.300 Blk For PA Deer Season

    My friend Brian Miller sent this to me.

    Making an Ar-15 legal for Pennsylvania deer season.

    I have wanted to use my 16″ M4 AR in deer season. Unfortunately in my home state of Pa, in stock configuration, that is not legal.  So I decided to remove the gasblock and gas tube, and machine a ring out of aluminum to block the gas port.


    I decided to use my Vortex Viper PST 2.5x10x44 in a QD Larue mount.  This is the optic I am planning on using for open class in 3-gun next year. The scope might be bordering on overkill, but it is what I had laying around.  I do not pick up the front sight post in the scope when it is mounted.



    It would not matter because the front post is coming off anyhow.

    I have always wondered approximately how much velocity is lost cycling the action, so I decided to chrono my shots before and after my gas system was blocked.

    Now I realize this small test is not terribly scientific, but the results were interesting to me.

    Cute little devils aren’t they.

    I used hand loaded ammo with the charges weighed exactly the same on my digital scale. I shot the groups at 50 yards in the same environmental conditions.

    5 rounds 110 grain Vmax with gas system intact:
    High 2267 fps
    Low 2251 fps
    Average 2257 fps
    ES 16
    SD 6

    Group size at 50 Yards


    5 rounds of 110 vmax with the gas system blocked:
    High 2291
    Low 2255
    Average 2267
    ES 36
    SD 13
    Group size:


    When cycling the action I racked the bolt and pushed on the bolt catch to lock back the bolt on each round. Then dropped the bolt by hitting the catch.  I thought it would be the most consistent method.  I am not really sure what is going on here relative to the group size.  Both groups felt the same when the shots broke, I called no flyers in either group. I have heard rounds fired out of an AR where the bolt was dropped manually was not as accurate, but I had always dismissed it. Maybe I should reevaluate that thought.  Shooting the rifle with and without the gas system did feel different to me.  Shooting it semi, the shot would break and the crosshairs would rise then drop back on target.  Without a gas system, they would rise and not really settle for me. This is attributed to the mass of the bolt carrier and buffer slamming back into battery.  I am looking forward to trying this rifle out this year.  Running the data through my Strelock app on my phone, I think it will work fine for digging them out of the brush on my property.


    Nicholas C

    Steadicam Gun Operator
    Night Vision & Thermal Aficionado
    Flashlight/Laser Enthusiast
    USPSA competitor

    Any questions please email him at [email protected]