what would be the biggest caliber wildcat of a 223 case that I could get decent velocity out of?I had a passing thought of using my cz 527 for deer hunting.I know its made in 7.62 x 39 but I was just wondering.

jb,
You leave a lot open to conjecture. When you say:
"biggest caliber wildcat of a 223 case that I could get decent velocity"
Are you specifying the .223 case, or the .378 case head/boltface? I ask because the boltface will also accept the .222 Remington magnum case, which has a small but significant increase in powder capacity. Generally speaking the 223 case is referred to as the _X45mm case, and the .222 Mag case is the _X47mm case.
My knee-jerk reaction is to recommend the TCU line of cartridges. They are the 6mm, 6.5mm, and 7mm TCU. Dies are easy to get, and relatively cheap. Also you can cover a very wide range of bullet weights with these cartridges. Say a 55gr bullet in the 6mm, to a 160gr 7mm bullet in the 7mm, albeit with velocity on the lower end. All could be made up with the slightly longer 47mm case. The 6X47mm has been around for years.
The largest caliber I'm aware of is the 30 Apache, which, IIRC, is the 223 necked to 30 cal with no other significant changes. There is a plethora of applicable bullets with this one.
I guess what it boils down to is what you consider "decent" velocity, and what game you want to take, at what range.
Make sure you have enough velocity at your max range to ensure bullet performance, and make sure you have enough bullet for the game. Following these two rules, you won't be disappointed.
Beware of getting into the wildcat game though, it is a slippery slope.

I would have to see ifthe magazine length is enough for the longer case.
I would prbably need something for whitetail only to a max of 300 yds,usually less than 50.
6.5 or 7mm would be about perfect.better get out some manuals and study

338 works nicely it is also the bigest thing you can fit in a 223 case

how about a 9mm? Waaaaay back when Chairman Jeff built a "super nine"...neck the 223 case straight up, and what do you have? It has the same diameter body as a 9mm. Headspace it on the mouth and you'd have something...different!

Rich
DRSS
Knowledge not shared is knowledge lost...

A gun writer here in Australia, necked a 223 up to .277. He used a Sako action, managed to fit 6 in the mag and from memory was achieving 2700 fps with a 130 gn Win power point projectile.
He did this before the new 6.8mm cal came about. He did mention that Speer were making a 110 gn pill that would be ideal.
I'll find the article if you like.
Malcolm

Don't forget the 5.6x50 magnum. It's the 223 case stretched out even farther. Neck it for 6.5 and use 95 to 130 grain slugs. The 100 gr. BT should be ideal.

http://www.stevespages.com/jpg/cd56x50magnum.jpg

Dang it, now you have me thinkin'!!!

jb,

I built a 6X45 on the CZ527 action a few years ago. The 6X45 is dead easy to load and makes a great lt. deer rifle. I have been able to get 2900+ with a 80 gr bulllet. I would place the cartridge at 150-200 yd max for deer. The magazine has no extra lenght so that is a major constrant, as max OAL is 2.26. I would worry a little about TC cartriges as I feel the sharp shoulder would give feeding problems in a CZ.
Good luck,

Bob

Wooters' old 25-222 Copperhead might be fun and would let you play with bullets in the 60-117 grain range. The 30-221 (dba 300 Whisper) will fit but I don't know if it will feed. Otherwise buy another CZ527 in 7.62x39 and have it rebarreled to 6.5 Grendel.

A couple of years ago I built a 25-204 and it will duplicate the factory 250 Sav. 100gr NPT's at 2800 fps, 87's at 3000 and 75's at 3150. It has worked so well on deer that it is my go to deer rifle now. The 204 Ruger case is like an improved 222 Rem Mag. easy to work with and a great selection of manufactures. I think it would be a little long for the CZ action my COL is 2.460.

375win

I believe Kimber had a .257 on the .223 case. Something like ".257 Kimber". Little light, but deer at closer ranges, smaller deer, o.k. Decent velocity, but with 6mm ULG/ TCU... Why?Cute rifle I could not afford.

As I recall, the case is about .378 diameter. So if you headspaced on the mouth, you might squeeze in a .375 bullet. Or .358. I think someone suggested .338. Then there is that European 9.6 (.366) bullet. How odd you want to be? Of course with that powder capacity you are not going to rival the .375 H&H even with the "hot lands" factory loads... But you should exceed the .38/40 of yesteryear. How much velocity/range is "enough?" I suspect you would find the 6mm or 6.5mm or 7mm TCU's decent and satisfactory. luck.

using 30-30 bullets would be max imho good for lower velocity functional impact.

with the higher preasure you can run getting 30-30 ballistics would be the goal.

the 6.5 to me makes the most sense with all its wide variety of bullets. shoot 120 grainers and have fun.

The 257 Kimber is on a blown out 222 Rem Mag cace and the capacity is just slightly more than my 25-204 but the Kimber brass needs serious case prep as the shoulder is moved forward and the body straightenned, The 25-204 is a straight neck-up. The Kimbers shoulder is just a little farther forward than the 204 that it needs alot of the case forming also to be used for the Kimber.

375win

quote:

Originally posted by nordrseta:
( buy another CZ527 in 7.62x39 .

I like the way your thinking

I just found a set of 25/223 redding dies I purchased to buid a rifle, I originaly thought of the 25 TCU, which is almost the same but was not sure how the TCU would feed in a bolt with the 40 degree shoulders. I did not think of the 204 necked up. I decided on the 25/223 just because the dies came around at a good price and thought this was a good middle of the road between the 25/222 and the 25x47 (222 mag).

I think I am going to build this on a 700 action, #2 countour, 20" tube in a 13 or 14 twist and limit the bullets to 75 and 87 gr.

I have had a 30X223 in a Remington XP100 for quite a few years. Used it for Metallic Silhouette shooting. I used a 150 gr. spire point and out of a 15 in. bbl. I was able to get about 2400fps. Easy to load. Not much shoulder left. The 338 will leave very little shoulder and is better to headspace on the case mouth.

I have a 7mmTCU with a 26" douglas barrel on a mini-mauser action. With a 120gr bullet i have chronographed it at a little over 2800fps. A real nice tack driver as well. Nice litte pill,and of coarse no recoil.

What kind of velocities would a 223 necked up to 30cal, get with a 125 grain bullet?

This would be in a 20" barrel.

Or, what about a 7mm 140 grain bullet? Could it break 2600fps?

The late Tony Barnes used the 30 Remington case shortened in his Sako pistols and got some decent velocities. He shot elk, moose and deer with it.

My choice was the 6x45 (6mm/223) and a 75 gr. Barnes X for 2900 FPS in an 18" barrel..It is an excellent deer rifle, weighs 5 lbs on a my L-461 Sako acion. I have shot a number of deer, antelope, varmints and African plainsgame with it. It is a well balanced caliber. It will also shoot a 100gr. bullet at 2700 FPS and that caliber and load are very popular with South Africans..