Breech plug not clocking right

[Terry Reynolds]

If I set the plug to clock with the GM barrel flat the makers mark will be on the same flat as the flash hole. I’ve always read that the makers mark needs to be on the bottom. Is my beech plug threads to short clock correctly?



Thanks

[Marvin S]

I’m doing my new GM barrel and plug right now. First thing I did was chamfer plug some and turn it a bit to root diameter so it would not crush the first thread when bottoming against barrel. Mine timed great but is 180 degrees out with maker and caliber on top. 1.000 divided by 18 is .05555 advancement per full turn for 5/8-18. So I’m figuring.025 to .027 removed from plug and Barrel will get me there. Divide .056 by 8 for each flat but maybe err on the slim side to creep up on it.

That’s my plan anyway, someone with more experience may have a better one to help you.

You plug don’t appear to be up against the barrel and will probably crush the first thread and make it difficult to remove, that’s what mine wanted to do. By the time it bottoms on barrel and plug/breech face it will probably be like my 40 cal with markings at top.

[Stoner creek]

Not the case with the Green Mountain barrels. Get your files out and make it fit. Most importantly make sure that it fits correctly inside the barrel. I’ve filed off the GM stamps plenty of times. You don’t have to worry about runout in any direction with those barrels.
Great question! Rock on!!!!

[alex e.]

It looks as if you're breechplug is not making contact with the end of the barrel

[bgf]

In my limited experience, the threaded section of GM barrels is longer than some breech plugs, so you may need to take a bit off the barrel to get the plug close to seating (at least up to the partial thread behind the rifling), then work plug and barrel together until they align the way you want and the plug is seated correctly.  I prefer the makers mark on bottom flat, though it may just be old school superstition.

I had a Rice barrel and a breech plug with almost exactly same threaded length (~1/2" iirc) and they went together very quckly, but i spend much more time on GM barrels getting the plug seated and lined up because of the longer threads, not to mention steel that is quite noticeably harder, but they are great barrels!

[Gunnermike]

FYI - Green Mountain has some pistol barrels on sale - look under the "Limited Quantities" section.  The barrels range from $52 to $55, the normal price now is $75.
Mike

[EC121]

The maker's mark up or down came from the Douglas barrels.  The rest don't matter.

[Frank]

The maker's mark up or down came from the Douglas barrels.  The rest don't matter.

Douglas barrels always had some run out hence the need to have the marking on the bottom or top flat. All barrels made today are concentric so it doesn’t matter. Just draw file the makers mark off.

[Eric Krewson]

I filed off the back end of my GM barrel and used normal length plug so the fence on my lock lines up with back end of the barrel. Once I got a good seal inside, the logo was on a side oblique flat, I didn't want to fool with it any more so I punched the logo flat and filed it away.

[Terry Reynolds]

Thanks for all the advice, it was helpful and got the job done. Good seal and plug clocked right.