Caliber designation

lysanderxiii said:

The shoulder location of the .270 Winchester is at the same place as it is on the .30-06. On both the shoulder starts at 1.948" from the base. The .270 Winchester is slightly longer because the shoulder is the same angle but the neck is smaller in diameter, so there is extra material that needs to go somewhere when you resize the case to the smaller neck diameter.

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I know the .270 case is longer, and never knew exactly why. Your comment makes as much sense as anything. Nor did it ever make sense to me for the shoulder angle (etc) to be changed; other than to satisfy someone's ego to call it a ".270 Dorkson Special".

lysanderxiii said:

EDIT: the length stamped on the headspace gauge of a .270 Win is longer than that stamped on a .30-06 because the .270 Win uses a reference diameter of .375" versus the .440" of the .30-06. If you measure a .30-06 case to a .375" reference diameter you get the same length - 2.0526" for both (check out the SAAMI drawings).

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I do look at the schematics in the 'several' loading manuals I have. I presume they are derived - if not flat copied - from the SAMMI information. I have verified the longer length of the .270 case and as I said either, never have understood the point. But I'm young yet.

lysanderxiii said:

.280 Remington has the shoulder moved forward 0.050", so it cannot be chambered in the .270 Winchester barrel.

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Okay. Not having either, I've never paid attention to that measurement. But it also makes sense.

lysanderxiii said:

If you shot a .270 Win in a .30-06, nothing really bad would happen, and you aren't going to force a .308 bullet into a .277" hole, so the .30-06 in a .270 Win is not a problem.

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Shooting a .277" bullet down a .308" hole will not cause much back pressure. I should think the rather mediocre 'seal' resulting from an under sized bullet would allow the expanding gas to escape, lowering pressure and over all being a bit disappointing. Unless that extra length of case on the .270 case was wedged between bullet and leade generating a serious pressure spike. (I've never tried it and it is NOT on my list of experiments.) I have had at least (rather informal) one report of such instance. He said 'things were messed up' but didn't expound. From the conversation I don't think the rifle was destroyed. (That conversation was in 1967 or 1968.) I suspect a .30-06 case with bullet would chamber in a .270 Win chamber without a great deal of effort. (Never tried it, I could be wrong.)

lysanderxiii said:

However, you might be able to jam a .284" diameter bullet into a .277" hole if you really try, which is why .270 Win is the same as .30-06 and .280 Rem is a little longer.

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That seems a great deal more possible. However, a .284' bullet in a .277 bore would likely not be tragic. Not recommended by any means but umlikely to cause a catastrophic (blow up) failure. Probably the greatest damage would be to dimensions of chamber and need for rebarreling (which I would just as soon avoid). Depends on bullet construction I'd say.

Archie said:

That seems a great deal more possible. However, a .284' bullet in a .277 bore would likely not be tragic. Not recommended by any means but umlikely to cause a catastrophic (blow up) failure. Probably the greatest damage would be to dimensions of chamber and need for rebarreling (which I would just as soon avoid). Depends on bullet construction I'd say.

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It would cause a tremendous pressure increase with an already high pressure cartridge.

The dimensional differences you were unaware of betwixt the two cartridges exist for good reason, and you should keep your thoughts on the relative safety of firing the wrong cartridges in a given weapon to yourself.

Unless one is knowledgeable enough to know alternate designations for the same cartridge, the ammunition should always match what is marked on the firearm. There are absolutely multiple cartridges with similar denotations which can chamber and fire in a weapon which was not designed for them and could fail catastrophically. Never guess, never assume. You only get one pair of hands, one pair of eyes and one life; contained explosions in those hands and directly in front of your face are not something to be cavalier about.

MachIVshooter said:

It would cause a tremendous pressure increase with an already high pressure cartridge.

The dimensional differences you were unaware of betwixt the two cartridges exist for good reason, and you should keep your thoughts on the relative safety of firing the wrong cartridges in a given weapon to yourself.

Unless one is knowledgeable enough to know alternate designations for the same cartridge, the ammunition should always match what is marked on the firearm. There are absolutely multiple cartridges with similar denotations which can chamber and fire in a weapon which was not designed for them and could fail catastrophically. Never guess, never assume. You only get one pair of hands, one pair of eyes and one life; contained explosions in those hands and directly in front of your face are not something to be cavalier about.

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Come now, he is not suggesting that it is safe to do. If someone says your less likely to die from running your car into a wall at 30 mph compared to 60 mph, that does not mean they are advocating wall ramming.

lysanderxiii said:

.280 Remington has the shoulder moved forward 0.050", so it cannot be chambered in the .270 Winchester barrel.

If you shot a .270 Win in a .30-06, nothing really bad would happen, and you aren't going to force a .308 bullet into a .277" hole, so the .30-06 in a .270 Win is not a problem.

