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Posted: 6/17/2006 2:01:35 PM EDT
[#1]
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Posted: 6/19/2006 2:22:48 PM EDT
[#2]
I just calipered a 3/32 drill bit and that's 0.093, I seem to recall that being the "good" size......
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Posted: 6/19/2006 11:04:49 PM EDT
[#3]
If you pick up a Novesky krink brake you may not need to modify the gas port. THe krink itself will increase back pressure. |
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Posted: 6/23/2006 12:26:47 AM EDT
[#4]
I have had my best luck with the gas port hole around .095-.105.
I have gone to using the shorter buffer tube, longer Colt style spring, and in the bolt style buffer with a JP Ent. adj. gas block. I can adust it for single shot use and all the way up. |
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Posted: 6/23/2006 3:32:07 AM EDT
[#5]
Thanks for the info, but I an unclear on your answer as to your setup...... shorter buffer tube being pistol length (like a bushy)? longer Colt spring as in an extended slide 1911 spring? and I'm not sure on what you mean by bolt style buffer............. |
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Posted: 6/27/2006 1:02:34 AM EDT
[#6]
I just re-worked a 7.5" barrel this weekend, reference this post
This barrel uses the pistol length gas system. I ran it with a carbine length buffer tube and carbine buffer and spring. It came with the port drilled at 0.081" which is WAY too big. 0.059" is more like it. I was using M855 as my test fire ammo. The failures to extract have gone away now if you keep the barrel under about 300 degrees. |
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Posted: 6/27/2006 3:56:57 AM EDT
[#7]
Randall, how far from the muzzle was the barrel in question's gas port? mine's right around 3", and after my (uneducated) interpretation of the graph of muzzle pressure on your site, I thought bigger would be better. I have a pigtail to soften the presure spike and will probably switch that to a fat boy tube with what I've heard about pigtails failing......
I have yet to fire this upper, I just bought the parts last week and will be trying it out this weekend. |
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Posted: 6/27/2006 6:49:23 PM EDT
[#8]
2.8"
There is no rule about bigger/smaller being better. What's CORRECT is whatever size port that will get the PROPER amount of gas to the carrier to run the action. More gas is not necesarily better. Now, if you use a pigtail, you are changing the gas flow because it expands more before getting to the carrier and you would therefore need a larger port. With the pistol length ga system, you have so much pressure available, that you don't really need a large port, even with there being so little barrel past the port. It's always a balancing act... 
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