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The Range
Rifle & Shotgun Discussion
My 300 Blackout will not cycle subsonic
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<blockquote data-quote="Sanford" data-source="post: 2794282" data-attributes="member: 27733"><p>With a 16" barrel and mid length gas system it 'should' be able to cycle using subsonic ammo even without a can. It's usually the shorties - under 10" - that need the can to cycle with subs.</p><p></p><p>Have you tried generously lubricating the buffer spring? I once had a problem similar to that you describe and a bit of white lithium grease rubbed up and down the buffer spring solved it. </p><p></p><p>Unless it's a pinned gas block you should be able to check alignment by loosening it and sliding it forward to check the soot mark around the barrel port (most gas blocks are drilled enough larger than barrel ports that the leave an easily seen ring). If not right, adjust as appropriate when you put it back. Oh - and might as well check the gas port size while it's open, too. There's a pretty good discussion of port sizes here: <a href="http://micromoa.com/300-blk-port-size-testing/" target="_blank">http://micromoa.com/300-blk-port-size-testing/</a></p><p></p><p>Does the bolt lock back on an empty magazine shooting the subs? Have you tried the "plunk test" - BCG removed, muzzle pointed down, manually dropping a round into the chamber should go "plunk" ... if it doesn't easily go all the way in you might need to compare with some factory ammo to see if maybe you have a sizing issue. In fact, getting some factory subs for comparison might not be a bad test in any case.</p><p></p><p>Can't really think of much else to post at the moment, other than "good luck!"</p></blockquote><p></p>
[QUOTE="Sanford, post: 2794282, member: 27733"] With a 16" barrel and mid length gas system it 'should' be able to cycle using subsonic ammo even without a can. It's usually the shorties - under 10" - that need the can to cycle with subs. Have you tried generously lubricating the buffer spring? I once had a problem similar to that you describe and a bit of white lithium grease rubbed up and down the buffer spring solved it. Unless it's a pinned gas block you should be able to check alignment by loosening it and sliding it forward to check the soot mark around the barrel port (most gas blocks are drilled enough larger than barrel ports that the leave an easily seen ring). If not right, adjust as appropriate when you put it back. Oh - and might as well check the gas port size while it's open, too. There's a pretty good discussion of port sizes here: [URL="http://micromoa.com/300-blk-port-size-testing/"]http://micromoa.com/300-blk-port-size-testing/[/URL] Does the bolt lock back on an empty magazine shooting the subs? Have you tried the "plunk test" - BCG removed, muzzle pointed down, manually dropping a round into the chamber should go "plunk" ... if it doesn't easily go all the way in you might need to compare with some factory ammo to see if maybe you have a sizing issue. In fact, getting some factory subs for comparison might not be a bad test in any case. Can't really think of much else to post at the moment, other than "good luck!" [/QUOTE]
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My 300 Blackout will not cycle subsonic
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