Dear all, this in my first message as I have just become a member 2 minutes ago!

I am thinking of building a 270/08 ( using standard 20 degree shoulder, ie 7mm/08 cases necked down at accept .270 bullets )

What barrel length would you guys recommed?
I,m thinking about a twenty four and a half inch barrel, with a 1:10 twist!

I will be building the rifle on a Howa action.

I live in Australia, and will be using the Rifle on Pigs, Goats and Fallow Deer
I also invite and load data and I have it in mind to use Nosler 130 grain Ballistic Tips to start with

I'm not a wildcatter...but the Q comes to mind why?

I'm thinking that there wouldn't be a nickle's difference (5 cents) between it and either the .270 and/or the 7mm-08 and you can buy both of those all over the place.

The reason you wild-cat (again I don't do it) is to get an improvement on what is on the shelf. Say a .270 AI or an 08 improved (which are not much of an improvement...especially compared to the .280) make more sense

I don't think that it is logical.

Hi Dale and welcome to the forum...

The 270-08 is a fairly popular round as is it's bigger cousin, the 270-284...

Here are a couple of loads that I have loaded for the 270-08 using Noslers 130 gr. Ballistic Tip...

CASE: W-W 7mm-08 necked down to 270-08

PRIMER: CCI-200

POWDER: IMR-4350 / 46.0 gr.

BULLET: Nosler 130 gr. Ballistic Tip

VELOCITY: 2,890 fps.

.................................................. .................................................. ..............

CASE: W-W 7mm-08 necked down to 270-08

PRIMER: CCI-200

POWDER: IMR-4831 / 46.0 gr.

BULLET: Nosler 130 gr. Ballistic Tip

VELOCITY: 2,762 fps.

Both velocities listed are from 22" barrels...


Both loads have been fired in various 270-08 barrels and were perfectly safe but as always, start at least 10% lower than listed load and work up gradually, watching for signs of excessive pressure...

Your barrel length should be just fine for this cartridge as should the 1-10" twist and the 130 gr. Ballistic Tip for busting pigs, goats and fallow deer....

A

Hi Dale and welcome to the forum...

The 270-08 is a fairly popular round as is it's bigger cousin, the 270-284...

Here are a couple of loads that I have loaded for the 270-08 using Noslers 130 gr. Ballistic Tip...

CASE: W-W 7mm-08 necked down to 270-08

PRIMER: CCI-200

POWDER: IMR-4350 / 46.0 gr.

BULLET: Nosler 130 gr. Ballistic Tip

VELOCITY: 2,890 fps.

.................................................. .................................................. ..............

CASE: W-W 7mm-08 necked down to 270-08

PRIMER: CCI-200

POWDER: IMR-4831 / 46.0 gr.

BULLET: Nosler 130 gr. Ballistic Tip

VELOCITY: 2,762 fps.

Both velocities listed are from 22" barrels...


Both loads have been fired in various 270-08 barrels and were perfectly safe but as always, start at least 10% lower than listed load and work up gradually, watching for signs of excessive pressure...

Your barrel length should be just fine for this cartridge as should the 1-10" twist and the 130 gr. Ballistic Tip for busting pigs, goats and fallow deer....

A

Guys, I was googling the .270-08 and that's what brought me to this site and this post. (I now am a member here.)

I need HELP :confused: comparing the ballistics of the 270.08 and the .260. Need your opinions contrasting the two calibers. Need your opinions on the two in target shooting (F Class) as well as wild game.

Let me be more candid. I'm stuck in a position of having to offer advice on these two calibers and know a 'little' about the .260* and nada about the 270-08.



Warthogg


*As an example, I know the .260 will remain supersonic all the way to a 1000 yard target.

Warthogg,

The 6.5 bullets usually have a higher ballistic coefficient and sectional density over that of the 270 and as such, for long-range shooting, the 260 will have a slight advantage over the 270-08...

The main thing I have noticed about the 260 round or any 6.5 caliber for that matter is that you need to first decide on what bullet weight range you are wanting to shoot and then match your barrels twist rate accordingly. With the 270-08, a 1-10" twist rate will cover all bullet weights from 110 gr. up to 150 grains with excellent accuracy for all weights...

With loading die availability and the inherant accuracy of the 260 Remington, for both game and targets, I think the 260 would be a better choice. Like I said before though, match the twist rate to the bullet weight range you want to shoot...

By the way, welcome to the forum and God Bless....

