MK262 clone 77Grain 5.56 load problems / updated OCW tests

[YourAlterEgo]

Let me know if I need to post the pics in a different manner.

This is with a 5.56 NATO 16" bbl. 23.2 is book max, do not try to replicate this without your own workup from the book.
All my cases/primers looked fine except for what I suspect was the 2704fps load on the last set. One shell casing out of this bunch had ejector and extractor marks. As most say, I think 23.2gr produced the best accuracy, but will probably load 23.8 for things that go bump in the night.

Click the pic, click it again on imgur to see full size.
<a href="http://imgur.com/2dAo9Oo"><img src="http://i.imgur.com/2dAo9Oo.png" title="Hosted by imgur.com"/></a>

This is just from the last time out, but all days followed the same trend. All are from a bag up front, no rear bag or vice. Grid it true 0.5"
24.0
Just noticed. The tattered hole at the upper right is someone elses errant shot (my subsonic friend's)

23.8
some jack hole thought it would be funny to poke 30cal holes in my target while I was waiting to go down range. Would have been funnier if he could put a group together.

23.6
Did not shoot this day

23.4

23.2

together, lower part is someone else that was shooting open sights, and not for accuracy (suppressed subsonics)

 

[pmclaine]

I'll edit till images show up correctly.

This is with a 5.56 NATO 16" bbl. 32.2 it book max, do not try to replicate this without your own workup from the book.
All my cases/primers looked fine except for what I suspect was the 2704fps load on the last set. One shell casing out of this bunch had ejector and extractor marks. As most say, I think 32.2gr produced the best accuracy, but will probably load 32.8 for things that go bump in the night.
<a href="http://imgur.com/2dAo9Oo"><img src="http://i.imgur.com/2dAo9Oo.png" title="Hosted by imgur.com"/></a>

Fact check.

Do you mean 23.2 and 23.8? 32 anything seems kind of high for 8208 no?

 

[YourAlterEgo]

Fact check.

Do you mean 23.2 and 23.8? 32 anything seems kind of high for 8208 no?

yes, the rest of the data is/was correct as shown

 

[ArmyJerry]

Thanks for the pics, you should go back and edit that number.

 

[YourAlterEgo]

Done. And that is exactly why people should not be loading based on what someone else says they got away with. One little typo can change your world.

 

[ArmyJerry]

I will be hitting the range tomorrow, running through 22.9-23.8, 10 rounds each 0.1 increment, 77 gr Nosler, 2.260 OAL, Lapua brass, going to do 5 rounds each through the 10 FP with McGowan Barrel and 5 each through the 20 inch RRA with Fulton barrel.

 

[pmclaine]

I will be hitting the range tomorrow, running through 22.9-23.8, 10 rounds each 0.1 increment, 77 gr Nosler, 2.260 OAL, Lapua brass, going to do 5 rounds each through the 10 FP with McGowan Barrel and 5 each through the 20 inch RRA with Fulton barrel.

Please update how it works out.

I just loaded up some 23.2 8208XBR under 77 Nosler CC for my 16 inch LMT CQB 1/7. Probably get a chance to fire them next week.

 

[ArmyJerry]

shitty results today, i will try again with better prepped brass

 

[pmclaine]

shitty results today, i will try again with better prepped brass

23.1. 23.2 and 23.3 all seem to impact in the same relative spot. Is that the criteria for judging where your OCW would be? 23.6, 23.7 and 23.8 look to impact similar.

Ill be shooting tomorrow testing out some ARComp loads. Ill bring a few of the 23.2 8208XBR loads I made last night and post up how it worked out in my carbine.

 

[leid]

AFAIK, there is still no 5.56MM NATO pressure load data published for lMR 8208XBR propellant. Load development above published .223 SAAMI pressure should be worked up slowly with all due caution. With that said: One of the accuracy loads that has been circulating among shooters for several years now is the 77gr. SMK over 23.8gr. IMR 8208XBR in LC brass. This load using #41 primer chrono'd 79 FPS slower that BHA MK 262 MOD 1 in the same 18" Krieger barrel fitted with M4 can. But the 8208 load had some very interesting qualities: accuracy was 0.5" at 100yds. with MV 2746/ES 38.06/SD 13.85. The load also proved to be very thermally stable with MV varying only 18 FPS from -10F to + 135F. So the 8208 load will shoot pretty much the same in winter, summer, or in a warm barrel. I have not yet had the opportunity to shoot this load at LR but it definitely appears to be worth testing with.

