View Full Version : MK 248 MOD 1
Has anyone loaded their own 300 Win mag to the mk 248 mod 1 specs? And, what is the brass life that you have encountered?
jpgm
eightmillimeter
10-09-13, 02:46
A guy I shoot with tried it in two rifles. In a factory Savage it was definitely too hot and the brass was toast (Lapua). In his Remington with a custom Bartlein barrel it was also to0 hot, but the brass was reloaded 1X, I do not think he will get more than 2x reloads out of them.
That particular load of H1000 is way too much in my opinion, brass life will be the least of your concern. That load is kind of a beast, QL puts it at like 70K PSI under perfect conditions.
A guy I shoot with tried it in two rifles. In a factory Savage it was definitely too hot and the brass was toast (Lapua). In his Remington with a custom Bartlein barrel it was also to0 hot, but the brass was reloaded 1X, I do not think he will get more than 2x reloads out of them.
That particular load of H1000 is way too much in my opinion, brass life will be the least of your concern. That load is kind of a beast, QL puts it at like 70K PSI under perfect conditions.
This begs the question of what do these two civilian rifles actual chambers look like, specifically the throat length, diameter and angle.
You can see below why the chamber pressures are higher.
http://i122.photobucket.com/albums/o254/bigedp51/183911_zps5aff5dc9.jpg
http://i122.photobucket.com/albums/o254/bigedp51/m14chamber_zps93174da1.jpg
As a side note the SAAMI interchangeability warning for .223/5.56 ammunition did not come out until 1979 when the military introduced M855 ammunition that required a longer throat. I'm saying this because my Savage .223 has a longer throat than my two AR15 rifles do. ;)
eightmillimeter
10-09-13, 18:28
This begs the question of what do these two civilian rifles actual chambers look like, specifically the throat length, diameter and angle.
You can see below why the chamber pressures are higher.
http://i122.photobucket.com/albums/o254/bigedp51/183911_zps5aff5dc9.jpg
http://i122.photobucket.com/albums/o254/bigedp51/m14chamber_zps93174da1.jpg
As a side note the SAAMI interchangeability warning for .223/5.56 ammunition did not come out until 1979 when the military introduced M855 ammunition that required a longer throat. I'm saying this because my Savage .223 has a longer throat than my two AR15 rifles do. ;)
First thing to remember in this case is that there is no "mil spec" for the .300 Win Mag, Black Hills was simply given the task of loading ammo to a certain desired spec that would not blow up a loose throated military gun on a hot day. The 248-1 load is 70K PSI under nominal conditions in mil barrels, and thusly, should not shock people when its too hot for your average 300 mag.
First thing to remember in this case is that there is no "mil spec" for the .300 Win Mag, Black Hills was simply given the task of loading ammo to a certain desired spec that would not blow up a loose throated military gun on a hot day. The 248-1 load is 70K PSI under nominal conditions in mil barrels, and thusly, should not shock people when its too hot for your average 300 mag.
If it is shot by the military it has mil-spec requirements and Black Hills was awarded the contract to manufacture this "mil-spec" ammunition after reviewing all the bids made by the other manufactures.
http://usarmorment.com/pdf/300WM_load%20data.pdf
http://www.dtic.mil/ndia/2009infantrysmallarms/tuesdaysessioniii8524.pdf
Hitchhiker
10-10-13, 09:31
I had the original load and components data somewhere. The powder is H1000 and the bullet is the 220 grain Sierra Match King. It is loaded longer than the SAAMI maximum cartridge length. I think it is or was 3.5 inches. It might be 3.45" or somewhere around there but the original length was suppose to be 3.5 inches.
I have about 20 cases from M248 mod 1 that was shot by an acquaintance through a rifle that was set up for it during a range outing a while back. About 75% have some degree of gas leakage around the primers. It's too doggone hot. I understand why they went with the projo they did and loaded it to the level they did, but I have to think that SOMETHING with a better BC could have given them the degree of forgiveness and transition they were looking for at a lower pressure.
Hitchhiker
10-10-13, 09:55
Oh, the load I had was for the MK248 Mod 0. Two different powders were used in that one and the primers weren't crimped as they are in MK248 Mod 1.
