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+--- Thread: short stroke or back lash? (/showthread.php?tid=725)
short stroke or back lash? - hugh - 07-06-2011
Hello,I'm working up a load for a LW 24 with inhanced bolt carrier on a Bushmaster xm-15 e2s lower...Runs great with the original .556 upper on it but with the 6.5 ,while starting in mid range powder loads it will slide lock but as i go higher then it fails to lock...
Will failure to slide lock happen from back lash as well as from short stroking???
I'm still not seeing any signs of over pressure so far...When I pull back the charging handle then it will lock. I'm not shure if i should load them hoter or just back off...
Could the 8208 powder be to fast for rifle length sistem???
short stroke or back lash? - LRRPF52 - 07-06-2011
hugh,
Need more info. There is an optimal apex of gas pressure to operate the AR and most other gas operated systems with certain bullet weights, charges, reciprocating masses, and recoil spring weights. If the gas expansion is too quick, it escapes out the bleed holes in the bolt carrier visible in the ejection port area, leading to a short-stroke, just as an under-pressured system would do.
It would be helpful diagnosing your system to know:
* bolt carrier weight (you said enhanced) M16, AR15, something different?
* gas port diameter
* gas system length
* lower receiver extension length
* buffer length/weight
* bullet weight(s)
* powder and charge weight(s)
I prefer to use a heavier buffer with the Grendel, not the standard AR carbine length buffers for 5.56. If you have a rifle-length stock/extension tube/buffer/recoil spring, that's better than a lighter carbine buffer with shorter spring. When trouble-shooting a new rifle/carbine, I recommend taking 2 or 3 buffer weights to the range with you. I really like the Spike's Tactical ST-T2 tungsten powder buffer for my 16" Grendel carbine, but you will need something different for a rifle-length tube if you have that.
LRRPF52
short stroke or back lash? - hugh - 07-06-2011
Well,LRRPF52, I ment to say inhanced bolt with carrier...The upper was built by SAOD with the carrier they provided and seems to be a standerd type (not the light race gun type)...The stock has the typical A3 tube and spring and yes it is a rifle length system. I've been trying different weight bullets,100 gr nos.bul tip,120gr sbt and 123gr.horn amax...
So far the amax groups best at 1/2 min ... All the rest of the things you ask I dont really know. I will say that I've been running with a dry bolt, could that be a reasion for gas to prematurly escape causing a short stroke? Had an experiance with the .556 were oil found its way into the chamber causing a case seperation. So I try not to get too much oil in the carrier and slam on an empty chamber. Scary stuff.