Alternate Powders for overbore cartridges

[Bill308]

I am building a new custom rifle in 7mm RSAUM and only have 2 lbs of H4831sc left. With the powder shortages I have been unable to find H4831sc and many other powders anywhere.

I am mostly going to be shooting Sierra and Berger 180's (and Nosler ABLR 175gr for hunting) out of my rig and while H4831sc and Reloder 25 seem to be the goto powders, I cannot find them in stock anywhere (or I'm too late and they're sold out); however, I am able to find Norma MRP and IMR 7828ssc in stock and I am curious if any of you have ever worked with MRP or 7828ssc?

Looking at the burn rate charts Norma MRP seems to be a dead match for H4831sc and IMR 7828ssc seems to match up with Reloder 25. That being said, just because they are close in burn rate doesn't mean they'll perform the same way, so I'm looking for some experience here. For those of you who have played with MRP and 7828ssc with overbore cartridges, what has been your experience with ES/SD?

I'm leaning toward MRP because there seems to be more information out there. The Berger reloading manual actually lists MRP and 7828ssc and shows them both at 97% fill ratio and very close in the velocity they yield with only .5 gr difference; however, 7828ssc is a slower powder so I'm not sure what is going on here. The big question then becomes does either have an advantage in the ES/SD dept? Thank you

Bill

 

[357Mag]

Bill -

Howdy !


FWIW -
In my 6mm wildcat, IMR7828 & SSC seemed very close to RL-22 on burn rate & useable charge. I was runnin' in the 43.5gr range w/ I7828
and 6mm 105's.

DK if that helps, at all ?


With regards ,
357Mag

 

[Bill308]

When I look at the burn chart MRP is right next to H4831sc and Reloder 22 while IMR 7828ssc is right next to Reloder 25. So maybe 7828 is a better match for the heavy 180's

 

[wboggs]

I have used MRP in a .300WM, 22-6mm, and 338 Ultra Mag., all with great success. Get high velocity and great accuracy. It is hard to obtain but it is a great powder.

 

[MrMajestic]

IMR 7828 SSC produces some very nice velocities in my 7mm RM's with accuracy equaling the best of others. Doesn't seem to be as clean as the other "go-to" powders for the Magnums, JMHO.

 

[MTlager]

With the 180 grain bullets my 7saum's shoot better and get more velocity with 7828ssc vs. H4831. With 168's the H4831 works better. Also check out RL22

 

[medic727]

I shot a 7SAUM in f-class for 2 years, 3000 rnds. After trying different powders (too many), H-1000 was recommened. I found it to be the most accurate in my shooting 175 SMKs. More importantly the H-1000 was very insensitive to temperature, shot very clean ( ~150 rnds between cleanings, Wipe Out foam, ~12-15 patches), and, relatively speaking, cool burning. In MY rifle I found several nodes between 59.5 and 63.3. At 63.3 I was getting 3100 fps. Brass life was excellent. After 8 firings I had 1 case neck seperation. This may have been caused by neck turning a little too far into the shoulder.

 

[waterfwlr]

Ramshot Magnum.

 

[Bill308]

Thank you medic727. Unfortunately H1000 is unavailable as well as I missed out a couple weeks ago. Very good to know it is temperature tolerant (I live at 7500') and clean as both are important to me. It's a slower powder which probably accounts for better case life. One thing, my barrel will be 26" and I'm wondering if that's too short to get the full benefits of the slower powder.

 

[Bill308]

IMR 7828 SSC produces some very nice velocities in my 7mm RM's with accuracy equaling the best of others. Doesn't seem to be as clean as the other "go-to" powders for the Magnums, JMHO.

Seems to be an issue with IMR with it being a bit dirty. Now I'm really curious about MRP

 

[ShootDots]

IMR 7828, when brought up to "reasonably" top pressures, is one of the cleanest burning powders on the market, comparable to VV N540 and N550.. I have shot a pile of it and that has been my experience..

 

[Bill308]

I have used MRP in a .300WM, 22-6mm, and 338 Ultra Mag., all with great success. Get high velocity and great accuracy. It is hard to obtain but it is a great powder.

Well that's just the thing, it appears to be prevalent right now. It is a bit slower than 4831sc which should help with the 180's. How dirty, how temp sensitive and how consistent ES/SD it is are my big questions right now.

Remember folks. I am trying to figure out what would be the best powder that is available right now, I realize the powders I've mentioned May not be the "best" for my application but I'm limited to what is available which is not much. Thank you

 

[Bill308]

IMR 7828, when brought up to "reasonably" top pressures, is one of the cleanest burning powders on the market, comparable to VV N540 and N550.. I have shot a pile of it and that has been my experience..

Really? Ugh, now this is becoming difficult. How is it with temp variations? I ask because I think this powders burn rate will more ideally suit my situation

 

[ShootDots]

Actually if you are up in the clean burning range and NOT AT THE RAGGED EDGE, it is quite stable... I find that it usually has a "large window" where you have a really good accuracy node, still clean burning and stable..

 

[Bill308]

Thank you Benjamin. If you don't mind educating me a little bit, what do you mean by the "clean burning range", I have not heard this concept before as I usually load based on accuracy and speed. Also when you say "ragged edge" are you referring to extreme pressures?

One final thought, are you loading for the 7mm SAUM or another cartridge? Thank you

 

[Erik Cortina]

I tried 7828 SSC in my 300 WSM. I am no longer a fan.

 

[ShootDots]

I used it in my 7mmMag and a load in my 300 Win... I shot 175gr Nosler Partitions in West Texas for Mule Deer. I also shot 180gr Ballistic Tips in my 300Win.. Usually, the larger the powder capacity, the larger the "window" of opportunity to find a good accuracy node that has several 10th's of a grain of powder where accuracy and e.s.'s stay pretty much the same. Two examples: My 7mm Rem Mag with 175's shot "about the same" with 62.0 to 64.0grs of powder. Now in the "older" loading manuals that was near the top BUT not AT THE TOP of "max-loads"... it was a bit warm, NOT HOT, but at 63.2grs it shot awesome. In West Texas you have single digits temps in the morning and 90 degrees in the afternoon. I never had any problems with that load at either extreme.. Example #2: with my .300 Win and 180 Ballistic tips, it shot GREAT at 75.5 all the way thru 77.0grs.. I chose 76.0grs and never looked back. None of those were at the ragged edge, however, they were near the top and it burned CLEAN... I hope this answers your question(s)... if not, continue to ask and I will do my best to answer..

 

[Bill308]

I tried 7828 SSC in my 300 WSM. I am no longer a fan.

Any way I can get you to share more information? By saying you're "no longer" a fan implies that you once were? When did you like it and what changed your mind?

 

[Bill308]

What about Accurate Magpro? It falls right inline with Hodgdons H1000 on their burn rate chart and Accurate claims they made it for short mags. I've read that it does tend to be a bit temp sensitive so that concerns me some, but if it's close to H1000 then maybe it's worth trying?

 

[white121]

+1 for reloaded 22 as a alternative to H4831 it has been very accurate for me with more than 1 caliber and has not shown temp sensitivity for me from 80 degrees down to 30.