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Tex
August 29, 2000, 16:41
This could be the problem. If you shorten the bbl how much should you open up the port? Can I do this through sight-gas block? If so, how big a reamer?, drill bit? Thanks, Tex

gunplumber
August 29, 2000, 17:19
.118" (3mm) for 16", .116 will USUALLY work for an 18", depending on condition of gas system componants.



------------------
T. Mark "Gunplumber" Graham
gunplumber@arizonaresponsesystems.com
Arizona Response Systems
5501 North 7th Avenue, Phoenix, AZ 85013
623-873-1410 http://www.arizonaresponsesystems.com

Tex
August 29, 2000, 22:44
Thank you, gunplumber I do appreciate the info. Tex

mrorange
December 01, 2000, 17:59
Just a couple of questions.....I did a search of the archives first, but there seems to be a little bit of disagreement in the various posts, so I thought it would not hurt to ask.
What is the correct size for the gas port size on a 16 inch barrel with no muzzle device, crowned barrel only? I have seen posts stating anywhere from .116 to .144 . Which is the best compromise for good reliability, but wont beat the heck out of the gun from excessive gas?
If I am reading things correctly, to open up the gas port you remove the front sight, spring, etc, and drill straight through the gas block? Also, do you just use a normal drill bit or is there some special type that needs to be used?
How does .118 translate into a drill bit? In other words, what size drill bit is the same? 3mm?
I appreciate any info, hoping to do this right the first time.

gunplumber
December 01, 2000, 19:45
3mm is .118. ,144? You've gotta be kidding? Probaly a misprint. Greater than .125 is hard to imagine - at .144 youd need to ream the gas plug too.



------------------
T. Mark "Gunplumber" Graham
gunplumber@arizonaresponsesystems.com
Arizona Response Systems
5501 North 7th Avenue, Phoenix, AZ 85013
623-873-1410 http://www.arizonaresponsesystems.com

mrorange
December 02, 2000, 01:30
The .144 came from a post from Grubstake on 10/03/00 as follows:

I chopped one to 15" and had to open the gas port up to .144.I could have gone a bit smaller but through trial and error decided to open it to that size.I like for the gun to run with the gas set at 6-7 so theres margin for wear,fouling etc.My bolt carrier DOES NOT hit the rear of the receiver hard at that setting.Only gently touches it.Your threads are 9/16-24 LH.Theres only an .002 difference in pitch angle between them and 14X1.0 LH(AK thread)Ive done several barrels w/the 14 MM die and gotten good results on all.The 9/16 muzzlebrake only starts to pick up the difference in pitch toward the last 2-3 threads.HTH

The 3mm came from one of your posts from 11/23/00 as follows.... http://www.fnfal.com/forums/smile.gif

from my experience, .116" USUALLY works on an 18" and .118" USUALLY works on a 16", but you need to drill with block in place as the hole in the block is < .118" (3mm)
------------------
T. Mark "Gunplumber" Graham
gunplumber@arizonaresponsesystems.com
Arizona Response Systems
5501 North 7th Avenue, Phoenix, AZ 85013
623-873-1410 http://www.arizonaresponsesystems.com

Thats why I was looking for clarification as there seems to be a pretty wide range. Thanks.

Dan at VOW
December 02, 2000, 02:15
mrorange, one reason that GP recommends that you don't open it up any more than .118 is that it is more than likely that it will start to shave copper off the jacket of the bullet. Not only will this cause the gas port to become blocked it could also cause a blockage in the barrel. HTH, Dan at VOW.

W.E.G.
August 03, 2001, 22:39
moved to FAQ

W.E.G.
August 21, 2001, 21:54
moved to FAQ

runnin an gunnin
March 03, 2002, 13:14
So what size drill bit do I need to use to open the port out to .118? :)

Thanks guys,
David

blackbird
March 03, 2002, 14:48
There's a link to a nice printable drill and tap chart posted at the bottom of http://www.falfiles.com/cgi-bin/forums/ultimatebb.cgi?ubb=get_topic&f=3&t=003739

BTW... I have an STG-58 ( http://www.falfiles.com/cgi-bin/forums/ultimatebb.cgi?ubb=get_topic&f=8&t=000557 ) that has the stock .095 gas port opening with a 16.25" barrel and no muzzle device (i.e. no additional back pressure from this source). It shoots fine and reliably at a gas setting of "3". You might want to try before you drill.