Thoughts: 6.5 RPM, 270 Win, or 280AI for re-barrel?

I think I'd do a 6.5 PRC or 6.5x284 before I went with the RPM. The only issue I could see with an 8 twist 270 is could you seat the bullets out far enough to keep the base out of the powder charge.
My experience (all but limited) with 243 Win and 6mm Creed tells me it's harder to tune if that's the case.

I have to read up more on the rpm but from what I've seen I like the round, but brass and ammo will probably be harder to find and more money then the 280ai. I would go 280ai mostly I like the 280 and I'm a Ackley fan. If going with a 6.5 I've been really liking my 6.5 prc, but the 6.5-284 is really good and uses the rim size you are looking at.

When I go to the sporting goods stores Im seeing 280AI on the shelves pretty frequently now. I don't think you'll have any problem getting good brass and you wont need to fireform 30-06 brass.

My main problem with the 6.5 RPM is that it's from Weatherby. Im not a fan of single source components and during the pandemic Weatherby ammo was going for about 100 dollars a box around here.

Have you looked at the 6.8 Western?

.280 AI hands down.

I’m at 6.5 fanboy at heart but I wouldn’t choose the RPM I just don’t see it staying around for long oh sure Weatherby might continue to carry it but it will be Expensive to shoot if it had to be a 6.5 (what I would do) I’d make a 6.5-06 and be perfectly happy with it easy to form brass great bullet selection plenty of horsepower that’s just me ymmv

I'm a fan of 7mm rounds so I'd go with the 280AI for several reasons. First there are soany good bullets available in that diameter for reloading purposes. Near magnum performance from a standard case. Non belted, in a pinch non A I brass, factory 280, can be used and fireformed at t h e same time with little loss of velocity or accuracy and the round will give excellent performance with the entire line of 7mm bullets. Thec270 though better heavier projectiles are available there isn't as many so your choices areore limited and eont give the same level of velocity and bullet energy as the 280 AI.

As for the Weatherby cartridge, you are limited in case availability, sure the whole line of 6.5 bullets gives lots of choices, but anything that I've seen in Weatherby has considerably higher cost.

With an aftermarket barrel and handloads 270 will do everything the 280 will do. But if you're going to that much trouble I'd go 280AI too. Real world gains in performance are tiny. But its just easier to make it happen.

Twenty years ago 270 ammo was a lot easier to find if limited to factory loads. But for better or worse 270 is slipping in popularity at the same time 280 seems to be slightly surging. In the future 280 ammo and brass may well be easier to find

Anchorite said:

My 20 year old M70 270 sure likes the looks of the newer heavies, so I am thinking of sending it to Pac Nor for a new pipe.

I like the idea of a 1x8 over the factory twist for the heavier .277 offerings now, but as I sit this morning with my coffee my mind wanders to two alternate choices, specifically the 6.5 RPM or the 280AI?

The RPM appears to be the answer to the question never really asked, and how about brass availability and feeding? The heavier .277 projectiles sure make any advantage the 6.5 may have on paper appear less than stellar, or am I missing something else?

The 280AI probably only shines with heavier bullets and quality (read Lapua) 30.06 brass necked down.

None of these options presents difficulty in loading, except maybe the AI on fire forming.
I’m not interested in the 6.5CM really either, unless I am just completely missing something. I also have zero desire to go magnum, having had over the years a few Wbys and sold/traded off and kept my ‘ol faithful M70 stick.
I’ve killed a lot of deer and hogs over the years, I’ll probably not ever get out west, but if I do, seems any of these will be fine for antelope, sheep or elk.
Thoughts? Opinions? Criticisms?

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I've never worked with an RPM, but that length in 284 case might give you issues feeding from a gun design to run more tapered cases, also might not.

But if we're looking at pure performance, capacity is king. I don't remember how long the Winchester actions are, But if you've got 3.5-3.6 you could probably put some pretty serious zing on a 153Atip..... Again, whether or not that offers you any real world advantage.... It's up to you to decide.

