H&H Mag & lyman 375449JN

[AlaskanGuy]

I have this original A-Bolt 375 H&H.... It is different from most of the newer A-bolts as it has a 1-14 twist.... I been helping out a buddy with the newer version, and his just loves the boolit with 50 grains of 4064.....His gun is a 1 in 12 twist.

My goal with this heavy hitter is to get 2 inch groups at 200 yards or better consistantly. I have promised my son to take him on a brown bear hunt this spring, and on my bucket list is to take a big one with cast.....

I have been fighting with trying to get this same load to shoot in my gun with the 1 in 14, and it hates them. I am lucky to get a 5 inch group at 100 yards.... That load chrono's at about 2000 fps ... Soooo i laddered around with a couple other powders....

3031 started at 41 through 46 grains.. Did ok with with 41 grains, but groups got progressivly worse as i climbed up....

2400 started at 27 and ran up to 29.... Same issue, did ok at first with 27, but as i climbed up the ladder, again the groups fell off...

Tumbling was not an issue, everything looks clean when it hit the paper.... So, i know that my gun likes stuff under around 1900 fps... No problem.... But the biggest problem is that I ran out of magnum primers..... I shot some with regular CCI No 200 primers, and several failed to fire, and one fired late after i had picked up my head...

My opportunities to pick up magnum primers are slim and none.... I do have the following large rifle primers at my disposal....

CCI BR-2
FEDERAL NO 210
CCI 200..

Any ideas??? I need something to continue my development with.... I am a firm believer of dacron, and every single load that i am working with in this heavy uses dacrom to keep the powder on the primer, and i still got misfires.

AG

[smoked turkey]

AlaskanGuy I am also doing some load development in my 375 H&H. I don't know the twist rate of my Weatherby Mk V but I can tell you my results and might give you something to think about. I tried 50 gr of 4064 but didn't find the accuracy I am after. What has worked for me the best so far is 34 gr IMR 4198. I chrono it at 1799'/s. At 125 yards off the bench I can get two shot groups at 0.5", but seems I always mess that wonderful group up when that third shot goes off. Even at that the over all groups are certainly hunting quality at 2"-3".This is using my 375449 which is sized .377, and weighs in at 276 gr as a WDWW with approx 2% tin added. I have also shot some AA5744 and IMR SR4759 at approx 1700'/s. I get pretty good accuracy with those too. I seem to get another 100'/s out of the 4198 with slightly better accuracy. My trouble is my 4198 is almost gone and I have the other two. So I am trying to figure out what to do. I am taking the 375 to Africa, leaving Feb 1, so I don't have much time to work out this load and get it dialed in at 200 yards. I will be after a couple of the larger plains game animals, the Blue Wildebeest, and the Red Hartebeest. I am hoping the 1900 ft-lbs of the cast boolits will do the job if I do mine. Hope this helps in your load development. Oh yes I added this as an after thought, I am using mag primers with this load of 4198, no filler.

[btroj]

2400 is a great powder but I think it maxes out in usefulness for you in the 1800 fps range.

I would be looking at 4895 in the 50 to 55 gr range. Use a bit of Dacron the locate the powder and see how it does. My CZ really likes it, good for 2100 to 2200 fps.

What you need to keep in mind is that at some point 2400 has such a rapid pressure rise that it kicks the bullet in the butt so hard that the bullet can deform. This can destroy accuracy.

Think of slower powders like 4895 or 4064 because of the more gentle acceleration.

[AlaskanGuy]

Its all about the energy, and being able to focus it when you pull the trigger.....

I will prolly have to re-evaluate the 4064 for a lower vel load..... I used 50 before, thinking i need to try down in the 45 grain range... But i cant find any vel data for it down there... 40 gr will give me 1680 according to lyman published data.... Not sure if that will give me the needed energy though.

I have no access to 4198 or 4895 though... Wish i did... Lots of good load for it I see.... So i will have to load down a bit... Problem is primers... No magnum primers around here.....

AG

[btroj]

AG, take a look at this article. Lots of great info.

http://www.castpics.net/subsite2/ByCaliber/Cast%20in%20the%20375%20H_H.pdf

[AlaskanGuy]

Yes sir... I have actually talked to beagle a couple of times about that article.... It was a real good read...

[starmac]

Which mag primers do you use. I may have a workable idea.

[Larry Gibson]

I use 46 gr 4895 with a 1 1/4 gr Dacron filler with that bullet in my M70 three six bits. It runs close to 2200 fps. I'm thinking that 50 gr 4064 is pushing that bullet too hard? I suggest you do drop back to 45 gr of 4064 and try again. Even with the 14" twist 2" groups (1 moa) might be a bit overly optimistic goal, especially with a softer hunting alloy. Is that level of accuracy really needed for brown bear? I get 3 - 4" groups consistently at 200 yards and consider that more than adequate for hunting but that's me.

If you have access to a slower powder such as any of the 4350s, RL19 or H4831sc you might try those. With those you should be able to push to 2300 - 2400 fps with that 14" twist with 4-5" consistent groups at 200 yards. That would be good bear "medicine".

Larry Gibson

[wmitty]

If you are needing more velocity, paper patching sure seems to be the easiest route from what I've seen. I have pushed the Lyman 378674 to well over 2000 fps after sizing it to .368" and patching up to groove dia.