Frame pressure for different cartridges

[trotterlg]

Just for fun I calculated the pressure in pounds that a cartridge puts on a Handi frame when loaded to the SAAMI maxium pressure.  It is interesting the results you get.  I used the cartridge case diameter at the breach not counting the rim of a rimmed cartridge.  The pressure formula is Pi times the raidus of the cartridge diameter squared times the SAAMI pressure limit.  

30-30 42,000psi gives 5,871 pounds trying to push the action open.

45-70 28,000psi gives 5,605 pounds

.223   55,000psi gives 6,039 pounds

12 gauge 11,500psi gives 5,748 pounds

30-06 60,000psi gives 10,519 pounds

Now I understand why only the newer actions can be re-barreled in the 30-06 family of barrels, however it looks like the shotgun actions are good for the low pressure and smaller case cartridges.  Just an observation, but it would seem that a 12gauge action would handle a .223 or a 45-70 barrel just fine.  Larry

[Mac11700]

but it would seem that a 12gauge action would handle a .223 or a 45-70 barrel just fine

Perhaps for those SAMMI loads...but a trip thru most current reloading manuals...and you'll find some rather higher pressure loads for the 45-70...and with that case head size...well..it's still a-lot of force acting on the actions..

Mac

[Fred M]

trottlg

30-30 42,000psi gives 5,871 pounds trying to push the action open.
45-70 28,000psi gives 5,605 pounds
.223 55,000psi gives 6,039 pounds
12 gauge 11,500psi gives 5,748 pounds
30-06 60,000psi gives 10,519 pounds

I would be interested to know how you arrived at those figures? Please explain.

[Haywire Haywood]

Wouldn't the amount of rearward force have something to do with what it's pushing against in the other direction?  I.E. bullet weight?  I dunno, seems logical, just speculating.  I do know that a muzzleloader with a charge and wad doesn't kick a bit, but add a projectile and...Ta-da... you have recoil (force against the rear of the action).

This is going to be one of those boring threads where formulas and theories are flying and the trig books get dusted off.   :?

Ian

[Fred M]

trottlg

Sorry you did say how. Except the pressure is inside the the case, and the inside diameter of the base is what the pressure acts on not the outside diameter. This also changes with the different makes of cases.

30-30 42,000psi gives 5,871 pounds trying to push the action open.
45-70 28,000psi gives 5,605 pounds
.223 55,000psi gives 6,039 pounds
12 gauge 11,500psi gives 5,748 pounds
30-06 60,000psi gives 10,519 pounds

As a sample the 06 case at the pressure ring measures .468 outside.
the inside is depending on make say 0.400  R^ x Pi x 60000= 7536 to 8500  lbs.
To get a good measurement you need to cut the case bottom in halve.



See the furthest case on the right. Since the pressure is distributed over the larger outside base area there is a reduction of thrust in proportion
of the inside to the out side  400/480 = 17% less thrust or 7534 x.17 =1281 or 7534-1281= 6253.

[Mac11700]

This is going to be one of those boring threads where formulas and theories are flying and the trig books get dusted off. Confused

No it's not...Fred supplied pictures

Mac

[R.W.Dale]

How does the 500 magnum fit in with this discussion. Because now we have a Handi chambering that has a larger case head than belted magnums but has a pressure rating of 60,000psi?

[Mac11700]

Krochus:

In my humble opinion...even though the cartridge is rated at 60,000 PSI...I'm unsure if you can get that much from it...in a Handi...without case stretching and cases sticking.The Hornady ammo is rated at 50,000PSI...only some of Corbons ammo is at full house pressures for it...I'm just therorizing here...and I'm basing it on what happens in the rest of the Handi family when you start pushing cartridges to the max...

Have you loaded any of the 500 S&W up to max yet for it?

Mac

[R.W.Dale]

Krochus:

In my humble opinion...even though the cartridge is rated at 60,000 PSI...I'm unsure if you can get that much from it...in a Handi...without case stretching and cases sticking.The Hornady ammo is rated at 50,000PSI...only some of Corbons ammo is at full house pressures for it...I'm just therorizing here...and I'm basing it on what happens in the rest of the Handi family when you start pushing cartridges to the max...

