7mm/6.5 Weatherby RPM

[300 PRC CUSTOM SAKO]

archeratlrg,

Your 35 sounds very interesting. What bullet and what velocity are you getting?

I have one that duplicates the 8mm RPM. I get 3,054 feet per second with the Hammer Hunter 198 grainer and 3,120 with the Hammer Shock hammer. The rifle weighs 7 1/4 pounds ready to go. It's based on the Weatherby Mark V ultralight with a 24" barrel with a .650" muzzle.

Recently I was thinking I need to buy one of the Back country 2.0 Ti. I think it should be rebarreled to .35 before it is even fired.

A note on 6.5 WBY RPM brass. I have found that it must be annealed even if new and unfired. Strongly recommend annealing every case.

 

[ARlife4me]

U r wrong it is a magnum in both capcity and performance

 

[archeratlrg]

View attachment 498173

Anyone done a 270 on the RPM brass? If so, how has it gone, what are your experiences?

 

[highdrum]

U r wrong it is a magnum in both capcity and performance

Lol it's essentially a non magnum of short magnum performance. Holds near the exact same amount of powder as a 300wsm, more than a saum. Nearly same as 7prc. All the cases I just mentioned, are magnum ala the 535 bolt face.

 

[pavementends]

A list of case capacities and length would be a helpful resource. If it included RSUM, WSM, PRC and the RPM one could make useful comparisons when dreaming of wonder chamberings. The advent of medium actions from several sources with the longer magazines lets use keep the longer bullets out of the case body. Bottom line, what are we trying looking to accomplish?

 

[Rich Coyle]

Hey Rich, wha weight bullet is that 8mm Hammer hunter?

Sorry to take so long. It uses the Hammer Hunter 198 grain at an average of 3,054 fps. I tried the 185 and got 3,120 fps. So far everything I shot with either dropped at the shot.

 

[archeratlrg]

Sorry to take so long. It uses the Hammer Hunter 198 grain at an average of 3,054 fps. I tried the 185 and got 3,120 fps. So far everything I shot with either dropped at the shot.

It looks like you're getting about the same velocity with that 198 that I am with the 200gr Accubonds in my 8mm Gibbs. I don't have the stock finished yet on my 8mm RPM stock so can't start loading for it. What powder are you using and what was your start load?

 

[Rich Coyle]

It looks like you're getting about the same velocity with that 198 that I am with the 200gr Accubonds in my 8mm Gibbs. I don't have the stock finished yet on my 8mm RPM stock so can't start loading for it. What powder are you using and what was your start load?

For the 185 grain Hammer bullet I use 74 grains of 760 and a Rem 9 1/2 M primer The 198 grain Hammer Hunter bullet uses 72 grains of H4350 and the same primer.

Sorry. I don't remember starting loads.

 

[archeratlrg]

For the 185 grain Hammer bullet I use 74 grains of 760 and a Rem 9 1/2 M primer The 198 grain Hammer Hunter bullet uses 72 grains of H4350 and the same primer.

Sorry. I don't remember starting loads.

Thank you,this will get me started. I still need to get back to you on 358 RPM.

 

[archeratlrg]

View attachment 226543
Here is what the case looks like now that the barrel has been bored to 8mm. It fires the Hammer Hunter at 3,054 feet per second. One can never redo the first three shots. They made a 1/4" group! I then fired two more and the group opened to 9/16". By the way when loaded like this one to fit the magazine there is .400" jump to the rifling. That is the only way I work up loads for my hunting rifle.

What action and magazine length Rich?

 

[GL Brandt]

Anyone try necking this case down to 6mm? That'd be a barrel eating beast but also legit awesome…there's no end to monster overbore 22s, 25s, 26, 27 now (with the Nosler), 28, 30, and 33 cal cartridges but for whatever reason there's an actual gap at 6mm. 240 wby is the biggest factory offering (besides the very obscure 244 holland and holland which is exactly what you think it is ) and for wildcatters while I have heard of the 6mm Mach 4 (a 7 rem mag or .264 Winnie necked down) it's very uncommon, they just stop at 6-284 and 6-06. Probably cuz they know better but I don't, dang it!

My brother built a 25 rpm it really a shooter., but the barrel went after 500 rounds.I think it was a bad barrel.

 

[Calvin45]

My brother built a 25 rpm it really a shooter., but the barrel went after 500 rounds.I think it was a bad barrel.

Considering that a .257 weatherby can outlive that I'd say you're right.

But I do need to ask….what exactly entails a rifle barrel having "went"?

Cuz for some folks that's a .25 moa barrel opening up to .75 moa. For others the barrel, ammo, and operator were never capable of that to begin with (I generally fall into the latter category). I feel that when some folks say their 257 wby or 7 stw were burned out in 500 rounds and others say that's all nonsense and they're at 1500 rounds and still hunting successfully it has to be more about individual standards of acceptable accuracy than about differences in individual barrels. That and how they're run of course. Keep shooting any fire breather cartridge when the barrel is too hot to touch and you'll do this to yourself.