takedown bolt shotgun and sub-caliber inserts

woodchopper said:
yes and no

it would provide more mass and a larger effective 'case head' so it would have a longer impulse over a larger area, but the energy will be the same.
Click to expand...

That is true. The impulse time is the bases for the argument of no smokeless in a black powder made gun even at same pressure. So your right it doesnt change the energy but changes hows its applied and ts slower and thats ideal for not breaking things
 
Evanguy said:
Close to 5000 ftlb of bolt thrust.

.475 internal base area (just a guess based off case od and brass thickness)
28,000 psi. ( saami 45-70 trapdoor max pressure)

Most often its calculated with the external base dimension to have some built in safety factor and its way easier. Most lists you find online is using external. Using the OD of the base a 223 has 6800 and a 30-06 has 10,000 ftlb bolt thrust for comparison.


There is case grip. I believe it was P.O ackley that was doing some testing and removed the locking lugs from a rifle and the bolt didnt open when the case was roughed up before firing. Hard to calculate what it would be though. As its based off that case the chamber condition, also the brass makeup and the pressure then you could start calculate the friction.
Click to expand...

CIP rates 43mauser at 2800 bar (40500 PSI) if I'm not making a mistake anywhere (data from https://bobp.cip-bobp.org/uploads/tdcc/tab-ii/tabiical-en-page53.pdf)

which would give me ~ 7000 ftlb very conservatively - so 223 at least should be ok comparing to your calculations, but 308 not so much :(

this wiki (yes, yes) https://en.wikipedia.org/wiki/Bolt_thrust gives some numbers and matches your calculations for 223 (6833 lb) and 308 (10279 lb)
 
There are two ways that the insert could apply backthrust to the breech. Gas pressure on the muzzle end of the adapter (classic floating chamber application), and backthrust resulting from the adhesion under pressure of the cartridge case to the adapter. These would probably not be substantial.

If the diameter of the inner base of a .30-06 case were, say, .400", its area would be 0.126 square inches. A=pi times square of the radius. If maximum pressure is 45,000psi, then 0.126 times 45,000 equals 5670 lbs applied.
A .223 might have an internal area of .08 square inches (.16x.16x3.14159). With a pressure of 50,000 lbs, backthrust of 4,000lbs.

A steel adapter should be able to contain the hoop stresses generated by a .223. Backthrust should be less than that generated by the original cartridge.

Combined headspace of the adapter and cartridge should also be considered. If loose, a ruptured .223 case head would be most undesireable.
Firing pin fit and diameter are also an issue. Blown primers can result from a large diameter firing pin coupled with a sloppy fit.
 
Last edited:
40k in a 43 mauser is crazy talk. I wouldnt do that unless its in a 98 mauser. With new manufacture barrel

I have one built on a 98 mauser and i run it to 30k thats 55gr of h4895. Heavy load for a 71
 
You must log in or register to reply here.
Back
Top Bottom