Krag brass in the 303 update

[303carbine]

I have shot the same Krag brass five times with no signs of brass seperation, they still measure the same after that many fullhouse reloads. The commercial 303 Brit Federal brass show obvious signs of stress along the casehead with only three fullhouse loads of the same powder. I believe one more reload is all the Federal brass will take before full seperation of the casehead.
I have heard for years about how Krag brass works in the 303 Brit, I am definitely no longer a skeptic.

[303Guy]

Very interesting, thanks! Mind you, I've said before that with light lubing of loaded cases I have had zero case failures with any make of case. But then I'm not known for loading to max pressure.

[Multigunner]

Very interesting, thanks! Mind you, I've said before that with light lubing of loaded cases I have had zero case failures with any make of case. But then I'm not known for loading to max pressure.

One must be sure not to lube cases of any full power loads. Theres been some confusion among Lee Enfield collectors over the term "oiled in the service manner". I looked through numerous WW1 era military manuals and regulations for musketry before finding out the exact meaning of the term.
To prevent grime transferred by dirty hands from sticking to cartridges they wiped down each cartridge with a piece of flannel lightly moistened with a thin preservative oil, not a lubricating oil. The cartridges were then set aside to dry before placing these in chargers.
There was no actual lubricating effect from the microscopically thin residue of the thin oil left on the cases, all it did was discourage dirt and/or mud from clinging to the cartridge while loading.

If a chamber is noticeably rough some lubrication may actually be beneficial, at least when light loads are used, but if the chamber is in good condition lubricated cases can pose a danger when full power loads are used.

Best all around if chamber walls are honed and free from machine marks or pitting and cartridge cases are smooth.

PS
When using commercial sporting ammo or handloads primer back out with pressure trapped in the primer pocket (up to 900 PSI) momentarily absorbs some back thrust on the bolt face. Mil spec ammo normally has staked primers and theres no cushioning effect since the primers don't back out.

[303Guy]

It seems that the Krag brass has a heavier wall (?) near the web which would be the reason for better case life. The thrust load absorbed by the case would be distributed over the length of the case by elastic elongation while with thinner walled cases the case grips too much thus concentrating the load near the web where it suffers plastic elongation. So two factors would be at play; the thicker wall grips less and then has the strength to drag the case against the chamber wall spreading the load. At higher pressure all bets are off.

At lower pressure the entire bolt thrust can be from the primer alone while the case is held forward in the chamber. This can be seen by the primer having backed out and not reseated.

If the case settles back onto the bolt face before peak pressure then case to chamber grip will absorb up to 10% of the thrust but if the case is gripping enough to hold the thrust closer to peak pressure before setting back it will hammer the bolt and this effect can be seen on LE's with excess head-space where the lug recess actually get peened and can jamb the bolt altogether.

I would think that if the case base is undersize in the chamber the expansion of the case above the web would also result in high bolt face thrust due to plastic deformation taking place in that area so it may be a good idea to fire-form undersized cases with lower pressure loads.

[Multigunner]

It seems that the Krag brass has a heavier wall (?) near the web which would be the reason for better case life. The thrust load absorbed by the case would be distributed over the length of the case by elastic elongation while with thinner walled cases the case grips too much thus concentrating the load near the web where it suffers plastic elongation. So two factors would be at play; the thicker wall grips less and then has the strength to drag the case against the chamber wall spreading the load. At higher pressure all bets are off.

At lower pressure the entire bolt thrust can be from the primer alone while the case is held forward in the chamber. This can be seen by the primer having backed out and not reseated.

If the case settles back onto the bolt face before peak pressure then case to chamber grip will absorb up to 10% of the thrust but if the case is gripping enough to hold the thrust closer to peak pressure before setting back it will hammer the bolt and this effect can be seen on LE's with excess head-space where the lug recess actually get peened and can jamb the bolt altogether.

I would think that if the case base is undersize in the chamber the expansion of the case above the web would also result in high bolt face thrust due to plastic deformation taking place in that area so it may be a good idea to fire-form undersized cases with lower pressure loads.

Sounds like you have a good handle on it.
I suspect a certain amount of elastic deformation of the case can contribute to protruding primers of fired cases. The case stretching only a little and snapping back to some extent while there's still residual pressure in the primer pocket.
When lower pressure loads expand the case only enough to momentarily form a good neck seal the case may not expand beyond its elastic limits.
That's something you aren't likely to see with full pressure loads.

Also while the cases used by the OP may have thicker walls we can't assume that other .30-40 cases from other manufacturers will also have thick walls. Some use the same drawing machinery for .303 and .30-40 cases. Milspec .303 cases usually have thick walls, much like milspec 7.62 cases, with resulting decrease in powder space compared to thinner walled commercial cases.

Seller and Belliot .303 cases I'm used in the past have good thick rims and fairly thick walls, but they seem to have used an alloy of brass that just isn't up to par, which causes very poor case life even with a good chamber and fair headspace.

