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Thread: how short 75gr from a 1-9" can you go?

  1. #1
    Gunco Addicted for life j427x's Avatar
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    Postak how short 75gr from a 1-9" can you go?

    weird day today--

    and this ain't no april fools joke either.

    today i want out and tried some 75gr ammo on my 11.5" barreled 1-9 twist DPMS XM-177a2 replica.

    conventional wisdom is that 1-9" twist rate is ok with a 20" or 24" barrel with the 75gr ammo.

    it might work with a 18" or possibly 16" 1-9 barrel but is getting iffy.

    75gr slugs in a 1-9" twist rate barrel- 14.5" 11.5" or shorter is a no-no as the bullet is going to tumble as close as 25m. this is where a 1-7" twist barrel is a MUST HAVE.

    having some extra 75gr ammo , hand-loads and wolf, i thought i would just see how far out the 11.5 DPMS 1 in 9" could shoot before it started tumbling the overly long bullets.


    @ 25m i fired a string of 5 hand-loaded rounds through a cardboard box that was about a foot deep.

    no tumbles at all. so i loaded up some 75gr wolf ammo and tried again. and a got another string of perfectly round holes in and out of the cardboard.


    so i moved the target to 50m and fired 12 rounds of wolf 75gr--same result--perfectly round holes with no signs of a tumble in or out.


    the target then moved to 100m and another 12 rounds fired same results!

    12 clean round holes in and out of the box!

    ok i am getting all weirded out because all the mall-ninjas say you GOT to have a 1-7" twist barrel this short to stabilize a 75gr!

    i move the box one more time to 175M from my shooting position just KNOWING it HAS TO KEYHOLE @ 175m

    with iron sights i pop of another 12 rounds of wolf at the bottom of the box which is much smaller than the sides of the box i was shooting at.

    about 8 of the rounds hit the bottom of the box and go through the top --again perfectly round holes in from the bottom and out through the top!


    now i am thinking this wolf must be 55gr and miss-marked 75gr on the package i'll try ONE MORE TIME with my 75gr hand-loads.

    i fire off another 12 rounds 7 hit the box square and one glancing hit.

    all the hits are perfectly round with no sign of a keyhole wtf??? --LOL

    the 75gr ammo didn't make that "worring" sound the 63gr makes when it hit the ground and bounced up either--

    it shot almost exactly like 55gr except the poi was slightly left and slightly low @ 25m very nearly one the money @ 50m

    i didn't try further as a 11.5" is not likely to be used much beyond 175m --200 max and that box was getting awful small @ 175m about the limit for my 47 year old eyes off handed with iron sights--

    i would have never thought the 1-9" could do that well that short with the 75gr slugs--


    ya never know till ya try though!

  2. #2
    GuncoHolic kernelkrink's Avatar
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    I've never understood why people think a shorter bbl will affect the spin of bullets versus a longer bbl. Maybe one of those super shorty pistols where the point of the bullet is past the muzzle, but in something like 10" plus? With a 1 in 9" twist rate, the bullet has already made one complete revolution by the time it hits the muzzle. Unless you have a poorly fitting bore to bullet, the bullet engraves and engages the rifling immediately, it doesn't "skid" straight down the bore for 11 inches before sudenly "catching" the rifling and starts to spin. Shorter bbls can even be more accurate than longer ones, the shorter bbl whips around less when fired. You lose range due to lower velocity and greater drop, but with less bbl harmonics to deal with the shot to shot consistency is there.

  3. #3
    Gunco Addicted for life j427x's Avatar
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    krink-- i kind of think it might be somehow more related to the ammo.

    this 11.5" barrel with 4.75 of simulated moderator/flash hider manages to stabilize the 75gr bullets very well and the velocity seems reasonable for its intended use. plinking for me--but certainly good enough for CQB situations with the 75gr ammo.

    this very same barrel acts like it is barely stabilizing the shorter 63grain ammo with bullets tumbling after they hit cardboard or a beer can--LOL? weird. but it loves the 75gr wolf--?? LOL!

    i have shot 75gr slugs through 20" and 24" barrels with 1-9" fine yet i have seen a few 16" that didn't like the 75s though--

    i am at a loss really as the 75s don't seem to be on the edge of stability either-- they shoot exactly the same as they do from the LMT 14.5"+ 1.75" blind pinned FH, or 16" charles daily with 1-7" twist.

    granted the DPMS 1-9" is closer to a 1-8.75" twist

    i just don't know what is going on--

    i think i'll try my del-ton 1-9" 16 middy and see what it does with the wolf 75gr ammo when i find the time and see if it can handle the 75gr ammo as well.

    all my other stuff is 1-7"---

    PS we need to get 4th to try some 75gr from his 7" super-shortie and see if it is trying to key-hole 25-100m--!

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    tired of idiots vz58's Avatar
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    my 14.5" 1 in 9 at 200yards on the 75 amax is fine...

  5. #5
    Gunco Addicted for life j427x's Avatar
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    Postak

    Quote Originally Posted by vz58 View Post
    my 14.5" 1 in 9 at 200yards on the 75 amax is fine...

    interesting, who made your 14.5"?

    i am beginning to think the idea that you have got to have a 1-7" for 75 gr for short barrels may be just mall-ninja pillow-talk!--LOL

    it would be nice though if we could find the reason some 1-9" barrels react poorly to 75gr ammo and others love it.

    so far from my on stock of barrels it is looking like all the 1-9" barrels will be ok with 75gr ammo including the shorter ones.

    and this flies in the face of all the mall-ninja gurus on the interwebs!

    anybody else have experience with 1-9" twist barrels firing the 75gr ammo?

    we should build our own 1-9" barrel database for gunco---LOL!

