The 6.8 WCF, or .270 AI, w/ 1:8 Twist Rate Rifling. (or .280 AI)

[Garandimal]

- The 6.8 WCF, or .270 AI, w/ 1:8 Twist Rate Rifling -
(or .280 AI)
​

They have to call it something - whether std. or AI, if they are goin' to up the twist rate to 1:8.

While am both a fan of the heavier-for-caliber .270 WCF(150 gr.) and .280 AI(160 gr.), and consider'em ballistic twins...

... they both suffer, abit from different reasons, when faced with the prospect of heavy, 0.310 SD hunting bullets and 24" Bbls..


The .280 Rem., even in its AI iteration, lacks the case volume to drive the .284"/175 gr.(SD 0.310) bullet at an optimal velocity for ~ 300 yrd. MPBR(+/-3") shooting (~ 2900 fps at the muzzle).

The .270 WCF could just about do it (and certainly the AI variant could), stuffed with RL-26, w/ the .277"/165 gr.(SD 0.307) bullet, but for the OEM 1:10 rifling twist rate that fails to stabilize it.

Which leads to the horns of a dilemma.

This ole 22" Bbl'ed M700 .270 WCF.

​

1. Been replaced in the field by the soulless game-scythe FN/Winchester EW/SS .270 WCF, also w/ a handy 22" Bbl.

2. Is now at best a back-up - but more accurately a Freezer-Queen.

3. Been the target of countless re-bore/chamber/Bbl'in' schemes.

4. Always wanted it in a 24" Bbl.


So, given the current and building wave of Heavy .277" (165-175 gr.) bullets, especially in the ELD variety (though a 165 gr. Partition or Grand Slam would also be sweet, but as yet non-existent)...

Would re-Bbl'in' with a 24"/6.8 WCF(or .270 AI) with a 1:8 twist, be a worthwhile and timely thing to do?

Or, just hop on the well-established .280 AI bus, that doesn't quite hit the marks, academically, but from an engineering standpoint, will definitely do the work.

As stated, there is little to gain in the .270 WCF/.280 Rem.,150/160 gr. bullet wt., respectively.

This is about the heavy woods/LR 165-175 gr. offerings.

Recoil for both would be in the medium .30-06 range, but it's a heavy walnut stocked rifle w/ pad, and would probably go w/ a heavier contour on the 24" Bbl as well, so say a 9 lb+ scoped rifle.

TIA




GR

 

[LoonWulf]

I'd do either the .270 or the Gibbs, but I already own a .280AI.

With my 280s 26" I can drive 160 class to 3000fps using rl-23. Rl-25 ran out of case before hitting pressure, but 26 being less fluffy might make the difference with both the .280ai or the .270ai.

 

[BreechFace]

280ai, Loading long and extending the magazine length with a Wyatt Outdoor Magazine Box as much as possible with the 280ai, I think one could get some gains with a powder such as RL-25.

A cavity back hunting bullet in .284 would be nice for such and adventure.

Is any of this going to matter to an Elk? No, 160 NP’s at 3,000 FPS is more than adequate, but adequate is not why many reload.

 

[Armorer 101]

A very important question, are you going to do the deed or hire it done. It makes a world of difference. You can build a jewel for a bit, but if hired the check book comes into play quickly. I build my own, have a full shop, but do not sell.

Were it me I would build a 26” 280 AI with the 1-8. I would use the old 700 and make it trued and squared, cut threads .010 over, with 100% lug contact, if not already done, then have Accurate Plating hard chrome it in satin, put a LW air gauge SS barrel on it threaded .010 over with a 1/4” lug and a single set trigger. Based on the web site Jard makes a single set for a 700 at under $200.

Check w a dealer about buying a LW barrel for you, their price is much better. I use a magnum sporter contour and put a recessed crown on them myself. R powders are good with the 280 AI as is VN, just a bit more pricey.

 

[Garandimal]

I'd do either the .270 or the Gibbs, but I already own a .280AI.

With my 280s 26" I can drive 160 class to 3000fps using rl-23. Rl-25 ran out of case before hitting pressure, but 26 being less fluffy might make the difference with both the .280ai or the .270ai.

