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Thread: 223/5.56 ammo for 1/7 twist

  1. #1
    Member veteran-USMC's Avatar
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    Jul 2013
    East Coast

    223/5.56 ammo for 1/7 twist

    Gentlemen its been a few moons & sunrises since active duty in the Marines but having seen the writing on the walls I returned a Windham Weaponry-223 AR rifle (disguised as a Bushamster)
    and bought the rifle that we rolled in the mud,rain,heat(100degrees),snow and took this baby apart blindfolded and the dam spunky rifle kept on ticking-- the Colt M16. Well today I bought the
    Colt M4-6920-AR rifle. This rifle has a 1/7 twist and I am asking ammo opinions for this rifle that will be part of my home defense.
    Thank-you & Semper Fi
    Last edited by veteran-USMC; 11-12-2013 at 04:53 PM.
    USMC...helping enemies of America die for their countries since....1775 !

  2. #2
    Join Date
    Apr 2011
    Columbus Ohio Area

    223/5.56 ammo for 1/7 twist

  3. #3
    Member veteran-USMC's Avatar
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    Jul 2013
    East Coast
    Quote Originally Posted by joshrunkle35 View Post
    Thank-you for the link. I wonder what 223/5.56 ammo LE uses out of a 1/7 twist barrel?
    USMC...helping enemies of America die for their countries since....1775 !

  4. #4
    Join Date
    Feb 2011
    DFW, TX
    The loads listed in Doc's thread, maybe?

  5. #5
    Black Hills loads 77gr SMK I believe, which would be an excellent home defense load. I have a stash of their blue box reloaded ammo and it is excellent. The red box is their first run ammo.

    I personally use 64gr gold dots as they are easier to find for me. For LE use, the barrier blind loads like Gold Dots would be a good overall choice.

  6. #6
    Site Supporter Sean M's Avatar
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    Feb 2011
    In the back of beyond
    I think you made a good call on the selection of that particular rifle. Of course, I'd still recommend giving it a once over, looking at the spots Wayne mentioned. Even the pony has a bad day once in awhile. But it is rare, and it is really hard to beat a Colt for GP at a price most people can swing.

    Seriously go through Doc's list of recommended ammo. Of course, the highest speed, lowest drag ammo doesn't do you much good if it isn't available in a quantity that is useful and affordable. Fortunately, he has several brands and stock numbers listed in detail. Current craziness aside, most of it is fairly easy to find. I suspect that in another few months and we will start to see availability increase. It is creeping back towards "normal" (whatever that is....).

    I won't bother to regurgitate what he has posted because the reality is there are very, very few people as qualified to discuss the detailed analysis and points of performance regarding ammunition in a public forum as he is. I'm not one of them.

  7. #7
    Join Date
    Feb 2011
    S.W. Ohio
    Quote Originally Posted by veteran-USMC View Post
    Thank-you for the link. I wonder what 223/5.56 ammo LE uses out of a 1/7 twist barrel?
    Excellent choice in a rifle by the way.

    The type of shooting and the engagement distances that most LE agencies train for aren't even in the same ball park as spending a day on the KD course. So realistically, almost any load on Doc's list would work.

    My agency uses the Winchester 64 gr bonded (RA556B), for what it's worth.

    For your needs, I wouldn't get too wrapped up on finding the perfect load. Find one that is on Doc's list. This will ensue you have a loading with adequate penetration and that will do all the things you want your round to do when you shoot it inside of not-so-nice people.

    But also ensure the round you pick is easily available to you, and that you can obtain enough to verify your zero and function check it. Then put aside a few extra for rainy days. Or for stormy days.

    And as one of my Marine brethren, you'll remember that it's still all about putting rounds on target and using good tactics. Before the opposition can put rounds on target. If I had to chose who was watching my back in a bad situation, I'd prefer a trained Marine with M855 ball in his rifle, than a Mall Ninja with the latest and greatest ammo. Just saying...

    Happy belated Birthday...