A

Like it's parent case, a 20 inch varmit wgt bbl would suffice and give you a little more repeatability when shooting more than one round. Trade the 24 for the 20 hvy bbl, you won't notice the wgt difference littly handier in the bush.

Like it's parent case, a 20 inch varmit wgt bbl would suffice and give you a little more repeatability when shooting more than one round. Trade the 24 for the 20 hvy bbl, you won't notice the wgt difference littly handier in the bush.

Re barrel twist bullet weight, I've been a believer for a good many years now.

In 5.56/.223, the 1:9 twist will handle a vareity of bullet weight but the accuracy sweet spot is 69 grns.

I'm not a wildcatter...but the Q comes to mind why?

I'm thinking that there wouldn't be a nickle's difference (5 cents) between it and either the .270 and/or the 7mm-08 and you can buy both of those all over the place.

The reason you wild-cat (again I don't do it) is to get an improvement on what is on the shelf. Say a .270 AI or an 08 improved (which are not much of an improvement...especially compared to the .280) make more sense

I don't think that it is logical.

stinky,

points well taken.

The .270 casing and bullet is too long to fit in the particular weapon I have in mind. Soooo.......in the .260 or the 270-08, improvement would be had but improvement over the .308 and I can ONLY choose between the .260 and the .270-08..

Improvement over the standard .308 is what I'm after.

W.Hogg

stinky,

points well taken.

The .270 casing and bullet is too long to fit in the particular weapon I have in mind. Soooo.......in the .260 or the 270-08, improvement would be had but improvement over the .308 and I can ONLY choose between the .260 and the .270-08..

Improvement over the standard .308 is what I'm after.

W.Hogg


7MM/08 ACK IMP OR 270/08 ACK IMP Both will leave the 308 for dead for sure

7MM/08 ACK IMP OR 270/08 ACK IMP Both will leave the 308 for dead for sure

Sooooooooo, now to find out about the .270-08 ACK IMP.







WartH.

WartH, when considering any wildcat, there are three rules of thumb that you can use to very closely predict performance. All use two constants and one variable.

* If case capacity and bore size are constant, potential velocity varies inversely at one half the percentage change of bullet weight.

* If case capacity and bullet weight are constant, potential velocity varies at one fourth the percentage change of bore area.

* If bore size and bullet weight are constant, potential velocity varies at one fourth the percentage change of case capacity.

The wildcat you are considering changes the bore size, so let's compute a bit. A .264" bore has a cross sectional area (bullet base) of .055 Sq in, and a .277 bore has .060 Sq in. The .264 is 8% smaller, so a same-weight bullet in the .270-08 will have a muzzle velocity of 2% more. Why? because the gas has slightly more "piston" area to push on and the shorter bullet of the same weight will have less friction.

Whether that slightly higher velocity (if we assume 2800 fps, 2% is only a 56 fps gain) is offset by lower sectional density is up to you to decide.

BTW. the third rule is why the so-called "Ackley Improved" rounds aren't all that much improved at all. Blowing out a case to get an 8% volume improvement (which is about average), gives you only about that same 56 fps boost UNLESS YOU LOAD TO HIGHER PRESSURES. Anybody who boasts that his fabulous new AI chamber gives him 200 fps more than the parent chamber is running the round at significantly higher pressures, plain and simple. Unless he also changed the powder to magic pixie dust.

This usually starts a firestorm with AI lovers, but science is science and opinions are only opinions.

Believe Rocky is correct in the above. Have been an AI fan for some years and have noticed the best advantage is case longivity. The normal 4 to 5 percent increase in velocity is accomplished by the equal amount of increased powder charge.

Guess I'm coming full cycle, but of late have taken more and more to the old standard cartridges and trying to develop better loads with the newer powders and bullets that are available.

In fact, when you blow a case out, you have to increase the charge weight a bit just to get back to the ORIGINAL velocity. That often takes up most of the volume you gained.

The only advantage I've seen in AI cases is that they don't tend to stretch as much. But that's all.

In fact, when you blow a case out, you have to increase the charge weight a bit just to get back to the ORIGINAL velocity. That often takes up most of the volume you gained.

The only advantage I've seen in AI cases is that they don't tend to stretch as much. But that's all.


This is getting scary.

You folks are so good at explaining that I fear I'm actually beginning to undesrsatnd !!