The .270 WCF - will already hit that 3K fps. mark with the ballistic twin 150 gr. and RL-26 powder.

So this is about thinkin' outside that box.

165-175 gr. bullets at 2900 fps., with ~ 58-60 grains (plus a couple for AI) of RL-26 powder and a 24" Bbl.


Frontier - for a std. '06 cartridge.




GR

 

[Garandimal]

A very important question, are you going to do the deed or hire it done. It makes a world of difference. You can build a jewel for a bit, but if hired the check book comes into play quickly. I build my own, have a full shop, but do not sell.

Were it me I would build a 26” 280 AI with the 1-8. I would use the old 700 and make it trued and squared, cut threads .010 over, with 100% lug contact, if not already done, then have Accurate Plating hard chrome it in satin, put a LW air gauge SS barrel on it threaded .010 over with a 1/4” lug and a single set trigger. Based on the web site Jard makes a single set for a 700 at under $200.

Check w a dealer about buying a LW barrel for you, their price is much better. I use a magnum sporter contour and put a recessed crown on them myself. R powders are good with the 280 AI as is VN, just a bit more pricey.

It's been glass bedded (by me), and has the OEM trigger which is an old icicle friend.

Shoots well under MOA w/ careful handloads, and a little over w/ most factory fodder.

Not a smith - so am just lookin' at a Bbl. change, 24", probably stainless, probably heavier than the OEM sporter contour.

A heavy hunting rifle.


Yet another scheme...




GR

 

[BreechFace]

The .270 WCF - will already hit that 3K fps. mark with the ballistic twin 150 gr. and RL-26 powder.

So this is about thinkin' outside that box.

165-175 gr. bullets at 2900 fps., with ~ 58-60 grains (plus a couple for AI) of RL-26 powder and a 24" Bbl.


Frontier - for a std. '06 cartridge.

GR

A ballistic twin the 270 would be IF one can hit 3,000fps in a 150gr Nosler Partition as compared to a 160gr Nosler Partition at 3,000fps. I'm not up on 270 ballistics, but that seems warm unless talking a longerish barrel. The 280ai can barely do it with more case capacity, I believe the 270Win has just a small amount less case capacity than the standard 280Rem. I'm not saying it can't be done, just discussing here.

280AI
.284 160gr NP @3,000fps, BC=.475, SD=.283 (6.25% more mass)


270 Win
.277 150gr NP @3,000fps???, BC=.465, SD=.279 (6.25% less mass)

 

[BreechFace]

@Garandimal your 270Win is a fine cartridge, its been getting elk hunting done around my parts for a very long time; but as a gun nut I can understand your predicament.

 

[LoonWulf]

The .270 WCF - will already hit that 3K fps. mark with the ballistic twin 150 gr. and RL-26 powder.

So this is about thinkin' outside that box.

165-175 gr. bullets at 2900 fps., with ~ 58-60 grains (plus a couple for AI) of RL-26 powder and a 24" Bbl.


Frontier - for a std. '06 cartridge.




GR

I just went looking for rl-26 again, so far still no luck. If you can find it, and don't have huge temp swings it should be the beezneez.

 

[BreechFace]

Took some time to review some 270 Win ballistics and loads, haven't looked into them in a while.

So, you've gained 100fps over the fastest previous load for the 150gr 270Win load with RL-26?

That's impressive to say the least for 270Win and would put it equal to the 280ai with a 160gr with more case capacity.

 

[Garandimal]

Took some time to review some 270 Win ballistics and loads, haven't looked into them in a while.

So, you've gained 100fps over the fastest previous load for the 150gr 270Win load with RL-26?

That's impressive to say the least for 270Win and would put it equal to the 280ai with a 160gr with more case capacity.

NOTE: Patriot Revere is a 24" Bbl.

​

Alliant Powder
also has a .270 Win. load for the 150 gr. NP: 60.8 grns RL-26 for 3022 fps (24" Bbl./COAL 3.23").

Now, the work is to get the 165 gr. to shoot like that (2950 fps+).




