Not knowing anything about them, can they be modified to other same family cartridges given the rotary magazine or best left alone. Are the magaines as finicky as the MS bolt rifles for bullet shape, length, etc. Just wondering.

Kind of depends on what you are trying to achieve. In my experience, the 22 HP, 25/35, 30/30 and 303 Savage are basically on the 30/30 case and will work with that rotor. Bullet shape does not seem to matter as long as the overall length is not exceeded. I started out with a takedown 22HP featherweight that had been rebored to 6mm/30/30 Ackley improved by P.O. Ackley himself in the 60's. It worked and fed fine with the stock rotor and that is a big difference in dimensions. In the more modern actions, I would think that the rotor for the 308 case family would probably work with about anything within reason based on that case, 260, 7/08, 358win etc. I bought an N.O.S. 303 Savage barrel and installed it on my 6/30/30 and it fed fine, did the same with my 25/35, put on and headspaced a 303s barrel and no issues. Maybe I just got lucky!

Thanks for the reply.

get 1 or more!!! they are slick !

Are there any 40 caliber rounds that would be suitable for this action, 405 Winchester comes to mind. Anybody with any experiences gone this route.

A .405 would be too long. Think .308 length.

38-55 and 375 winchester were the largest factory diameters. The 358 winchester is the one I would love to have.

Thanks all for the information.

The rotor magazine will limit what you can do as stated above, I see no need for anything bigger than the 284 or 308 for that matter..The 358 isn't any better killer than the .308. A real good gunsmith can convert them and do the rotor work. The best Ive seen is Dennis Olson, Plains, Mt. I bought a .308 that had the chamber ruined by a crackpot gunsmith and got the gun dirt cheap..Had Dennis run a 284 reamer in it to clean up the chamber, so it was a 30-284, it duplicated the 30-06..Did another with a 338-284, and it duplicated the 338-06..Dennis can grind a rotor to fit, most smith cannot do that has been my experience.

By the way, if anyone has a 99F in .308 I would like to buy one.

I got one by asking on AR..good place to do gun deals of all kinds, except perhaps the really high dollar stuff and that's mostly auction stuff imo..Turns out this 308 MOd. 99F I got on AR is a super accurate bug hole shooter, under an inch for 3 shots at 100 yards..A good lever action saddle gun for sure.

Mic McPherson has lots of good how to data on the 99 including a few pages on doing a 375-284 in his book "Accurizing the Factory Rifle"..Lotsa other good ideas and "fixes".

As an aside...found TWO 99's in a hole in the wall gun shop I didn't know was in town...one I'm thinking hard about...an OLD 1927 (supposedly) 250-3000 take down, 26" bbl that would make a nice brother to my 300 Sav, samo-samo...NOT A COLLECTOR...but would be nice just to have as a pricey wall hanger...<400 bucks...lever zip tied so I couldn't see much of the bore...a couple of 1917 "sporterized" to various extents, all matching numbers and a ton of other "gun show" pieces and parts...ALL the clip fed rifles were missing the clips...heh, heh, heh...but were available at extra cost. A few Arisaka's, Enfields, Mauser's and other military "stuff"...original "old" ammo and a 50 dollar 303 Mk 410 rnd mag being passed off as a Ishapore 308 mag. I will definitely go broke now for certain.

Good Hunting

$400 is a steal for a TD IF THE BORE IS GOOD. May not be worth that if the bore is bad IMO..I buy. sell, and collect a lot of 99s..great caliber however. I have on in about 85% over all condition with a minty bore, that shoots under a half inch with almost any load for 3 or 5 shots...I might sell it some day but it will cost like hell due to that kind of guarenteed accuracy or 'll just keep it forever..