Quarter bore fans; opinions wanted, what would you do?

[Calvin45]

Hey all, I have a barrel I want to build with, not now but in the next few years. Originally I was going to go full throttle and pursue the highest velocity possible just for fun, no practicality needed.

It's a 32 inch bartlein .257 1:10 twist very heavy barrel, and is presently chambered in 25-06AI. Throat is in good shape at present.

I was originally going to build either a 25-300 wby, 257 stw, or even a 25-300 RUM off of it, leaning mostly towards the .25-300 wby for a few reasons, Peterson making 300 wby and 6.5-300 wby brass among the greatest reasons but also I already have 257 wby dies for the neck sizing portion of this and 450 ackley dies that with the decapper expander unit removed should do just fine to resize the body. And with the lightweights that the 1;10 twist is limited to I have serious doubts that even out of a 32 inch pipe the RUM capacity would meaningfully outrun the full length wby or stw case but I could be wrong. It's already threaded for a savage action which I have. And if I went full length magnum it'd clean up the existing chamber completely without any need to set back or rethread the beast.

But now I'm second guessing this too…

I already have a 257 wby and a pile of brass for it…and I'm sure that out of a 32 inch barrel the .257 would already be STUPID FAST, perhaps there's not much to be had going bigger than that, again with a 10 twist and the bullets were limited to here. If I could shoot the 130+ grain bullets it would be different. I would have to have the barrel set back and rethreaded I think though based on my studying of case dimensions/chamber prints.

I'm also reluctantly considering just leaving it alone as the 25-06 AI that it is except inexpensive dies for that chambering seem to not exist or be hard to find so that's the downside, I'd also need to obtain brass and fire form it which kinda lessens its appeal regarding longer barrel life if I'm using that life to fire form cases too. But maybe that's a non-issue, I've never actually had to fire form before, no experience yet with builds or wildcats. But I do imagine that a 32 inch .25-06 ai would likely outrun my current 24 inch .257 weatherby, possibly by a bit.

Anyway, what would YOU do if you wanted a .25 cal speed demon on a bit of of a budget with the supplies on hand I've mentioned? Leave it as a .25-06AI, set back and rechamber to .257 weatherby on account of existing supplies and that round being about the practical top end, or just listen to your heart and go flat out with a full length magnum overbore monstrosity to take full advantage of the 32 inch barrel length and see just how fast we can go, barrel life be damned….it is a long enough barrel that a person could easily set it back quite a few inches after the first 500 rounds or so if need be.

Input please, and as always I just like talking about all this stuff with you people so do chime in!

@Fiftydriver you're about the foremost authority on big 25s in my opinion, again IF LIMITED TO A 10 TWIST what route would you suggest?

 

[Calvin45]

Also asking, what kind of velocity difference would one expect going from 24 inches to 32 with a 257 wby, a .25-06ai, or one of the truly big cases wildcats? Again, I know Kirby has actually done it so I'm especially curious about his insight.

@FEENIX I believe you've experimented with .257 wby at different barrel lengths too, correct?

 

[FEENIX]

@FEENIX I believe you've experimented with .257 wby at different barrel lengths too, correct?

Personally, I just had 22", but I shared the info (benchmarked from each other) with ones with longer barrels and different twists. In my initial pressure test, I was pushing the 163 Chinchaga at 2915 FPS with H1000. I have some loaded with Retumbo next.

 

[del2les]

Kinda' went down this path decades ago, but instead of chambering for 257Wby, since back then, I did not like the double radius shoulder and I had a lot of 7mmRM brass on hand, I went with a 25-7mmRM. Similar performance to the 257Wby in same 1/10" twist.

Going with ever larger case capacity than the 257Wby rapidly gets into diminishing returns, as the 257Wby is already well in the overbore category. So, if it were me and I wanted a very good 25 cal speed demon in a 32" tube, I would not go beyond the 257Wby or similar capacity. It should give very good vels from a 32". Though, I never went beyond my current 26" in the 25 cals.

