Gas piston "AR10" at 300 yards with factory ammunition - 10 shots in 70 seconds.

Discussion in 'Rifle Country' started by MCMXI, Apr 26, 2010.

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  1. MCMXI
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    MCMXI Contributing Member

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    There has been some discussion over the past year about gas piston ARs and accuracy. The target below isn't too bad for a "battle" rifle with all rounds fed from the magazine, zero feeding/ejection problems, some ammunition stored in questionable conditions and 10 shots in 70 seconds. The Leupold scope has M3 dials which means 1 MOA clicks for elevation and 1/2 MOA for windage. The TM reticle with mil stadia doesn't help much either. After realizing that I needed + 4.5 MOA on the elevation, and realizing that 0.5 mil holdover = 5.4" at 300 yards, I decided to hold on center with +5 MOA elevation. I think I could get the group down to around 1 MOA, or slightly better, with reloads.

    I shot 42 rounds yesterday and could feel significant differences in perceived recoil i.e. some rounds felt "hotter" than others. I put this down to possible corrosion between the bullet and case neck. When I spoke to my gunsmith after the match, he told me that I should have seated each bullet 0.002" deeper to break any "bond" between the bullet and case neck ... duh ... wish I'd thought of that. Regardless, this POF is simply a joy to shoot ... :).

    Range: 300 yards
    Position: Prone with bipod and rear bag
    Target: 300 yard F-Class
    Ammunition: OLD lot of Federal Gold Medal Match 168gr
    Course of fire: 2 sighters in 2 minutes, 10 rounds in 70 seconds
    Rifle: POF P308 (gas piston "AR10" with 20" barrel)
    Optics: Leupold Mark 4 3.5-10x M3 (TMR) with 100 yard zero
    Weather: Hot and full value 7 ~ 8 mph wind (fairly consistent)

    S1: Elevation = +5 MOA, Windage = -2.0 MOA
    S2: Elevation = +4 MOA, Windage = -2.0 MOA
    Shots #1 ~ #10: Elevation = + 5.0 MOA, Windage = -2.0 MOA (hold on center)


    [​IMG]

    :)
     
    Last edited: Apr 28, 2010
  2. Dr. Tad Hussein Winslow

    Dr. Tad Hussein Winslow member

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    Thumbs waaaay up! :D
     
  3. Winston_Smith

    Winston_Smith Member

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    Nice shooting 1858. I have been watching your threads about this rifle as I wait for mine to ship :)
     
  4. MCMXI
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    MCMXI Contributing Member

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    Thanks guys!! This POF has real potential and with the right load should shoot under 1 MOA "rapid" fire at 300 yards. That's more than acceptable for a "battle" rifle. Even the group above is acceptable for many situations that a .308 might be used for. I'll work up a load over the next few weeks and be ready to try again at our next match on 5/16. I'll report back.

    :)
     
    Last edited: Apr 26, 2010
  5. C-grunt

    C-grunt Member

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    Good shooting. Those POF rifles are really nice.
     
  6. Birddog1911

    Birddog1911 Member

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    Sounds like a great setup. Can't wait to see your groups when you get more familiar with the rig!
     
  7. MCMXI
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    MCMXI Contributing Member

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    C-grunt & Birddog1911, thanks ... :) . I think it's pertinent that I mention that I was given four boxes of Federal Gold Medal Match (white box, lot # 21N297) a few months ago by someone that doesn't shoot anymore. As I mentioned, they weren't stored under the best conditions. A friend and I shot 5 rounds each of this lot a few months back to compare to my reloads and some American Eagle 150gr ammunition.

    http://www.thehighroad.org/showthread.php?t=505871

    All 10 rounds were shot over my CED M2 chronograph and if you look at the data you'll see that the ES was 77 fps and the SD was 20 fps. Compare this to my reloads or a new box of AE and which were both half that. This adds credence to my feeling that there were some consistency issues with this ammunition.

    Here are a couple of photos of the POF P308 in its current form. I'm going to swap the scope for another Leupold Mark 4 3.5-10x M1 FFP model with the TM reticle. That scope is currently on an AR15 but this rifle deserves finer adjustments i.e. 1/4 MOA elevation and windage and the FFP feature won't hurt either.

    [​IMG]

    [​IMG]

    :)
     
  8. RonE

    RonE Member

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    Good shooting and a nice looking rifle.
     
  9. CSestp

    CSestp Member

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    I must be lost or something. Cool rifle and all, but that isn't that great of a group with a scoped rifle in the prone with a bipod in 70 seconds. Try iron sights sitting in 60 seconds. Just got off of the qual range about a month ago and scored a group around the same. The only diff is I'm fired a much smaller round 5.56 which yes i understand the recoil, but in all honesty when you qualing you only have around 40 seconds cuz you start in the standing then gotta plop down and find a good natural point of aim.
     