Wart

You are treading into a hazardous situation. Remember the 280 Rem has a longer case body length so that the 280 CANNOT be loaded into a 270 chamber. When Winchester came out with the 7mm and 277 Magnum short cases, they had a recall to modify the 7mm chambers so that the 7mm could not be loaded into the 277 chamber. What happens when you(or more so a new owner) size 7mm-08 cases for your 270-308 and inadvertantly forces a 7-08 into the 277 chamber. Your future grandson may empty his skull at the shooting bench. I'd say forget the interest in this venture. Ackley Improving won't do a thing to alleviate this problem.

Uh huh, that's the problem of mismatched headstamps. Going one step down is fine if somebody somewhere loads a .270-08 cartridge (that they found on the ground) into their 7mm-08 rifle, there isn't likely to be a problem other than wondering why it went "Blooop" instead of "Boom!"

But if you necked up from a .260 and somebody found one, they just conceivably might be able to cram your .270-08 into their large-tolerance rifle's chamber. Pressures would be high, but I doubt that anything other than the shooter's bowels would let go.

That's why I always neck down. I make my .25-308 cases from 7-08 brass (I started making it before they came out with the .260) and won't buy a 7-08 rifle just to be sure. With WW brass, I can even use .308s to make .25-308 - Federal brass is too thick in the neck.

The necks are to thick on 308 Federal brass to use in my 7mm-08 which aggravates me because I have a bunch of it.

Do you have a way to inside neck ream or turn the case necks?

A

If Trailblazer is like me, we'd rather pee into a wall outlet than turn case necks.

Well put, Rocky. I do have a way to turn them but I also have other brass that works w/o turning so it hasn't come to that.

WELL BOYS
I am on my second 24" barrel on my 270/308 IMP IN 5 YEARS
My working loads
140 GR 2850 FPS
130 3000
110 3100
90 3400 THINK ABOUT THAT

You must be happy with it, RH. Good on ya.

I will point out that if it weren't "Improved" and if it weren't being pushed quite so hard, you'd still be comfortably on your first barrel - but the choice is yours.

You must be happy with it, RH. Good on ya.

I will point out that if it weren't "Improved" and if it weren't being pushed quite so hard, you'd still be comfortably on your first barrel - but the choice is yours.


I thihk 5 years is good
It get used most week ends .WE can hunt all round year hear
THE 130 has been tested at 3180 fps
The working loads are mild
i would not have got it rebarrel if it was not a grate number :cool:

I think that 3180 would have me running for cover, RH. The problem with AI cartridges is that they can mask what we call "traditional pressure signs." About the only way to match standard .270 speeds with a smaller case is run that case at higher pressures - and you are getting significantly more than standard .270 speeds, so your pressures would scare me.

3180FPS WAS A TEST LOAD ONLY . 3,000fps with the 130 gr is about the same as the standard 270 WIN
ROCKY
Yes slite increase in volumn
Yes does hide pressure
But the most important fact'is in its blown out form it is capable of working at muck higher pressure,
By reducing head to bolt thrust , also reducing case head seperation .
Radial pressures inside the chamber are higher
Part of the reason why there is very little pressure sighns on the case head is because there is a lack of head to bolt thrust ,
If high pressure worries you, you might like to stay away from the WSM when the 300 WSM hit the market ,pressures exceeded the 300 weathby magna .
The 180g generated over 66000,psi and may be the highest pressure factory cartridge ever produced .

Oh, I DO stay away from them, I assure you! I'm a throughly non-magnum kind of guy.

High pressure doesn't necessarily scare me, in cases designed for it. But blowing out standard cases does nothing to make them stronger - and they weren't made for the kinds of pressures AI fanatics subject them to. Couple that with the pressure-masking factor and it's the main reason some AI fans think their rounds are magical. They aren't; they're just operating at scary pressures.

I'm currently working with the 5-35 SMc which is being standardized by Savage (you can order them from their Custom Shop). Some of the loads the cartridge developers suggested to me test out at 70K+ on my Pressure Trace gear. Whoooeeee. They are also getting 4500 fps - on the shots when the bullets stay together long enough to get past my chrono!

A cartridge that reduces case head to bolt face thrust is a step in the right direction . TAKE NOTE in no way have I indicated to you the case its self would be stronger ,
Just a few questions ,,
Have you personaly used the 270/08 IMP ACK ?
How long did you use it for ?
WHAT game did you take and what range
What pressures did you obtain with the 140g and the 130g pills and the verlosity you obtained ?
THANK YOU KINDLY

I'm not arguing, rock hard. Just stating general facts that are well known to professional ballisticians everywhere.

