quote:

If a weapondesign is so weak, that there would be any risk, or material stress, when a chamber is wet. This design is both POOR AND HASARDUS.

Exactly! But some do like to keep their cases dry for that reason. Dry but polished.!?

Still, it has been proven that some rifles with their low pressure cartridges will hold the case in place with the locking lugs removed. The person doing the tests, however, did not fire them from his shoulder.

quote:

I think Ackley did an experiment with shooting a partially disassembled lever action where nothing held the action shut but his hand on the lever.

I would not try that with my hand and a lubricated case.

Hell no!

My theory is that a lubed case will deliver less stress to the locking system by allowing the case head to seat firmly against the bolt face at a lower pressure, thus reducing the suddenly applied load factor. Anyway, the important thing is my cases last forever when I lube them.

303Guy,
Judging by your handle, it seems you might be loading for a Lee Enfield. In this situation, lubing of the cartridge may well be beneficial; at least from a brass life standpoint. I don't think it does much to reduce stress on the locking system but it probably doesn't do a lot of harm either.
At low pressures, the 303 case will usually adhere to the wall of the chamber sufficiently well that the primer will protrude. At factory pressures, the case still adheres to the chamber wall but, because the pressure is high enough to exceed the alastic limit of the brass, the brass stretches until the bolt face is contacted. If the rifle has too much headspace, the case will separate. If the rifle has no headspace, initial firing pressure will transfer nearly 100% to the boltface. As the stretchy Lee Enfield doea just that (stretches) the transfer will be reduced until such time as the brass elastic limit is reached. At this point, transfer will again approach 100%.
tnekkcc,
Screw a bunch of engineers. We common gunsmiths can show surprising insight and are probably wrong no more often than the engineers (see; collapsing buildings, falling cranes, exploding shuttles, etc. etc.) Regards, Bill.

I was being an arrogant unhelpful egotistical a$$hole when I said something patronizing to gunsmiths.


What does it all mean?
I forgot Bill Leeper still posts here.
Sorry.

Yup, 303 Brit and hornet. Both behave the same. That is a very clear explanation you gave, Bill. I find that hornet cases grow by vertue of not haveing a shoulder to headspace on. But I discovered I can headspace on the case mouth with my rifle. My cases stay at 35.72mm. Yoo-hoo! It's like loading for a pistol.

I did load for a 223 once. I don't remember ever stretching a 223 case. If I recall, I was only concerned with consistant case to chamber wall grip with the 223. (Can't say whether it made any difference).

I have no idea how much stress might be induced by the 'suddenly applied load' principle. In theory, with zero preload and zero headspace, it should be nearly double the load produced by the peak pressure if the action were mounted on a solid block. (This is due to the elasticity of materials). But because the action recoils and there is case to chamber wall grip, this would likely be much less. But if there exists excess headspace and the case grips the chamber walls untill the pressure is near its peak and then 'lets go', it will strike the bolt face with some appreciable velocity, akin to being struck by a hammer. So one can expect the excess headspace to increase exponentially.

I must say, I have seen a surprizing number of stretched cases lying around at ranges. These include 6.5x55, 7.5x55 and 308. The only 8x57 cases I have found didn't even show expansion at the pressure ring area.

No 4 bolthead sizes:
0 - .629 to .625 in.
1 - .625 to .630 in.
2 - .630 to .635 in.
3 - .635 to .640 in.

But the larger sizes are no longer available, so I have been Silver soldering shims the bolt heads.

SAAMI is .054" to .064" on the cartridges rims and .064 to .071" chamber.
That is a kosher range of .017" in headspace.
But I have allot of brands of 303 brass, and it is mostly from .057 to .064.

Then there is the lugs in the rear with a thin wall bolt body in compression.
I calculate:
movement = [Force] [ length]/[[area] modulus]
movement = [chamber pressure][case ID][length]/[[area][ modulus]
movement = [ 60 kpsi] [.107 sq. in][4.2 in]/[.236 sq. in[30 M lb/ sq.
in]
movement = .0041" @ 65k psi chamber pressure
movement = .0038" @ 60k psi chamber pressure
movement = .0029" @ 45k psi chamber pressure
movement = .0019" at 30k psi chamber pressure

In a GOOD chamber, the 303 brass design can probably take 80 kpsi, which is almost certainly more than large rifle boxer primers will take with the Enfield firing pin and firing pin hole.

What does it all mean?
Bill is right, with wimpy loads, the 303 can grab the walls and not stretch.
That is becuase brass that is partial neck resized on FL dies will headspace on the shoulder, but with factory loads, the brass is stretched .004" by bolt compression, and the elastic limit of the brass is .002", then the brass stretches .002" with every shot, and is soon ruined.

Thanks for that tnekkcc (and to Billtoo). I love understanding the exact mechanics of what is happening (for some odd reason).

Would you two folks be kind enough to offer an opinion on chambering a No.4 to some caliber using a 6.5x55 case? Larger case volume, larger case base area, slightly higher pressure factory loads (for the 6.5). I also like the 7x57 case ( the 257 Roberts gets my fancy) but the rim is thinner than the 303 case and factory pressure for that round is higher than the Swede I think? Anyway, is it wise to create a wildcat that 'could' be loaded to pressures exceding the action's design capability? (What if someone else gets hold of it and starts loading to case design pressure?) I am happy to load a Swede case to 303 pressure, even with its larger case base area for a No.4 acton but is it wise? (I am thinking of larger case capacity to get better performance at 303 pressure and a necked down 303 has a rather short neck).

what if you had your 280 reamed out to a 280 gibbs, or open the bolt face and go 7mag. I would imagine if you set the barrel back enough it could take care of any chamber issue, however the amount of setback needed may not be to your liking, I say send the gun to westpac so he can report back on if the chamber is really out of round

I brought it to another Smith and he checked it out. He said that the chamber was not "off center". I left the rifle with him as he is going to set the barrel back and turn it into an Ackley.