GR

 

[BreechFace]

@Garandimal thats impressive

 

[Garandimal]

The 160 gr. .277" NP may also be an option, leaving the rifle as is.

Reports of 3,000 fps from a 22" Bbl. with the 150 gr. NP's, using RL-26?

...may yield 2,900 fps with the 160 gr.

... and that's an on-the-shelf bullet.


Am concerned w/ pushing the Speer GS past 2,800 fps - although that mild and inexpensive load still produces 1,500 ft-lbs at 300 yards.


Have contacted PAC-NOR RE: a 24"/R5/1:8 twist/.270 WCF Bbl.




GR

 

[old heeler]

NOTE: Patriot Revere is a 24" Bbl.
View attachment 955108
​

Alliant Powder
also has a .270 Win. load for the 150 gr. NP: 60.8 grns RL-26 for 3022 fps (24" Bbl./COAL 3.23").

Now, the work is to get the 165 gr. to shoot like that (2950 fps+).




GR

I read that article in Handloader and pretty interesting.

https://www.handloadermagazine.com/270-winchester-0

 

[Garandimal]

I read that article in Handloader and pretty interesting.

https://www.handloadermagazine.com/270-winchester-0

I saw that, thanks.


Am getting concerned w/ the over-pressure issues, mainly primer pockets, RE: these heavy RL-26 loads.

​

If they show no "conventional" signs of pressure, save Case Head Expansion/Primer Pockets?

Then how does that happen?

My guess is that it is creating a very hot, but slowly developing, heat bubble.

And this is softening(elastic) the case heads.


This hypothesis is also supported by the reports that these heavy RL-26 loads are insensitive to Bbl length differences between 22" and 24".

A very large, hot, persistent bubble, with little reduction w/r/t volume increases due to bullet travel.


Which then has me also thinking about Throat Erosion.




GR

 

[LoonWulf]

I saw that, thanks.


Am getting concerned w/ the over-pressure issues, mainly primer pockets, RE: these heavy RL-26 loads.

​

If they show no "conventional" signs of pressure, save Case Head Expansion/Primer Pockets?

Then how does that happen?

My guess is that it is creating a very hot, but slowly developing, heat bubble.

And this is softening(elastic) the case heads.


This hypothesis is also supported by the reports that these heavy RL-26 loads are insensitive to Bbl length differences between 22" and 24".

A very large, hot, persistent bubble, with little reduction w/r/t volume increases due to bullet travel.


Which then has me also thinking about Throat Erosion.




GR

That's part of the penalty for playing at the top of the ladder. Brass and barrels quickly become consumable items.
With RL-23 I'm running above book max for rl-22 in my 280AI, I haven't seen any critical pocket or case head expansion with Hornady, Nosler, or Winchester brass. Switch to Federal and I get a 100fps jump in velocity, flat primers, and loose pockets in 2 shots (noticeable case volume difference). That's telling me that my loads are right at top end, and I'm GOING to ware my equipment out sooner rather than later....even tho the other brass shows no major issues.

RL-26 probably holds pressure longer, which is expect to cause even more ware on the barrel at least.



Nother thought is that while RL-26 isn't horribly temp sensitive (from what I've read) if your temps swings are large enough, you could probably go from ok to dangerous if loads were worked up near the bottom of the temperature range.

Again part and parcel of playing at the top end.

 

[old heeler]

I saw that, thanks.


Am getting concerned w/ the over-pressure issues, mainly primer pockets, RE: these heavy RL-26 loads.

​

If they show no "conventional" signs of pressure, save Case Head Expansion/Primer Pockets?

Then how does that happen?

My guess is that it is creating a very hot, but slowly developing, heat bubble.

And this is softening(elastic) the case heads.


This hypothesis is also supported by the reports that these heavy RL-26 loads are insensitive to Bbl length differences between 22" and 24".

I read article and my 270 1/10 twist Lilja barrel @ 24 1/2" and it long throated on Rem action.


A very large, hot, persistent bubble, with little reduction w/r/t volume increases due to bullet travel.


Which then has me also thinking about Throat Erosion.