I fired this group off an outdoor wooden benchrest which has quite a bit of lateral movement in it from repeated freezing/thawing. IMO, this load has more raw accuracy in it than I can demonstrate given the benchrest.

 

[pmclaine]

Fired my 8208XBR 23.2 grain, 77 NOS CC at 2.26 COAL, WCC 1X brass, WSRP. It will be my go to load for my 1/7 16 inch LMT. I don't know how it compares to MK 262.

These are the first 5 rounds of the day. They were loaded into the mag and I fired all five maintaining same target acquisition. Im not sure of the order of strike so I don't know if the one out of group was cold bore, bolt lock back or more likely just because I suck. I fired five but I see 4 holes. The hole furthest left looks somewhat oval and may be two or as with the one out of group I may suck and thrown a round off paper.



The next five rounds were fired round robin style with three other AR Comp loads I was testing. It was the first target shot and no shot dealt with bolt lock back. I adjusted my sights right one click on the KAC 200-600 BUIS for these five shots. I don't know what order the shots impacted in.



The ARCOMP loads 22.1 grns at 2.26 same brass/primer

 

[Nortex]

Anyone run much of the 262 type stuff out of a 14.5 " barrel? I was going to try the Sierra or Nosler stuff also found some Berger tac OTM bullets to try out.

 

[colt933]

Loaded the 2.245" for the MK 262 Mod 1 to avoid runout with the 77gr Sierra.

Alaska is on to something with the seating depth.

I had 1MOA accuracy but low velocity with the following load with 3 different barrels: Krieger 20" 1/7, DD 18" CHF S2W 1/7, DD 16" CHF 1/7. Velocities were 2450-2600fps depending on barrel. I had hoped for sub MOA and also 2700fps at least from the 20" barrel.

77SMK with cannelure
24.0gr Varget
WIN NT once fired brass, annealed, sized, trimmed
CCI#41
2.26"
Redding taper crimp


But then I changed a couple of things: reduced COAL to 2.245" and used a Lee FCD. This gave me .5MOA accuracy in both DD 18" and Krieger 20" barrels, and over 2600fps and 2700fps respectively - a solid 100fps velocity gain in both barrels. Haven't tried the 16" DD barrel yet but I will this Saturday.

Honestly I think the reduction in COAL gave me most of the gains in accuracy and velocity.

 

[Alaska]

Also suggest a CCI 41 or 450 primers with 24.0 to 24.2 of TAC with the 77 MK.
This will increase your Vel a tad.

 

[bruddah]

Yup.

23.5-23.8gr 8208XBR with a CCI-450 and a 77gr bullet...peas and carrots, peanut butter & jelly.

Why the 450 primer? Isn't that a magnum primer?

Tag to listen in on the chatter concerning 77's and 8208XBR.

8208 is my go to powder for 77gr SMKs out of my BHW 18" SPR.

 

[BoilerUP]

-450 primer is magnum, similar to 41s and a bit more tolerant to 5.56ish pressures.

That said, I've used -400s and Rem 6.5s without issue, but now my standard small rifle primer is the -450 due to pressure tolerance and lower ESs in my 223AI.

 

[bruddah]

-450 primer is magnum, similar to 41s and a bit more tolerant to 5.56ish pressures.

That said, I've used -400s and Rem 6.5s without issue, but now my standard small rifle primer is the -450 due to pressure tolerance and lower ESs in my 223AI.

Gotcha. Thanks for the clarification!

 

[gunsnjeeps]

Changes are afoot. I forget about this thread until it popped back up. I am moving on to a Dillon 650, at least for 200 and 300 yard ammo, 600 may still be T-7. Anyhow with the Dillon Varget does not seem suited for progressive loading (based on reading, haven't set up the press yet) so I picked up a few pounds of 8208 in the last few weeks and just ordered 2 cases of Tula 5.56 primers. I still have a good quantity of Varget and CCI400's on hand so if nothing else I'll do my case prep on the Dillon until I work up a new load.

Thanks for the 8208 info, it'll cut my work up considerably. More to follow.

 

[Alaska]

Does anyone know the rationale behind the 2.245 seating depth? I'm guessing it's for consistency as M855 is 2.245 as well - they also measure identically on my RCBS case gauge (ogive is the same).

It had something to reducing bullet runout.

 

[Alaska]

Why the 450 primer? Isn't that a magnum primer?


