Barrel and Comp

[01G8R]

I'm building my first open gun and I have a question about the barrel and comp fitting. Should the comp bottom out on the end of the barrel or the shoulder behind the threads? I'm using a KKM barrel and Bedell comp. Without modification of either part the back of the comp is hitting the barrel shoulder behind the threads. Looks like about three threads are showing in the comp. Thanks.

[jid2]

With it bottomed out on the shoulder you should face the end of the barrel to remove the 3 threads overhanging so the end of the barrel is flush with the first port in the comp. Re-crown the opening of the barrel after facing it, and align ream the comp to the barrel once it's been locktited in place. Also make sure you have clearance for the barrel to unlock from the slide, gap should be around .003" between the comp and face of the slide.

Edited November 14, 2010 by jid2

[Matt Cheely]

You'll have to relieve the barrel or the inside of the comp so it will thread on far enough to give you room to match it to the slide.

[ExtremeShot]

I'm building my first open gun and I have a question about the barrel and comp fitting. Should the comp bottom out on the end of the barrel or the shoulder behind the threads? I'm using a KKM barrel and Bedell comp. Without modification of either part the back of the comp is hitting the barrel shoulder behind the threads. Looks like about three threads are showing in the comp. Thanks.

It doesn't really "bottom out". You need to bore out the end of the comp on a lathe. Make the bore diameter a thou or two larger than the diameter of the barrel behind the threads. Any larger and you'll have a gap. As far as depth, stick the comp on barrel and screw it on as far as you can. Then measure the distance between the comp and the front of the slide. I'd go 10 or 20 thou past that. Here's some pictures of the last comp I made.

Darren

[ExtremeShot]

Thought I had some pictures of the final comp fit....can't find them. Sorry.

[01G8R]

Thanks for the info. I relieved the comp so that it goes on and the end of the barrel is even with the first port.

Should the barrel bottom out in the comp for a tight fit or should I just screw the comp on until the barrel is even with the first port and loctite or epoxy it in place? I thought I should remove material from the front of the barrel to get the comp to index properly when tightened. The comp has material that will stop the barrel from extending into the first port.

[ExtremeShot]

Thanks for the info. I relieved the comp so that it goes on and the end of the barrel is even with the first port.

Should the barrel bottom out in the comp for a tight fit or should I just screw the comp on until the barrel is even with the first port and loctite or epoxy it in place? I thought I should remove material from the front of the barrel to get the comp to index properly when tightened. The comp has material that will stop the barrel from extending into the first port.

Don't worry about bottoming it out. If you are able to snug it up (which I highly recommend NOT doing), then your comp ports probably won't be straight up.

Most people red loctite it and/or put a set screw in it. If you use red loctite, the comp and barrel threads must be super clean with no oil residue.

I wouldn't remove any materials from the barrel. If you do, you could mess up the crown (you could put a burr on the inside of the barrel) and mess up the threads. The .685-40 threads are VERY easy to get cross threaded. DO NOT FORCE ANYTHING. I got a comp cross threaded on a barrel once and I ended up screwing up the barrel and the comp. To fix the problem I had to turn the barrel down to a .581-40 and make another comp.

Normally you want a gap a couple thousandths wide between the comp and slide. You should be able to see daylight between them but at the same time the gap won't be noticeable. However, when the barrel unlocks, the rear of the barrel comes down and the front of the barrel comes up. When this happens, the comp will hit the front of the slide. So to fix this, you need to cut a 1 or 1.5 degree angle on the comp OR on the front of the slide. I cut this angle on the comp. Additionally, you need to provide a couple thou of clearance when cutting the angle.

So, when you finally fit the comp, you screw it on until it comes back and touches the slide. Usually you'll be screwing it on and get to the point where it's indexed correctly but you see a gap. Then if you turn it one more full revolution then it will hit the slide. That is the position you are looking for. Next you cut the 1/1.5 degree angle either on the slide or the comp while at the same time providing the 1 or 2 thou clearance.

I don't really pay attention to where the front of the barrel and first port are located relative to each other. Over-the-counter comps will usually have approx. 0.5 inches from the back of the comp to the back of the first port. Your barrel will typically have the same distance sticking out of the front of the slide.

Hope this helps,

Darren

[ExtremeShot]

PS: Obviously if you don't care about a gap between the comp and slide, don't turn it that last revolution (as described above). You'll have the gap, but not have to do all the work I described.