Piston System Gas

mdmp5

Gunny Sergeant
Full Member
Minuteman
  • May 7, 2009
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    I have an MCX in 300 blk. I noticed that it gets pretty dirty. If I open the gas block, does that mean I will get less gas blowback through the barrel, because more gas enters the piston cylinder? Essentially, would it be the opposite scenario of direct impingement or is it the same thing?
     
    So you're thinking about shooting supersonics with the gas block set for subsonics?
    Well, the extra gas metered through the block should act on the piston with that much more force, speeding up unlocking, extraction, and ejection. If the action opens before pressure drops (to "normal" levels) in the barrel, you'll actually get more gas into the receiver. Sig probably has it worked out so that you don't break anything, but, at a minimum, you will have increased felt recoil. Worst case, you'll have decreased reliability and accelerated wear.
    Try different loadings to see if any one shoots cleaner than the rest.
     
    I was gonna still switch it to (-) with the supers regardless. I am just curious as to why it gets really dirty and if there was a correlation with the gas setting
     
    Without seeing your rifle run, I'd guess that it's overgassed from the factory (for reliability) and that it's unlocking while gas pressure is still high in the barrel. If it was a regular AR, you could mess around with different weight buffers to keep it locked up longer. Since you don't have that buffer component, about all you can do is find a cleaner loading to put through it.