I've never used a 270-08 AI, but that neither means I can't discuss it or that the round doesn't obey the rules of physics. Making a cartridge case a little bit bigger or straighter doesn't sprinkle it with magic pixie dust. It's still just a tube of brass. Add more of the same powder and you get more pressure. Always. Whether the effects of that added pressure are detectable by "traditional signs" is moot - the pressure itself is still there. If you add too much, you erase whatever safety margins were designed into the rifle/cartridge system. Let one added thing go wrong (hot day, hot rifle, flawed brass, hot powder lot, slightly larger bullet diameter, fouled bore...) and your magic rifle/cartridge turns to junk. With your body parts right next to it.

I've always said that just calling a cartridge "Improved" doesn't mean it's automatically better.

Thank you for being honest and addmitting you have never used a 270/08 IMP .
I am sorry if you thought I was trying to stop you from discusing this matter ,
Would I be correct if I said that you have never set your eyes on the cartridge in question .
Of cause enough pressure in the right place will bust any riffle .
What you have stated is all basic knowledge ,
Rocky I would like to read your understanding of why, the so called traditional pressures sighns are not vissible .
I think calling a cartridge by any name including imp does not necessarily indicate it is a better cartridge ,with or without the bull crap [ AUSSIE VERSION OF PIXIE DUST]
THANK YOU.

I have not laid eyes on the 270-08AI, but I have seen an unimproved 270-08 as well as a 7-08AI. Even though there are no standardized dimensions for any AI round, the 7-08AI is probably so much like the 270 that they'd appear identical. They do look businesslike and "aggressive" for lack of a better descriptive.

My theories about the lack of traditional pressure signs in AI rounds stems almost directly from their decreased backthrust. It's a double-edged sword. While less back thrust is the main reason for the added case life and decreased need to trim (no longitudinal stretching), it also masks any primer flattening, ejector marking and even heavy bolt lift simply because the case head does NOT move back against the breech as hard as in a non-improved cartridge. Tests show that some AI cartridges will stay in the chamber when fired even when there is NO bolt in place to stop it!

That can be good from a safety standpoint because there is almost no longitudinal stress on the receiver. But it can also be bad (double-edged thing again) because some reloaders will just keep packing powder into an AI case in the belief that they must still be safe. They clearly are not because what they're doing is (as mentioned above) simply erasing the safety margin of physical strength built into the cartridge and rifle design.

One of the three general rules of reloading performance states that if bore diameter and bullet weight remain the same, velocity varies at one fourth the percentage of case volume change.

Translated, that means if you increase the volume of your cartridge by eight percent, you should expect a velocity boost of about two percent. Eight percent is about typical for an AI conversion of a .308-based case. So the AI version of the 270-08 should only get two percent more than the non-AI.

Comparsion should be easy if there were a factory 270-08, but of course we're talking a wildcat OF a wildcat, so there isn't. We CAN, however work back from the standard .270. If a regular .270 holds about 62 grains of water, and a standard .308 holds 54, the .308 is about 15% smaller. Adjusting a smidge for the neck diameter change, lets make it 16% smaller. So the velocity of a .270-08 ought to be about 4% less than of a .270. Using 3000 fps as a guide, a .270-08 should get 2880 if loaded to the same pressure as a .270.

Now we boost the .270-08 to an AI, adding eight percent of volume. Our two percent boost adds 58 fps for a new expected velocity of 2938 fps. Almost, but not quite back to standard .270 performance.

So looooooong explanation of why I get raised eyebrows if velocities for the .270-08AI are higher than for the standard .270. It should not be possible UNLESS the working pressure is much higher. How much higher? Neither of us knows unless and until that rifle gets a strain gauge system installed and those loads are tested. But we KNOW they're higher than standard .270 pressures.

What happens when you(or more so a new owner) size 7mm-08 cases for your 270-308 and inadvertantly forces a 7-08 into the 277 chamber. Your future grandson may empty his skull at the shooting bench.

Perhaps a better alternative is the 270 IHMSA. For a young shooter it will send a 110 or 130 gr bullet at app 2500 in a 22 inch barrel. It is not as powerful a round but in IHMSA it will topple the steel, in a pistol. Cases will be harder to form, loading data a bit harder to find, and dies will be more money but the rifle will be a little sweetie for a young shooter.