    Semper Fidelis

  8. #8
    Member Gadfly's Avatar
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    Jul 2011
    DHS is still using Speer Gold Dot 64grn (GDSP)... They do a TON of testing before buying in the huge volumes they request.
    “A gun is a tool, Marian; no better or no worse than any other tool: an axe, a shovel or anything. A gun is as good or as bad as the man using it. Remember that.” - Shane

  9. #9
    Good pick up on the rifle. I hope you enjoy it.

  10. #10
    Quote Originally Posted by Gadfly View Post
    DHS is still using Speer Gold Dot 64grn (GDSP)...
    For some very good reasons . . .

    Speer LE 64 Grain Gold Dot Range Report

    Speer has expanded its line of Gold Dot ammunition to include rifle ammunition in 223 Remington. The ammunition examined for this post is loaded with a 64 grain bonded soft point bullet that has less exposed lead at the meplat than Federal’s 62 grain Trophy Bonded Bear Claw bullet that is used in their LE223T2 load.

    The 64 grain Gold Dot bullet has a boat-tail and a cannelure. This load is charged with a ball powder that according to Speer is a “flash suppressed propellant.” The primers are sealed and crimped in place, however, there is no sealant at the case mouth.

    The 64 grain Gold Dot bullet has a nominal length of 0.825” and a specific gravity of 10.0. A barrel with a 1:9” twist should stabilize it quite well.

    From ATK’s website:

    “Like their handgun counterparts, the Gold Dot rifle bullets are constructed using Gold Dot technology. The process of joining the jacket and core one molecule at a time eliminates the potential for the leading cause of bullet failure—jacket/core separation. It also ensures impressive weight retention through barriers as tough as auto-glass.”

    The 64 grain Gold Dot load was chronographed from a 20” Colt M16A2 barrel, a 16” Colt light-weight barrel and a 14.5” Colt M4A1 barrel. All of the barrels have chrome lining, NATO chambers and 1:7” twists. 10-shot strings of the load were fired over an Oehler 35-P chronograph with “proof screen” technology. All velocities listed are muzzle velocities as calculated from the instrumental velocities using Oehler’s Ballistic Explorer software program.

    Accuracy testing
    (technically precision) was conducted following my usual protocol of firing 10-shot groups from a concrete bench at a distance of 100 yards using my 24” Krieger barreled AR-15. This barrel has a 1:7.7” twist. The free-float rail of the rifle rested in a Sinclair Windage Benchrest and the PRS stock was stabilized in a Protektor bunny-ear rear bag. Wind conditions were monitored using a Wind Probe. Sighting was performed using a Leupold Competition Series scope with a mirage shade. The scope was adjusted to be parallax free at 100 yards.

    Prior to testing the 64 grain Gold Dot load, I fired a 10-shot control group using hand-loaded 69 grain Sierra MatchKings. That group had an extreme spread of 0.86”. Three 10-shot groups of the Speer LE 64 grain Gold Dots fired in a row had extreme spreads that measured:


    for a 10-shot average extreme spread of 1.12”! I over-layed those three groups on each other using RSI Shooting Lab to form a 30-shot composite group. The composite group had a mean radius of 0.33”.

    For comparison, previous testing of the Black Hills blue box 75 grain MHP load fired from the same set-up as above produced three 10-shot groups at 100 yards that had an average extreme spread of 1.14” and a mean radius of 0.37” for the 30-shot composite group.

    Velocity Update for the 64 grain Gold Dot

    Manufacturers typically use bolt-action “test barrels” to obtain their advertised velocities for their ammunition. These test barrels are usually 24” long and often have minimum spec SAAMI chambers. These factors combine to give ammunition higher advertised velocities than the velocities that we actually obtain from our AR-15s. Also, due to its gas operating system, the AR-15 looses 20 fps or more of velocity compared to an equivalent barrel without a gas system.

    As an example, Hornady advertises the velocity of their 55 grain TAP load as 3240 fps. When fired from an AR-15 with a 24” Krieger barrel with a 5.56 Match Chamber (and of course a gas operating system) the muzzle velocity of the 55 grain TAP load was 3167 fps, for a difference of 73 fps from the advertised velocity.

