Looking for a bolt thrust reference chart. I would like to know the bolt thrust for the following cartridges at typical factory velocities and pressures:

500 Jeffery- 535 or 570 grain loads.
450 Rigby 500 grain loads.
416 Rigby 400 grain loads.
300 Win Mag 180 grain loads.
308 Win 150 or 165 grain loads.

Thanks in advance.
Matt

Never seen a chart. Roughly = (Case head area in square inches) x (nominal pressure in PSI)

Example: if case head (rim) diameter of .804" = .508 square inches. If Nominal pressure of say 55,000 PSI x .508 SI = Bolt Thrust of 27,940 lbs on the bolt face.

Onviously, there is a direct relationship between case head diameter and bolt thrust given pressure as a constant.

So as long as the shooter weighs at least 28,000 lbs or more then she won't move backwards upon firing.

quote:

Originally posted by Macifej:
Never seen a chart. Roughly = (Case head area in square inches) x (nominal pressure in PSI)

I know that you said "roughly", and to be clear I'm not taking you to task...

I have almost always seen the formula given as you did above: "pressure x case head area". I believe this is entirely incorrect and(usually) makes belted and rimmed cartridges appear to have more bolt thrust than comparable rimless cartridges. It also make cartridges with rebated rims appear to have less bolt thrust than comparable cartridges with standard case heads.

In other words, a rimless cartridge would have the same bolt thrust weather you turned down the rim(making it a rebated rim) or expanded the rim(making it a rimmed cartridge) if everything else was left the same.

Bolt thrust is actually a function of pressure and the area of the rear internal wall of the case(as that is what the pressure is actually able to "push" on). The area of the case head has nothing to do with bolt thrust.

So a 375 Ruger would have more bolt thrust at 60k PSI than a 375 H&H at 60k PSI because the Ruger has larger surface area(or cross section) inside the case.

Example given would fit BMG case with a .800"
diameter base and rim. But the thrust area is on the
inside diameter, which is hard to measure, and the
sides of the case stick to chamber on firing and
the case takes up part of the thrust.So the above formula
is multiplied by 2/3 which gives actual "bolt" thrust.
2/3 of 27,000 lbs in above example is 18,000.
500 Jeffrey is a .620" base, with .307 sq in cross section,
say times 50,000 psi, gives 15,000 lbs, times 2/3
gives 10,000 lbs of "bolt" thrust. I highlight the
word bolt, as this thrust isn't directly related to
recoil, which is controled by speed, bullet wt,
gun wt, etc.ED

It is ID of the case, at max, but it's just as easy to compare outsides, though not as accurate. 60k On a half inch is the same bolt thrust, every time. Just like a pound of feathers weighs the same as a pound of mud.

Metallic adhesion...

Cartridge casee is not floating in the chamber-it immediately expands and adheres to the chamber walls, albeit the case strecthes to fill the chamber void radially and longitudinally....

I think one would have to stretcha case mechanically, record the effort and then convert it into PSI and then subtract that figure from any surface area computations....

More complex a question/formula either attempt.

Bottomline is: Who cares for other than academic purposes? It has no relevant application to guns otherwise, does it?

As long it is is quite a bit less than the shear strength of the lugs/lug recesses, we are good to go.

The engineers figure the cross section of the sidewalls,
and times it by the tensile strength of brass.
This gives a figure of what case would take of the
thrust without a permanent stretch. Then they take
co-efficient of friction of the sidewalls (based on
dry, oily,etc) times the area of sidewalls, times
the psi.
Using bmg, base side cross section is about .15 sq in
times tensile strength of brass, about 50,000 psi
gives 7500 lbs thrust it can hold without failure.
With a gun of normal headspace.
Using bmg case with about 5 sq in of surface in sides.
If dry, co-effiecent is about .04, times 5 sq in
gives .20 times say 60,000 psi, gives 12,000 lb thrust
the case friction against the sides is holding.
More than brass holds, which is why most calibers with
extreme headspace at high pressure, the brass stretches permanently.

