Reading the thread below I would like to know what calibre in " is a 12 bore rifle and what is the ballistic performance,

and also what is the most powerful Nitro round that could be done on the greener 12 gauge could it take a .600 nitro ??

[ 11-18-2003, 14:25: Message edited by: PC ]

You should talk to Marrakai about this one PC .

Try this link.
http://www.australianhunting.net/phpBB2/viewtopic.php?t=1422

(hope it works)

Bakes

Thanks Bakes, he also hangs out here a bit to doesnt's he ??

Thanks for the help Bakes.

PC:
Bakes has assumed you mean the Greener 'Empire' SxS shotgun, however there has been quite a bit of discussion on using the Greener'GP' single-barrel gun.

I think the GP sidewalls are a bit on the thin side for full nitro loads in cases with large head diameters. As I understand it, the total force on the breech is equal to the peak pressure multiplied by the area of the case-head (plus or minus brass strength, case friction against the chamber walls, etc). The .400 3-inch generates 16 tons peak pressure, whereas the .600 only generates 14 tons per square inch. Because of the difference in case-head size, the .400 potentially exerts 3.73 tons on the breech, whereas the .600 exerts 5.34 tons. A Winnie Super-X 12-bore at 10,500 psi, presumably safe in the original GP, exerts 2 tons on the breech.

The 'Extraordinary Gentlemen' elsewhere on this forum are planning to build an oversize GP frame to successfully contain the '12 gauge from hell- short', though the Martini-Henry or Martini-Enfield actions are more heavily built than the GP and might be suitable for cartridges up to .577 head size. Admittedly the GP would allow greater chamber wall thickness. Its a trade-off.

I seriously doubt that big straight cases like the .600 could be made to chamber in the Martini action. They would have to be almost straight in-line with the chamber before being pushed in, and this may not be possible with a 3-inch case in the 'tipping-block' Martini. The usual 'express' cartridges for the Martini-actioned big game rifles of the day were short bottle-necked variants of the more popular calibres.

I know Martinis are stronger than most people think: a mate here in Darwin shoots factory .30-30 cartridges in a Martini Cadet wearing a re-chambered stainless Mini-30 barrel! The Cadet action is quite small compared with the GP.

12-bore rifles were usually bored .729, so the groove diameter could be anything from .735 to .740. Projectiles were probably most often .735 diameter.

Marraki,

thanks for your help mate, I am not sure if it's worth trying to find a greener or not ??

I saw a 1909 argentine at my smiths to day already set up for the .404 Jeffery and I just said "I want it" it just had sex appeal....you understand

I am bloody hopeless

pc jansa arms had some for sale gps

I have often wondered how much back thrust there actually is on a 30-30 Win.

SAAMI maximum pressure is listed as 38,000 CUP
for the 30-30,yet I have examined many fired cases where the primer protruded .010 or more from the case head.This condition to me indicates that there is not enough back pressure to reseat the primer.

Perhaps there is not as much actual back pressure on a straight medium pressure cartridge
as many think.The elongation pressure of the case,coupled with the grip of the chamber walls may be absorping most of the back thrust.

I would speculate that a plastic shotshell may produce more back thrust than a brass case.

Has anyone done any scientific studies on the subject?

WC