 

[MagnumManiac]

I went through all this back in 2000/1 developing all sorts of wildcats and settled on the 416 Rigby case, 300WSM and 300 Weatherby.
With the WSM & Weatherby case, we were looking for top velocities with the powders available at the time. The Weatherby case was just too large for 25, 26, 27 & 28 with the slowest powder being 7828 and that had just been dropped for importation here, so RE22 was it.
We decided the WSM was perfect and, this turned out to be spot on and we built 25, 26, 27 & 33 to play with. Had 1 guy wanting a 35 so built that too.
The only disappointment was the 33-300WSM, it just couldn't come close to 338WM velocities with anything but the 200g weight.
(I will add that the introduction of RE25 really made these wildcats worthwhile.)

Now to today with our ultra slow powders, you could easily run the 25-300 Weatherby with Retumbo, H50BMG, N570 or other slow powders and have a great performing round.
The 25-300RUM is gonna burn barrels fast, even with H50BMG which is one of the coolest ultra slows available. I am not sure what you want to do with the rifle, but I feel the RUM case is even too voluminous for even 7mm and the powders available.
My other thought is this, now that we have the 6.5-300 Weatherby, and I have one in the works too, it would be very simple to neck it down to 25 and go from there, it's going to outstrip the 257 Weatherby by a good margin and powders today will support it well.
I have been amazed with the velocities I have had with Retumbo in my 257 Weatherby with 110g/115g bullets well above 3500fps and my 270 Weatherby with 150g Partitions above 3500fps too.

Sounds like a great project and I look forward to hearing more.

Cheers.

 

[lancetkenyon]

I had a 28" 1:10" .25-06AI that would push a 100 TTSX @ 3600fps. 32" should get you to 3700fps+/-.

 

[Calvin45]

I went through all this back in 2000/1 developing all sorts of wildcats and settled on the 416 Rigby case, 300WSM and 300 Weatherby.
With the WSM & Weatherby case, we were looking for top velocities with the powders available at the time. The Weatherby case was just too large for 25, 26, 27 & 28 with the slowest powder being 7828 and that had just been dropped for importation here, so RE22 was it.
We decided the WSM was perfect and, this turned out to be spot on and we built 25, 26, 27 & 33 to play with. Had 1 guy wanting a 35 so built that too.
The only disappointment was the 33-300WSM, it just couldn't come close to 338WM velocities with anything but the 200g weight.
(I will add that the introduction of RE25 really made these wildcats worthwhile.)

Now to today with our ultra slow powders, you could easily run the 25-300 Weatherby with Retumbo, H50BMG, N570 or other slow powders and have a great performing round.
The 25-300RUM is gonna burn barrels fast, even with H50BMG which is one of the coolest ultra slows available. I am not sure what you want to do with the rifle, but I feel the RUM case is even too voluminous for even 7mm and the powders available.
My other thought is this, now that we have the 6.5-300 Weatherby, and I have one in the works too, it would be very simple to neck it down to 25 and go from there, it's going to outstrip the 257 Weatherby by a good margin and powders today will support it well.
I have been amazed with the velocities I have had with Retumbo in my 257 Weatherby with 110g/115g bullets well above 3500fps and my 270 Weatherby with 150g Partitions above 3500fps too.

Sounds like a great project and I look forward to hearing more.

Cheers.

That's what I'm thinking. Almost certainly gonna go with the .25-300 wby for all those reasons. At present I have saved some 75 grain hammer hunters, 90 grain absolute hammers, 100 grain Nosler ballistic tips, and 115 Bergers.

I've gotten the 75 hammer (HBN treated as well, as are the bores of my rifles) to a chronographed 4150 feet per second with mild pressure signs out of a 24 inch weathebry vanguard .257 wby. Norma brass and rl17. My burning (and totally ludicrous, unnecessary, pointless etc…) desire if I go this route will be to see how close to an honest 5000 feet per second a 25-300 wby with a 32 inch pipe and a hex boron nitrided bullet and bore could crank a 75 grainer haha.


I also really do beleive there are some actual benefits to both the weatherby curvy shoulder, long neck, and generous freebore, especially in really really overbore designs.

This is what my heart wants to do, my dang brain keeps putting its .02 in and making me second guess it

 

[M1A1ABRAMS]

That's what I'm thinking. Almost certainly gonna go with the .25-300 wby for all those reasons. At present I have saved some 75 grain hammer hunters, 90 grain absolute hammers, 100 grain Nosler ballistic tips, and 115 Bergers.

