Any 300 WM shooters using mil.pec Mk248 Mod1

[longshot2000]

... not sure if this is the right forum. It is not a reloading question...

want to to know which guns anyone is shooting the mil.spc 300 WM 220 grain round?

It is now available from a few providers, surplus from Lake City Federal ammo. It is higher pressure charge and an over-sized length ammo. As I recall it is 60k pounds of pressure and 3.5" compared to 3.35" give or take.

i have a mil.spc Mk13, with Lilja barrel and Stiller action. I feel good with this setup. I also have a Barret MRAD.

three issues I can think of:

1) how will the increased length (all in the bullet, as brass is no different in outer measurements) affect shooting, headspace, chamber, etc.

2) at what point does "high pressure" over SAMMI specs cause a concern to safety

3) with higher velocity and pressure, what effect does that have on barrel or bolt wear

thanks for any thoughts. Looking for examples of who is actually shooting this ammo.

 

[LRI]

2012. I was approached by a Federal Agency about this very subject. I solved it on a MK13. Have built several since then. Here is one we just wrapped up.

Your running a "top fuel" version of the 300WM. Throats and bore specs need to be right to pull it off. You'll know when you goofed as a mallet gets added to your kit for opening the bolt.

Barrel life? The barrel is a consumable. 1000 rounds and your about done. Just the cost of doing business. Same thing with the brass. Maybe 4 or 5 reloads and primers go to hell. This cartridge is loaded to a velocity. 2850 +/- 50fps is the standard. So yes, it's hot. Not absurdly hot, but certainly "well done." FWIW with the right setup I've been able to knock on the door of 3050fps and still get the thing to work. Primer pockets however turn into a "glory hole" after just a couple cycles. They no play nice. . .

Here is a link detailing the cartridge specifications: http://usarmorment.com/pdf/300WM_load data.pdf

It's a fringe cartridge designed to emulate the performance of the 250 Scenar in a 338 LM. Remember, it's a "fire and forget" cartridge. Squirrel teams aren't known to be conducting brass calls after the war stops.

If you take all this in and agree to play the game by those rules, its pretty bad ass. +3.5 rounds per pound increase over the 338 LM. Great if your out killin and have to hump this stuff. From the taxpayer perspective its much better. The study I was involved with penciled out to where 338LM cost the US taxpayer somewhere around $20 to $25 per round expended in the heat of the Middle East Shit Show. By contrast the MK248 Mod 1 was cents on that dollar. Logistics are not cheap and the AF loves to bill other branches of service.

Have fun, hope this helps.

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[longshot2000]

2012. I was approached by a Federal Agency about this very subject. I solved it on a MK13. Have built several since then. Here is one we just wrapped up.

Your running a "top fuel" version of the 300WM. Throats and bore specs need to be right to pull it off. You'll know when you goofed as a mallet gets added to your kit for opening the bolt.

So, if one does not have the barrel chamber for the linger round, is the effect a jam, or lack of accuracy in the shot?

 

[NukeMMC]

The "A191" chamber, unsure if it was modified for the MK248 Mod 1 (190gr Mod 0 = A191, 220gr Mod 1 =AB43) is a longer throat (about .060" more freebore than a match chamber) and if you try shooting either in a short-throat rifle you will be the recipient of what Chad described above - need a mallet for bolt lift - if you don't end up with some excess gas in your face from popping primers. Lack of accuracy is questionable as AB43 spec is for the ogive to be ± .010", and SMKs are tolerant to jump or jam, so it will be reasonably consistent in giving you excessive pressure.

I was issued some A191 back in the 90s. Shooting that out of a match-chambered 300wm was a MISTAKE. Heavy bolt lift, a couple pierced primers, headstamp was about halfway wiped slick!

Back in 2011 I had AJ Brown build me a 300wm with the Lilja barrel and A191 chamber. It did just fine with A191. Never had any AB43 to run thru it but my "go-to" load for it was a 208AMAX with 77.2gr H1000 and .010" off the lands (don't remember the OAL). That gave me 2925fps. My 190SMK load was 73.5gr Re22 and a .020" jump that gave me 3100fps. Both were 1/2-5/8 moa loads for that rifle. When he built it and we were talking about what barrel, he said they would rebarrel the Frog rifles after 1500-2000rds, whether they needed it or not. He had seen more than a couple that were beyond 2000rds and shooting well (remember this is a "minute-of-man" rifle). For whatever reason, the Lilja barrels were doing well as magnums where the McMillan and Hart barrels they used for the early pre-MK13s were 1500rds tops.

Picture is 3 shots at 200yds with the H1000 load when I was monkeying with torque on the 3 bedding screws.

 

[rpk762]

I have been shooting the 220gr SMK for almost 20 years. Back in the day it was a popular caliber and bullet for 1,000yds competition. Almost all of my barrels have been Lilja 3 groove tubes. What was the real change for me was HBN. I am getting 3015fps with my current tube. The slowest since using HBN and 3 groove tubes was 2950. I am not getting heavy bolt lift problems, the primers look good and I am not getting any ejector marks on the brass.

I do not like having my bullets set into the body of the case. Every rifle is different my friend has a 300wm and he can't get anywhere near a full powder charge so setting the bullet deep into the casing works well for him.