Would there be any real advantages to shortening a M4? Can a 25gr bullet in the M4 be loaded down to 2500fps with the same accuracy? I'm trying to find something that's small and quiet to shoot rabbits and squirrels out to 200yds. Can this be done on the .223 boltface or do you need a smaller case? thanks

I have necked down .360 DW brass to .17 Mach IV. It is a lot of work. You would have to do the equivalent with Fireball brass (which is a multiple sizing and annealing process). This is a lot of work, but I guess you probably already know that. How about a .17 Bumble Bee (see the latest Hornady manual under handgun rounds)? That may be more what you are looking for, though I don't believe it is on the .223 case head.
If you were to shorten Fireball (Mach IV) brass by 0.2 inches, I believe you would have essentially a rimless .17 Saunders Jet, which is going to be faster than 2500 with a 25 gr. pill, and not a whole lot quieter. This would give you the advantage of dies available from RCBS, though.
Maybe you could shorten the Mach IV even further. This would be a custom die proposition as I think the .17 Mach IV or .17 Saunders Jet may have too much taper to allow you to just grind them down.
There are a host of smaller .17s out there - the Squirrel, Ackley Hornet, Ackley Bee, but I can't remember dimensions off the top of my head.
Get Kindler's and Saunder's books and go from there.

I shoot the 17 Squirrel. 15 gr Berger with 205M primers and 8.9 gr. of 296 for 3720 fps. quieter than a Hornet and good to about 200 yrds. At 2500 fps I think you will run out of steam with anything I can think of. I have a 6MM K-Hornet that shoots a 55 Nos. B-tip at 2700 and it certainly runs out of power at 150 yrds. I can get 3 shots under 1/2 inch at 100 yrds consistently.
May be what you are looking for.
Brooks

Thanks guys for the information. I think I'll order a couple of .17 books and rethink this a bit. If a short, quiet case on a .223 boltface is not realistic, then what bolt action repeaters are available for the Bumble BEE and the Squirrel besides Ruger and Browning? Since noise is a concern and the shots are inside 150yds, maybe a .14 would be better.

what about a 1/7 twist 221. If the bullet were seated deep the case would have a reduced capicity and a mililary 223 case could be formed reducing the case capicity by 1 grain. I have been wanting to try this for a while but cant come up with a reason yet. It just may make a great 200yd gun with the heavy 80gr bullets. It would get the nod on a windy day over the 17cal.

Brno makes an action that would accept the Hornet case. Also it has a .223 bolt action.
Brooks

My stream of consciousness post above contained a few errors. Data for the .17 Bumble Bee is in the Hodgdon loading manual. The .17 Saunders Jet is 0.12" shorter than the Mach IV, not 0.2".
Best action for it would probably be the TC Contender with the barrel made by one of the custom makers - Virgin Valley, Bullberry, SSK, Mike Bellm. The Contender single shot is light and short and easy to carry. Watch it though, this little gun becomes addictive, as you can buy other barrels to use on the frame for a lot les than a new gun. I have 11 barrels for 3 frames.

[This message has been edited by Rob (edited 07-13-2001).]

If you want quiet, You'd be better off going up in caliber. Somewhere out there in net land is a mild quiet loading of the 223 using as I recall blue dot, and as I recall, the velocity is in the ball park of what you are looking for. You can load hornet bullets and they will perform at the velocity you will be using them at.