GR

 

[Garandimal]

That's part of the penalty for playing at the top of the ladder. Brass and barrels quickly become consumable items.
With RL-23 I'm running above book max for rl-22 in my 280AI, I haven't seen any critical pocket or case head expansion with Hornady, Nosler, or Winchester brass. Switch to Federal and I get a 100fps jump in velocity, flat primers, and loose pockets in 2 shots (noticeable case volume difference). That's telling me that my loads are right at top end, and I'm GOING to ware my equipment out sooner rather than later....even tho the other brass shows no major issues.

RL-26 probably holds pressure longer, which is expect to cause even more ware on the barrel at least.



Nother thought is that while RL-26 isn't horribly temp sensitive (from what I've read) if your temps swings are large enough, you could probably go from ok to dangerous if loads were worked up near the bottom of the temperature range.

Again part and parcel of playing at the top end.

PAC-NOR - said for an original contour (no re-bedding) 24" Bbl./stainless/R5/1:8 Twist/.270 Win., Installed/action trued...

... $605.

So, while pondering that (or a new Patriot Vortex Scoped Combo in .30-06 SPG):

Have several .270 WCF/22" Bbl./1:10 Twist loads that are interesting:

1. Speer Grand Slam(HC) 150 gr.
H-4831sc or RL-26.
~2900 fps.

This would push my IMR-4831/~2800 fps. woods load from 300 yds., out to a 350 yd. Western load. (But I don't know if the bullet will take the extra stress on a 25 yard hit.)

2. Nosler Partition 160 gr.
H-4831sc or RL-26.
~2850 fps.

This would push the envelope to 400 yards, plus be more reliable in the woods when "the food chain" may be in question.

3. Barnes TSX 140 gr.
IMR-4831
~ 2950 fps

This would be a good 350 yd. Western load that would also be very reliable in the woods. BERGER Stability Calculator says it is marginally stable at that velocity. (SG=1.40 <1.5)
Have a pile of this Custom loaded (Pierce Precision/Ted Nugent) that runs ~ 2890 fps (SG=1.39 <1.5) but have yet to shoot any at 300+ to test it.

If the GS 150's hold up in close, and the Custom TSX 140's don't scatter and keyhole at 350...?

Might just stick w/ the H-4831sc GS and Custom TSX load and call it a day.


And the current "Extreme" H-4831 Aussie powder is supposed to totally insensitive by temp.

Not really a problem between the South and West... but one never knows where the next hunt may be.

So IMR, at these high pressures, will get a pass.




GR

 

[LoonWulf]

I like the bullet choices, the GS USED to be a really tough bullet, not sure what current production looks like, but the others should both do fine from muzzle burn to 400ish yds when launched at their respective velocities.


You might also take a look at H1000, and 7977 if there's any available locally. Ive GOT some 7977, but no easy access to a .270 anymore. I was gonna try it in my .280AI (and I still can to see how it compares to other stuff), but I bought another 3lbs of RL-23 and am going to continue buying that as I can afford it, so haven't had the impetus to mess with 7977 in the AI yet.
Actually all three of those are supposed to be temperature insensitive.

And that's a pretty good price for a new barrel, installation, AND action work! Think Shaw charged me 350ish for just barrel work last time I sent a gun in and 500ish for the one I had them do action work on.

 

[Garandimal]

I like the bullet choices, the GS USED to be a really tough bullet, not sure what current production looks like, but the others should both do fine from muzzle burn to 400ish yds when launched at their respective velocities.


You might also take a look at H1000, and 7977 if there's any available locally. Ive GOT some 7977, but no easy access to a .270 anymore. I was gonna try it in my .280AI (and I still can to see how it compares to other stuff), but I bought another 3lbs of RL-23 and am going to continue buying that as I can afford it, so haven't had the impetus to mess with 7977 in the AI yet.
Actually all three of those are supposed to be temperature insensitive.

And that's a pretty good price for a new barrel, installation, AND action work! Think Shaw charged me 350ish for just barrel work last time I sent a gun in and 500ish for the one I had them do action work on.

At 2800 fps MV? Still tougher than a Core-Lokt.


