Marksmanship/ ammo question | AR15 Forums

Marksmanship/ ammo question

Discussion in 'AR Talk' started by unussupra, Feb 13, 2007.

  1. unussupra

    unussupra Guest

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  2. HighPowerShooter

    HighPowerShooter Guest

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    1-12 is WAYY to slow a twist for the 62gr bullet..... in a 1-12" barrel shoot 55grs and lighter... that is why the bullets are keyholing....
     
  3. M1ALover

    M1ALover Guest

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    What HPS said ;)
     
  4. Bravo One Niner

    Bravo One Niner Guest

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    Damn it! High power shooter is right again !
     
  5. cheechako

    cheechako Guest

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    unu

    Maybe you have a different type of photobucket account but on mine I have 3 options for posting a photo. URL, HTML, and IMG. If I use the IMG option the photo will post directly onto my reply.

    Ray
     
  6. Inland44

    Inland44 Guest

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    Man! That's ugly when you get keyholing like that. At 25 yards, too. What a difference a few grains in the bullet makes. You need a 1:9 barrel minimum for 62 gr. Like they say, 55 gr or less for 1:12. M193 would be the correct ammo.
     
  7. Orlando

    Orlando Guest

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    So is 55 gr OK in a 1:9 barrel?
     
  8. Snake45

    Snake45 Guest

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    My RRA 1:9 barrel makes nice round holes, about 1 MOA, at 100 yards with every brand of 55 grain ammo I've tried.
     
  9. HighPowerShooter

    HighPowerShooter Guest

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    well I AM due to be wrong about something soon..I usually screw up real good after being right a few times....... :lol:
     
  10. unussupra

    unussupra Guest

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    This is Q3131A 55gr ammo, same rifle and distance.

    [img=left]http://i151.photobucket.com/albums/s160/unussupra1/target3.jpg[/img]

    I was just suprized at how short a distance the round tumbled out of control.
     
  11. Big Ron

    Big Ron Guest

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    Just my 2 cents, first time in competion tried in my SP-1 at 100 meters canted hits.Back to 40-50's

    TO HIGH POWER


    TO THOSE WHO SERVE
     
  12. Cap'n Dex

    Cap'n Dex Guest

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    Is it the "ss109" type bullets? I read somewhere its not necessarily the bullet being 62gr, but the fact that because of the steel core, the bullet is longer, therefore it shall not stabilize as nicely in a slower twist barrel. Does that mean that the slower twist barrel will stabilize a 62gr lead core bullet though? :wink:

    I need to get out to the range, and wing some mouse bullets down range. Its been a long time, and I used to be pretty good with my A2, and now I probably suck. :lol:
     
  13. Hummer

    Hummer Guest

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    There is another way to look at this little quirk. I have done rather extensive testing and while the accuracy opens up considerably with the old 1/12 barrel will still print around 6" at 50 yards.
    M855 will deliver the bullet with centerline (yaw) of the bullet about 75 degrees to the line of flight at 25 yards.
    At 50 yards the M855 will be about 30 degrees.
    At 100 yards the M855 is almost recovered and still shows yaw on paper. The dispersion at 100 yards was about 13" if I remember correctly. Or about the same accuracy as a 12 gage slug gun.

    OK what causes the high lethality of the 5.56 round? Yep it tumbles. About 4 inches inside a body the bullet starts to tumble and causing massive wound cavitation and exits the body point towards the shooter and generally breaks apart at the cannelure.
    This was well documented by Army Wound Ballistics Lab Col Martin Fackler, Commander in 80s.

    It stands to reason a massively yawed bullet presented to the body (read bad dude) will have more surface area contact sooner and break up even quicker and velocity is dampened more quickly and dump most all it's energy in the wound tract rather than wasting it blowing out the back side. If it should exit the body there is less lethality for it to continue through walls.


    I call this the ice pick principle. Are you likely to go down quicker from being hit in chest with 10 pound sledge hammer or stabbed with ice pick.

