300 RUM, 200g Accubond, H50BMG

[jmden]

Hi,

Have folks been using this combination of components with any luck? If so, what are the numbers for your particular rifle, i.e. velocity, powder charge, etc.

Thank you,

Jon Denham

 

[remingtonman_25_06]

I have not used the H50BMG, however I have had very good luck with H-1000 and 200g SMK's. I shot a 3 shot, 4 inch group at 800 yards with 94g of H-1000, velocity was 3197fps, OAL= 3.66".

 

[Chilly Willy]

My accuracy load with the 200 grain Accu Bond is:

84.5 grains of Retumbo
Winchester Mag rifle primer
bullet seated to the recommended COL (3.75 I think)
I get 3000 FPS about 3 ft from muzzle
and completely penetrate 1/2" steel @ 100 yards.

I primarily will use this load to hunt moose in northern Ontario

 

[remingtonman_25_06]

Whoops, I misread the topic starter. For some reason I had 200g SMK stuck in my head. I have a very accurate load worked up in my completely stock Rem 700 LSS in 300 RUM and the 200g Accubond. 92g of H-1000, Fed 215, OAL=3.640", 3104fps. I have shot a 1.5" 3 shot group at 525 yards with this load. Shot through 3/8" steel at 525 yards. I also shot my 5x6 bull at 512 yards with this combo. Hit 2 of 3 shots. 1 behind the shoulder, 1 in the shoulder. I only got a couple words to say, it was messy.

 

[Brent]

The little I've shot H50BMG and the Accubond, it does have impressive MV, but in my case groups went to hell. Now, I've only tried one load, pretty near max too, and this is in my 30-338 Lapua Imp not my 300 Ultra, but they are very similar.

I've not tried H1000 either, mainly been having good success with Retumbo. RL25 shoots real well too, just about 50 fps slower than Retumbo though...

91gr Retumbo under a 210 JLK, 210M seated to the lands at 3.897 shot somewhere between .2 and .5 MOA with 3 shots with the first load I tried. This really means nothing to me because I only fired two groups. I'll have to print a few more consecutive ones to see how that holds up.

 

[jmden]

Brent and all,

You tested H50BMG with you 30-388 Lapua Imp., right? What was your powder charge?

It just seems a waste of case capacity to use 90-95 grains of powder with the 200g bullets on such a big case as the 300 RUM. That would indicate to me that a guy should be using a slower powder with that size bullet and fill that case up some more--not compress it, just fill it up. I got ejector pin marks at 93 grains Retumbo and am at 94.4 grains of Re25 for my hunting load. I just think that leaves too much room in the big case and wonder if we're not taking advantage of it due to powder selection in part. Comments?

 

[Brent]

John,
You're right, density seems much more appropriate with H50BMG or one of the slow VV powders.

I tested 100.0, 102.0 and 104.0gr H50BMG. Pressure was about 65, 70, and 75k psi respectively. I consider 102gr a max load.
MV was also 3200, 3250, 3330 fps respectively.

I will play with the load a little more though. Primer, OAL and I'll know if it'll shoot at that speed.

I'm satisfied with 3150-3200 fps using Retumbo if not, accuracy is very good. Like you say though, 90gr is pretty low for this case, but it does seem to work just fine, heck even 84gr RL22 shot real well in the Lapua.

I wondered if RL22 or H4831 would really be too fast of powder, but couldn't resist the urge to see if things really tighten up moving to a little faster burn with less muzzle pressure.

No doubt in my mind that these cases could use more barrel length, especially if even slower powders are used. I think with a 30 caliber we just may have just about maxed out the case capacity for these powders. Maybe 40" barrels with slower than H50BMG would do better??

I think with Retumbo we're already running in the fast burn range, probably why accuracy is what it is in the bigger 30's.

 

[jmden]

Brent, Could you comment on what you wrote here further: "I think with Retumbo we're already running in the fast burn range, probably why accuracy is what it is in the bigger 30's." This along with an earlier comment about lower muzzle pressure with faster powders left me wondering what I don't know about this. Are you saying that a faster burning powder will be burned up by the time the bullet reaches the muzzle and this can affect accuracy? I'm not real experienced here, so this is a new concept to me if I'm hearing you correctly. Please explain.

Thank you,

Jon Denham

 

[jmden]

I've also been wondering about the slow VV powders for the 300RUM. Anybody had experience with these? Are they "temp insensitve"? I've worked with VV N560 with my 30-338 Win Mag. and it seems very consistent...

 

[jmden]

I've also been wondering about the slow VV powders for the 300RUM. Anybody had experience with these? Are they "temp insensitve"? I've worked with VV N560 with my 30-338 Win Mag. and it seems very consistent...

 

[Brent]

Jon,
Just meant to say that Retumbo is probably on the fast side for this size of case, in a relative sense that is, and yes, muzzle pressure is raised the slower the powder, and/or the lighter the bullet used. Takes longer to hit peak pressure, bullet is further down the tube by the time pressure drops down and it can affect the bullet on exit if it's high. Much of the same thing using too slow of powder with a light weight bullet that gets down the bore real fast. Generally it has to have a faster powder behind it in order to hit peak pressure soon enough to generate the best speeds, if not muzzle pressure will also be high. I think most of the BR guys try to stay on the faster side of the burn rate, but a lot of it also has to do with better ES numbers too.

If you think about it, Retumbo is a pretty slow powder, add to that heavy bullets and they balance out to get good burn in a 26-30" barrel with 90-100gr. The higher the load density, the more peak pressure moves away from the muzzle though, just not as rapidly as it moves toward it going to a slower powder, so the net effect is it moves toward the muzzle.

Take H50BMG, it has 102gr at my max load, rise time is slower but load density is much better, the net effect is more muzzle pressure in the same length barrel though.

It would be my guess that Retumbo in a 30" barrel would about equal H50BMG in a 34-36" barrel, muzzle pressure wise.

I've never used the VV powders yet, but there's a place here in town now that has a pretty good selection for better prices now, so I'll probably add a few to the cabinet sometime soon. I have no idea why, but they recently stopped carrying 8# jugs of Retumbo and 5# jugs of RL25, I was too bummed to even ask why.....

 

[Brent]

Jon,
Just one more possible reason. Harold Vaughn may have wrote about it in "Rifle Accuracy Facts". He does cover muzzle pressure, I do know that, I'm sure that's where I must have learned about it.

BountyHunter has read his most excellent book, and he shoots the 1K BR game and might have formed some opinions about this and even recall Harold's tests off the top of his head.

I think that some of the ES issues probably stem from slower powder = bigger, longer grains. Possibly this creates a more inconsistant burn in general, a more inconsistant flame front, I just don't know. One thing's for **** sure, H50BMG is like giant grains of IMR4064!It could be more suceptable to inconsistancies as a result of settling during transport, chambering, unless it's a good compressed load, just not sure.

I'll have a look a Harold's book and see what he found.

 

[jmden]

So you believe that this increased muzzle pressure caused by slower powders is responsible for poor accuracy. I must confess, that even though I've done a ton of reading, this is a new and interesting concept to me. Is that likely why some folks have reported poor accuracy with H870 (and you with H50BMG) with the 300RUM?