Have you loaded any of the 500 S&W up to max yet for it?

Mac

 Yes I have and it,s no fun. 345gr cast at 2200fps the new extractors have no problem with ejection.

[trotterlg]

I guess it would be debatable as to which diameter to use, inside or outside, I think the outside is what to use, the case is really just a piston in a bore, so the entire area of the movable piston is what I used.  The amount of energy imparted to the frame is dependant on the bullet weight, but the pressure is the peak pressure in the chamber.  Larry

[Fred M]

I have seen and fired a .500 S&W Hand gun, the case is pretty straight.

So the inside has to be around .500 or a bit less at the botoom.
Say .460??. The outside of the case maybe .540 ?

9966 lbs @ 6okpsi less outside distribution 460/540 = 15%  9966x.15 = 1495.   9966-1495= 8471lbs of back thrust. This close but not excact.

60 Kpsi is pretty hot for a pistol cartridge?

I have seen some loads for the 45-70 with a 600gr Barnes SP bullet at 1400 ft/sec going 54Kpsi. Of course that is well within the strength of a Handi and a Ruger. In a Handi this load kicks out nearly 30 ft/lbs of recoil energy equal to a 300Wby.  Ouch :eek: [/i]

[Fred M]

trotterlg

I guess it would be debatable as to which diameter to use, inside or outside, I think the outside is what to use, the case is really just a piston in a bore, so the entire area of the movable piston is what I used. The amount of energy imparted to the frame is dependant on the bullet weight, but the pressure is the peak pressure in the chamber.

The case can't be considered a piston like a bullet, since the chamber restrains it from moving. Most any long time hand loader has experienced case head separations where the forward part of the case is stuck solid to the chamber walls. The pressure will cling the case to chamber walls restricting any movement,

 The inside base will get the same pressure as the rest of the inside case. Due to the elasticity of the brass it will follow the elasticity of the steel. So the pressure against the standing breech is that generated by the diameter of the inside base.

The spring back of the brass is greater than the surrounding steel allowing the brass to be removed. When you, with high pressure, exceed the elastic limit of the steel you got a badly stuck case.

This is why it is important to have a dry oil free chamber and cartridge  to prevent the case becoming a piston causing very high back thrust. You only want the pressure to act on the base bottom without adding inertia with an oily chamber.

[trotterlg]

If the case won't move or elongate the brass will fail at a fraction of the chamber pressure, that is why a case head seperates, you really can't count on the brass for any strength of the rifle, it is only a seal to keep the gasses from coming out the back.  Larry

[Fred M]

trotterlg

High pressure will elongate the brass, even though it sticks tight to the chamber walls. At about 55kpsi brass is very malleable and will flow in the direction of the least resistance. At that pressure it is well past the elastic limit. Only the chamber hold it together. Also of very short duration nevertheless it is there.

 It is called elastic brass flow and cases get thin at the pressure ring, and come apart. Brass flows forward into the neck because gases push against the shoulders. And you don't need head space for that but thinning speeds up with too much head space.

Brass flow will make your cases long. That is why you need frequent trimming. More so with long sloping shoulders. If you shoot cases long enough even in a good solid chamber with steep shoulders you will have to ream the necks to remove the brass flow to make clearance for bullet release. I know I do it all the time for may BR ammo.

Steep shoulders prevent some brass flow but you still get it even with AI cases.

[Mac11700]

It's more than a seal for the chamber...the brass takes the initial pressure spike and the chamber walls are supporting the case...the brass does start to flow..but the pressure is already dropping...it's a 2 part system with both parts needing to work in conjunction with the other...

Mac

[ScatterGunner]

sequence of events:

1 - cartridge is placed in chamber and action is closed
2 - hammer is cocked
3 - trigger is pulled and the firing pin begins to move forward
4 - firing pin strikes and drives the case to whatever it headspaces on
5 - firing pin compresses and fires the primer, the powder ignites
6A - cartridge pressure rises expanding the case to chamber walls
6B - rising pressure drives the primer out to the boltface
7A - pressure continues to rise, the case stretches to the bolt face
7B - the primer is also driven back into the prime pocket
7C - the buller leaves the neck, pressure also causes brass to flow into the neck
8A - the bullet travels down the barrel and pressure begins to drop
8B - the case springs back somewhat from the bolt face
9 - with dropping  pressure, case releases itself from the chamber walls
10 - bullet exits barrel and the pressure soons drop to atmospheric

all that in about 2 milliseconds from step 4 !

sg

[Mac11700]

That's almost correct...with the exception of before the bullet enters into the rifling...the pressure has started to abate and drop some...and... on certain centerfires cartridges...there is a secondary pressure spike at or near the muzzel...this has been shown in a few differnet calibers...mainly in the larger capacity cartridges likesome of the RUM cartridges...and on some of the Weatherby cartridges.

