OK, now start doing your homework - all the rook calibers
   
(You need to Login or Register to view media files and links)
Scroll down onto Rook rifle cartridges
Each caliber will open up and provide the details for that caliber

Holland & Holland made only 2 Rook calibers
.297/250 Rook: a black powder round that fires a 56 grain lead bullet
Parent case for the 297/250 is a 22 Hornet
.295 (.300) Rook: a black powder round that fires a 120 grain lead bullet
There is no Parent case for the 295/300
(You need to Login or Register to view media files and links)

So again, unless you want a Safe Queen, you best contact H&H with the serial number of your rifle to determine which caliber it is.  Also ask them for a source for brass (Eley possibly until 1962) or any other British source because you won't find these caliber cases outside of Great Britain 

Quote:

If you contact H&H - you might be surprised they tell what the caliber really is?  Original Rook calibers were modified to no end and H&H might have chambered your rifle for one of these different calibers.  If not ... time to start reforming from a Parent case
Let us know your final result because your chamber appears to not be a slam dunk

Almost certain the cartridge this rifle is chambered for is a short (7/8") version of the .310 cadet. The Flemming book lists the dimensions for the longer case and they are a perfect match. He mentions the shorter case but could not find an example of the ammo to measure. Re-boring this rifle would be a sin.

(You need to Login or Register to view media files and links)

The .310 cadet used a heeled bullet between 83 and 125 grs. I believe the ring in your chamber cast is where the chamber ends, the throat beginning where the tapered portion starts to lead into the bore.

Things are starting to fall into place. 

I’ve compared the .310 Cadet to the casting I made and it sure shootin looks right with only two differences. One is the case neck on the Cadet is .327 while my casting came out at .346 however I’m betting if I were to trim the case to the 7/8” (.875) length it would be a match to my chamber. That leaves the question of the bullet diameter. As you know the groove on my rifle came out at .314 and the .310 Cadet uses a .324” heeled bullet. 

Hmmmmmmmmm??????? Do you think it would be a reasonable solution to trim the cases to length (.875”)  which may bring the neck dimension to maybe around .341” and crimp a .314” bullet? Seems like that might not be such a great solution. That said, might you have any suggestions?

Edit: Actually I forgot to account for the wall thickness of the case. Anyone have a .310 Cadet case and if so would you mind measuring the wall thickness? I grabbed an arbitrary rifle case I had and it measured .011” thick X’s 2 and then subtract that from the estimated .341” case neck OD and I come up with a possible case ID of .319”. Which gets me a lot closer to being able to use a non-heeled bullet correct?

Hi Guys,

Have a few updates. I stopped by an LGS and bought a box of 
32-20’s manufactured by Black Hills Ammunition with a max psi of 14,880psi. I called their business and was told this, along with the statement that the majority of their loads live somewhere between 12k-13k psi. Not that it means anything, just what I was told and thought I’d pass on the information. What else? I also measured four places as compared to the chamber casting I made and all dimensions on the 32-20 cartridge were smaller than the casting.

Rim was identical
Base -.012
Shoulder -.004
Neck -.007

Here is a picture for your viewing pleasure 

Hi All,

Just wanted to take a moment to thank everyone for their help. Took the old girl to the range and had a great time. It shoots great and put a smile on my face to get it running again. After a lot of research and numerous phone calls I came to the decision that it would do best with 32-20 cases so that’s what I did. These were loaded to around 12Kpsi and were nice and mild. 4 grains of Unique pushing a 115 grain bullet shoots to the sights, man am I lucky to have found a load that works so quickly. Here’s a pic of the target from 50 yards. Not bad for my first time out. Looking forward to many years of shooting with my new little treasure.

Firpo - take this into consideration:
*The bullet diameter of a 32-20 is 0.3125
* The groove diameter of your rifle is 0.314
* A smaller diameter 32-20 bullet will not provide the best obturation in grooves for best accuracy, plus you will have gas leakage which leads to bore leading
So ... order the Accurate mold I posted in this thread that is 0.314  but suggest you order it with a 0.315 diameter - cast the bullets - reload your rounds & I'll bet your groups will improve
clone of the Ideal 31356 - 125gr bullet ...
(You need to Login or Register to view media files and links)