I’ll post some pictures of items that has helped me to address over and under pressures for the ID system of AR platforms, especially for suppressor and SBR issues.
Most of my experiences started with AR15/M16 Shorty/M4 - 223 based caliber and continues towards the 308 AR10.
Tim LaFrance twin tube expansion chamber solves over pressure for suppressed AR15 16” barrels as well as short pulse pressure for full-auto and semi-auto SBRs. SBR length barrel require larger barrel gas ports and 16” barrels don’t. The LaFrance system is difficult to find because Tim retired from SureFire last year after designing their suppressors. Chris at KNS buys several NIB LaFrance twin tubes every year and offers them once a year.
www.knsprecisioninc.com/contacts
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JP Ind adjustable gas blocks works to limit or increase gas pressures as needed. They also offer adjustable gas blocks for 308 mid diameter barrels.
www.jprifles.com/1.4.6_gs.php
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Armalite’s Super SASS adjustable gas block is absolutely incredible gas system. It’s simple to use and researched for the best results. Personally I never mounted one onto a different manufacture’s AR 308 rifle or barrel, but I would guess in could be done by a competent gunsmith. I believe the only issue of concern would be the gas key link up with the Armalite’s adjustable gas tube…?
www.armalite.com/ItemForm.aspx?item=1010...73-9e49-8b550aadc53b
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Hydraulic buffers alone will not solve pressure issues, but as an added feature accommodates adjustable gas block affects for lower muzzle rise and felt recoil. Hydraulic buffers will increase the range of adjustment for gas pressures, especially the ITT Enidine Buffer.
www.midwayusa.com/find?userSearchQuery=Enidine+buffers
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One of the most important issues of concern for subsonic center fire rifle ammo is barrel twist rate...! 1 - 10 rate is minimum for 180gr to 220gr projectiles and some of my shooting buddies have gone to 1 - 8 twist rate to stabilize above 220gr projectiles.