8208 is my go to powder for 77gr SMKs out of my BHW 18" SPR.

I have heard good things with 8208 for the 5.56 with Heavy bullets

H4895 and Varget really do very well in my MK 12 with 77 MK and CCI 41 or WSR primers

 

[mikeinfwa]

My First Experience with TAC Powder

Here's my results with 24.0 Grains of TAC.

Rifle = Windham Varmint Exterminator 20inch 1x8 twist
Bullets 77 SMK and 75 Hornady with cannelure
CCI 41 Primers
LC13 Brass once fired fullsized
Distance 400 yards
Bipod with rear bag support
80Degrees
Calm winds
77 SMK COL 2.26
75 HC COL 2.25
Note: groups might have been little tighter as I mosquitoes were swarming my face, neck, arms

77 SMK = 6 inch grouping
75 Hornady = 7 inch grouping

Here's some Chrony speeds today:

60 Degrees Overcast Sky
10 Shots / string

77SMK
WC13 Brass
C41 Primers
AVG: 2707
ES: 41
SD: 14

77SMK
LC13 Brass
C41 Primers
AVG: 2691
ES: 63
SD: 17

75 Hornady HPBT with cannelure
LC13 Brass
C41 Primers
AVG: 2704
ES: 56
SD: 16

http://www.snipershide.com/shooting/images/attach/jpg.gif

 

[355sigfan]

Never got good results with TAC. The best loads I have used for accuracy using 77 grain Sierras and Noslers are as follows.
BEST LOADS in Larue Stealth with 77 grain SMK bullets

24.1 grains (Sierra recommended Accuracy load)

1. 2574
2. 2589
3. 2613
4. 2613
5. 2599
Average 2597
Spread 39
Accuracy .568 Best 4 All 5 groups .73 (one called flier ruined average)


Load 23.8 grains of Varget Remington Match primers 77 grain SMK

1. 2455
2. 2480
3. 2538
4. 2495
5. 2530
Average 2500 Spread 83
Average 5 shot group .66

N135 21.8 grains 77 grain SMK

1. 2448
2. 2545
3. 2534
4. 2519
5. 2459
Average 2501
Average 5 shot group .65

22.6 grains of H335

1. 2524
2. 2505
3. 2483
4. 2529
5. 2521
Average 2512 Spread 46
Average 5 shot group size .72

So I started off with a goal of building a 77 grain 5.56 load capable of 1moa for my new project. It’s an 18” Noveske SPR Suppressed.

Well, that’s where I started and it seems I am still there…

In a perfect world, or rather normal world, I would have a number of choices for components. Spending the past eight months I collected:

-1K once fired mixed brass
-1K FGMM SM Rifle Primers
-1K Nosler 77 Grain CC Match Bullets
-8lbs of Ramshot Tac

After some research I started my loads at standard length with 24.0 Tac. The first 10 rounds of this showed promise, which followed with another 10 rounds. This load was shot at around 40 degrees initially so I was concerned about loading up a bunch until further testing could commence. Pressure signs were there with a slightly flattened primer. No obvious swipes were found. My concerns were that higher ambient temps would cause pressures to rise.



The best 5 shot group came in with a Average MV at 2682 FPS.



Mid Spring I tested 10 rounds loaded at 24.4 Grains of Tac. Pressure signs were expectedly more pronounced and the accuracy dropped off. Compared side by side with 24.0 the choice seemed obvious. While I netted another 40-50 FPS it didn’t matter because it didn’t shoot.



I loaded 50 Rounds for further testing with 24.0 Tac.

This brings us to several weeks ago where on a hell of hot day I had a chance to put that 24.0 load to test. 101 Degrees, and I let it bake in the sun for a while. This was shot under much different conditions and POI changed about a 1” high 1” right. 10 rounds fired, 3 X 3 shot groups with a single cold clean bore starting it off. It didn’t set the world on fire but met my goals with one of the groups falling right in well under ½ MOA. Pressures were similar to that seen before, velocities were also very close to before.





So a few days ago I decided to take out the steel and shoot 2 X 5 shot groups at 200 yards. Here’s the results…………. Basically a overgrown 4” group netting 2MOA. It was windy 10-15mph, with .4 mil held for wind, but even at that this sucks.





Where do you think I should go from here? I still have another 30 or so loaded up at 24.0. Going back through the targets so far the load has produced some good groups but not very consistently. This is mixed brass, I understood that going into this venture. I just don’t know how much there is to be gained separating the brass out by head stamp. There is a good portion of WC, FC, LC and Nato.