If it is shot by the military it has mil-spec requirements and Black Hills was awarded the contract to manufacture this "mil-spec" ammunition after reviewing all the bids made by the other manufactures.
http://usarmorment.com/pdf/300WM_load%20data.pdf
http://www.dtic.mil/ndia/2009infantrysmallarms/tuesdaysessioniii8524.pdf
Not that it matters, but I believe Federal was awarded the Mk 248 Mod 1 contract, not Black Hills. Unless it was rebid in the last couple of years.
Thanks for all of the replies. The loading is definitely a screamer. Too bad it's not realistic for those of us who cannot afford virgin brass every time.
jpgm
eightmillimeter
10-10-13, 23:06
Not that it matters, but I believe Federal was awarded the Mk 248 Mod 1 contract, not Black Hills. Unless it was rebid in the last couple of years.
Black Hills got the Mk248 Mod 1 contract. Federal got the Mk316
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Hitchhiker
10-11-13, 06:24
The chamber specs for the rifles call for SAAMI spec dimensions and SAAMI spec headspace for 300 Winchester Magnum. There is nothing special or unique about the rifle chambers the military uses.
Black Hills got the Mk248 Mod 1 contract. Federal got the Mk316
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Do you know when the contract was awarded our could you point me to a good source? There's an ATK press release from 2009 stating that Federal had won the contract so I'm curious.
U.S. Department of Defense
Office of the Assistant Secretary of Defense (Public Affairs)
Contract
FOR RELEASE AT
5 p.m. ET
No. 404-09
June 08, 2009
NAVY CONTRACT
Federal Cartridge Co., Anoka, Minn., is being awarded a $49,900,000 firm-fixed-price, indefinite-delivery/indefinite-quantity contract for 300 Winchester magnum ammunition. This ammunition will be used by U.S. forces engaged in combat and by the Navy in Match Team competition. Work will be performed in Anoka, Minn., and is expected to be completed Jun. 2014. Contract funds in the amount of $1,319,768 will expire at the end of the current fiscal year. This contract was competitively procured with multiple proposals solicited via the Federal Business Opportunities website, with one offer received. The Naval Surface Warfare Center Crane Division, Crane, Ind., is the contracting activity (N0016409-D-JQ56).
http://www.defense.gov/contracts/contract.aspx?contractid=4043
13--.300 WINCHESTER MAGNUM AMMUNITION
Solicitation Number: N0016409RJN30
Agency: Department of the Navy
Office: Naval Sea Systems Command
Location: NSWC Crane Division
https://www.fbo.gov/index?s=opportunity&mode=form&id=be2b7f5eaff1afbca4c14781eedbf8ab&tab=core&_cview=1&cck=1&au=&ck=
I'm retired with nothing to do and all day to do it, and its amazing what you can find when you know Google is your best friend.
Meaning I did know the answer to your question until I Googled a few key words. :smile:
What I find "strange" is why didn't Remington or Winchester bid on the contract? ATK already has the very lucrative contract to produce ammunion at the Lake City Army Ammunition Plant. And General Dynamics Weapon Division owns the old Remington powder manufacturing plant in Canada and the Winchester powder plant in Florida. The world is changing faster than I can keep up with, and the old names I grew up with are biting the dust.
eightmillimeter
10-11-13, 12:40
Silly me I was getting something confused. I know black hills is making one of the special purpose rounds but I cannot remember which one. Now I am thinking it is the 338 Lapua...
Chasing after that load doesn't make sense to me. The mil had to settle for that load to accomodate a wide range of guns. Better BC bullets can be used and tuned to your own rifle.
As far as brass life, I don't know what BH uses... but their regular red box 300 WM brass sucks balls. I got a few hundred rounds from a guy who shot some Blackwater sniper class and almost none of it would hold a primer with acceptable tension. Had to shit can all of it. :(
I was looking over my notes on the 220 gr SMK in 300 and found an interesting (at least to me) WinMagial Factoid.
I tried these bullets with the EXACT same EVERYTHING... except brass.... two different brass kinds... Norma and RWS.
74.0 gr of H1000 in both... loaded on the same scale, during the same session. The Norma shot 2740 FPS SD 10, and the RWS shot 2818 FPS SD 12. 78 FPS pick up just on the lower case capacity of RWS. (24" 5R barrel BTW)
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