The 280 AI will definitely handle heavier bullets than the 270 will even in AI form.
Again, my experience with a standard 270 is that I had a hard time pushing 150s to 2,900 without pressure signs. I would expect the newer super pointy bullets to have significantly less bearing surface then the older 150 hunting bullets I have experience with, which might negate some of the issue.
Best loads I've got for a 24-in 270 or 150 around 2850-2900, Best loads I've got for a 280 AI or 162s at 3050-3100from a 26-in. All done on Hornady 280ai brass.
This is actually faster than many of my 24" 7mag loads.

Out of curiosity, I also shot some 190 grain atips out of my 1-9 in twist Ridgeline..... shot pretty well at 100. Don't know how much bc loss there is or if they will go wonky at longer range, those were my last 3.


In terms of hunting practicality, and considering what you already have, id honestly suggest getting a .270AI barrel done with a 1-8 twist....IF your happy with your .270 now, the additional speed and bullet weight range is all at the cost of another die set ( unless you're using a Hornady set, then all you need is the 270 AI sizing die), and a barrel.

.280 AI definitely. More weights and types of bullets available plus better ballistics. I must add that .270 is my least-favorite cartridge.

Not a fan of rebated rims. They are just… WEIRD! The 280AI is nice. My choice would be a 6.5-284 in a long action. Can throat it & run run the very heaviest 150gr+, with OVER .700 BC now, and will easily reach out past a mile. But that’s me.

What is your plan with this? It’s main purpose. I’m a for fun target shooter, hence why I would go 6.5-284. I like to have the ability for mile performance, but I’m not worrying about it taking game at extreme distance, & I can do without any extra recoil, powder usage, etc.

Another I’d choose over the RPM is the
6.5-06AI. My good friend in Arizona had his Winchester 70 rebuilt into an 6.5-06AI. He actually doesn’t shoot it much because he got bored of it. He enjoys working up loads for his rifles. He loaded the first rounds for it & it cloverleafed.. FIRST time out. Tried other bullets, other powders. Every group a cloverleaf! No fun for him, LOL. But.. he’s a strange bird anyway Most would love that performance.

So, what is your intention with this one?

6.5 PRC seems to fit your itch pretty well but I'm always going to have a fondness for the 270 Winchester.

Have you considered a standard (non AI) 280? The AI version certainly has it's advantages, and many fans, but the original is also an excellent all-around cartridge.

First I've ever heard of the 6.5 RPM, I had to go read up on it. Weatherby has had a long tradition of supporting their cartridges, but none of them have ever become what I would call ecconomical. So assuming they stay in business brass will probably be available for a good while to come. The one that plucks my heart strings is the 280 AI

David Hoback said:

Not a fan of rebated rims. They are just… WEIRD! The 280AI is nice. My choice would be a 6.5-284 in a long action. Can throat it & run run the very heaviest 150gr+, with OVER .700 BC now, and will easily reach out past a mile. But that’s me.

What is your plan with this? It’s main purpose. I’m a for fun target shooter, hence why I would go 6.5-284. I like to have the ability for Mike performance, but I’m not worrying about it taking game at extreme distance, & I can do without any extra recoil, powder usage, etc.

Another I’d choose over the RPM is the
6.5-06AI. My good friend in Arizona had his Winchester 70 rebuilt into an 6.5-06AI. He actually doesn’t shoot it much because he got bored of it. He enjoys working up loads for his rifles. He loaded the first rounds for it & it cloverleafed.. FIRST time out. Tried other bullets, other powders. Every group a cloverleaf! No fun for him, LOL. But.. he’s a strange bird anyway Most would love that performance.

So, what is your intention with this one?

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The 6.5-284 IS rebated, the RPM is just lengthen to turn it into a true long action cartridge....
I didn't think about the 6.5 -06 but that would be a good option too.

LoonWulf said:

The 6.5-284 IS rebated, the RPM is just lengthen to turn it into a true long action cartridge....
I didn't think about the 6.5 -06 but that would be a good option too.

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I never said it wasn’t. Simply stated rebated rims look weird…which they do. But, can’t argue with the 6.5-284’s performance over the last couple decade. Hence it being my choice. I was responding to the OP having two choices of the like.

