Prairie Dog Hunt 2016  (How to Prevent AR-15 Jams)

This is what a typical "fail to feed" jam looks like when using light loads.

        The AR-15 is a super reliable rifle, and they can be improved to deliver outstanding long range accuracy.   I’ve spent years working on these rifles, and there are a jillion aftermarket parts available for them.   However, I've seen a lot of these rifles jam (just like any other semi-auto) if the ammunition is not 100% correct for the rifle.

        Our 2016 prairie dog hunt involved two of us using AR-15 rifles with 40 grain bullets.   We used lightweight bullets mainly to reduce barrel jump, so we could see the bullet impact.   (It is rewarding to "see" a prairie dog get blasted.)   Sometimes they fly 6 feet in the air while spinning like a propeller.   Sometimes a prairie dog will explode like a clay bird, and sometimes they just disappear with a familiar sound . . . . Whack!

Lightweight 40 gr. bullets have such a mild recoil, you can almost always see the bullet impact.

        As usual, we brought a few thousand rounds of ammo for this trip, and since we were in a pinch for time, we decided to use affordable a factory load made by Fiocchi.   Our previous testing proved that this ammo delivers consistent accuracy (better than MOA) in all of our rifles.   At 3,620 fps, these are HOT, flat shooting loads.   However, as hot as these loads are, they didn’t always operate the AR-15 action.   I originally tuned my rifle for 69 gr Sierra Match King bullets.   To avoid intermittant "fail to feed" jams, I decided to use my AR-15 in single shot mode.   This also keeps your fired brass on the shooting bench - and out of the weeds.

        "Fail to feed" symptoms are very common, because most semi-auto actions rely on your ammo to operate the action.   This means that your ammo needs to produce enough pressure to fully operate the action.   I’ve also found that you can even shoot steaming hot maximum loads (with lightweight bullets) that fail to raise pressure quickly enough (and long enough) to always drive the bolt carrier fully to the rear.   When bolt travel is limited, it causes intermittent “fail to feed” symptoms.   This is caused by the reduced travel of your carrier, and it is called “short stroking”.

        It’s easy to test your rifle for "short stroking” by simply firing one round with an empty magazine inserted.   Do this several times, and If the bolt doesn’t always lock to the rear, you can bet that your loads will eventually cause the intermittent “fail to feed” symptom.   When testing any ammo for a semi auto, you should fire a lot of rounds this way to be sure you have 100% reliability.   Most shooters just see the "fail to feed" symptom without ever knowing what caused it.

        “Failure to feed” symptoms can also be caused by incompatible parts, but those situations are fairly rare.   There are things you can do to "tune" an AR-15 to operate with lightweight loads.   I’ve experimented with lightened bolt carriers, lightweight spring buffers, different muzzle brakes, carefully fitted gas tubes, and lighter recoil springs.   Getting the best combination of parts is the goal.   You’ll need a lot of ammo (and a lot of time) to verify complete reliability.   However, using the correct (tested) ammo is by far the most important factor to ensure a consistently reliable AR-15 rifle.

These huge extra weights on this forearm reduce barrel jump.   They
allow me shoot heavier bullets and see the bullet impact.

        Next year, I might use my standard AR-15 load with the 69 gr SMK bullet.   I've also almost seven extra pounds to the forearm of my rifle.   I cut (3) steel tubes, filled them with melted lead, and bolted them on three sides of the quad rail with scope rings.   This rig works great when shooting from a bench.   It now allows me to see the bullet impact even with heavier bullets.   The heavier bullets will operate the action perfectly.   I’ll can now use heavier bullets that can reach out to 600 yards.   They will also buck the wind better on long shots.   After verifying my new trajectory chart, I'll be ready for my next prairie dog hunt.




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Larry A. Willis,   Innovative Technologies
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