I've been thinking I need one of these maybe in a Contender carbine. Would want to be able to shoot the heavier bullets, 85 to 100 gr. What do you guys think about these two? Thanks Nimrod308

You must not want it for hunting. The 85 grainers are at the upper end of usable bullets for hunting in either the 6mm-.223 or the 6 TCU. I've owned a number of these over the years in both rifle and pistol format. In rifles, the 80 grain Speer is the way to go for deer. You'll get plenty of tissue destruction and ample penetration. In the pistols, the discontinued 80 grain Sierra SSP was my do-it-all projectile and was used on everything from vermin and varmints to deer and some of Texas' smaller exotic species. I even used that bullet in rifles with good results, but for larger critters such as deer, the 80 grain Speer is a tad tougher.

There's really no appreciable ballistic difference between the 6mm-.223 (6x45) and the 6 TCU. The primary difference is that the case shape of the TCU is somewhat better suited to single shot actions like the Contender. The minimum body taper and sharp shoulder allows better "gripping" of the chamber by the case walls and , subsequentally, results in less backthrust against the frame, though this is a little moot with the .223 case head size. For me, the primary benefit with the TCU is slightly less frequent case trimming (I HATE trimming!). With that being said, I prfer the simpler 6mm-.223. Simply run it through a FL 6mm-.223 die, load and go. There's no case forming necessary.

If you do elect to try the heavier bullets, keep in mind that you'll need a 1:8 twist. All of my small-to-medium capacity 6mms have had a 1:10, but then again, I never intended to shoot anything heavier than 80 or 85 grains.

I think the 6x45 and 6x47 using around 68gr bullets makes a nice varmit rifle. I presently shoot a 6x47 factory Rem 40x with a 1/12 twist barrel.
Problem in either caliber is getting velocity with those heavier 80 gr bullets, myself I've never shot them in either the 6x47 or 6x45 just didn't seem the right bullet. Think the 250 case would be more in line with the velocity I would want out of an 80 gr 6mm bullet.
When you get into 1/7 or 1/8 twist in 6mm you need to watch case capacity for velocity and I don't think the 223 case would work. Alot of good information on http://www.6br.com and those guys cover just about all the 6mm. Well good luck.

I've been using the 6x45 or 6mm-223 since 1986 and have used it for both varmint and whitetail deer.

For deer, I use speer 80gr spitzer bullets over 28 grains of AA2300 with a MV of around 2700fps. YOu can get a little more velocity with H335. H322 proved to be the most accurate in my pistol with 25.5gr of powder with a MV of 2550.

I have not had any problems taking deer from 40 yards on out to 225 yards. If placed behind the shoulder, it will bring down the deer. Only had one deer run 50 yards after being hit. Most fell where I shot them.

YOu can go back and read some of the articles written by Bob Milek about the performance of the 6mm-223. that's where I got my start with this caliber. It has proved to be one of the most accurate barrels I have.

Either one will make a good varmint and/or deer cartridge.

I owned a carbine with Bullberry 6TCU 12 twist, agree with Bobby Tomek.

IF I wanted another to replace the one I sold, I would build a 10 twist (the 12 worked but barely on 85BTHP) and use a 6x45 as you don't have to form a case to get max accuracy and loads.

Keep IT Simple, 6x45, load and go.

my 6 X 45 is not a round for 85-100 grain bullets.....go from there...