If you took inside cross section of .38 sq in times 60,000 psi
bmgs are loaded to, gives about 23,000 lbs thrust, minus
about 7,000 lbs case takes up, gives 16,000 lb thrust.
The simple outside measure, times psi, times 2/3 formula, gives
a little more which is safety factor in favor of the gun.
And all gun makers try to design lugs to have at least 3 times
the shear rating as the bolt thrust for biggest load.Ed

Lilja briefly covers this and lists the most common inside diameters encountered.
lilja tech

The average bolt thust as opposed to the peak would be greater with something like a 7mm STW than a 458 Lott because average pressure would be higher, assuming the same peak pressure.

OK, the formula on the Lilja website is straightforward and easy to use. The chart giving inside diameters of the caseheads gets me a long way with all of the cartridges on my list but the 500 Jeff. Now I just need to know the max PSI (not CUP) for all of the above cartridges and I'll have my answers. Does someone have this info to share?
Thanks
MATT

.620 max exterior diameter ....580 boltface or there abouts
44k cup is ABOUT 51K psi

Using the formula for bolt thrust calculation found on the Lilja barrels website, Here is what I've come up with so far:

Bolt thrust= Area x Peak chamber PSI
Area = 3.1416(HS/2)squared
HS = I.D. of casehead

BOLT THRUST
450 Rigby: 11388 @ 58,000 MAX PSI
416 RIGBY: 9253 @ 47,125 MAX PSI
300 WIN MAG: 8866 @ 64,000 MAX PSI
308 WIN: 7005 @ 60,175 MAX PSI

I found a link to a page with CIP standards in "Bar", as well as utilizing some PSI info found on Wikipedia (1 bar roughly equals 14.5 psi).

I found an article in realguns.com regarding the 500Jeff. The article gave a backthrust number of 10612psi for the 500jeff along with numbers for a few other big bores. The number given for the 416 Rigby was only about 25psi less than my calculation. However, backthrust given for the 458 Lott was about 2500psi higher than my calculations. This leads me to believe that a differnt formula may have been used by the "Realguns" author.

500 Jeffery:
Using the .620 exterior (all my other calculations used interior diameter )diameter that Jeffeosso just mentioned and a max CIP standard psi of 47850 (3300 BAR), I come up with a bolt thrust of 14,446 psi. This seems very high.

My math skill may not be on the highest order, and I may be using a formula that does not take into account enough variables. I don't know. I don't even know what a "Bar" unit is.
If someone can see some errors in my calculations, please correct me.

Thanks for all your help.
Matt

Americans just use an antiquated measurement system; Bar is metric pressure. These different measurements are most often encountered when discussing gauge pressure on turbocharged cars. Germans (Porsche, Audi, et al) generally use Bar where Americans (Buick GNX, Neon SRT) would use PSI.

You've got me curious as to what set this off; what are you trying to do?

"CIP standard psi of 47850 (3300 BAR), I come up with a bolt thrust of 14,446 psi. This seems very high. "

That is why you multiply by 2/3 to get actual thrust.Simple
and fairly accurate..ED

quote:

what are you trying to do?

Mounting rear facing 500 Jeffs in his European model Dodge Neon Turbo no doubt ...

quote:

You've got me curious as to what set this off; what are you trying to do?

I've posted here before on AR that I am having a 416 Rigby built on a standard 98 action. I knew that the 416 Rigby has relatively low bolt thrust due to its low operating pressure. I just wanted to know what the bolt thrust of other cartridges (bigger and smaller) is, just for a comparison.

C-Matt

quote:

I come up with a bolt thrust of 14,446 psi. This seems very high

The calculations DON'T give you PSI bolt thrust, they give you pounds FORCE bolt thrust.
You can than use that FORCE number and the AREA of your bolt lugs to work out the shear strength of the lugs. Area * pressure = force. Force / area = pressure

A 30-06 with outside base area of .18 sq in, at 60,000
psi will be same bolt thrust as the 416 Rigby with .27 sq in
base area at lower 40,000 psi, that factory loads.
Which is about 7200 lbs of thrust or force.
60000 x .18 = 10800 x 2/3 = 7200 lbs thrust.
40000 x .27 = 10800 x 2/3 = 7200 lbs thrust.
Average bolt gun has 31-35,000 lbs of shear strength built into
the locking lugs. Strength of steel properly heat treated is
about 140,000 psi, and engineers cut that in half as we
are dealing with shock loads against lugs, say for an Enfield
with a lug cross section of about .5 sq in times 70,000 psi
half of 140,000, gives a shear rating of about 35,000 lbs. Ed

