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Posted: 2/19/2013 10:09:24 PM EDT
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Okay, so a little background.
I recently got a used 1980 Romy G kit with original barrel from a guy. I say used because he build it into a rifle himself using a horrible home made receiver and did a horrid job of welding the trunnions in....and when I say horrible, he canted the front trunnion to the right side when he welded the receiver on so that the carrier actually rubbed the right side of the trunnion hole leading into the gas tube, evidenced by worn bluing. If you looked straight down the stock thru the rear sight, the front sight base was 1/4 inch off to the right  .....amazingly enough, it actually shot fine...go figure.
So I am bringing this back to life on a Nodak receiver and just started tearing it apart, which is where the trouble began. I spent the better part of 3 hours trying to get the barrel pin out, without a hydraulic press. Tried the BFH approach, shattered 2 punches. Tried using my heavy duty drill press, to push down, no luck. Finally ended up drilling pilot holes in each side from my punch to ride in for easier hammering, no luck. I was using a 10 pound sledge at one point. Finally got it to move one direction after drilling it completely thru with a small pilot hole and drilling most of the way thru with the larger big and hammering on the side that wasn't drilled out as deep. This is the the pin viewed from the right side where I drilled it the deepest, I tried hammering from this side first with no movement: http://i748.photobucket.com/albums/xx127/btf5437/Pin3.jpg This is the pin viewed from the left side (serial number side), I was able to get it moving by beating from this side after drilling out the other side: http://i748.photobucket.com/albums/xx127/btf5437/Pin4.jpg Now the problem. After getting it out I realized that there was a large lump of metal on the side of the barrel pin and also one in the hole of the trunnion and a rut of missing metal in the trunnion leading up to the lump. There was also a small lump and rut on the barrel side of the pin as well. This was caused by the factory that installed them, as I was only able to get the pin to back track thru the damage that was already created. The arrow indicates the direction I was able to get the pin to come out. http://i748.photobucket.com/albums/xx127/btf5437/Pin.jpg Here you can see the height of the lump on the pin which should indicate the depth of the rut in the trunnion, haven't measured but I am guessing to be a 32nd or so high. http://i748.photobucket.com/albums/xx127/btf5437/Pin1.jpg This is the smaller lump on the bottom of the pin that faced the barrel. Minor rut on the barrel. http://i748.photobucket.com/albums/xx127/btf5437/Pin2.jpg In this picture the arrow indicated the direction the pin was pushed out and the rut behind the lump is outlined. http://i748.photobucket.com/albums/xx127/btf5437/Pin7.jpg Same picture without any markings. http://i748.photobucket.com/albums/xx127/btf5437/Pin6.jpg You can see the height of the lump in the trunnion in this pict. http://i748.photobucket.com/albums/xx127/btf5437/Pin5.jpg So I have been trying to formulate a plan. I haven't pressed the barrel out yet and was thinking I should dremel out the lump in the trunnion and then enlarge the trunnion hole with the barrel still in there to accommodate a larger pin which should remove any evidence of the ruts caused by the previous pin and at the same time maintain factory headspace. But, I am not sure if slightly enlarging the hole is a problem for the barrel or the trunnion, for function and for safety. Also not sure what size I should go to. I don't even know what size the hole is now or the pin that was in there. From what I understand the pin should be a couple thousandths larger than the hole, but I just don't know for sure. I am a novice hobbyist when it comes to metal machining and would appreciate any advice I can get on this. |
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Easy fix. Get an oversize pin from AK Builder.
.302 Barrel Pin They also sell a .315 if it is that bad. Romanians are notorious for being overly tight, |
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Quoted:
Easy fix. Get an oversize pin from AK Builder. .302 Barrel Pin They also sell a .315 if it is that bad. Romanians are notorious for being overly tight, Okay, thanks. Is the .315 the largest you can go with out thinning out the wall of the barrel too much? |
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I think I found my answer.
Brownells lists the original pin as 7mm or 0.276 The slightly over sized barrel pin converts from 0.302 to about 7.67mm. Ak-buliders directions say to drill out to 7mm and then ream to hole to .300 The largest over sized barrel pin is listed at 8mm or 0.315. They say to use a .314 reamer but don't list the size of drill bit you should use to drill the hole first. The difference listed between the pilot hole and the reamer for the .302 pin is .024 So if that transfers straight across to the .315 pin then I would take .024 from the .314 reamer to come up with a pilot hole of .29, or a size L drill bit, and I could probably get away with using a 9/32 which is the next size down. Does that sound about right? Also what sequence should I use? I imagine I will probably have to us the 8mm pin to remove the damage. Should I drill the 9/32 pilot hole now and put off reaming the hole until I reinstall the barrel after the trunnion is riveted in? Or should I drill the pilot and ream now before removing the barrel? Or should I wait to drill anything until after the barrel is reinstalled? Or am I over thinking this....... 
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Did you check the headspace? I would do that first to see if it is good. If it is GTG, then drill it out just under .300. How close you can get with out going to far depends on what you have for a drill press. After you have done that, look into the hole to see if you have cleaned it all up. If so remove barrel. When you re-install the barrel, get the holes lined up perfectly, now check your headspace again. If every thing looks good, ream the hole to final size and install pin.
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Quoted:
Did you check the headspace? I would do that first to see if it is good. If it is GTG, then drill it out just under .300. How close you can get with out going to far depends on what you have for a drill press. After you have done that, look into the hole to see if you have cleaned it all up. If so remove barrel. When you re-install the barrel, get the holes lined up perfectly, now check your headspace again. If every thing looks good, ream the hole to final size and install pin. Okay cool, I will go and get the go/nogos tomorrow. Thanks |
| Another thing you will want to keep in mind is the that the pin hole is almost never square with the trunnion. I think I would use a 7mm bit and run it through the hole with a hand drill and let the bit find the hole. Then shim the trunnion as necessary to center you drill press on the hole itself. |
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