barrel fitting frustration

[JonD.]

I need some help guys. I have successfully fitted a couple of barrels with good luck, but both only needed just a small amount of pivot material removed with a drill bit wrapped with emery cloth. I recently bought a barrel That requires shimming and I'm having a sore time getting it to fit right. The barrel is in great condition and looks to be unaltered from the factory and looks like it hasn't been opened and closed much at all. I have been using pop can material which I measured with my micrometer to be .004 thick. With two pop can shims I still have a gap that won't close on a piece of paper which is .003" thick. With three shims(.012") the barrel won't close at all. I went back to two shims and started folding and smoothing out aluminum foil which is .001" and gradually increasing the thickness placing the foil shims between the two can shims. At .010" and 011" I still have a gap greater than .002", but when I get to .012" it won't close. I have tried fitting it to two different receivers with the same result only different thickness of shim. I haven't removed the ejector and used a file to check and see if there is a high spot on the breech face, which will be my next step, Probably should have done this first. For now I've pulled what little hair I have left out and quit for a while.  Any help or advice would be greatly appreciated.

[quickdtoo]

When you place a shim in the .375" diameter pivot, you effectively reduce the size of pivot, so the best way to get a good fit is epoxy a shim thicker than what you think you'll need, then restore the .375" opening in it that's just deep enough for the barrel to fit good.

Tim

[revbc]

Be sure you are fitting the shim evenly and out to the edges of the barrel lug, because that is where the load points are at.

Bobby

[JonD.]

When you place a shim in the .375" diameter pivot, you effectively reduce the size of pivot, so the best way to get a good fit is epoxy a shim thicker than what you think you'll need, then restore the .375" opening in it that's just deep enough for the barrel to fit good.

Tim

I see. Hadn't really thought about it, but indeed the barrel lug radius is going to change with the shims in place, the shim is really just establishing a starting point and then you will still need to fit after the shim has been put in place with the proper size radius(.375 diameter file or around a 11/32" drill bit or dowell with emery cloth) until you get a good lock up.

[wreckhog]

In actual use, more than 1 aluminum shim will slip and loosen. 1 shim will compress, just not as fast. And they only take a minute to replace.

[rdlange]

I had similar problems.  Here's the answers I got...

http://www.gboreloaded.com/forums/index.php/topic,215164.msg1099159409/topicseen.html#msg1099159409

Happy Holidays...

[cwlongshot]

Be certain that you need to relieve the hinge. I have fit dozens and dozens of barrels and have needed to "relieve" but one. I have had to square a couple breeches, and clean up some lug welds.
Is your barrel a ejector or extractor? When fitting a ejector barrel, I like to remove the ejector completely. You can also remove the trigger guard to "see" the relationship of the latch and the shelf.

Its better to look three or four times then to remove steel form the wrong place.

Many times on a stubborn fitting, I'll stop when it gets to be monitions. Then let it sit for a day or three. Coming back with a fresh outlook. Many times the problem becomes quite obvious. Just this afternoon, I was fitting the new heavier latch springs and found the the side of the latch was dragging on a bit of casting slag on the side of the receiver. The dremel made quick work of it and now I can see the much more stoning of the shelf would have ruined the barrel. Another time I just couldnt put my finger on the problem... I removed the extractor to find a weld was standing a bit proud and touching the inner sides of the receiver. I ground it down and finished fitting the latch easily.

CW

[Singleshotsam]

I had a god awful time trying to fit a metal shim to my .223 bbl.  I finally bedded the piviot using JB Quik (stick form) and it came out wonderfully.  Here's a link of how I did it.

http://www.gboreloaded.com/forums/index.php/topic,165918.msg1098756211.html#msg1098756211

[JonD.]

Thanks for all the help guys.  After checking with a depth micrometer and dowell pin, the barrel groove showed to be .010" short. I filled the groove in with JB Weld and plan on using a milling machine and 3/8" end mill to restore the groove to exact specs. I'll let you know how it goes. Not sure how the straight JB will hold up to recoil(.450 Marlin) but if this doesn't work out, my next step is to weld up the groove and then try again.

[petemi]

I've been very fortunate fitting barrels.  I had one I had to shim at first, and then I bought a couple of extra SB2 frames, swapped things around, and now everything locks up perfectly without tinkering.....and I still have two extra frames.....soon to grow into .500 and .444

Pete