  10. rattletrap1970

    rattletrap1970 Member

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    Nice rifle. I'm not all that enamored with that ridiculous tacticool stuff on the front, but, to each his own. How do you like that Magpul stock? I always said that's what I'd get when I eventually get my AR10.
     
  11. MCMXI
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    MCMXI Contributing Member

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    You're right, that it isn't a great group but you are missing the point. You say that you "scored a group around the same" whereas I posted the actual target with actual measurements. Did you measure the group or are you just guessing? Regardless, this is stage 1 of my efforts to show what a gas piston AR may or may not be capable of since this has been a point of contention for many anti-gas piston "purists". The rapid fire drill is a good test of whether or not the POI moves significantly up/down/left/right as the barrel heats up. I also mentioned and provided a link to some chrono data for this lot of ammunition indicating a possible problem.

    As for iron sights, I'm very familiar with what is or isn't possible at 300 yards. I shoot alongside (and pull targets for) many very competent service rifle shooters ... folks that shoot in the 480 to 500 range week in and and week out ... many of them are active military. You mentioned that you were shooting sitting with 10 rounds in 60 seconds ... wouldn't that put you at 200 yards rather than 300 yards? All 300 yard service rifle shooting is prone but you mentioned "qualifiying" so is that a diffferent course of fire? The 300 yard F-Class target shown above has a 1.42" X ring and a 2.85" ten ring whereas the 300 yard high power service rifle target (SR-3) has a 3" X ring and 7" 10 ring.

    :)
     
  12. MCMXI
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    MCMXI Contributing Member

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    All of the P308s come with the MRR (Modular Railed Receiver) so that's why it's on mine.

    http://www.pof-usa.com/p308/p308.htm

    Like you I'm not enamored with it either since it places the center of the scope higher than it needs to be (3" above the bore) and I have no intention of or interest in hanging any accessories off the rail (other than the TROY BUIS shown). As for the PRS, I have one on an AR15 too and I like them both ... a lot!! The PRS shifts the center of gravity back to the center of the mag well which helps with offhand shooting and they offer plenty of adjustment. If you go with a PRS stock you'll need a rifle length .308 buffer. I added some weight to the DPMS buffer that I'm using and changed the buffer spring to a TUBB CS .308 flat-wire spring. I also swapped the regular cam pin for a roller cam pin from POF. The timing is WAY better than the set up that the rifle came with. I also added a Geissele SSA trigger which is excellent.

    I'll be working up a load over the next three weekends using Varget and 168gr SMKs ... the next match should be interesting.

    :)
     
  13. Heavies

    Heavies Member

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    I can't wait to see how that will turn out. Im sure that it'll shoot Way tighter.
     
  14. CSestp

    CSestp Member

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    you are right on the sitting 200 part, lost my mind for a moment. and no i have no target pictures to post so I suppose with that said i could have key holed all 10 rounds in 14 seconds. So in other words point made.
     
  15. MCMXI
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    MCMXI Contributing Member

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    CSestp, not a big deal. I hope to do better once I have a load worked up. I may even shoot 20 rounds in 70 seconds at the next match since I had plenty of time. I usually do that drill with a bolt action rifle and 10 rounds seems like a lot at that range. With the semi-auto I could have fired a round every 2 seconds since I was barely moving off the target with each shot and didn't lose my sight picture as I usually do when working a bolt.

    Heavies, welcome to THR.

    :)
     
    Last edited: Apr 30, 2010
  16. Still 2 Many Choices!?

    Still 2 Many Choices!? Member

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    Nice shooting! I know it's not right to covet another man's wife, but is it okay to covet another man's rifle:)? An AR-10 type rifle may have to be in my near future, like next year after X-mas! I just need to do more research on POF, or the standard gas system, makes, models, magazines, and the concensus on who makes the best one. Don't get me wrong, I love my FAL, but a 300+yard precision rifle she ain't.

    Still 2 Many Choices!?
     
  17. MCMXI
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    MCMXI Contributing Member

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    I don't know what your budget is, but a good friend has a Knights SR-25 and recently received a LaRue OBR (ordered almost a year ago). Both are VERY, VERY accurate. He told me that the SR-25 is sub 1/2 MOA with his reloads and the OBR is similar, both at 200 yards. I don't expect the POF to be that good but I'm hoping for consistent 1 MOA performance during rapid fire drills at 300 yards. 1 MOA for slow fire stages (20 shots in 20 minutes) at 600 yards would be nice too but maybe too much to hope for ... we'll see.

    :)
     
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