockup engagement depth if the gunsmith actually fit the upper barrel lugs. As a result of this lockup the barrel cams on the bushing. Bunker bushing just rotates because of radial barrel protrusion. NM type bushing has reliefs that gunsmith makes when fitting to allow barrel camming/lockup without bushing bind. EGW angle bore still requires some fitting. Good gunsmith can do it all ways! Here's old 52 advertisement from back in the day.
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Post by chopper on 10/27/2020, 1:33 pm

Jon Eulette wrote:Either you know how to fit a bushing or not! 1911 barrel locks up into the slide locking lugs which puts approximately 1 degree of rotation for lockup. Most barrels can give you 0.045" of lockup engagement depth if the gunsmith actually fit the upper barrel lugs. As a result of this lockup the barrel cams on the bushing. Bunker bushing just rotates because of radial barrel protrusion. NM type bushing has reliefs that gunsmith makes when fitting to allow barrel camming/lockup without bushing bind. EGW angle bore still requires some fitting. Good gunsmith can do it all ways! Here's old 52 advertisement from back in the day.
Jon
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 At $165, I wonder when that advertisement was? In theory that round bulge would be the perfect way. I read on the forum that they weren't as accurate at 50 yds, but maybe that was in the ammo selection, not sure.
  Stan

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Post by Blsi2600 on 10/27/2020, 2:24 pm

Bunker bushing is $35.00 at Harrison 1911 parts.

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Post by Jon Eulette on 10/27/2020, 3:11 pm

 At $165, I wonder when that advertisement was? In theory that round bulge would be the perfect way. I read on the forum that they weren't as accurate at 50 yds, but maybe that was in the ammo selection, not sure. wrote:  Stan
I recently had contact with someone who can get x-ring groups at 50 yds with proper ammunition loaded for the barrel. The machine rest groups at 50 yards were very impressive. The older ammunition from this era could do it!
And the right load today!
Jon
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Post by fc60 on 10/27/2020, 3:13 pm

Greetings,

I have seen Colt manufactured 38 KIT barrels with the spherical knob on the end of the barrel. The barrel was the 0.570" version, not the 0..500" diameter. (Gosh, I miss the '60's.)

One day, when I get bored, I plan to machine some M52 barrels. I have a radius forming tool I bought that needs to be put to use.

Cheers,

Dave
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Post by Allen Barnett on 10/27/2020, 4:13 pm

Bill Blankenship shot a "out of the box" Model 52 in centerfire matches as a National Champion.  Only thing done was a little trigger work to make a good trigger great!  So said my Dad who worked on Blankenships guns before he left the AMU.

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Post by chopper on 10/27/2020, 4:21 pm

Jon, would you use that round bulge barrel on your 1911 38 special builds also?
Stan

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Post by james r chapman on 10/27/2020, 4:48 pm

AXI also

https://accuracyx.com/product/axi-360-match-barrel/

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Post by Jon Eulette on 10/27/2020, 5:00 pm

chopper wrote:Jon, would you use that round bulge barrel on your 1911 38 special builds also?
Stan
I have not tried one yet. I do like the egw angle bored bushing. I don't think it matters much about which bushing is used, that's a small portion of the accuracy when fitting a a barrel. It's a little forgiving because barrel cams and locks up in bushing when it locks into slide lugs.  Hood and lug fit much more important.
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Post by jglenn21 on 10/27/2020, 7:06 pm

I have pretty good luck with the Bunker bushing.. Jerry Keefer was a fan of it also..

I have some old colt barrels from the 60s that have the radial bushing area cut into them. no idea of the smith involved as I've had them for a long time..  been a concept for a while..
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Post by inthebeech on 10/28/2020, 7:49 am

[quote="james r chapman"]AXI also

https://accuracyx.com/product/axi-360-match-barrel/

[url=https://servimg.com/view/18137582/336][img]https://i.servimg.com/u/f15/18/13/75/82/2ae3e210.png[/img][/url][/quote]


These dudes might actually have something here.  If that spherical lug is taller on top and bottom, which I think I'm seeing, then they're on the right track if you're going to be tight at one degree angular misalignment and slipping at zero.  I feel so much better now that I only have to write these guys a four thousand dollar check. Eight grand was going to be a bit of a squeeze. :pirat:
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Post by WesG on 11/1/2020, 5:09 pm

That DOES NOT work. Theoretically. A pin in a donut is not the same as a ball in a cylinder.

That said, over a degree or 2, the interference is quite small. 2° on a .550 dia barrel with a .1 radius 'ring', is a bit less than a half thou'. A tick over a 'tenth' at 1°.  Barrel dia from 'memory' ...

Sketched in SW, 2D profile only.

What you do lose, either way, is wear surface. Line contact doesn't give you much.

I fit an angled bore bushing to my SA barrel. Took a bit of thinking, and a fixture so I could bore it out to fit. And then some stoning for clearance, opposite a standard bushing, so it could close up.

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Post by james r chapman on 11/1/2020, 5:33 pm

WesG
The 360* AXI barrel works fine.
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