David White did some experiments with parent cases, their improved offspring and others that I thought might be interesting to the members here. This was done in TC type barrels with out a closed breach. The "flapper he devised to fire the cartridges with drove the improved cases .004 deeper in to the chambers than their loaded position and the expanding brass held them there.

Fire forming loades back out of the barrels from 1/2 to 3/4s of an inch, but the cases were prevented from ejecting the barrels in all cases. A 35 Remington fired in the same way had cases exit the barrel at 12oo, 800 and 1300 feet per second, which would exert considerable backthrust on any action. Here is a link in case you would like to read the experiments and related materials for yourselves, Rusty.

http://www.bellmtcs.com/forum/index.php?act=ST&f=24&t=1...aa10400c3db7c23ba23g

I can say i have read it and I am a believer. I currently shoot a 6mm 30-30 Imp. which is nearly the same as Davids. Total body taper on my Imp. is .004" with a 40 degree shoulder. Although I could confortably load up from where I have now I like the way it shoots and cases last forever. 58 gr. Vmaxs will run 3400 fps. with no trouble.

SKB2706: That's pretty impresive, Rusty.

I have a question about this experiment done by D. White. How did he come up with the velocity of the ejected 35 Rem brass? Did he set up a chronograph behind the breach "just in case it happened"?

Reading the article, David set up a chrono after a couple of the cases were ejected, just to see what the velocity would be. Tapered cases and the 44 mag came out of the barrel pretty fast.
Good read. I save it in my computer as I have been toying with the idea of a improved cartridge for a new barrel on one of my contenders.

Mike

rusty - you outta see what it does to prairie dogs.............lets just say it gives up nothing to my 22-250.

If you don't mind making up the brass ....minimum taper/sharp shoulder rounds are the cat axx for break action guns. There are no feeding issues, backthrust is the number one limiting factor for standing breech guns and max pressure.
Perfect example
.223 AI or for that matter a 22/30-30 Imp. in a Contender carbine loaded up to max. is less than 100 fps slower than a 22-250 in an Encore using 50 gr. bullets.

I thought it would be easy to match the 6.5 JDJ ballistics with the 6.5X50 Japanese and being a cheapskate I could avoid the cost of the custom dies. So off to JDJ's outfit SSK industries went my 14" 6.5 TCU barrel. It was returned promptly with a fine looking chamber and I set forth to set new records and use the brass I had purchased to use in my Type 38s. They all have the oversize chambers that MUST be a trait of the Type 38 and I refuse to waste good brass on them!

I started loading the Super 14" 6.5X50 and was very happy with the accuracy, but lackluster velocity hardly exceeds the TCU and that is burning more powder. Disappontment set in and it went into barrel storage til Rich Jake announced on the net that he had decided he wants to buy one. I offer to let him test mine and make his decision after that.

He did some testing and found the same thing I did. Little increase over the TCU compared to other cases (with far less body taper) that do well in the Contender!!

Results of his testing are posted several different places on the net and I assume doing a search for Rich Jake will find one or more of his write-ups of the experiment. Poking around I came across the barrel justthe other day and thought maybe I should dig it out and do some testing with 100 grain bullets later on in the winter (can you say AFTER deer season).

All that to say that "Taper Matters".

I had hope for louis' 6.5x50 barrel. After Receiving the barrel & running it through I found that I was having all kinds of problems reaching the velocity it should have easily attained. It seemed that this cartridge suffered from severe pressure swings with a very little powder change. Very large flat primers happened regularly as well. I think that if that cartridge were Ackley Improved it would probably do very well. I believe that the sharp taper in the cartridge didn't allow it to work well in the Contender.

I hope that Louis will try to AI that cartridge. Unfortunately to do that he'd have to have custom dies made. I think it would be a good experiment Louis to see for sure, if you have the Money to gamble on it. Otherwise I think the Bower 6.5 maybe the way to go to save that barrel.

The custom die price is a one time expence. Sure the cost is substantially more but that cost is quickly forgotten when you are getting the results you want. It probably pays to go with a cartridge that is a known entity when considering paying for custom dies. Having barrels rechambered costs as much or more than the custom dies cost. It might be better to start from scratch with a new premium barrel from a maker that you trust and of good reputation...Rusty.