Thumper

[Topshot]

AZShooter, Nice rig. Looks like a .308win on steroids.
I bet it is an easy rifle to shoot.

I will keep you informed on my project. Here is a photo of the first few shots on paper.
The first shot was after bore sighting it. Then a rough adjustment to get closer to the center of the target on the second shot.

I then made a fine adjustment and fired the last three powder charges of 118gn, 120gn and 122gn. These three shots landed very close to each other which surprised me.
I'm going to try 124gn, 126gn and 128gn next and see how they go.

 

[elkaholic]

AZShooter, Nice rig. Looks like a .308win on steroids.
I bet it is an easy rifle to shoot.

I will keep you informed on my project. Here is a photo of the first few shots on paper.
The first shot was after bore sighting it. Then a rough adjustment to get closer to the center of the target on the second shot.

I then made a fine adjustment and fired the last three powder charges of 118gn, 120gn and 122gn. These three shots landed very close to each other which surprised me.
I'm going to try 124gn, 126gn and 128gn next and see how they go.

Pretty impressive for three different loads........Rich

 

[benchracer]

Quite awhile back, I remember reading about a cartridge designed by JD Jones of SSK industries. He necked up .460 Weatherby to accept .510 bullets and called his creation the .50 Peacekeeper. It was capable of launching the 750 AMAX @ 2200fps from a 23" barrel.

The Peacekeeper concept seems to be very similar to the Thumper referenced here, so I don't think it is a crazy idea at all.

 

[benchracer]

Like your project. Always thought there is a place for slow heavy bullets. High BC longer barrel life and in some instances moderate recoil.

A few years ago Cheytac had the .375 350 gr Sierra MK made for them. I wanted to try that bullet in my 375 Taylor unfortunately the twist wasn't fast enough. When I built a 338 RCM sporter I borrowed some 300 gr Sierra MK from a friend and tried them. Got over 2200 fps from a 22" barrel and the light bulb went on.

I built a long throated 338 RCM in a LA to shoot the 300 gr Sierra MK and then later switched to the 300 gr Bergers when they showed. Am getting 2525 with a 30" barrel and it is lots of fun to shoot. Long strings before barrel gets warm. Excellent accuracy and moderate recoil. Fouling is also minimal. Downrange drift and energy is impressive too.




Keep us informed on your progress.

I have a 338-06AI build in the works and am interested by what you did with your RCM. I have been looking high and low for the thread detailing your build, though, and can't seem to find it, only other threads that mention it. Can you point me in the right direction?

Once I have my AI back, I may try to convince elkaholic to expand his Sherman family to include a .338 version.

 

[elkaholic]

I have a 338-06AI build in the works and am interested by what you did with your RCM. I have been looking high and low for the thread detailing your build, though, and can't seem to find it, only other threads that mention it. Can you point me in the right direction?

Once I have my AI back, I may try to convince elkaholic to expand his Sherman family to include a .338 version.

We could do that now I have a 300 reamer so all you would have to do is use a 338 throater...........Rich

 

[elkaholic]

Actually, a better way would be to chamber with a 338-06 reamer, but run it in another .030" and then clean it up with a Sherman reamer. We have done this with the 6.5 reamer to make 270 and 280 Shermans. Based on the 300 Sherman results I have had, you would be very close to a 338 WM. I don't want to hijack this thread though, so pm me if anyone is interested.........Rich

 

[benchracer]

Good Deal! I will PM you when I am ready... Ditto on the hi-jack and apologies to the OP!

 

[AZShooter]

Benchracer,

PM sent

 

[Topshot]

An update on my load testing.
COAL 5.052" Fed 215 Mag Primer. Beecher Brass. 750gn A-Max.
AR2209 112gn 2106fps
114gn 2124fps
116gn 2120fps
118gn 2157fps
120gn 2142fps
122gn 2162fps
124gn 2191fps
126gn 2239fps
128gn 2284fps
Accuracy and pressure is still ok so going to go for 2400fps tomorrow.

 

[benchracer]

It will be interesting to see where your velocity tops out. You have substantially more case capacity than the parent case for the .50 Peacekeeper and 7" more barrel length, so I would expect 2400 fps to be easily achievable.

 

[Topshot]

Success today. I made it to my target velocity of 2400fps without excessive pressure

130gn 2305fps
132gn 2327fps
134gn 2346fps
136gn 2416fps
138gn 2452fps

 

[AZShooter]

Congratulations not only did you get past 2400 fps but with the fastest load you surpassed 10,000 ft/lb of energy!

 

[elkaholic]

Nice work! I will be looking forward to seeing what it does on game.........Rich

 

[Topshot]

Yeah, very happy with the results.
This morning I took it out and tried a load of 135gn at 1000 yards.
I dialled up 32moa from a 100yards zero and started landing great big lumps of lead onto an old 4kg gas cylinder. Great fun.
Quite impressed with its ability and accuracy.
Over the next year I will do a bit of hunting with it and report back how it goes.
This is going to be interesting.