Ordered 16lbs of MP 842 Powder (similar to WC 842). Need good source of starting load data.

[turbo_vanner]

I've had good luck with their wc-844 and H335 data, but there is a pretty well documented connection there.

The MP475 on their site is supposed to be next to IMR 4064 on their burn chart, I've been curious how similar they are.

 

[P7M13]

Probably wasn't the best choice for my first attempt at using surplus powder.

Perhaps you'll burn through a pound of it finding the best loads for each bullet, and I'd bet you'll find MOA or better performance. Worst case, you bought enough powder for 5K rounds of cover fire in 223, 2500 rounds in 308. That itself is fun.
There's something imminently satisfying when you reach for that big jug and it's almost empty, and terrifying if you don't have something to replace it. I stopped buying surplus years ago when I started shooting a batch that seemed significantly underpowered compared to the commercial equivalent.

 

[osprey]

I would use h322 data and start 10% lower than the min published charge and work up. A chronograph is the best investment a guy can make for this type of work.

 

[arakboss]

I would use h332 data and start 10% lower than the min published charge and work up. A chronograph is the best investment a guy can make for this type of work.

What would make you want to use H322 data to work from?

 

[osprey]

It is what I used for my work ups of wc 842 for 223 in the past and it was fairly close.

 

[arakboss]

It is what I used for my work ups of wc 842 for 223 in the past and it was fairly close.

That's interesting. American reloading said to start at 10% below WC 842 data so I will look at H322 data. Do you have any records for those WC 842 loadings and how they performed?

 

[osprey]

That was many moons ago and even if I still had the data I would be hesitant to share it. Every batch of surplus is a little different as far as burn rate goes, so my data would only be a casual reference point. As a few others have said 20 grs would be a good start point with 55 or 60 gr bullets. I also would highly encourage the use of a chrono. No serious reloader should be without one.

 

[P7M13]

I also would highly encourage the use of a chrono. No serious reloader should be without one.

+1

 

[arakboss]

MP 842 just arrived. I will put together a few 20gr loads this weekend. We'll see if they even lock the bolt back on carbine gas rifle. If they do, I will very slowly work up from there. If the 20gr load doesn't have enough energy to lock the bolt back I will have a few 20.5gr loads as back up and maybe a few 21gr loads too. I have way to many firearm projects going right now to spend much time with this powder but I am sure eager to see how it compares to WC 842 and what the minimum load is that fully cycles the action in a carbine gas rifle.

 

[arakboss]

OK I have five of each loaded up at 20, 20.5, 21, 21.5 and 22 grains of MP 842 surplus powder topped off with a Berry's 55gr bullet. I loaded to the cannelure and used the Lee FCD to lightly crimp them.

I am going to use my newest carbine gas build with a 16" 1/7 twist 5.56 barrel to blast these off. I will of course start with the 20gr load. I will load these single feed.

 

[osprey]

Well any results to post?

 

[arakboss]

Well any results to post?

Not yet.

 

[Nitro6r]

I have been looking for data on where to start for MP842 and couldn't find it anywhere, but this thread always comes up so I want to post this for the next guy. Your rifle is probably different. This only applies to my rifle! But.....

In a savage bolt with 20" barrel that is generally in the middle ground as far as pressure and velocity:
New Lapua Palma 308 brass, Winchester SR primer, MP842 (lot #03192), 2.805 COAL, Sierra 168 HPBT Matchking, Chrony F1 @ 10 paces from muzzle, front/rear bags
Hand measured, very light seating pressure, outside turned necks, etc. Single fed
39 Grains = 2337
40 = 2502
41 = 2440
42 = 2607 Starting to flatten primer
43 = 2652 Same primer flattening
44 = 2704 Ejector imprint (stopped here)
All of these were within 2" vertically at 100 yds and there was very little horizontal dispersion (like 1/2" or so).

Mostly to help with searches I add WC842, MP 842, WC 842 The label says to use WC 842 data, but that doesn't seem readily available for 308 either. I hope this helps someone. Start low! People say this is the same powder as CFE-223, but that max load is 49 grains on Hodgdon's site and would seemingly be very dangerous in my rifle if used with this powder. CFE-223 starting load is 46.6; 2.6 grains over my real-world max determination. This is its own powder for sure, not just a cross reference, at least from the numbers I got!

 

[arakboss]

Well any results to post?

I finally had the opportunity to test out the rounds I loaded from 20gr to 22gr. None of them showed any pressure signs and I didn't get any bullets stuck in the barrel. The bad news is none of them locked the bolt back on the empty pmag. I loaded one round at a time to see if they would lock the bolt back. Next step is to load some at 22.5gr and maybe 23gr and see if I can get bolt lock back.

It was the first time firing this home built rifle and I ran some factory loads through it first to test the function of the rifle. The bolt locked back on the factory rounds.

 

[Badger Jack]

I just ordered 16 pounds of MP 842 powder. It is suppose to be similar to WC 842. Seller recommends "Work up all loads using WC 842 minus 10% Minimum Load" ...

I keep hearing/reading about this powder being "surplus", and from pulled cartridges- it is not. The instructions from some to mix several containers and then separate them for consistancy MIGHT be viable IF this were actually older surplus powder of unknown batches, but, even then I would question the value of doing this. Powders today [last 15+ YEARS] are made to highly exasting requirements, and it is not likely that you will have noticeable variations from batch to batch.

SMP-842 is one of several powders produced by St. Marks Powder, 7121 Coastal Hwy., Crawfordville, Fl. 32327-2918, (850) 577-2824 and they are a subsidiary of General Dynamics.
The plant is a former Winchester ball powder plant, built in 1969 or thereabouts, and was transferred to St. Marks Powder Company in 1998.

Their powders are marketed under both Winchester and Hodgdon brand names, and loaded into comercial ammuntion made by MANY companies, (including Match .22 LR ammo used in the Olympics, which I suspect may be Federal Gold Medal Match), and also found in Winchester, Hornady, Remington, CCI, Speer, and several foreign makers, such as Aguila, and SAMSON [IMI?].

So, why not try contacting the MAKER of the powder instead of using questionable formula based on "similar" or "supposed to be the same as..." powders?

 

[awshoot]

... And it can be used over and over in the future. ...

Providing you don't shoot it. Speaking from personal experience here.

 

[arakboss]

Just wanted to share that another member loaded up some of the MP842 powder at 22.5g grain with a 55gr pill and was got the bolt to lock back. He indicated that there were very slight pressure signs at 22.5gr. Don't have any pics of brass or details on rifle used.

 

[michaeldw]

You might find it real similar to IMR 8208 xbr when you get done with your testing

 

[gmerkt]

Providing you don't shoot it. Speaking from personal experience here.

Yes, I've heard stories. I myself have only blown off one of the rods. The Chrony is made in Canada. When I went to replace a rod, I discovered that it's in a metric size. Which I couldn't get from Home Depot or similar but I was able to fabricate one that fits. But doesn't break down into two sections.

Checking speed with shot shell loads, that can result in damage. Wads can fly off in weird directions.

 

[arakboss]

This thread discusses the round which uses the smp 842 powder.

M885A1 Side note. 1/9 twist produced groups half the size of 1/7

http://www.americanrifleman.org/articles/2014/5/21/testing-the-army-s-m855a1-standard-ball-cartridge/ Interesting bit, The big take away for me though was how much of a role the twist rate played in group size. The U.S. Army replaced its green-tipped 5.56x45 mm NATO, M855 standard ball...

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