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9/19/2017 7:27:10 PM
Posted: 9/6/2010 3:29:53 PM EDT
just put a new barrel on and now im short stroking , will eject the last round fired but wont cycle far enough back to pick up the next round . also wont cycle back to catch the bolt catch. im about 99percent sure its becouse i didnt get the holes on the gas block lined up perfectly. anyone tell me how to line up the holes correctly? is there a trick to doing it?
didnt have this problem until i changed the barrel
Link Posted: 9/6/2010 3:50:41 PM EDT
[Last Edit: 9/6/2010 3:51:16 PM EDT by kakirubi]
Which gas block did you install and what barrel length was the rifle before the new install?
Link Posted: 9/6/2010 4:08:50 PM EDT
Originally Posted By kakirubi:
Which gas block did you install and what barrel length was the rifle before the new install?


and what length barrel? Who made the barrel?
Link Posted: 9/6/2010 4:14:28 PM EDT
[Last Edit: 9/6/2010 4:46:17 PM EDT by cpac97civic]
same 16" carbine.
http://www.parts4ar15.com/ar-15_accessories/product/GB-4RA.html



DANIEL DEFENSE barrel
http://www.brownells.com/.aspx/pid=29320/Product/AR_15_M16_M4_BARREL
Link Posted: 9/6/2010 5:15:06 PM EDT
[Last Edit: 9/6/2010 5:26:36 PM EDT by Gatorhunt]
Did you space the GB 1/32" forward off the shoulder of the barrel (remember there usually would be a HG end cap there) ... chances are your restricting gas flow by not having the gas port in the barrel aligned with gas port in the GB.

ETA .. to get the proper spacing from the shoulder I took an old round hand guard end cap and cut it so it will slip over the barrel behind the GB.
Link Posted: 9/6/2010 5:20:42 PM EDT
Yep, I bet the gas block is mis-aligned.

As far as indexing it properly, this is the technique I have used with success:

Use a straight edge to make a mechanical pencil mark on the gas block seat from the gas port all the way to the shoulder of the seat. If you picture the barrel as a globe, this will mark the "longitudinal" position of the barrel gas port.

Now place the very edge of the gas block so that it half-way covers the gas port opening in the barrel. Tighten one set screw to hold the block in place, then using the mechanical pencil circumscribe the barrel using the edge of the gas block as your stencil. This will now give you the "latitudinal" axis of the gas port's position on the barrel.

Next, make a mark on the face of the gas block indicating the position of the gas block gas hole. If you are going to dimple the barrel, after lining up your "longitudinal" mark on the barrel with the mark on the gas block face, you can now look through the rear set screw hole for the latitudinal pencil "ring" mark you've just created on the barrel and mark the spot for dimpling. Of course, you will want to tighten it down verify that its positioned correctly by blowing air from the muzzle end of the barrel while plugging the chamber (with something like a mop, patches, etc). Look listen and feel for air movement.

OF COURSE, this technique assumes that your rear set-screw hole and the gas port opening in the gas block index EXACTLY (or sure as hell close-to) 180 degrees from each other. If they don't, then the above won't work.

Link Posted: 9/6/2010 6:43:25 PM EDT
I'm guessing the gas block isn't matching up with the port...
Link Posted: 9/7/2010 1:45:31 AM EDT
yeah the end cap is still there.
Link Posted: 9/7/2010 1:47:57 AM EDT
Originally Posted By cpac97civic:
same 16" carbine.
http://www.parts4ar15.com/ar-15_accessories/product/GB-4RA.html
http://www.parts4ar15.com/mm5/graphics/00000001/GB-4RA.jpg
yeah the end cap is still there.


DANIEL DEFENSE barrel
http://www.brownells.com/.aspx/pid=29320/Product/AR_15_M16_M4_BARREL


Link Posted: 9/7/2010 6:04:09 AM EDT
There has been reports of that DD barrel having an undersized gas port. I had the same issue.
Link Posted: 9/7/2010 12:32:15 PM EDT
Originally Posted By comp1911:
There has been reports of that DD barrel having an undersized gas port. I had the same issue.


so how did u fix the problem? seen someome tap the hole with a 1/16 drill bit?
Link Posted: 9/7/2010 6:18:04 PM EDT
Originally Posted By cpac97civic:
Originally Posted By comp1911:
There has been reports of that DD barrel having an undersized gas port. I had the same issue.


so how did u fix the problem? seen someome tap the hole with a 1/16 drill bit?


Yeah, in the archive thread the guys were opening up to 0.063-0.068. I opened it up to 0.063 but have not had a chance to test it.
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