cloning MK262 ammo

Re: cloning MK262 ammo

Out of my 20" Krieger 7.7 twist DCM gas gun, on a nice day with temps in the 80's,
I got the following numbers with MK262 :


M252 1st string 2786 2778 2789 2784
2nd string 2791 2798 2737 2775

My goal was to clone a load using CFE223 ((Federal Match AR Primers, Commerical Brass):

My final load is 25.5 grs: 2803 2788 2783 2791

No pressure signs at all, and the groups are on par with the MK262.

Mike

I looked up and saw I'm a PFC. Wow, I haven't been an E-3 since 1976. If only all other things as they were in 1973 :>)
 
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Re: cloning MK262 ammo

Using imr8208 today w/ 77 nosler CC in my AR with a 18" FN 7 twist chrome lined barrel (rifle length gas)

charge weight & velocity
23.4 = 2654
23.6 = 2681
23.8 = 2697

23.8 grouped very well, going to try again as well as a charge of 24 grains in the next couple days. Before this test 22.9 to 23.1 was the last node.
 
Re: cloning MK262 ammo

I finally settled on a simple load that pretty much does all I want, runs to six hundred, and loads in a Dillon.

Stole it from Phil Arrington, who could actually be called someone who knows a bit about the AR platform, and all the other stuff they shoot at Perry...

24.8 of aa2520 and a somewhat decent LC case, Wolf SRM primer, and a 77 Nosler or a 75 Hornady, BTHP or the Amax, they all seem to run fine for me....

First time over the chrono with my 20 inch service rifle, four shots went 2846,2829,2841,2842.

Same gun runs the original brown box 262 at 2892, 2873,2879, I only chronoe'd three, sorry.

So I have a progressively loaded round that's easily under an inch (with iron sights, my bolt gun will one hole these), es of 17, sd of 7.

I think for all intents and purposes I've finished looking.

As an aside I would caution folks that 2520 is one of the powders that has a tendency to have a lot of variation from lot to lot, I've shot 25.1 of rl15 behind a 75 in this rifle, and in some guns that would have smoke in your face, so work up to this load.

Sean
 
Re: cloning MK262 ammo

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: tactserv</div><div class="ubbcode-body">Out of my 20" Krieger 7.7 twist DCM gas gun, on a nice day with temps in the 80's,
I got the following numbers with MK262:


M252 1st string 2786 2778 2789 2784
2nd string 2791 2798 2737 2775

My goal was to clone a load using CFE223.

My final load is 25.4 grs: 2803 2788 2783 2791

No pressure signs at all, and the groups are on par with the MK262.

Mike

I looked up and saw I'm a PFC. Wow, I haven't been an E-3 since 1976. If only all other things as they were in 1973 :>)
</div></div>

How do you like the CFE powder?
 
Re: cloning MK262 ammo

Love the CFE223. It meters great through my Dillon, doesn't seen to be temp sensitive, and the barrel cleans up quickly.

When my 7.62 gun gets here, I will try and see how it does in that caliber.

Mike
 
Re: cloning MK262 ammo

Test:
Create a handload that duplicates Black Hills “Blue Box” 77-grain ammo.

RESULTS:

Short version:
23.9 grains Ramshot TAC and 77 SMK loaded to 2.250” (magazine length) duplicates velocity of Black Hills Blue Box.
This is a 97% density load (not compressed) – you can hear the powder rattle in a loaded round.

Keep reading if you want the long version.

Rifle used for test: AR-15 rifle with 20” barrel.
Chronograph used for test: Chrony Beta Master.
No software was used for velocity-estimation. All velocities reported here are actual shots fired over a chronograph.

I attempted to shoot 10-shot strings to gather the chronograph data.
You will notice that the data sets do not all contain 10 shots.
The Chrony chronograph sometimes simply failed to display the velocity.


It looks like 23.9 grains of TAC will get you the same velocity with the 77 SMK as the Black Hills “blue box.”

In case you are wondering “Why TAC powder?”

Here are the reasons:
1. There is ample internet rumor that Black Hills uses TAC for this load.
2. Pulled powder from an actual Black Hills load appears visually identical to the powder from an actual jug of TAC powder. In each case, the powder appears to be “flattened spheres” of varying size. Yes, I am aware that there are various gunpowders that have this appearance.
3. The weight of the powder charge removed from a round of Black Hills blue-box 77 grain ammo just happens to weigh 23.9 grains. (Given the vagaries of scale calibration, I will concede that the weight could be 23.8 or 24.0).
4. The chronographed average velocity of several rounds of Black Hills blue-box (2702 fps) just happens to fall right in between the chronographed average velocities of 23.8 grains of TAC (2693 fps) and 24.0 grains of TAC (2747 fps)respectively.

gunpowderTAC.jpg


gunpowderBHBB.jpg


23.8 grains Ramshot TAC
77 SMK 2.250” (magazine length)
August 12, 2012
Ammo temperature approximately 75 degrees Farenheit

005.jpg


.
.
.

24.0 grains Ramshot TAC
77 SMK 2.250” (magazine length)
August 12, 2012
Ammo temperature approximately 75 degrees Farenheit

006.jpg


.
.
.


24.2 grains Ramshot TAC
77 SMK 2.250” (magazine length)
August 12, 2012
Ammo temperature approximately 75 degrees Farenheit

007.jpg


.
.
.

bhbblabel.jpg


Black Hills “Blue Box”
77 SMK
December 26, 2011
ammo temperature approximately 90 degrees Fahrenheit

008.jpg


Lastly, you may be interested to know that the bullet I pulled from the Black Hills ammo has a cannelure, and obvious evidence of a circumferential crimp.

smk77cannelure.jpg


Velocity duplicates of Black Hills 77-grain “blue box” according to Quickload
(scroll down for chart)

Black Hills 77-grain “blue box” ammo consistently chronographs about 2710 fps through the rifle I use for all my AR15 ammo testing.