I've gotten the 75 hammer (HBN treated as well, as are the bores of my rifles) to a chronographed 4150 feet per second with mild pressure signs out of a 24 inch weathebry vanguard .257 wby. Norma brass and rl17. My burning (and totally ludicrous, unnecessary, pointless etc…) desire if I go this route will be to see how close to an honest 5000 feet per second a 25-300 wby with a 32 inch pipe and a hex boron nitrided bullet and bore could crank a 75 grainer haha.


I also really do beleive there are some actual benefits to both the weatherby curvy shoulder, long neck, and generous freebore, especially in really really overbore designs.

This is what my heart wants to do, my dang brain keeps putting its .02 in and making me second guess it

You could just give me your barrel and save yourself a lot of frustration and money. I will run it as a AI.

 

[Phil Rizzo]

Get a 25 Sherman long action reamer and clean out your AI chamber.
There is 280 AI Peterson brass available.
Capacity between 71-72grs H2O

Would you happen to know your AI capacity?

 

[MagnumManiac]

So, if it were me and I wanted a very good 25 cal speed demon in a 32" tube, I would not go beyond the 257Wby or similar capacity. It should give very good vels from a 32". Though, I never went beyond my current 26" in the 25 cals.

This was true decades ago, but with slower powders being available all the time, overbore really isn't a thing anymore. It was true when 4350 was the slowest powder available when the term was coined, but is no longer applicable because more velocity can be had than 4350 achieves…

Cheers.

 

[DUCKMAN11]

Hey all, I have a barrel I want to build with, not now but in the next few years. Originally I was going to go full throttle and pursue the highest velocity possible just for fun, no practicality needed.

It's a 32 inch bartlein .257 1:10 twist very heavy barrel, and is presently chambered in 25-06AI. Throat is in good shape at present.

I was originally going to build either a 25-300 wby, 257 stw, or even a 25-300 RUM off of it, leaning mostly towards the .25-300 wby for a few reasons, Peterson making 300 wby and 6.5-300 wby brass among the greatest reasons but also I already have 257 wby dies for the neck sizing portion of this and 450 ackley dies that with the decapper expander unit removed should do just fine to resize the body. And with the lightweights that the 1;10 twist is limited to I have serious doubts that even out of a 32 inch pipe the RUM capacity would meaningfully outrun the full length wby or stw case but I could be wrong. It's already threaded for a savage action which I have. And if I went full length magnum it'd clean up the existing chamber completely without any need to set back or rethread the beast.

But now I'm second guessing this too…

I already have a 257 wby and a pile of brass for it…and I'm sure that out of a 32 inch barrel the .257 would already be STUPID FAST, perhaps there's not much to be had going bigger than that, again with a 10 twist and the bullets were limited to here. If I could shoot the 130+ grain bullets it would be different. I would have to have the barrel set back and rethreaded I think though based on my studying of case dimensions/chamber prints.

I'm also reluctantly considering just leaving it alone as the 25-06 AI that it is except inexpensive dies for that chambering seem to not exist or be hard to find so that's the downside, I'd also need to obtain brass and fire form it which kinda lessens its appeal regarding longer barrel life if I'm using that life to fire form cases too. But maybe that's a non-issue, I've never actually had to fire form before, no experience yet with builds or wildcats. But I do imagine that a 32 inch .25-06 ai would likely outrun my current 24 inch .257 weatherby, possibly by a bit.

Anyway, what would YOU do if you wanted a .25 cal speed demon on a bit of of a budget with the supplies on hand I've mentioned? Leave it as a .25-06AI, set back and rechamber to .257 weatherby on account of existing supplies and that round being about the practical top end, or just listen to your heart and go flat out with a full length magnum overbore monstrosity to take full advantage of the 32 inch barrel length and see just how fast we can go, barrel life be damned….it is a long enough barrel that a person could easily set it back quite a few inches after the first 500 rounds or so if need be.

Input please, and as always I just like talking about all this stuff with you people so do chime in!

@Fiftydriver you're about the foremost authority on big 25s in my opinion, again IF LIMITED TO A 10 TWIST what route would you suggest?

There is a difference between fast and really fast. Fast for me is 3600fps really fast is 3800fps+.

The window for the law of diminishing returns gets smaller and smaller with bore size as you know. And as I've said before I'm personally a gain per grain kinda guy. I refuse to burn 10 more grains of powder to get 100fps more velocity. So for me that rules out 25stw and the like. I also am not a huge fan of belted magnums. I don't hate them but there are better options out there to build a wildcat out of. If I were so inclined to build a cartridge in that 80+ grains of powder capacity I'd likely use a 300prc lapua case instead of anything weatherby.