Mac

[trotterlg]

What I find curious is that NEF will fit a 12 gauge 3.5 inch magnum barrel to a any SB1 or SB2 frame and that magnum round would place about 7,500 pounds of load on the frame, but they won't put a 30-30 barrel on a SB1 frame even though it would be over a thousand pounds less load.  Just wondering if it has more to do with some sort of legal defination of shotgun or rifle than it has to do with the strength of the action.  Larry

[Mac11700]

SB-1 frames are manufactured different...they don't heat treat the frames...the SB-2's they do...hence the higher pressure cartridges are used.

Mac

[Fred M]

Mac.

there is a secondary pressure spike at or near the muzzel...this has been shown in a few differnet calibers...mainly in the larger capacity cartridges likesome of the RUM cartridges...and on some of the Weatherby cartridges.

By what means is this possible?

 I just ran a pressure curve on a 378 Wby Mag with a 300 gr bullet  113.0gr of H4831 Max PSI 63687 MV 3000 ft/sec. Barrel time 1.23 mil/sec

The chamber pressure reaches max at a bullet travel of 2.2" stays there till bullet travels to 2.6" then pressure drops to 32988psi at 10" bullet travel and gradually drops to 12689 at 25" bullet travel in a 26' barrel.

No where along this curve is a pressure spike near the end of the barrel.

I never heard of this muzzle pressure spike. I can't even imagine how it is possible. Can you explain this phenomena.

Ah but we was talking about thrust against the standing breech and a piston driving rearward.

[trotterlg]

Mac11700:  I know they say that, but why can they put a barrel on a SB1 frame that loads it to 7,500 lbs of pressure and not put a barrel on a SB1 frame that makes 5,800 lbs of pressure?  Larry

[Mac11700]

It's not that hard to figure out if you take into consideration to total ballistic picture. Shot gun loads while having a certain amount of pressure...ie 8,000  to 15,000 psi loads...they also have the slowest recoil impulse time... while they do have a larger cross sectional area to apply the back thrust...it doesn't really do this...by the time the shell is moving reward..the brass ring has already swelled enough to restain it's reward movement and the pressure has begun  dropping off...also the plastic is more malable than any brass casing....This is how they have gotten away with the high velocity sabot's...A long time ago...Mike Jordan of Olin explained this to me...this was way back when he was the product manager there.

Mac

[trotterlg]

I don't know, it is very hard for me to believe that the head of a paper and brass shotgun cartridge could restrain 15,000 psi, or even a tiny percent of that.  It has to be hard back against the receiver before the load gets out the barrel, plus, because it is so slow, the pressure must be high for a very long time.  If there is 15,000psi in the barrel you can bet there is 15,000psi on the head of that shot shell.  The shot shell is much lighter than the load it is shooting, so it must accelerate faster towards the rear than the load does to the muzzel.   I am only wondering if NEF is in some position that makes it either illegal, politically incorrect or finacially disadvantageous for them to put rifle barrels on their modern shotgun frames, the numbers I see just don't show me why it is dangerous.  Larry

[quickdtoo]

Ask MtJerry what happens when a high pressure caliber barrel is used on an SB1 frame!!

http://www.graybeardoutdoors.com/phpbb2/viewtopic.php?t=66901&highlight=270+sb1

[Mac11700]

I never heard of this muzzle pressure spike. I can't even imagine how it is possible. Can you explain this phenomena.

I'll find the related material for you Fred...in which they were testing the "Pressure Trace " system and saw this in the larger capacity cases.