An old trick used to fire form .30-06 cases to fit the usually over sized base area of re-chambered 7.7 Japanese rifles is to wrap a layer or two of cigarette paper around the base of the case to keep it dead centered in the chamber. That way it expands evenly all the way around.

[303carbine]

The case of the Krag isn't any thicker, it's bigger in radius at the casehead and fills the 303 chamber better.
I am looking at the cartridge drawings right now, the 303 measures .455 at the casehead, the Krag measures .457.
This small difference makes the Krag brass fit the 303 oversize chamber better and the brass does not expand and deform like the Brit stuff does.
Of course, the Brit chamber was designed this way to make sure all ammo from different manufacturers will fit, especially if the ammo is dirty.
It's simply a matter of better chamber fit with the Krag brass.

[brassrat]

I have been recently loading .303 and bought and returned some new 30/40 Rem. brass. It was.452 and exactly the same as my factory.303. from PPU.

[303carbine]

I have not measured the Remington brass, I have a bunch of new Winchester, it's .457 at the casehead.
I guess the 30/40 Krag brass measurements are not all the same.
.452, that's big difference from the Winchester stuff.:holysheep

[Multigunner]

The case of the Krag isn't any thicker, it's bigger in radius at the casehead and fills the 303 chamber better.
I am looking at the cartridge drawings right now, the 303 measures .455 at the casehead, the Krag measures .457.
This small difference makes the Krag brass fit the 303 oversize chamber better and the brass does not expand and deform like the Brit stuff does.
Of course, the Brit chamber was designed this way to make sure all ammo from different manufacturers will fit, especially if the ammo is dirty.
It's simply a matter of better chamber fit with the Krag brass.

You can't really judge by the cartridge drawings, they usually give maximum dimensions rather than actual dimensions of cases for different manufacturers. The better quality chamber drawings show maximum and minimum specs at each point of measurement.

Chamber drawings can also be misleading since many of the WW1 era rifles had their chambers enlarged using enlarging reamers to allow for overly fat cartridges. The original manufacturing specs allowed for some lee way , partly to allow for dust and such on the battlefield, but WW1 ammo was often out of specifications which negated that lee way.

Looks like you lucked out in getting some good fat .30-40 Krag cases, so you are well ahead of the game. Good show.

[303carbine]

I measured some new 303 brass, they are .448, the other Federal Krag are .452 ?
The Winchester are bigger for whatever reason!

[Multigunner]

I measured some new 303 brass, they are .448, the other Federal Krag are .452 ?
The Winchester are bigger for whatever reason!

I've heard of reloaders forming .303 cases from the .405 Winchester case to take advantage of a thicker rim.
You might check specs for the .405 case head and see if these may share the basic case drawing procedure with the Winchester Krag cases. That would explain the thicker than average base.

Another possibility is that the machinery used to draw these cases is a bit worn, that was the major cause of over sized military cartridge cases during WW1. They didn't refurbish the machinery when they normally would have in peace time.

[303carbine]

I've heard of reloaders forming .303 cases from the .405 Winchester case to take advantage of a thicker rim.
You might check specs for the .405 case head and see if these may share the basic case drawing procedure with the Winchester Krag cases. That would explain the thicker than average base.

Another possibility is that the machinery used to draw these cases is a bit worn, that was the major cause of over sized military cartridge cases during WW1. They didn't refurbish the machinery when they normally would have in peace time.

That makes sense, anything is possible.

[Multigunner]

Just checked the cartridge drawings for the .405 Winchester.
The maximum base diameter is .462, maximum rim thickness is .073.
The .073 rim would only be usable for a .303 if the rifle had near or over maximum milspec headspace. My rifles have .068 or less headspace so I would have to thin the rims to use that case.
The base diameter is about max for a milspec .303 chamber, though enlarging reamers some times widened the chamber beyond that to allow use of out of spec cartridges.

For the .405 case to be a viable option the rifle would have to be worn to the point that reloading with any in spec case would be un productive.

Those are maximum figures so its not unlikely that run of the mill .405 cases would have base diameter closer to the .457 of the Krag cases you have. Its very likely that Winchester used the same drawn blank for both cartridges, and possibly others as well.

[303Guy]

I have a rifle - an 1896 action with a cavalry carbine barrel that has suffered some thrust face set back in the lug recesses. I used mispec brass which is thicker and lighter loads with paper patch to fill the worn bore and throat. I didn't see any effects from the initial excess headspace which I assumed was there. It shot pretty good (although I did have to increase the powder charge once the bore polished up). The main reason for using the thicker walled cases was for the thicker neck which held the patched boolit well without neck sizing. My other cases were too loose. The smaller case capacity was a bonus for the desired lower pressure loads with H4227 and filler. Everything about those cases seemed just right for that chamber and bore. I use those same thick walled cases in my over sized bore pig gun (which hasn't taken a pig yet).