I think short and fat is the way to go in 257cal personally! I'd look at doing a 25SS or 25max or 25wsm or 25mega. With that long tube you could definitely get a full powder burn with something in the n565 range with a 70-75gr load and a 90gr hammer.

You could clean up the existing chamber with a 25 sherman reamer after setting it back a few threads and get 3800fps pretty easy with a 80-90gr mono.

And how fast are you trying to go? Are you just trying to go fast or are you looking for any type of consistency? Even in a 10tw you run a risk of over spinning 257cal varmint style light bullets up around 4300fps or 310k rpms. It's unlikely but definitely possible with any light cup and core 257cal varmint bullet.

Kirby's 25stalker is probably the biggest column of powder in a "for sale" wildcat 257cal cartridge that i can think of. I'm not familiar with it but I do know it's big.

Edit....

I just read you are thinking of trying to push a 75gr hammer to 5000fps.

 

[Calvin45]

There is a difference between fast and really fast. Fast for me is 3600fps really fast is 3800fps+.

The window for the law of diminishing returns gets smaller and smaller with bore size as you know. And as I've said before I'm personally a gain per grain kinda guy. I refuse to burn 10 more grains of powder to get 100fps more velocity. So for me that rules out 25stw and the like. I also am not a huge fan of belted magnums. I don't hate them but there are better options out there to build a wildcat out of. If I were so inclined to build a cartridge in that 80+ grains of powder capacity I'd likely use a 300prc lapua case instead of anything weatherby.

I think short and fat is the way to go in 257cal personally! I'd look at doing a 25SS or 25max or 25wsm or 25mega. With that long tube you could definitely get a full powder burn with something in the n565 range with a 70-75gr load and a 90gr hammer.

You could clean up the existing chamber with a 25 sherman reamer after setting it back a few threads and get 3800fps pretty easy with a 80-90gr mono.

And how fast are you trying to go? Are you just trying to go fast or are you looking for any type of consistency? Even in a 10tw you run a risk of over spinning 257cal varmint style light bullets up around 4300fps or 310k rpms. It's unlikely but definitely possible with any light cup and core 257cal varmint bullet.

Kirby's 25stalker is probably the biggest column of powder in a "for sale" wildcat 257cal cartridge that i can think of. I'm not familiar with it but I do know it's big.

Kirby's stalker is a beast but is on the .58 cal bolt face of the .338 lapua and Norma magnums so it's right out for me. The 257 Allen magnum is basically a .25-300 rum improved and is even bigger than the stalker but notably less efficient, if I recall even Kirby decided it was too much of a good thing. If I'm mistaken I hope he chimes in!

I have actually thought about the .300 prc case but there's just so many reasons it'd be a pest as well! And as for the cartridge geometry…

Perhaps I'm old fashioned but I certainly got no problem with the "leggy and curvy" shape of the weatherby, even if "short and fat is where it's at!" Nowadays

 

[DUCKMAN11]

Kirby's stalker is a beast but is on the .58 cal bolt face of the .338 lapua and Norma magnums so it's right out for me. The 257 Allen magnum is basically a .25-300 rum improved and is even bigger than the stalker but notably less efficient, if I recall even Kirby decided it was too much of a good thing. If I'm mistaken I hope he chimes in!

I have actually thought about the .300 prc case but there's just so many reasons it'd be a pest as well! And as for the cartridge geometry…

Perhaps I'm old fashioned but I certainly got no problem with the "leggy and curvy" shape of the weatherby, even if "short and fat is where it's at!" Nowadays

I hear ya. And I'm not just thinking about the chamber but the dies as well, also quality brass. 300prc bushings dies are everywhere. I've never experienced the prc clickers like everyone else.

You could neck down a 26nosler or maybe even 28nosler which would be similar to 257stw

 

[Calvin45]

I hear ya. And I'm not just thinking about the chamber but the dies as well, also quality brass. 300prc bushings dies are everywhere. I've never experienced the prc clickers like everyone else.

You could neck down a 26nosler or maybe even 28nosler which would be similar to 257stw

I didn't even think of that but now it's on the brain too dang it. My buddy even has a 28 Nosler…perhaps some of his brass needs to be donated for "science"