<span style="text-decoration: underline"><span style="font-weight: bold">Quickload</span></span>
These loads were determined by Quickload version 3.6.
http://www.neconos.com/details3.htm
Quickload is a fairly expensive computer program for reloaders.
Quickload has been around in various forms since 1987.

<span style="text-decoration: underline"><span style="font-weight: bold">Comparison history</span></span>
The only load listed here, and actually tested over a chronograph, is the load for TAC powder. For all intents and purposes, TAC provided a velocity identical to the velocity obtained from Black Hills “blue box” 77-grain ammo with the Sierra 77-grain MatchKing bullet. Moreover, the powder I inspected from an actual 77-grain “blue box” cartridge weighed exactly 23.9 grains, and had an appearance exactly like Ramshot TAC powder.

<span style="text-decoration: underline"><span style="font-weight: bold">Quickload consistently predicts about 90 FPS faster velocities than actually obtained over a chronograph.</span></span>
Based on my empirical testing of various loads over the chronograph, and comparing the chronographed velocities of those various loads, I have discovered that Quickload routinely predicts a velocity 80 to 100 feet per second faster than the velocity actually obtained by chronograph measurement when the ammo is fired in an AR15 type rifle. My theory for the consistent velocity discrepancy is that Quickload does not account for the loss of pressure due to gas escape through the AR15 gas port.

Black Hills 77-grain “blue box” ammo consistently chronographs about 2710 fps through the rifle I use for all my AR15 ammo testing. Similarly, 23.9 grains of TAC provides the same velocity with the same bullet. Quickload suggests that 23.9 grains should generate 2807 fps from an un-ported 20-inch barrel. Based on this consistent discrepancy, I have selected for my investigation, loads modeled by Quickload which also are predicted to be in the approximate 2800 fps range.

<span style="text-decoration: underline"><span style="font-weight: bold">Magazine-length dimensions</span></span>
All Quickload modeled loads assume bullet seated to 2.250” overall cartridge length.
SAAMI specification maximum length is 2.260”
I find that ammo loaded to SAAMI maximum length will sometimes be just a bit too long for AR15 magazines.
Ammo loaded to 2.250” or less never causes a feed-malfunction due to excess length.

<span style="text-decoration: underline"><span style="font-weight: bold">Pressure info</span></span>
The SAAMI industry specification for 5.56 NATO ammunition is 62,366 maximum PSI.
According to Quickload, all loads listed in the following chart fall below SAAMI maximum pressure, at 70 degrees temperature. This modeling exercise does not attempt to account for any variations which may occur due to temperature.

<span style="text-decoration: underline"><span style="font-weight: bold">Disclaimer</span></span>
This information is provided only for educational purposes. None of these loads are specifically recommended for any particular, or general, purpose. Persons using this information to construct live ammunition do so at their own risk, and with the understanding that this information may not be accurate, and that the result of use of this information may result in damage to property or injury to person.

BlackHillsBlueBoxcomparisonchart.jpg
 
Re: cloning MK262 ammo

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: W.E.G.</div><div class="ubbcode-body">

24.0 grains Ramshot TAC
77 SMK 2.250” (magazine length)
August 12, 2012
Ammo temperature approximately 75 degrees Farenheit

006.jpg

</div></div>

This is what I am using as well and it meters perfectly through a Dillon Powder measure.

MK12 MOD 1 SPR 18" TAC, 77g NOS CC, G.FL Brass, Wolf SRM
24.0g TAC
2767.0
2736.0
2720.0
2765.0
2765.0
ES 47
AVG 2751
SD 21
 
Re: cloning MK262 ammo

I've been running 24.5gr of RE15 or 24.8gr of VV N540 for velocities of 2758fps(AVG 10rd strings) and 2810fps in a LC 00-12 case lit by a rem 7.5 through a WOA 18" SPR bbl.
These loads have been worked up carefully and ONLY work when a Tubbs carrier weight system with tungsten insert is used in the BCG. Left out the CWS once and backed out two primers. Additionally the brass is only 1x use as this is an extremely hot load and the brass will not hold a primer for another loading.
 
Re: cloning MK262 ammo

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: hofhine1</div><div class="ubbcode-body">
24.8 of aa2520 and a somewhat decent LC case, Wolf SRM primer, and a 77 Nosler or a 75 Hornady, BTHP or the Amax, they all seem to run fine for me....

First time over the chrono with my 20 inch service rifle, four shots went 2846,2829,2841,2842.


As an aside I would caution folks that 2520 is one of the powders that has a tendency to have a lot of variation from lot to lot, I've shot 25.1 of rl15 behind a 75 in this rifle, and in some guns that would have smoke in your face, so work up to this load.

Sean



</div></div>

I use 24.5 grains topped off with either a moly coated Hornady 75 grainer or 77 Nosler CC, I get 2785 FPS from an 18 inch RRA SS 1/8. Submoa out to 300 yards. I have not shot paper any further than that, steel no prob out to 550. I could go hotter but I don't feel there is a need too. I have found AA2520 to be the most consistant powder I have used. I have been through three different lots and 24.5 is what it takes to get 2785 FPS. I could not get that consistancy from Varget, 4895 or 4064. I never have tried TAC as none of the LGS carry it and I doubt that I will as i don't think it will offer any adavantage over AA2520...