However, you might be able to jam a .284" diameter bullet into a .277" hole if you really try, which is why .270 Win is the same as .30-06 and .280 Rem is a little longer.

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You wouldn't be able to jam a 284 bullet into a 277 bore by hand, but what is entirely possible is you force the bolt forward and simply push the bullet back into the case until the bolt closes. You would also need to get the larger neck of the 280 case into the neck of the 270 win chamber, but given only a .005" difference in spec in loaded neck diameter between the two, its very possible and actually likely that you could have a combination of a thin necked case and generously dimensioned chamber that it would fit. The difference in neck diameter would definitely prevent a 30-06 from being loaded into a 270 chamber though.

MachIVshooter said:

It would cause a tremendous pressure increase with an already high pressure cartridge.

The dimensional differences you were unaware of betwixt the two cartridges exist for good reason, and you should keep your thoughts on the relative safety of firing the wrong cartridges in a given weapon to yourself.

Unless one is knowledgeable enough to know alternate designations for the same cartridge, the ammunition should always match what is marked on the firearm. There are absolutely multiple cartridges with similar denotations which can chamber and fire in a weapon which was not designed for them and could fail catastrophically. Never guess, never assume. You only get one pair of hands, one pair of eyes and one life; contained explosions in those hands and directly in front of your face are not something to be cavalier about.

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My plan for shooting an 8x50r-chambered Steyr M95 involves loading the gun with cartridges which are marked 7.62x54r and blazing away. I assure you it’s perfectly safe, and was routinely resorted to by Austrian soldiers in WW1. Apparently the reverse was also tried, with success. Anecdotally, it is feasible to rechamber, but not re-barrel, and to fire .323 bullets in a Mosin-Nagant’s 7.62mm barrel, without experiencing catastrophic failure -or much of anything at all except possibly somewhat reduced barrel life. I don’t plan to find this out for myself, and don’t advise anyone else to do so either, but I love to bring it up whenever someone gets a little too over the top about how one should not even speak about what might and might not chamber in a given rifle.

One day, the knowledge of how a .270 does or doesn’t chamber might prove very useful.

MachIVshooter said:

It would cause a tremendous pressure increase with an already high pressure cartridge.

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Not really. Unless you have physical proof such a combination would be catastrophic.

MachIVshooter said:

The dimensional differences you were unaware of betwixt the two cartridges exist for good reason, and you should keep your thoughts on the relative safety of firing the wrong cartridges in a given weapon to yourself.

Unless one is knowledgeable enough to know alternate designations for the same cartridge, the ammunition should always match what is marked on the firearm. There are absolutely multiple cartridges with similar denotations which can chamber and fire in a weapon which was not designed for them and could fail catastrophically. Never guess, never assume. You only get one pair of hands, one pair of eyes and one life; contained explosions in those hands and directly in front of your face are not something to be cavalier about.

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You list credentials claiming to have training and experience in such things. As such you should be aware of actual testing done of over sized bullets NOT causing any particular damage as you claim.

Cavalierly making comments about other's knowledge is indicative of a sophomoric attitude. You are dismissed.

Archie said:

Not really. Unless you have physical proof such a combination would be catastrophic.

You list credentials claiming to have training and experience in such things. As such you should be aware of actual testing done of over sized bullets NOT causing any particular damage as you claim.

Cavalierly making comments about other's knowledge is indicative of a sophomoric attitude. You are dismissed.

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Talk about straw men.

I said tremendous pressure increase. Whether or not that would have catastrpohic results depends on several factors. Doesn't change the fact that firing the wrong ammunition, and particularly ammunition with a bullet diameter larger than the bore was intended for, is a very bad idea. Even using bullets of the correct diameter but with exceedingly long bearing surface or of less malleable construction (all copper bullets, brass solids) with load data for normal cup & core bullets of the same weight can cause unsafe pressures.

For the record, though:

Archie said:

Probably the greatest damage would be to dimensions of chamber and need for rebarreling

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Would qualify as catastrophic. Metallugically speaking, the difference between a stretched chamber and a blown up gun is pretty much luck. The yield strength of tempered 4140 steel is just 15% below the ultimate tensile strength. Yield is where permanent deformation occurs, ultimate is where it flat out breaks. And if your barrel is 416 stainless, it only has half the strength of a 4140 barrel to begin with.

Of course, the chamber letting go is only one possible scenario. The other is bolt lugs shearing off and sending the bolt through your face.

These failures can and do happen with overpressure conditions, including bore obstructions, detonations, overcharges, wrong powder and incorrect ammunition.


I also never speculated about your knowledge or lack therof. You told us in plain English that you were unaware of the differences in base-to-shoulder dimensions of the .270 Win and .280 Rem:

Archie said:

Okay. Not having either, I've never paid attention to that measurement. But it also makes sense.