    Speer’s website reports the muzzle velocity of the 64 grain Gold Dot load as 3000 fps. When fired from my 24” Krieger barreled AR-15, the 64 grain Gold Dot load had a muzzle velocity of 2912 fps, for a difference of 88 fps from the advertised velocity.

    Terminal Ballistic Properties of the 64 grain Gold Dot

    Thanks to the efforts of Dr. G.K. Roberts, we now have some excellent answers to the questions of terminal ballistics pertaining to the Speer 64 grain Gold Dot LE load. The results shown below indicate the penetration of this load in bare ballistic gelatin as well as after having passed through auto-glass. Auto (safety) glass is one of the most difficult barriers (of those commonly tested) for 5.56mm/.223 Remington loads to penetrate and still perform adequately in ballistic gelatin.


    Notes on Data from the ATK Workshops

    The ATK Workshops have a history of failing to follow the proper protocols for terminal ballistic testing and of publishing misleading and fabricated data. As a simple example, the established method of determining the expanded diameter of a recovered bullet, is to measure the widest and narrowest portions “at the leading edge of the deformed bullet” and then average those two measurements to obtain the recovered diameter.

    Witnesses to some of the ATK Workshops have reported that the deformed bullets were measured at the widest portion of the bullet only and then that measurement only was recorded as the recovered diameter, thus giving exaggerated results.

    Further Inconsistences in the Test Procedures and Reported Data from the ATK Workshops.

    As I’ve previously posted, the ATK Wound Ballistic Workshop at Fort Collins on 6-26-08 has a major credibility issue regarding the 64 grain Gold Dot data. For this workshop, the stated test weapon was a 16” barreled RRA LAR-15. The Workshop reported a velocity of 2575 fps for the 64 grain Gold Dot fired from said 16” barrel.

    Now, look at the data from the ATK Wound Ballistic Workshop at Aurora on 6-24-08. This Workshop reports the velocity of the 64 grain Gold Dot as exactly 2575 fps, when fired from a (Colt) Commando with an 11” barrel. It would be next to impossible for two different barrels with a difference in length of 5” to produce the exact same velocity with the 64 grain Gold Dot. It's obvious that the velocity data for the 64 grain Gold Dot from one or both of the Workshops is false.

    Since the Workshops failed to accurately determine/record something as basic as the velocity for the 64 grain Gold Dot, I question the validity of any of the Workshops' reported data for the 64 Grain Dot; especially something as crucial as the penetration depth. An individual who was present at an ATK Workship stated this about the ballistic gel blocks that were used at the ATK Workshop:

    "the first gelatin block was calibrated initially at the beginning but the other blocks sat outside until they were shot and were not calibrated or the temp checked prior to use. I'm fairly certain that they were warmer than they should have been and without calibration the data was suspect, at best."

    More Fabricated Data from the ATK Wound Ballistic Workshop

    The ATK Wound Ballistic Workshops continue to demonstrate their lack of credibility. In their latest report entitled “Butte – Montana 5-27-09” they include more fabricated data for the Speer 64 grain Gold Dot.

    Speer advertises a muzzle velocity of 3000 fps for the 64 grain Gold Dot load when fired from a 24” barrel. During my own chronographing of the 64 grain Gold Dot load, I obtained a muzzle velocity of 2912 fps when fired from a 24” Krieger barreled AR-15.

    Using a 16” barreled M4, the ATK workshop claims to have obtained a muzzle velocity of 3000 fps for the 64 grain Gold Dot load. Using a barrel that is 8 INCHES SHORTER, the ATK workshop claims to have obtained the exact same muzzle velocity as advertised from a 24” barrel. It’s quite obvious that the ATK workshop never even chronographed the 64 grain Gold Dot load and then falsified their report using the advertised muzzle velocity. The irresponsible practices of the ATK workshops and their failures to adhere to established protocols for terminal ballistic testing renders all of their data suspect.


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