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    White Cracker 4thIDvet's Avatar
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    I go with the kernel on this one. Dont think that bullet is ever going too really tumble.
    Back when they first came out, many moons ago.
    Hitting something in the arm could cause the round too come out an eyeball.
    Thus began the rumors of the magical "black rifle" tumbling bullet.
    I dont know a damn thing about ballistics. But it was the bullet hitting something and deflecting causing the tumble. I guess?
    To this day. When people look at my ARs.
    "Oh that is the gun where the bullet flips around in the air."
    Frogman comes too my house, sniper, ptannjr. Rick and other members that can still see.
    Last time I went too the range I bump fired the 7".
    Hit everybody's target and the back berm with about 30 rounds before they started beating be with sticks.
    I just bought another case of ammo from Copes.
    Dont even know what the hell I ordered. Hey it was happy hour alright. Geez.
    I will go too the range and hide in the truck, in case any of those guys recognize me.
    Somebody can test it. But I dont buy the tumble theory.
    "Man needs but two things to survive alone in the woods. A blow up female doll and his trusty old AK-47" - Thomas Jefferson 1781


  7. #7
    Gunco Addicted for life j427x's Avatar
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    Postak

    Quote Originally Posted by 4thIDvet View Post
    I go with the kernel on this one. Dont think that bullet is ever going too really tumble.
    Back when they first came out, many moons ago.
    Hitting something in the arm could cause the round too come out an eyeball.
    Thus began the rumors of the magical "black rifle" tumbling bullet.
    I dont know a damn thing about ballistics. But it was the bullet hitting something and deflecting causing the tumble. I guess?
    To this day. When people look at my ARs.
    "Oh that is the gun where the bullet flips around in the air."
    Frogman comes too my house, sniper, ptannjr. Rick and other members that can still see.
    Last time I went too the range I bump fired the 7".
    Hit everybody's target and the back berm with about 30 rounds before they started beating be with sticks.
    I just bought another case of ammo from Copes.
    Dont even know what the hell I ordered. Hey it was happy hour alright. Geez.
    I will go too the range and hide in the truck, in case any of those guys recognize me.
    Somebody can test it. But I dont buy the tumble theory.

    some of the old a1's i was issued in SC had the tumbles pretty bad. and this is from a 20" colt!

    hell they would even tumble with the issue m193 55gr FMJ ammo.

    but these things had umteen jillions of rounds down the tube. and probably fired a half million rounds of blanks too which is the hardest thing you can do to a barrel IMHO is fire a bunch of blanks in FA over and over--LOL

    so it had all kinds of erosion problems, the throat was shot out, the barrel was pitted and patches of chrome were missing , the rifeling was very weak.

    it would still print a decent group @ 25M with 55gr but you would sometimes see a square cornered hole where one was wobbeling pretty bad--LOL

    with the slow turning twist of the old a1 combined with decades of abuse by boots --you will see some weird shit--

    if a 7" 1-9" barrel will shoot 75gr bullets and not tumble at usable ranges that would say a lot.

    one of the weird things about my XM 11.5" replica is it don't seem to like 63gr wolf or sb ammo. but it seems to love 55gr and 75gr ammo!!--LOL!

  8. #8
    Gunco Addicted for life j427x's Avatar
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    OK i got a email from a buddie that does a lot of his own loads and has been playing around with 1-9" barrels in various lengths.

    and this is what he told me.

    the longer bullets are sensitive to velocity loss. as long as you have sufficient velocity in the 75gr bullets/ loads they should be perfectly stable with 1-9" inch twist rate..

    it is the extra speed keeping the bullets stable with the longer barrels and not anything to do with the length. this sort of adds up.

    if i had to guess on my 11.5" firing 75gr ammo at a target 500m away probably would show some tumbles.

    i figure the 11.5" 1-9" barrel i have is at least good to 200M which is certainly enough range for such a short barrel-- 200m is about as far as i am going to shoot these days with open sights anyway--LOL

  9. #9
    tired of idiots vz58's Avatar
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    J427x, I cut my own 14.5 lightweight. Permanently attached a phantom style brake. Shot a .5", 5 shot group at 80 yards while developing loads(no bull shit, shot it, proved it move on ninjas). 1-9 CAN and WILL shoot 75 grains. I use 69 gr hpbt in it and hold about 1.0" or less with the eotec magnifier.

    We were issued an old a1 fun gun. One of our idiots and his buddys burned through mag after mag until they could light cigarettes from the barrel. At the next qualifying all it could do was keyholes. even at 25 yards. We soon discovered the reason why.

  10. #10
    Gunco Addicted for life j427x's Avatar
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    i don't have a 1-9" 14.5 to test but i do have a 16" middy that i am going to try out with the 75gr wolf.

    the 75gr seems to work fine in the 11.5" --better even that what is supposed to work in it the 63gr stuff.


    i don't have any 69gr to try in the 11.5" but was thinking of loading up some for it. i really don't see a need for the 69s yet as this 11.5" just loves the 75s--

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