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Posted: 11/27/2025 6:03:41 PM EDT
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I am about to buy a 5" 300 Blackout AR pistol with a 4" handguard. It does not have an adjustable gas block. I plan to run it 100% suppressed with subs. Will it run like it is supposed to without an adjustable gas block, or do I have to look at a pistol with an adjustable gas block? If I wanted to have the adjustable gas block with this current pistol. What do i need to do to make that happen? |
| Its not needed,but certainly helps. My original 300blk sbr i built in 2013 does not have one as it was pre-adj gas blocks. Shoots supers and subs just fine. |
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I have a couple of 300BLK guns and do run Superlative Arms adjustable gas blocks on them. One is dialed for supers, the other for subs. I put them on for potential tuning when I was building the guns. Once built, I did all sorts of tuning and am happy with the results, but you can go over board with this. I'm sure I did, but also enjoyed the experience. I like to tinker so it's worth it to me but as noted by others, you can tune without them. This really comes down to choice. I don't think there is a "right" answer. |
| There's a decent chance that it will barely function wide open, much less constricted with an agb. There's not much dwell time on a 5" barrel, plus you're using subsonic rounds which have weak back pressure by their nature (although a suppressor can up back pressure somewhat). Other folks may be speaking of their 7-10 inch barrels, but a 5" inch is really pushing the limits, even if the port were maxed out at .125". An agb is only useful for down regulating the gas. You actually may have to go the other direction and get a weaker spring (yellow) and a lighter BCG and buffer weight to achieve last round bolt lock-back, which is one measure of proper gassing. |
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