View Full Version : How-to Inch gas hole? (short gas)

June 10, 2002, 07:31
I'm WECSOGing a short gas system out of my Tapco "missing parts" kit. I've got the barrel turned down now, but I'm trying to figure out how to locate my gas port hole. An inch gas block came with my kit, which I prefer, but the hole is not in line with the front sight!!!! Any ideas on how to place this bugger. Is the inch port location the same place as on a metric barrel? By the way this shorty is lookin real sweet so far!!! I can't wait to get a receiver and get her together. I know a metric would be easier, but I like the open ears and the gas adjustment better than that of my R1/Izzy HB/Imbel carbine, not tools required!!! Thanks in advance guys.

June 10, 2002, 07:36
On the inch gas blocks the gas port is @ about 30 degrees, it should be accessable from the port for the gas adjustment.


June 10, 2002, 12:04
Thanks Cybercop, I'll try marking it through the site hole, and then finish the hole with the block off. I did notice that hole in the inch block was incline as opposed to straight in my metric. I'll let you all know how it goes. I'll probably do it Tues. or Wed., so if anybody has any other tips, keep 'em comin'.:)

June 10, 2002, 13:38
Just a thought here...how about cramming a China marker in the gas port of the FS. When you slide it one to the rifle and get the FS where you want it shove a nail through the top of the FS pushing down on the marker causing a mark on your bbl. You might have to remove all the waxy stuff of the marker and just use that.
Good Luck.

June 10, 2002, 17:58

So how critical is the location, fore to aft?(handguard/GB placement) Have you indexed the grooves in relation to the port. You really should try to!

At 1:12 (actually a little less?), and 4 grooves (?), you've got little "wiggle" room in the hole dept.

Index the grooves around the muzzle and re-mark them at the 12" mark on the bbl, top groove is #1. #2 comes up at 3" back (1/4 way, for 4 groove), #3 at 6" (180 degrees "off"), and #4 comes TDC at 9" back. IOW; 90 degrees per 3", or 30degrees/inch, Adjust as needed for variance in muzzle/groove placement.

The object of the exercise is to get the GP in the center of a groove. I didn't bother doing this w/ "Shorty", and had a minor port clog problem, and major copper"flash" on the piston head. Could be that the port was bisecting a land/groove, and jackets whizzing by at 2700fps tended to vaporize and blow thru the port onto the piston:D. Not fun to clean!

Once the location is indexed, locate the GB accordingly and drill THROUGH the GB port. Trying to locate and drill w/o the GB in place is a job and a half, and not, IMHO, necessary, desireable, nor easy. A full service machine shop, w/all the goodies MAY be willing to do it, but why?

Good luck,