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Do the 5 in 300 blackout uppers cycle subsonic and supersonic unsuppressed? If not will the 9inch 300 black cycle both reliably? — 2 Answers

by Jordan, from CA, United States Asked on January 27, 2019

Name SIG SAUER Sig MCX Upper Receiver Assemebly, M-LOK (4.5)
$1,999.99 $1,639.00 Save 18%
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Answered by Armando R., Gear Expert, from IL, United States, on September 04, 2019

The uppers should cycle with either ammunition, but when shooting sub sonic the action will cycle much more efficiently and properly with a suppressor.

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Answered by Kay, member, from CA, United States, on March 20, 2019

According to a variety of media articles, it will cycle both. However, I have read on forums that it has trouble with subsonic while unsuppressed. YMMV.

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