In a recent discussion*, I mentioned I like long float tubes on my ARs to cover as much of the barrel as possible. The idea is I want to keep the barrel from touching anything I might use as a rest, which could throw the point of impact off. Anecdotally I mentioned witnessing a fellow 3-gun competition miss by approximately 3 feet at 200 yards, when his barrel was hitting the peak of a simulated "rooftop" shooting position.
Folks didnt believe the claim, so, always wanting to add to my personal experience and knowledge, I decided to do an experiment and see for myself how important it is to keep the barrel from hitting your rest.
I set up using a ~15"-tall wood rest, on a target at 100 yards. Every round fired used the same point of aim. The rest was a little tall for my usual prone position, a situation common in practical shooting... that you don't get an "ideal" position.
I used my 3-gun rifle. It uses an 18" WOA SPR barrel, JP extended (15") free float Handguards, and vortex genII PST 1-6. The barrel's pretty thick... It uses a 3/4" gas block, and the profile is thicker than that all the way back to the chamber. Notice the hand guards extend past the rifle-length gas system. Ammo was 55gr hand loads.
Group A, 5 rounds. Fired in my "typical" position, with weak hand holding the tube against the rest to keep it on target in recoil. My first couple of rounds were the high/low fliers, as I didn't get in to a good position with the improvised rest, so I fired 5 instead of 3.
Group B, 3 rounds. Fired with the barrel resting on the rest. I put no weight on it other than gravity, keeping my weak hand back under the stock.
Group C, 3 rounds. Fired holding the gun against the rest like I did in group A, only with the barrel on the rest vs the Hand guards. This was awkward, trying to reach out that far.
Group D, 3 rounds. Fired with the barrel against the rest, putting just a rediculous amount of pressure down on it.
Measured from the center of group A, the groups impacted higher by the following amounts:
B: 5.5"
C: 15"
D: 20"
Some observations/thoughts...
-- I was surprised group B hit so much higher. I expected 1-2", not 5". Perhaps part of this was from letting the gun recoil (lift) vs holding it down. In hindsight, I should have also tried a gravity-only hold resting on the Hand guards.
-- I thought later I should have tried a lot of pressure on the hand guards to see if perhaps some of the flex was in the barrel nut or receiver vs the barrel.
-- Groups A and C are the most representative of what could happen in a match were I to hold accidentally resting the barrel on a prop vs the Handguards... 15 MOA of "why the hell didn't I connect, I called a good hit?!"
-- I wouldn't expect such a big difference with a standard barrel-mounted front sight. It would move with the barrel. I might try to repeat that someday with my hbar'd A2.
i expected some shift in POI, but this frankly shocked me. Of course, every gun, barrel, and ammo combination could be different. It does reafirm my opinion that an ideal setup should use as long of a float tube as possible to "protect" the barrel from touching a rest.
*https://www.indianagunowners.com/forums/long-guns/438168-my-perfect-ar15-setup-3.html#post7128490
-rvb
Folks didnt believe the claim, so, always wanting to add to my personal experience and knowledge, I decided to do an experiment and see for myself how important it is to keep the barrel from hitting your rest.
I set up using a ~15"-tall wood rest, on a target at 100 yards. Every round fired used the same point of aim. The rest was a little tall for my usual prone position, a situation common in practical shooting... that you don't get an "ideal" position.
I used my 3-gun rifle. It uses an 18" WOA SPR barrel, JP extended (15") free float Handguards, and vortex genII PST 1-6. The barrel's pretty thick... It uses a 3/4" gas block, and the profile is thicker than that all the way back to the chamber. Notice the hand guards extend past the rifle-length gas system. Ammo was 55gr hand loads.
Group A, 5 rounds. Fired in my "typical" position, with weak hand holding the tube against the rest to keep it on target in recoil. My first couple of rounds were the high/low fliers, as I didn't get in to a good position with the improvised rest, so I fired 5 instead of 3.
Group B, 3 rounds. Fired with the barrel resting on the rest. I put no weight on it other than gravity, keeping my weak hand back under the stock.
Group C, 3 rounds. Fired holding the gun against the rest like I did in group A, only with the barrel on the rest vs the Hand guards. This was awkward, trying to reach out that far.
Group D, 3 rounds. Fired with the barrel against the rest, putting just a rediculous amount of pressure down on it.
Measured from the center of group A, the groups impacted higher by the following amounts:
B: 5.5"
C: 15"
D: 20"
Some observations/thoughts...
-- I was surprised group B hit so much higher. I expected 1-2", not 5". Perhaps part of this was from letting the gun recoil (lift) vs holding it down. In hindsight, I should have also tried a gravity-only hold resting on the Hand guards.
-- I thought later I should have tried a lot of pressure on the hand guards to see if perhaps some of the flex was in the barrel nut or receiver vs the barrel.
-- Groups A and C are the most representative of what could happen in a match were I to hold accidentally resting the barrel on a prop vs the Handguards... 15 MOA of "why the hell didn't I connect, I called a good hit?!"
-- I wouldn't expect such a big difference with a standard barrel-mounted front sight. It would move with the barrel. I might try to repeat that someday with my hbar'd A2.
i expected some shift in POI, but this frankly shocked me. Of course, every gun, barrel, and ammo combination could be different. It does reafirm my opinion that an ideal setup should use as long of a float tube as possible to "protect" the barrel from touching a rest.
*https://www.indianagunowners.com/forums/long-guns/438168-my-perfect-ar15-setup-3.html#post7128490
-rvb
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