Barrel Counter Bored......

[musketjon]

I had my barrel counter bored to get rid of a belling problem caused by a lot of years of judicious cleaning without regard to muzzle wear. Using machinist's gage pins to check the MW it has "0" MW (a .300 pin fits but a .301 won't). The c-b is 3/16 inch deep. Does any one know FOR SURE if the reliability has been compromised? I am planning on taking it out this weekend to try it but was wondering if I should expect the worst-case scenario. I plan to open up the gas port 1 drill size at a time if necessary to get the reliability back if it doesn't work. Is there an ABSOLUTE maximum size that the gas port shouldn't be drilled larger than? I will be using # and letter drills in sucession if necessary for enlarging.
TIA
Jon

Information

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[dryheat]

Very inovative idea. I sure would like to hear the outcome. I know of folks who regularly lop an 1/8" off the end of barrels to "clean them up" and recrown and they just shoot them. I'd just take it oout and try it first; there may not be a need for changing any of the parameters. I've bought milsurps that have had c.b. barrels and I admit, it kind of turns me off aesthetically.

[Rick B]

My question will be if the gas system works properly now. You have removed enough barrel that compression may be lost with the gas port hole bing so close to the edge of the counter bore.. Let us know. Rick B

[BruceV]

Shoot it. You've got nothing to loose. You may or may not see an improvement in accuracy. You may or may not experience short-stroking. If the rifle was previously reliable, try a different type of ammo. If the problem persist, open the gas port up to the next drill size. If it works, good. If it doesn't, you've lost nothing. JMHO. Sincerely. BruceV.

[LavaTech]

I seem to recall that a couple years ago someone on the CMP Forums had counter bored something like ¼" or more with an increase in accuracy and no loss of function whatsoever.

[RCS]

Alot of the older M1 rifle imports from Blue Sky and others had barrels that were counter bored. Before that the 1903 imports from China also had aot of counter bored barrels. Years ago I saw some nice 1940 dated M1 rifle barrels, but each one had about 1/8" to 3/16" removed from the muzzle with a new crown

[musketjon]

Thanks guys for your words of encouragement. I'll get back to you after I shoot it this weekend. Let's all hope the gods will be smiling down on me and not laughing. I'll be in touch.
Thanks
Jon

[JustPassingThrough]

That counter bore won't effect the gas transfer to the gas cylinder in any measurable way. The bulk of the gas transfer actually occurs after the bullet has left the barrel. Only about 5% of the total pressure is seen when the bullet is between the port and the exit.

However, opening up the gas port even 1 mil can have a drastic increase in pressure seen by the op-rod. Port modification should be avoided if possible.

[jjroth]

muzzle of my M1, by Bruce of the DCM van back in 95.
No problem with functioning.
Still have the barrel as I swapped it out for a 7.62.

Do it!

[BDH]

M1 Carbines. My CMP Standard Products is counterbored about 3/4". It shoots great. Have fun!

Bruce