Don't get lost in the gun smoke, make a list of the needs and wants, advantages and disadvantages and pull the trigger on the decision.

I have not laid eyes on the 270-08AI, but I have seen an unimproved 270-08 as well as a 7-08AI. Even though there are no standardized dimensions for any AI round, the 7-08AI is probably so much like the 270 that they'd appear identical. They do look businesslike and "aggressive" for lack of a better descriptive.

My theories about the lack of traditional pressure signs in AI rounds stems almost directly from their decreased backthrust. It's a double-edged sword. While less back thrust is the main reason for the added case life and decreased need to trim (no longitudinal stretching), it also masks any primer flattening, ejector marking and even heavy bolt lift simply because the case head does NOT move back against the breech as hard as in a non-improved cartridge. Tests show that some AI cartridges will stay in the chamber when fired even when there is NO bolt in place to stop it!

That can be good from a safety standpoint because there is almost no longitudinal stress on the receiver. But it can also be bad (double-edged thing again) because some reloaders will just keep packing powder into an AI case in the belief that they must still be safe. They clearly are not because what they're doing is (as mentioned above) simply erasing the safety margin of physical strength built into the cartridge and rifle design.

One of the three general rules of reloading performance states that if bore diameter and bullet weight remain the same, velocity varies at one fourth the percentage of case volume change.

Translated, that means if you increase the volume of your cartridge by eight percent, you should expect a velocity boost of about two percent. Eight percent is about typical for an AI conversion of a .308-based case. So the AI version of the 270-08 should only get two percent more than the non-AI.

Comparsion should be easy if there were a factory 270-08, but of course we're talking a wildcat OF a wildcat, so there isn't. We CAN, however work back from the standard .270. If a regular .270 holds about 62 grains of water, and a standard .308 holds 54, the .308 is about 15% smaller. Adjusting a smidge for the neck diameter change, lets make it 16% smaller. So the velocity of a .270-08 ought to be about 4% less than of a .270. Using 3000 fps as a guide, a .270-08 should get 2880 if loaded to the same pressure as a .270.

Now we boost the .270-08 to an AI, adding eight percent of volume. Our two percent boost adds 58 fps for a new expected velocity of 2938 fps. Almost, but not quite back to standard .270 performance.

So looooooong explanation of why I get raised eyebrows if velocities for the .270-08AI are higher than for the standard .270. It should not be possible UNLESS the working pressure is much higher. How much higher? Neither of us knows unless and until that rifle gets a strain gauge system installed and those loads are tested. But we KNOW they're higher than standard .270 pressures.

ROCKY
In reguard to head to bolt thrust I think we both agree on this matter ,
As you would know the weekest part of most bolt actions is it lock up system .
The design of the chamber allows the firearm to work at higher pressures for that very reason The chamber wall pressures are very high and I have not denied this .
Most of the AI cartridges can work in relitive weak actions at high pressure for this very reason ,providing the chamber walls are strong enough ,
People have and will continue to yry extract the highest possible verlosity reguardless of case design and accident will still happen reguardless of what you or I say .
Firearm manufacturies are constanty trying to make cartridges and fire arms with increase verlosity,
and have done so for years that work at incredibly high pressures ,
I am not going to test my theory but I beleave the only way the case will bust is from the chamber walls and the action ring to expanding or fracturing and so allowing the case to expand past its elastic limits

True enough. My only reservation is that without some kind of measurement gear, reloaders are just guessing at the pressures they're getting. There's no warning until they experience "spontaneous omnidirectional disassembly." (Hope you like that term!) Remember that the firearm was designed to work safely at the given maximum pressure of the original chambering. Rechambering always removes metal, which has to reduce strength. So upping the working pressure after rechambering MAY be an iffy thing. Use extra caution!

For the record, though, the .270-08 is a great round. Efficient, accurate and almost as fast as a regular .270. One can say the same for the AI version as well.

ROCKY
You would know there are vissible sighns of high pressure and it only comes with experiance ,
However at this point you are living on the edge
You would already know most ACK IMP built on the parent 308 case retains the original body taper .
Only the shoulder is moved forward so increasing the body length slightly, the body length would depend on the shoulder angle.
No increase in body diameter at all ,
ACK was quite happy with the body taper on 308 case ,
Now if you where talking about that big fat one at 66,000 psi well there is not much meat around the that hole ,
I do not think the 270win could opperate at the pressures that I run at without the primers leaking