7mm Int Rimmed

[nfmMike]

So, can anyone tell me what is so different between the 7-30 W and the 7mm International Rimmed? They both have the same parent case, I notice that the neck of the Waters case is a good deal shorter, and the body of the IR is less tapered, with a sharper shoulder. Other than that, I don't see a huge amount of difference. Why would the Waters be labeled as more powerful? Couldn't the IR be given an "AI" treatment to move the shoulder forward, thus giving the same if not more case space over to powder?
 
I looked at the numbers in two different places, and it seems that the Waters round is termed "rifle? and the IR round "pistol". And the velocity numbers seem to bear out that the Waters is a more powerful cartridge. I wonder if the IR has the potential to come up to that level of performace?
 
Anyone out here know for sure?

[Lone Star]

The Waters is more powerful because it has more powder capacity.  The IntR was a fine case - I had one for a time - but it was designed for a purpose - knocking over steel silhouettes with a handgun.  It had more capacity than a 7TCU so it was more reliable on rams, but it did not have objectionable recoil - this matters during a 40 to 60 round course of fire.  The longer neck was deemed by some to handle cast bullets better that a short neck would, and the case capacity was just right for the popular powders, giving near-100% load density.

The only way the IntR could reach the performance of the Waters would be to move the shoulder forward - then it becomes the Waters.

[nfmMike]

LS - believe me when I don't mean to contradict you, but wouldn't it become a 7-30 W AI?

The only reason I ask is because it looks like the case is already straightened on the 7mm IR.

I didn't look at it from that perspective, I am glad you mentioned it. I have a Super 14 stamped 7mm TCU, but it has been rechambered with no identification, and with any luck, I can find a use for it. A 7-30 W case does not drop in all the way, but looks like it sets out about the difference between that and a 7mm IR. If I determine that to be the case, and it isn't a botched job by the previous owner, then I would like to think I can have the case portion of the chamber moved forward to make it 7-30 W AI. That would be very useful!

Thanks again for pointing that out.

[Jim S]

If you looked at the data in the Hornady manual the loads were developed in a 10" barreled Sterling single shot pistol. I had a 7TCU that had been rechambered to a 7 IR and with the max load of 748--40.0 grains if I remember correctly it would drive a 120 spitzed 2560 out of a 14" barrel TC. It was also quite accurate and accounted for some antelope and deer before I traded it off. The velocities of the 7/30 and 7IR were very close with the 7IR using a couple grains of powder less.