    Col Fackler at The Army Wound Ballistic Lab concluded the highest lethality of the M193 occurred in first 95 yards and it dropped off quickly thereafter. That distance is not much further enhanced with the M855 round.

    With this in mind when I had my old slow twist barrel ARs I used to load my home SHTF AR with the first three rounds out as M855 followed by 23 rounds of M193. Total of 26 rounds right? Why 26?

    Most all stoppages on M16 occur in the first round after reload as the stack is tightly packed and the first round has a tendancy to fail to feed. Therefore to enhance first round reliability I reduce the stack load so when I do pull the charger handle back and let it fly something good is going to happen.

    After all if you have not done any good with TWENTY SIX rounds the chances of success is not going to be significantly enhanced with another four chances and this is a indication that you need more training.

    OK accuracy is poor but indoors in a SHTF scenario I rather doubt we will be concerned with proper shooting position, sight alignment, hold and squeeze and group measurement. Assuming most houses are less than 25 yards down the hall, you lose nothing in the way of accuracy.

    With the incidence of home invasions on the rise the words of Confederate General Nathan Bedford Forrest ring true, "Get there the firstest with the mostest."
     
  14. Bravo762

    Bravo762 Guest

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    55 grain bullets will do right-well in a 1:9 barrel.

    Last year at The Ranch, we were hitting pepper poppers at 400 from the tower. I was using 55 grain FMJ Winchester white-box ammo, and the XCR - which has a 1:9 twist barrel.

    I missed one time at that distance - no matter how good I think I am, I've gotta screw up at least once ;-)
     
  15. Hummer

    Hummer Guest

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    That is excellent shooting and excellent lot of ammo. I hope you laid in about 20,000 rounds of it.
    Was that with a scope or irons? Free float barrel?
     
  16. Bravo762

    Bravo762 Guest

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    Thanks Hummer!

    I couldn't afford 20K, but I did pick up 7K. Unfortunately, most of it was expended in the combination of the CQB course, new weapon eval (the XCR), and a bit of practice. I did 'stop myself' before I dug into the last 2 cases though.

    The set-up was a 16" Robinson XCR, with what they term their 'light' barrel. I'm not saying it's not light - it's lighter than an HBAR, but it's not SP1 thin either. I'd personally call it a medium contour, or at least closer to medium than light. By design, the XCR barrel is freefloated, only supported at the barrel extension -about 1.5" and most of that is behind the chamber.

    The way I was running that stick (and the way I still have it) was with an Aimpoint M3 with the 2 MOA dot (with the M3 you've got the option of 2 MOA or 4 MOA dot models). I found that the Aimpoint M2 (all have 4 MOA dots) wouldn't let me reliably keep my rounds on a siloughette at 300 in the bright day. The reason I mention a bright day is because that means turning the dot intensity up. It doesn't increase the dot size, but the perception is that the dot gets bigger. At 300, with the intensity turned up, the 4 MOA dot essentially covered the siloughette side-to-side. Obviously the 2 MOA dot solved much of that, and in my experimentation, didn't cost me anything on time.

    When I was shooting the pepper poppers, the trick was to turn the dot power down to the minimum you could get away with and still have a solid aiming point. Of course, this was in the prone position, but with no support other than cheating as far as monopoding off the magazine ;-)

    The round 'body' part of a pepper popper is (IIRC) 12", so that'd mean a 3 MOA combo at that range. Like you said, not a bad combo.
     
  17. Hummer

    Hummer Guest

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    You are absolutely correct a 4 min DOT is only good for shooting back ends of northbound double decker buses and all things being considered a 2 Min DOT is real big.

    I turn mine down so I can see the target inside the dot and center that when I use that one. Only thing I have one on right now is a Marlin 336 in 35 Rem for a car gun. By the way a nice little combo as I can load 170 grain Sierra pistol bullets in it and it feeds like a champ.

    Did you see the thread about making cheap targets I put up? They are fun at 200 and 300 and go down when a fmj tags them.
    I guess you could call them pill poppers as they are hard to hit and will make a shooter out of folks that shoot them often. Get a set made up and give them a try.
     

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