The reality is I can’t develop a load for each head stamp, I just don’t have the resources for that. If I did, well I would have bought a single lot of LC but they just cant be had.

I accept some variations from mixed brass but I feel like I am back at square one

 

[AeroEngi]

Tagged for more info from anyone loading with Varget.

 

[mikeinfwa]

Added todays Chrony shooting velocities:

Here's my results with 24.0 Grains of TAC.

Rifle = Windham Varmint Exterminator 20inch 1x8 twist
Bullets 77 SMK and 75 Hornady with cannelure
CCI 41 Primers
LC13 Brass once fired fullsized
Distance 400 yards
Bipod with rear bag support
80Degrees
Calm winds
77 SMK COL 2.26
75 HC COL 2.25
Note: groups might have been little tighter as I mosquitoes were swarming my face, neck, arms

77 SMK = 6 inch grouping
75 Hornady = 7 inch grouping

Here's some Chrony speeds today:

60 Degrees Overcast Sky
10 Shots / string

77SMK
WC13 Brass
C41 Primers
AVG: 2707
ES: 41
SD: 14

77SMK
LC13 Brass
C41 Primers
AVG: 2691
ES: 63
SD: 17

75 Hornady HPBT with cannelure
LC13 Brass
C41 Primers
AVG: 2704
ES: 56
SD: 16

http://www.snipershide.com/shooting/images/attach/jpg.gif

 

[savagemann]

Hello all. New member here. Sorry to bring an older thread back up.
I have recently started working up some 75gr hornady BTHP match loads using 8208 for my new spr build.
I was curious if any of you guys have made any more headway with these loads.
I started at 22gr 8208 and worked my way up to 23.4gr.
I don't have a chrony yet, but will be working with one this weekend.
I seem to have hit 2 accuracy nodes that are quite far apart with my testing.
The best seem to be 22.5gr and 23.4gr of 8208.
I am seating to 2.245.
I brought them all the way out to 2.256 but 2.245 seems to work best for me.
I am using a medium crimp with a lee FCD.
The projos are non cannalure.
So, have you guys settled in on what is working best for you?
I will post back with my findings after this weekends range trip.

 

[gimpy]

Hello all. New member here. Sorry to bring an older thread back up.
I have recently started working up some 75gr hornady BTHP match loads using 8208 for my new spr build.
I was curious if any of you guys have made any more headway with these loads.
I started at 22gr 8208 and worked my way up to 23.4gr.
I don't have a chrony yet, but will be working with one this weekend.
I seem to have hit 2 accuracy nodes that are quite far apart with my testing.
The best seem to be 22.5gr and 23.4gr of 8208.
I am seating to 2.245.
I brought them all the way out to 2.256 but 2.245 seems to work best for me.
I am using a medium crimp with a lee FCD.
The projos are non cannalure.
So, have you guys settled in on what is working best for you?
I will post back with my findings after this weekends range trip.

23.2-23.4 should be one node, and another one that others have reported at 24.

 

[savagemann]

23.2-23.4 should be one node, and another one that others have reported at 24.

Thanks Gimpy.
I'm gonna work the 23.2-23.4 area and see where it gets me.
I'll have access to a chrony this weekend and will test it out then.
22.5 and 23.4 loads had almost identical POI which I found interesting.
They were both about 1moa at 100 yards.
Between 22.5 and 23.4 the poi was lower, if that makes sense.
All were 5 shot groups.
The rifle is a brand new build and is just breaking in.
I did have a couple 3 shot groups that were around .5moa with 22.5gr the previous range visit at 100 yards, but at that point hadn't worked up to the 23.4 charge.
This weekend I will be testing at 100 and 200 yards. I will report back with my findings.
Here is the rifle I am loading for.

 

[savagemann]

So, bringing this back from years ago..........
I finally had the opportunity to really stretch the legs out on this one last weekend.
Took her out to 820 yards and had no problems (once dialed in) hitting a 2/3 steel IPSC target 12x20".

The final load I settled in on for this thread was
23.4gr IMR 8208.
2.246" OAL
LC or PMC Brass
CCI400 SRP or Win SRP

It actually works well with several bullet flavors.
75gr Hornady Match
77gr Sierra TMK
77gr Nosler CC

They all perform well in numerous different rifle configurations from barrel lengths of 10.5" up to 18"