My RUM Finally Roars

[Mysticplayer]

Well guys, my RUM is finally finished and some powder has been burnt. Still in the early stages of load development but I should be able to get this thing shooting 1/2MOA or better (at 250yds anyways). Never meant to build a BR rifle.

The weather here has been extremely warm (34 to 36C) so barrel heat is a big problem. Don't think that H870 likes these temps either. Would get a nice group then a wild flyer. Vel definitely increased through the group. I am guessing these are pressure spikes. 240gr MK molied used throughout.

Vel is only at 3000fps at 98gr of H870. The barrel is 35" long (Bevan King) no taper on a Enfield P14 action. Action converted to cock on opening, speedlock, and tuned single stage trigger. Homemade thumbhole BR style stock with 15lbs of detachable ballast. Recoil is quite mild at a total weight of 40lbs. Scope is a 10X super sniper. Have enough elevation to make it out to 2000yds.

Shot at 1km at our 9X9 gong. Lots of close calls and a few hits. Didn't put up wind flag so can blame "some" misses on that. My guess is that the heat was not helping with the grouping of the rifle. More load development and hopefully cooler weather needed.

Those 240grMK are really hitting hard. Where other cals (165gr 30cal, 168gr MK) are just denting the steel, the 240 almost shot through.

After 1 year, the beast is done and with a little effort, should shoot at its potential (goal was 1/2 MOA at shorter ranges and MOA at longer). Will probably get my hands on some WC 872 and IMR 5010 surplus powder to try. There is still lots of room in the case and with a 35" barrel, might like more powder.

Darryl, if you read this would like your thoughts on 5010. I know you use 872 a lot but would want to know if the 5010 shoots well. There is lots of room in that case and I wonder if a slower bulkier powder could help with vel spreads and reduce LR group size.

So my quest to build good shooting, accurate, and economical cannons continue. The cost of this project was reduced greatly by the amount of work I could do myself (stock work, scope shimming, etc). For those looking at an entry level way of getting into LR heavy hitters, this may be a way you can go. The RUM and Tomahawk are definitely the bang for the buck when launching 240gr MK.

I hope to get some pictures of the finished rifle posted in the coming weeks. Let me know if you have any further questions or comments.

Jerry

 

[Boyd Heaton]

Jerry,I will suggest you to try Retumbo with the 240"s.I was getting a safe 3000 fps with a 30" barrel...With 10 shot e.s. below 10fps

 

[eb]

Congradulations Jerry , iam on a quest to do the same thing (build my own guns), have bought a lathe and am in the process of getting it hooked up . Will begin with a mauser in a small caliber and work my way up to the bigger ones. Keep us posted and good luck!!! ebb

 

[Mysticplayer]

Boyd, How much Retumbo are you using? How much space is left in the case? I seat my 240's so that the base of the bullet is above the base of the shoulder.

I like the results you are getting. However, I really like the price of the surplus powders with this rather hungry case.

ebb, good luck with building your own rifles. Midway has some good sales on now for different reamers, especially the wildcats that we love so much. I had the barrel install done by a smith. No lathe yet. I figure for the cost of a lathe, I can get a lot of barrels installed. I just focus on the stocks, bedding, scope and trigger work.

 

[Darryl Cassel]

Jerry

You might want to go to the Retumbo instead of the 5010.

The BIG stick powders such as 5010 seem to be VERY hard on big case 30 cal barrels and reduce life in them.

I knew of a 30/378 that was shot out 6" up the barrel after only 600 rounds, using 5010.

Good luck and I'm sure you will like the big boomer.

You mentioned about seeing the difference in the hits of the 240 gr is why I like that bullet the most compared to ANY 30 cal bullet made.

Later
DC

 

[ss8541]

Boyd, I would be very interested in how much Retumbo you are using. I ran out of Grizz, and Ramshot will not release any more. 50BMG is giving me to much velocity deviation. I was very happy with my Grizz load and the 240 MK at 3008 to 3030 depending on temp. Any help would be greatly appreciated. Otherwise I will just do what I have done in the past and take an educated guess. I would think that halfway between my RL25 load and 50BMG load would be a starting place, but I will review a few numbers first.
Thanks,
Vince

 

[Boyd Heaton]

I was using 85gr of Retumbo with the 240 in a 30" ten twist barrel....NOTE...THIS WAS SAFE IN MY GUN

.....There will be room left in the case.Mine was set at 3.700 C.O.L....Work up to that load.

 

[ss8541]

Good thing I talked to you Boyd. I would have started at 85 grains of Retumbo. With RL25 I went up to 88 for pressure then shot 87 (3020 fps) grains for groups. (My overall length averages about 3.74.) I got just a little bit of a sticky bolt at 88.5 grains of RL 25 in my rifle, so I backed off to 87 for a couple of groups using the same cases. I only got 3 loadings at that charge from a case though. I went to the slower powders looking for more velocity at that point. I ended up with about the same velocity with 96.5 grains of Ramshot Grizz (101 with Moly), but with less pressure. I have been loading hot gauging my Max working pressure on weather I can get 4 reloads out of a case or not. I had an extreme spread of 27 with the RL 25, which is another reason that I went away from it. It sounds like you have been having good luck with the Retumbo though so maybe I will be as lucky in my rifle. It does sound like I may end up with a little more powder for the same velocity though. I just realized I may have been having a real brain fart for part of this post. I was using Moly bullets. You did not mention any moly.
Thanks,
Vince
PS-anyone reading the loads I have posted I would highly recommend that you reduce by at least 10% to start a work up. I would also recommend taking into account the temperature at your location, and the fact that I was using moly bullets. I load hot for single pressure loads and then drop down for groups. I have never lost a primer or had a case failure, but that does not mean that you would be so lucky with these loads.