David Hoback said:

I never said it wasn’t. Simply stated rebated rims look weird…which they do. But, can’t argue with the 6.5-284’s performance over the last couple decade. Hence it being my choice. I was responding to the OP having two choices of the like.

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Ahhhh got it!

Performance is performance.

I'm a practical kind of guy. You're already deeply invested in .270. You have a great deal of experience with the round. It works for you, and you have only a new interest in stretching it's legs. Get the .270 barrel with a faster twist. It should still do well with 140 cup and cores for shorter range deer work. I'd actually download it a few grains as I do with my .280 Rem as I prefer eating venison to spreading it about the woods. You'll get the most out of some of the more exotic heavy bullet offerings as well. Brass will be abundant for the forseeable future. You'd be all set.

The .280 AI has some cool factor, but with heavies I'm not sure you'd be gaining much over the parent round .280 Rem. If larger Western game is in your menu, it does up the ante just a bit, getting closer to the vaunted 7RM in terms of raw kinetic energy downrange. That said, I don't think a critter will know the difference when you smack him with a 175 partition. The 28s do gain a bit in terms of bullet mass and selection for what it's worth.

Anchorite said:

My 20 year old M70 270 sure likes the looks of the newer heavies, so I am thinking of sending it to Pac Nor for a new pipe.

I like the idea of a 1x8 over the factory twist for the heavier .277 offerings now, but as I sit this morning with my coffee my mind wanders to two alternate choices, specifically the 6.5 RPM or the 280AI?

The RPM appears to be the answer to the question never really asked, and how about brass availability and feeding? The heavier .277 projectiles sure make any advantage the 6.5 may have on paper appear less than stellar, or am I missing something else?

The 280AI probably only shines with heavier bullets and quality (read Lapua) 30.06 brass necked down.

None of these options presents difficulty in loading, except maybe the AI on fire forming.
I’m not interested in the 6.5CM really either, unless I am just completely missing something. I also have zero desire to go magnum, having had over the years a few Wbys and sold/traded off and kept my ‘ol faithful M70 stick.
I’ve killed a lot of deer and hogs over the years, I’ll probably not ever get out west, but if I do, seems any of these will be fine for antelope, sheep or elk.
Thoughts? Opinions? Criticisms?

Click to expand...

I have a 8.5 twist .270 barrel on order already if that lets you know my recommendation.

Anchorite said:

My 20 year old M70 270 sure likes the looks of the newer heavies, so I am thinking of sending it to Pac Nor for a new pipe.

I like the idea of a 1x8 over the factory twist for the heavier .277 offerings now, but as I sit this morning with my coffee my mind wanders to two alternate choices, specifically the 6.5 RPM or the 280AI?

The RPM appears to be the answer to the question never really asked, and how about brass availability and feeding? The heavier .277 projectiles sure make any advantage the 6.5 may have on paper appear less than stellar, or am I missing something else?

The 280AI probably only shines with heavier bullets and quality (read Lapua) 30.06 brass necked down.

None of these options presents difficulty in loading, except maybe the AI on fire forming.
I’m not interested in the 6.5CM really either, unless I am just completely missing something. I also have zero desire to go magnum, having had over the years a few Wbys and sold/traded off and kept my ‘ol faithful M70 stick.
I’ve killed a lot of deer and hogs over the years, I’ll probably not ever get out west, but if I do, seems any of these will be fine for antelope, sheep or elk.
Thoughts? Opinions? Criticisms?

Click to expand...

Weatherby brought out the RPM to take advantage of the smaller 6 lug Mark V action. I have been thinking about getting the nice little 6 lug to go along with my Weathermark in 257 Weatherby Magnum. In the realm of North American hunting rifles, a Mark V in 6.5 Weatherby RPM will be among the very best, ballistically, as well as precision.
That being said If I understand you are thinking about rebarreling a model 70. In that case I would go back with 270 Winchester and shoot 140 gr. Accubonds or 150 gr. Partitions. Either of those will hold in the wind just fine for hunting. In my mind, if you cant kill it with a 140 gr. Accubond stoked from a good load of 4831 then time to graduate from 27 Cal.
My next step up would be something like 180 gr solid from a 300 Win Mag.

280ai for sure, but I’m very biased.