SCulp Posted May 14, 2006 Share Posted May 14, 2006 I understand their are 3 different gas system for the ar due to barrel length and the longer 20 inch AR makes the gun shoot smoother with less recoil. Does the mid length forearm model have a longer gas system. Is the difference noticable? I would appreciate any information about these gas systems as far as which is best and why and if the mid length is better than the carbine m4 length. Thanks Link to comment Share on other sites More sharing options...
George Posted May 14, 2006 Share Posted May 14, 2006 Full length gas systems can fit on barrel lengths as short as 17". The shorter the bbl, the shorter the gas system because the gas block has to be moved closer to the chamber. Gas is now tapped off earlier in the barrel which provides a more ferocious gas pulse. It's also earlier than normal and has a a different duration and fall-off than normal. All of which are not in the original design parameters for bolt carrier speed and action timing for the M-16/AR-15. 16" bbl's use a mid length gas system which provides a harsher/earlier than normal operating pulse and results in the bolt carrier (weighs one pound) slamming back and forth even harder than normal which slams the whole rifle around even more. All this happens long after the bullet has left the bore. This effect is most noticeable when shooting rifles with muzzle brakes which damp the actual recoil so all that is left is the cyclic motion from the bolt bashing around after the round is already downrange. End of story. Link to comment Share on other sites More sharing options...
SCulp Posted May 14, 2006 Author Share Posted May 14, 2006 Thanks George Link to comment Share on other sites More sharing options...
Patrick Sweeney Posted May 15, 2006 Share Posted May 15, 2006 Gas port location is the same on 16" and M4 carbines. If the harsher recoil of the shorter system bothers you, you can take steps to mitigate it. You can fuss with carrier mass, buffer weights and springs. You can use a rifle buffertube/stock on a 16" upper. You can install an adjustable gas block, to throttle down the gas flow. Link to comment Share on other sites More sharing options...
MyBoyElroy Posted May 15, 2006 Share Posted May 15, 2006 Gas port location is the same on 16" and M4 carbines. If the harsher recoil of the shorter system bothers you, you can take steps to mitigate it. You can fuss with carrier mass, buffer weights and springs. You can use a rifle buffertube/stock on a 16" upper. You can install an adjustable gas block, to throttle down the gas flow. To understand how different length AR gas systems function Google "dwell time" then gas port location vs. muzzle. Link to comment Share on other sites More sharing options...
wsimpso1 Posted May 15, 2006 Share Posted May 15, 2006 More detail at http://www.brianenos.com/forums/index.php?showtopic=35004 and http://www.brianenos.com/forums/index.php?...5&hl=gas+system This topic has been talked about before. What happens is that the people doing the writing become reluctant to repeat themselves, so you will not hear from them, but with the search tool, you can find what has already been written. If an old thread was useful, adda thankyou note, which brings it to the top again... Billski Link to comment Share on other sites More sharing options...
milanuk Posted May 16, 2006 Share Posted May 16, 2006 So... anyone here run a 'mid-length' gas system on a 16" tube? Link to comment Share on other sites More sharing options...
.40AET Posted May 22, 2006 Share Posted May 22, 2006 I'm using a mid length gas tube on a 18" barrel. If the mid length gas tube is in question, it runs 100%. Link to comment Share on other sites More sharing options...
Mig Posted May 22, 2006 Share Posted May 22, 2006 So... anyone here run a 'mid-length' gas system on a 16" tube? Yup, running just fine. Link to comment Share on other sites More sharing options...
MyBoyElroy Posted May 22, 2006 Share Posted May 22, 2006 So... anyone here run a 'mid-length' gas system on a 16" tube? Yup, running just fine. Do you happen to remember the gas port size? Run a pigtail? Thanks. Link to comment Share on other sites More sharing options...
Paule Posted May 23, 2006 Share Posted May 23, 2006 We build a lot of 16" middies. They run very well. Link to comment Share on other sites More sharing options...
Mig Posted May 23, 2006 Share Posted May 23, 2006 Do you happen to remember the gas port size? Run a pigtail? Thanks. Normal mid-length gas tube and don't recall the port size. Link to comment Share on other sites More sharing options...
wsimpso1 Posted May 23, 2006 Share Posted May 23, 2006 16" middies should run very well. It is inherently a more appropriate system for 16" guns, and should not need a pigtail or fat tube. I will also bet that Paule is using high quality barrels, chambers and parts, and that his shop also understands what they are doing. Those things all make a difference too. Billski Link to comment Share on other sites More sharing options...
logic Posted May 24, 2006 Share Posted May 24, 2006 Paule, What fluted barrel are you using in that picture you posted? Link to comment Share on other sites More sharing options...
Paule Posted May 24, 2006 Share Posted May 24, 2006 Billski, thanks for the kind words. The barrel in the picture started life as a Lilja blank. Contours are our own designs, which we have turned by Frank and Theresa's great crew at Compass Lake. I like the shiny ones for pics, as they show off the 7-flute design so well, but most folks like them with a little less bling. Link to comment Share on other sites More sharing options...
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