AR-15 Gas Port Sizes

Disclaimer: These are lists of compiled information from multiple sources. While we make our best effort to test and produce these should be considered for reference only. Any time you start messing with the gas port on your rifle you run the risk of destroying the barrel or causing it to be over gassed. It is much better to slowly work your way up to what you would be happy with.

Updated June 18th, 2015
AR-15 Platform 5.56mm
20" rifle 5.56   0.0935
20" rifle 5.56   0.096
20" rifle 5.56   0.098
16" mid 5.56   0.078
16" mid 5.56   0.081
16" car 5.56   0.0625
16" car 5.56   0.065
16" car 5.56   0.07
14.5" car 5.56   0.067
14.5" car 5.56   0.086
11.5" car 5.56   0.081
11.5" car 5.56   0.089
24" rifle 5.56   0.089
AR-15 Platform 7.62x39mm Conversion
20" rifle 7.62x39   0.12
20" rifle 7.62x39   0.125
16" car 7.62x39   0.078
16" car 7.62x39   0.081
16" car 7.62x39   0.0938
DPMS LR-308 Style Rifle
18" rifle 0.308   0.0960
18" car 0.308   0.0635
16" mid 0.308   0.078
16" mid 0.308   0.081
16" car 0.308   0.07
16" car 0.308   0.073
16" car 0.308   0.076
20" rifle 0.308   0.0935
20" rifle 0.308   0.096
AR-15 Platform 300 BLK Conversion Subsonic Ammo
16" car 300 BLK UNSUPRESSED 0.12
16" car 300 BLK UNSUPRESSED 0.125
16"  car 300 BLK SUPRESSED 0.106
16"  car 300 BLK SUPRESSED 0.11
16" pistol 300 BLK UNSUPRESSED 0.067
16" pistol 300 BLK SUPPRESSED 0.086
9.5" pistol 300 BLK UNSUPRESSED 0.093
9.5" pistol 300 BLK SUPPRESSED 0.093
8.1" pistol 300 BLK UNSUPRESSED 0.104
8.1" pistol 300 BLK UNSUPRESSED 0.12
8.1" pistol 300 BLK SUPRESSED 0.086
8.1" pistol 300 BLK SUPRESSED 0.093
         
         
AR-15 Platform 300 BLK Conversion Supersonic Ammo
16" pistol 300 BLK UNSUPRESSED 0.0625
16" pistol 300 BLK SUPPRESSED 0.059
16" car 300 BLK UNSUPRESSED 0.099
16" car 300 BLK SUPPRESSED 0.093
9.5" pistol 300 BLK UNSUPRESSED 0.073
9.5" pistol 300 BLK SUPPRESSED 0.067
8.1" pistol 300 BLK UNSUPRESSED 0.076
8.1"  pistol 300 BLK SUPPRESSED

0.067

The 300 Blackout data has been compiled from Micro MOA

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  1. Dave Nicholson asks Nov 6, 2019

    I have a 24” heavy barrel in 204 ruger what should the gas port size be?/Thanks

    1. Darren Peters answers Nov 6, 2019

      Well, I highly recommend contacting your barrel manufacturer to determine that. Good news is that an adjustable gas block can fix your problems if you go too large. Depending on the load you probably want to start around .089 and then work your way up to .110 if you aren't interested in an adjustable gas block.

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