Hi all....I am thinking about bringing back to life a fine but abused doublerifle by lining it much like Brily does with shotguns. For those interested, I am planning to re-regulate it with eccentric sleeves at the muzzles. The planned calibre is 375 X 2 1/2" flanged Niro express that has a working pressure of about 29 000 psi. In order to optimise the liner design, I was wondering if anyone knows how far from the breech the barrel pressures are about 1/2 of the breech pressures? Any help greatly appreciated. Cheers Kevin.

I can't find a 375 flanged by 2.5" in Quickload. I can find a 375 flanged, but it is 2.9" long.

Running that simulation at 29,000 PSI, shows a drop to about 15,000 PSI at 13 inches of bullet travel (i.e. 16" of barrel). 20 to be safe? HTH, Dutch.

Dutch...thanks so much for your help. That software program sounds quite sophisticated. The cartridge in its data base is the rimmed version of the 375 H&H. Nonetheless, your info gives me some idea of how quickly pressures disapate. If I gave you the case dimensions and capacity, is the program capable of running the calculations? Thanks Kevin.

Quickload can't, but it's companion program "Quickdesign" can create any wildcat out there, and can then export the design into Quickload. I do not own Quick-design.

HOWEVER, if you give me the approximate case capacity, in grains of water, I can simulate a similar capacity cartridge to (VERY) closely approximate the case you are working with. Knowing bullet weight and the preferred powder helps, too.

If you post on the Wildcat forum, some of the posters there might be able to assist you with a Quickdesign simulation.

You used to be able to download a demo of Quickload from neconos.com, their US distributor. HTH, Dutch.

Hi Dutch and anyone else following this who might have access to "Quick Design." (I suspect that I soon may purchase it!) The case is a rimmed case with no shoulder. Length- 2.5". Neck diam. - 0.397. Neck wall thickness - 0.010". Base diam.- 0.456". Base wall thickness - 0.030". Rim thickness - 0.060". Loaded length with 270 g bullet - 3.10". Case capacity 49.9 grains water. Suitable Powders - IMR 3031, IMR 4064, RL15. etc. Any help greatly appreciated. Cheers Kevin.

Ok, here's what Quickload comes up with, strong-arming it into a 49.9 grains of water and 2.5" case.

Because it is a MUCH smaller case than the .375 H&H flanged, the pressure rise and fall are much more rapid.

IMR 3031, 99% fill, 30.5 grains. 270 gr. Hornady Roundnose, 22" barrel. IMR3031 is near perfect, also worth trying would be N135, Norma 202, or Accurate 2520.

2003 BAR (29,055 PSI), max PSI at 0.7 inches of bullet travel. 15,000 PSI at 4.9 inches of bullet travel, 10,000 PSI at 8.2", and 5,000 PSI at 16.2". Add the 2.5" of case length to the bullet travel for barrel location.

Predicted muzzle velocity at 1730 fps (527 M/s), 1793 ft lbs (2431 Joule).

No buffalo slayer, this........ HTH, Dutch.

Dutch...THANK YOU THANK YOU THANK YOU. This confirms my suspicions and will allow me to make the liners very thin past about 14 inches, thereby avoiding a muzzle heavy gun balence. I think that your program is quite accurate. The original cordite load was 2000 fps from 26" barrels but this was also calculated with balistic pendulums.(circa 1900, pre-chronographs.) The modern chrono loads seem to be running about 100 fps slower.

The rifle is a 1903 Watson Bros double rifle with horrible pitted and worn damascus barrels. The idea is to bore them out almost completely and then turn barrel blanks to fit inside the existing bored tubes. With any luck, once completed and refinished, no one will be able to tell the work was ever done.

Regarding the cartridge. Given the rifle only carries express "V" blade sights I can't imagine using it much past 150 yards. (The sights are optimistically regulated for 100, 200, and 300 yards.) So long as one doesn't attempt a "texas heart shot" and uses decent bullets, I hope to use the rifle in timber for elk. Anyway, it's off to the lathe. Thanks again so much for your help. Cheers Kevin.