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Only one of us here is playing the ad hom game, sport, and it ain't me.

someguy2800 said:

You wouldn't be able to jam a 284 bullet into a 277 bore by hand, but what is entirely possible is you force the bolt forward and simply push the bullet back into the case until the bolt closes. You would also need to get the larger neck of the 280 case into the neck of the 270 win chamber, but given only a .005" difference in spec in loaded neck diameter between the two, its very possible and actually likely that you could have a combination of a thin necked case and generously dimensioned chamber that it would fit. The difference in neck diameter would definitely prevent a 30-06 from being loaded into a 270 chamber though.

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You're off by a factor of ten.

You will find that the difference in seating length between 270 Winchester and 280 Remington is 0.050 inch.

Archie said:

Not really. Unless you have physical proof such a combination would be catastrophic.

You list credentials claiming to have training and experience in such things. As such you should be aware of actual testing done of over sized bullets NOT causing any particular damage as you claim.

Cavalierly making comments about other's knowledge is indicative of a sophomoric attitude. You are dismissed.

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Would you shoot a .277 bullet in a 6.5mm barrel?

Or, an 8mm in a .311?

The interference is of the same magnitude.

And if by "actual testing done of over sized bullets NOT causing any particular damage" you are referring* to .312 bullets in a .308 bore, the interference is half that of a .284 in a .277, which means the volume of material to be displaced in the .312/.308 case is in the order of 1/4 less than the case of .284/.277.

Further, the pressure increase in not linear, if a .312 bullet in a .308 bore cases a pressure increase of 2,000 psi, doubling the interference DOES NOT mean a 2X increase, but more on the order of an increase of 5X to 10X, with jacketed bullets.

With a high pressure load, you will risk a case head blow out, at least.

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* If not please direct us to this research.

I'll settle this;

Let's see the hands of everyone who has fired a .280 in a .270 chamber.

Now all those who still have 10 fingers and two eyes, pull your hands down.

Archie said:

I know the man who (or was closely involved with) intentionally loading a .30-06 case with a 150 grain bullet using published loads at the time (1960s or 1970s). Except the bullet - of the correct weight - was an 8mm bullet (.323 inches). The rounds were loaded and fired in the normal way. The rounds were not perceptively different in loading, chambering firing or distortion to the case than 'normal' loads. My information comes from the person involved. I have every confidence in his honesty, memory and integrity. I do not know if the information has been publicly published. The agency was Marine Corps R & D.

I will also point out your claims are manifestly incorrect. The statement as written is misleading. It is not universal. The powder used makes a serious difference. Even if you are using this as a hypothetical example, the entire situation must be mentioned.

You have a point. A bullet too large to chamber (a .338 in a .224 for instance) would probably be problematic. The somewhat observed event of a .300 Blackout fired in a .223 Remington/5.56mm chamber presents a clear and present hazard, not to mention the .300 Blackout uses rather fast burning powder for a rifle. I don't believe one should attempt to load a .410 bullet in a .308 bore rifle. Aside from the bore difference, there is a weight difference.

I even submit the difference between a standard lead core, copper jacket bullet could be seriously changed by one of the newer designs of a fully copper bullet or those which are built to have less maleable interior.

None of those conditions are met in the presented case. But you decide your own problems.

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Let me have his name, date of testing, and any other information that you might have on this. I have friends with access to MCCDS's archives.

...if a .312 bullet in a .308 bore cases a pressure increase of 2,000 psi...

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A very important conjunction . . .

lysanderxiii said:

You're off by a factor of ten.

You will find that the difference in seating length between 270 Winchester and 280 Remington is 0.050 inch.

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I did not say seating length. I said neck diameter. I know that a 280 rem has the shoulder set forward .050” and so would not go into battery in a 270. I was just commenting on theoretical idea of inadvertently firing a 284 caliber cartridge in a .277 caliber firearm of some sort.

None of it makes any sense, just remember there are well over thirty cartridges chambered in .308 caliber.

MachIVshooter said:

never assume

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Failure on that point....
lead to THIS... one

Archie said:

Shooting a .277" bullet down a .308" hole

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One of my more recent projects.

NOS Barrel was marked .270win. Slapped it on the action and finished reaming to .270Win, then took it for a spin. Turns out it was a miss marked .30-06 barrel, and while the .270Win reamer cut the shoulder to the correct position, and cut a new neck in the leade of the 06 chamber, it didn't remove all the wider 06 neck....or magically shrink the bore.
which left an interesting shape to the cases on extraction (which was the first issue i noticed), and rounds bounced down range at some surprisingly sharp angles, and I quit playing with it for fear of hitting someone else's target stands.

H&Hhunter said:

Which is why the American .256 Newton is nothing more than a 6.5/06

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Not quite. Case dimensions are a bit different, capacity a bit smaller.

I am sure it confused people to hear that the .256 Newton shot a bigger bullet than a .257 Remington Roberts, but their eras did not overlap much.