How strong are the '73's?

[Nath]

Hmmm, I can not remember were I read that now my self! I am pretty sure it was in a respected British gun mag.

What I do know is guns in Brit get a stampmark on the barrel and the action/bolt.

I will have a look,,,,

N.

[Nath]

I am struggling to find any information on the test I suggested!

I need to stop spouting it from now!

Thanks.

Nath.

[Leverluver]

Nath

That may be referring the the old breech thrust CUP system. Lubing the case would not have any affect on a piezo chamber pressure system. Except for some older double's rounds that have no other baseline, I don't even think you guys use Base CUP much anymore. Most of the ones that were tested that way, have since been converted to the CIP piezo system.

[KWK]

I need to stop spouting it from now!

Hardly -- there's no reason not to toss ideas out among friends.

I haven't seen definitive proof on the effect of case cling towards neutralizing breech thrust. When I look at the thickness of the brass, I think to myself "Ackley was surely pulling our leg," yet others have reported similar results. There's an older gent retired from Los Alamos, I think it was, I tried to sweet talk into running stress simulations on this, but I don't think he's ever gotten around to it. If you search around the web you can find some simulations he's run along these lines, but it doesn't include a calculation of the net result of case cling at low pressures. I recall it concludes that at full power, the breech will carry a hefty load. It may well be at middle pressures cling can carry most of the thrust. Perhaps I should dust off that ME degree of mine and have a whack at it myself...

[KWK]

On this page one can find those interesting stress calculations, and I see he's been busy! He has done a lower pressure run, and it shows the brass can nearly carry the load at 35 ksi, which is down towards .30-30 pressures. This was done with the fairly thick brass of the .243. Perhaps more pliant .30-30 brass would have held on longer? Regardless, primer thrust is not neutralized. The little piston known as the primer has it's own cling but still delivers a surprisingly strong push to the breech.

At full pressure, the breech takes a pretty good thumping. I must study his results more closely (tomorrow night).

Karl

[Leverdude]

Brass isn't real strong stuff. Above moderate pressure I'd think the head would seperate if the case walls stuck to the chamber & nothing was behind it.

[Nath]

That is very interesting and thanks, it does have some effect on the lock up then when lubed but there are also other factors that can also increase bolt thrust or even induce some form of percussion to the bolt.

The thing of value to me is the time scale. If a brass case was inflated with air slowly to these pressures it would burst very early. Look at an air reservoir on an air rifle, because it is holding on to that pressure indefinatly it has to be alot thicker than a brass case even though the air pressure is way lower.

Even though actually bolt weights are impressive as in thousands of lbs it is over next to no time. We could stand an 8000lb weight if it was only on us for a fraction of a second.

Thanks.

Nath.

[Leverdude]

We could stand an 8000lb weight if it was only on us for a fraction of a second.

Well, that depends how thats applied. Bullets have much less than 8000 ft/lbs & zip right thru stuff in a fraction of a second.

[Nath]

We could stand an 8000lb weight if it was only on us for a fraction of a second.

Well, that depends how thats applied. Bullets have much less than 8000 ft/lbs & zip right thru stuff in a fraction of a second.

I mean as a dead weight.

Ft/lbs is a calc and not actual weight, the bullet in your example would not weigh 8000lbs.
It can be calculated so to demostrate theoreticaly that it could move a 8000lb weight one foot but in reality it won't.
Another way to put this is if a bullet could move 8000lb one foot then how many feet should a 8lb rifle move in the opposite direction?
Hence why I give no creedance what so ever to ft/lbs! (other than tightening down a cylinder head!)

Nath.

[Leverdude]

We could stand an 8000lb weight if it was only on us for a fraction of a second.

Well, that depends how thats applied. Bullets have much less than 8000 ft/lbs & zip right thru stuff in a fraction of a second.

I mean as a dead weight.

Ft/lbs is a calc and not actual weight, the bullet in your example would not weigh 8000lbs.
It can be calculated so to demostrate theoreticaly that it could move a 8000lb weight one foot but in reality it won't.
Another way to put this is if a bullet could move 8000lb one foot then how many feet should a 8lb rifle move in the opposite direction?
Hence why I give no creedance what so ever to ft/lbs! (other than tightening down a cylinder head!)

Nath.

I was joshin you, just forgot the smiley.

[Nath]

No worries sir

Nath.