That is cool info. Thanks ED!

quote:

Originally posted by hubel458:
A 30-06 with outside base area of .18 sq in, at 60,000
psi will be same bolt thrust as the 416 Rigby with .27 sq in
base area at lower 40,000 psi, that factory loads.
Which is about 7200 lbs of thrust or force.
60000 x .18 = 10800 x 2/3 = 7200 lbs thrust.
40000 x .27 = 10800 x 2/3 = 7200 lbs thrust.
Average bolt gun has 31-35,000 lbs of shear strength built into
the locking lugs. Strength of steel properly heat treated is
about 140,000 psi, and engineers cut that in half as we
are dealing with shock loads against lugs, say for an Enfield
with a lug cross section of about .5 sq in times 70,000 psi
half of 140,000, gives a shear rating of about 35,000 lbs. Ed

We do not compleetly agree on the excact figures. My calculations based on factuel inner casedimentions in several different brass brands gives the following theoretical max thrust in an oiled chamber
8000lbs from a 416Rig within specs
6666lbs from a 3006 with 60000psi

Static test we performed on numerous unaltered m98 actions
Boltsetback from 16.000lbs up to 30.000lbs all depending on brands and surface hardness
shear from 18.000lbs up to 38.000lbs

Static test performed on altered m98 (feedramp shortened .12", whidened fo accept and feed 416)
Bolstetback from 9.000lbs up to 20.000lbs
Shear from 9.300lbs up to 20.000lbs

Static test performed on altered m98 (feedramp only .05" shortened, but whidened to feed 416)
boltsetback from 13.000lbs up to 25.000lbs
Shear from 14.000lbs up to 25.000lbs

In all cases on the altered , first you have lugsetback on the lower counterhold(feedramp) in the action, followed by sheat of the uppet lug on the bolt followed by complete shear of the lover counterhold(feedramp)

For an 416rig you hawe an altered m98 action wit potential to carry from 9.000lbs to 25.000lbs, beeing used for a cartridge nominel producing 8.000lbs of thrust, but with capability to produce 12.000lbs- 15.000lbs of thrust, with no sighn of highpresure (caseheadekspantion or flattened primers) It can works, but in traditionel gunbuilding or designing, i find is "eksiting" to be polite.

While on a unaltered M98 action in a standardcaliber, you have an action capable og carrying atleast 16.000lbs beeing exposed nominel max with 7.000lbs, with little chance to load higher than 8.000lbs without clear sighns of high presure.


Most steel used for manny actions has properly heattreated(surfacehardened) rupturestrength around 95.000 psi, while tough hardened types has around 140.000psi
The shearstrength is often 15%-30% lower
Steel used in m98 is basically low carbonsteel beeing casehardened

I'll have to get out of the habit of oiling my chamber before shooting!

I wasn't referring to bolt setback in figuring the shear
rating of the bolt lugs on the bolt. Bolt setback in properly
treated actions and bolts, proper steel won't occur unless grossly over loaded,
which dents the seats mainly to start with. Notice I stress properly treated,
proper steels, in giving the info.

As for your thrust figures, they are exact based on your
method, BUT my point and formula is based
on not being able to get precise inner dimensions.
(And that inner dimension can be interpreted different depending
on where measured, in area where radius blends with the side.)
But ours gives a close safe figure. Like you say 6660- I show
7200, a safety factor in favor of the gun.And within 10%.

Even oiling chamber doesn't lower co-effiecent of frictin
to zero, an oiled chamber still has a quarter of the friction
a dry chsamber has.In my bmg example above an oiled chamber would hold
about 3,000 lbs thrust compared to 12,000 dry chamber.
That is 40% of the 7500 lb brass tensile strength I showed above.
So oiling chamber won't blow up the gun with regular bmg loads.
It just adds 4500 thrust to the bmg bolt but those guns have
the same 3 to one safety factor built into their bolt lugs.Ed