$605.

Less than another M1 rifle, or ~ another 1911-A1 or GLOCK I don't need.

For an OEM contour M700 24" Bbl. on a blued steel receiver.

Stainless or CS...?

Also:

Found a follow-up vid from the guy w/ the RL-26 pressure/accuracy problems.

Savage Rifle/22" Bbl./160 gr. NP:
- 60.0 grns RL-26: blown primer pocket!
- 59.0 grns RL-26: primers OK/loose/2927 fps.

FN/Winchester M70 EW/SS Rifle/22" Bbl./160 gr. NP:
- 58.0 grns RL-26: primers/pockets good/2875 fps./Sub-MOA group.

Which means maybe ~ 58.5 grns RL-26: should be OK for primers/pockets/2900 fps./Sub-MOA group...?




GR

 

[LoonWulf]

$605.

Less than another M1 rifle, or ~ another 1911-A1 or GLOCK I don't need.

For an OEM contour M700 24" Bbl. on a blued steel receiver.

Stainless or CS...?

Also:

Found a follow-up vid from the guy w/ the RL-26 pressure/accuracy problems.

Savage Rifle/22" Bbl./160 NP:
- 60.0 grns RL-26: blown primer pocket!
- 59.0 grns RL-26: primers OK/loose/2927 fps.

FN/Winchester M70 EW/SS Rifle/22" Bbl./160 NP:
- 58.0 grns RL-26: primers/pockets good/2875 fps./Sub-MOA group.

Which means maybe ~ 58.5 grns RL-26: should be OK for primers/pockets/2900 fps./Sub-MOA group...?




GR

Id go stainless, most of the cost is in the work, so might as well get a little longer barrel life and some corrosion resistance.....im becoming enamored to stainless barrels on blued/wood guns now that my cz is set up like that lol.

I haven't watched his videos yet, ill go check them out. From MY experience, 60gr would be about as much as would fit in a .270 case without serious compression. I don't know how the RLs react to being squished. I know Retumbo you can smash the crap out of and not have it do weird stuff, but others really don't like that. A 160 at 2900ish is still nothing to sneeze at.

 

[Garandimal]

Id go stainless, most of the cost is in the work, so might as well get a little longer barrel life and some corrosion resistance.....im becoming enamored to stainless barrels on blued/wood guns now that my cz is set up like that lol.

I haven't watched his videos yet, ill go check them out. From MY experience, 60gr would be about as much as would fit in a .270 case without serious compression. I don't know how the RLs react to being squished. I know Retumbo you can smash the crap out of and not have it do weird stuff, but others really don't like that. A 160 at 2900ish is still nothing to sneeze at.

.277/160 gr. NP at 2900 fps... would put my mind at ease.

It would cover the hole that the round has not bein' a higher twist 7mm or .308.

And would be at the top of my marksmanship recoil envelope.

Perfect.




GR

 

[Garandimal]

Id go stainless, most of the cost is in the work, so might as well get a little longer barrel life and some corrosion resistance.....im becoming enamored to stainless barrels on blued/wood guns now that my cz is set up like that lol....

Will pursue the stainless.

Worth uppin' the contour, maybe some fluting, at the cost of re-bedding?




GR

 

[LoonWulf]

.277/160 gr. NP at 2900 fps... would put my mind at ease.

It would cover the hole that the round has not bein' a higher twist 7mm or .308.

And would be at the top of my marksmanship recoil envelope.

Perfect.




GR

Ill see if I can get my hands on a .270, or maybe just screw that barrel I got into my American and say screw the bolt face fitting. Im getting the feeling that 7977 or 23 may be able to reach 2850-2900....and id like to know now.

 

[Garandimal]

Ill see if I can get my hands on a .270, or maybe just screw that barrel I got into my American and say screw the bolt face fitting. Im getting the feeling that 7977 or 23 may be able to reach 2850-2900....and id like to know now.

It's a hair quicker... but not by much.

Load density will be the issue.

RL-26 is very high.

According to QUICK-Load:

~58.5 grns of RL-26 is a 100%load for a 160 NP at Max COAL (3.34").




GR