I am only wondering if NEF is in some position that makes it either illegal, politically incorrect or finacially disadvantageous for them to put rifle barrels on their modern shotgun frames, the numbers I see just don't show me why it is dangerous. Larry

I sincerly doubt this assumption,we have been told by NEF that the SB-1 frames aren't heat treated and the SB-2 frames are...as to doubting if a shotshell can withstand the pressure...call Winchester and ask them..

Mac

[ScatterGunner]

the thread was bolt thrust !!!

but i've never seen a pressure spike when the bullet nears the end of the barrel either on any P vs T curves..

with all due respect, it really doesn't make any sense, the volume occupied by the burnt gases is expanding, that would intuitively mean the pressure is dropping and the gases are cooling.

we would need a tremendous amount of energy to build pressure to any significant level when the bullet is near the muzzle because the volume is so large.

propane gas has what is called an "Extinction Pop" when a flame burns out, i never heard of a similar effect on nitroglycerin or nitrocellulose based powders.

i'd like to see the supporting documentation you refer to.

a perfectly timed reflection from the initial shock wave that propagates up and down the barrel could cause something, but not any significant secondary pressure rise like that caused by the initial powder burn.

the reflection theory may be all wet too, the velocity of sound in steel is pretty quick compared to the bullet velocity. something make me think the velocity of sound in generic steel is 17,000 fps (??! any help here ??) with a bullet going 1000 fps down barrel, it would out in about 2 milliseconds, while we would be on the 34th reflection !!! the mechanical Q of the barrel would have to be astronomical for it to store energy over 34 reflections !

any mechanical engineers out there ?

sg

[Mac11700]

As soon as I find it I'll let you know...I have a mountain of articles and magazines to go thru to find it..It's quite possible what your describing is what they were talking about..it's been a few years since reading the story..if memory serves me correctly ..it was done at Charlie Sisk shop..on a 270 Weatherby rifle..and they were discussing the readings being given on this paticular rifle and others.Also the problems occured with trying this system with fluted barrels.I'm pretty sure it was in one of my Handloader magazines...but right now I can't recall which one it was in...most of my older ones are in storage.

Mac

[Fred M]

Scattergunner.

new math; 1 grouse + 1/2 oz lead = dinner

Are you ground sluicing with a 2-1/2" 410 :lol:  :lol:

I am an engineer but not a mechanical one but a few things rubbed off here and there. :wink:  We have a mechanical engineer who used to post  here, a Canadian from Ontario. Can't recall his name right now, my memory like my knees are not as strong as they used to be.

[Mac11700]

While this isn't the article it does explain a-little about this.Charlie Sisk was doing the testing...I'll keep looking...


Here is a picture of a 223 with the secondary spike...and their reasoning behind it..

This is characteristic of "finicky" bad loads and is probably caused by a pressure shock wave and/or secondary ignition because the powder burn rate is too slow. The exact cause of the secondary pressure spike may never be determined but it is real. Altering the bullet seating depth, powder charge and even adding a 35 lb. sand bag to the barrel did not eliminate or significantly alter the spike.

Some rifles can produce unusual pressures due to differences in throat dimensions or condition, bore wear, etc. In this rifle similar velocity and much better performance was obtained with faster powders that produced a consistent pressure curve without the second pressure spike.

http://www.shootingsoftware.com/barrel.htm

The amazing thing is ...as our equipment keeps getting better and becomes cheaper to own...there will be a-lot of new things coming to light...that hasn't been seen or explained before.

Mac

[Fred M]

Thanks Mac.

Never too old to learn something. This is very interesting. I am diminished. This is of course an anomaly of choosing wrong components.

The selection of powders and their properties with certain bullets is well established with "Quick Load". It is one of the most useful pieces of software I have ever used. I do a study on each load compare the chrono reading and adjust the parameters of the powder to coincide with the velocities.

You can adjust seating depth, powder charges to a 1/10gr, filling ratio, friction proofing, different powder brand, each change recalculates a whole new set of data. It also changes the graphs to the new data.
Adjusting a load with the most accurate barrel time is one of the features.

It is amazing how close further predictions are. So the event of using a too slow a powder is readily noticeable with the filling ratio and predicted pressure. Yes these are predictions but they sure keep you out of trouble.

With another move it will tell you the all the exterior ballistics of the load.