MK 12 mod 1 velocities

[RTH1800]

I chronographed my HCS MK 12 Mod 1 today. 5 shots each load. Temp 73 degrees.
All bullets 77 SMK
24 grains Ramshot TAC Wolf primer seated mag length. 2705 LC case
24.5 grains, same load 2738
Black Hills M262. 2755
Real issue M262. 2806

Just thought someone might be interested.

RTH

 

[Roscoe_M4]

Very interested and thanks for posting this! I've had a serious craving for a MK 12 Mod 1 for some time, but I'm not sure what to expect in the way of improvement from my current set-up. I thought the M262 were rated at 3050 fps - or is that velocity with a 20" test barrel?

How well does your MK 12 Mod 1 typically group with the M262?

 

[RTH1800]

Sir,
I have not shot the real MK 262 yet except to chronograph. Only have about 2K rds. Velocity spread was 30 FPS. My hand load was 4 FPS. All firing was done with a suppressor. Rifle shoots well under MOA to 800 meters. Will test the MK 262 soon.

 

[MSTN]

Good info - Thanks for posting.

That's about 100 FPS faster than my ASYM 77 SMK load. Pretty zippy! No wonder the Mk 12 Douglas barrels on a diet of Mk 262 have a reputation for going south quickly due to throat erosion.

 

[RTH1800]

MSTN,
I shoot mine quite a bit. Have about 3500 rds down it now. Still looks great and shoots well. Most all was with the above handloads and all was with 77 SMK. I do not do any rapid fire unless I am shooting at a running coyote etc. Mostly just one shot or two.

 

[MSTN]

I'll bet you know how to take good care of the barrel - and do. Our personal rifles, like us, lead a sheltered life compared to our military counterparts on the pointy end of the spear.

I'm going to try your Ramshot TAC load. Thanks for the info.

 

[RTH1800]

MSTN,
Be aware that some books list 24 grains as MAX. Others list up to the 24.5 grains I think. I have no issues but as always start lower and work up. Good luck.

 

[Laseredge]

MSTN,
Be aware that some books list 24 grains as MAX. Others list up to the 24.5 grains I think. I have no issues but as always start lower and work up. Good luck.

I was wondering about the max load for Tac/77 SMK a few days ago and checked the Ramshot website.
http://www.ramshot.com/wp-content/uploads/2010/09/WP_LoadSpec_1-23-14.pdf

The .223 pressure load max is 23.4 gr. (Page 23)
The 5.56 pressure load max is 24.8 gr. (Page 24)

So for a hot 5.56 load 24.5 should be OK.

 

[RTH1800]

It does seem fine in my 5.56 rifles. I think Sierra list a much lower max similar to what you state in the 23.x range.

 

[260shooter]

With the 24.0 gr load I have popped a few primers in higher temps (80 degrees and above). In those temps I run 23.4 gr and the velocity is the same as the 24.0 gr load in cooler temps. 77 CC bullet, Wolf SRM primer, prepped LC brass of same year.

 

[RTH1800]

What rifle and what chamber? I have shot mine in the 90's with the 24.5 load and no issue. What is the cc bullet?

 

[260shooter]

Rainer Ultra Match barrel, Wylde chamber. Nosler custom competition 77 gr bullet.

 

[bmk]

With the 24.0 gr load I have popped a few primers in higher temps (80 degrees and above). In those temps I run 23.4 gr and the velocity is the same as the 24.0 gr load in cooler temps. 77 CC bullet, Wolf SRM primer, prepped LC brass of same year.

I was wondering if a post like this would pop up. I've loaded and shot a lot of Tac over the years, and found it to be a nice powder for velocity, accuracy, and metering, but I noticed it was very temperature sensitive (compared to what I would like to see). According to the manufacturer, it is well within the acceptable norms for military powders.

My holds would be off 1-1.5 MOA at 400 yards, depending on the temperature alone.

I ended up having to switch to a more temp stable powder (Varget, then 8208xbr), since I hunt and shoot at 0 degrees to 100 degrees and everything in between.

 

[SRTM4]

Good info on the Mk262 velocities. I dont have a Chrongraph and am curious as to what the velocities are on the red box Black Hills .223 loads shooting out of a Mk 12 18'' Douglas barrel.

My wiz wheel is telling me that my velocites are running around 2600 fps. At 70-75 degrees at sea level Im having to come up to 8.9 mils of elevation at 800 yds. I dont have a rangefinder so my yardage may be off a few yards or so. Im using a measuring wheel to measure how far I shoot.

 

[Clusterfrack]

Good info. Thanks for posting. My buddy sent me his Mk12 / M262 OCW load data yesterday.

77 gr Berger OTM
24.1 gr IMR 8208 XBR
Length: 2.264-2.265 in
Primer: CCI #450
PMC once fired brass
Velocity: 2782 fps (18” barrel)
No pressure signs but use at your own risk and work up carefully.