6TCU versus 6BR

[Freestate101]

Does anyone have any personal experience comparing these two cartridges? If so: what are the differences in accuracy, velocities,using 70-95 gr. bullets), and barrel life? I use a 6CM for all of my shooting now, but am considering something using less powder and a little quieter for a med. range walk-around varminter. I would use the 6CM, but it's throated for the 115 and 107 gr. bullets. Any help with this will be appreciated.

Jim Berry

 

[olympian]

If Jim Harris is on here, he would be a good one to field this question. My understanding from him is the 6TCU runs a couple of hundred feet per second slower than the 6BR. For a walking varminter, I do not think one would notice a difference between the two in accuracy, practical velocity, or barrel life. Getting rounds to feed from a magazine might be a different situation. Both would work fine.

 

[Freestate101]

Thanks for the reply Olympian, I hope Jim chimes in also as I am very curious to find out if anyone has compared the two rounds.

Jim Berry

 

[TominSWNY]

I would put the 6TCU in the same category as the 6 ppc. The ppc has the edge in accuracy in a bolt gun. I have reached 3700fps with both rounds with 55 gr bullets.

 

[GrocMax]

For me, on 55's, 6BR 4000FPS 6TCU 3700.

 

[Chuckw]

I have built a number of both but i just love the TCU for a "hunting" rig. I built one on a 14 twist at 26" just to see how close it would come to running with a BR. It would do 3700+ with the 55's but i generally shot the 60gr sierra at 3600. Even shot some 80gr bergers at 3200. NO, it definitely wont keep up with a 6BR on a level playing field, but its about as good as you can do on a small BF receiver with UNLIMITED brass availability, and the ability to magazine feed. I shoot fast twist barrels now and have pushed the 95mk to almost 3100 but the brass didnt like it. I settled on 2950 and all is well. Cant wait to try the new 95 TMK. I have been doing all of my varmint, predator, and deer hunting with a TCU for the last 3 years. 2 big WT bucks, a good muley, and countless hogs and coyotes didnt know the TCU wasnt as good as the BR!

 

[th82457]

The TCU will feed much better than the 6mm BR in most rifles and does offer a much better availability of brass. Good Luck !

Terry

 

[GrocMax]

Just got the 6TCU 58vmax load done today. 3700fps, could probably hit 3800 and stress the cases a lot more.

Same bullet same powder 6BR 3900 with 3.7g more powder and 1" more barrel. Both shoot the 58 extremely well, 6TCU likes a light jam 6BR likes a substantial jump.

 

[Chuckw]

Just got the 6TCU 58vmax load done today. 3700fps, could probably hit 3800 and stress the cases a lot more.

Same bullet same powder 6BR 3900 with 3.7g more powder and 1" more barrel. Both shoot the 58 extremely well, 6TCU likes a light jam 6BR likes a substantial jump.

Thats very impressive velocity out of the TCU. What barrel length and what powder?

 

[GrocMax]

TCU barrel finished at 26" I think, 6BR is 27". 2200 powder hBN coated 58vmax. TCU was a custom reamer from JGS with like .050" FB 2.5 deg leade angle, 58's with a slight jam come out 2.345" OAL, base only 3/4 or less down the neck, there's lots of extra room in the case vs. a zero freebore. It likes 'em jammed about .010", groups really shrink up. About the only faster extruded powders I ain't tried yet are RL7 and N120. Compressed load of LT30 is quite a ways behind 2200. IMR4198 can't get enough in the case to make it worth trying.

 

[Chuckw]

I have built a number of both but i just love the TCU for a "hunting" rig. I built one on a 14 twist at 26" just to see how close it would come to running with a BR. It would do 3700+ with the 55's but i generally shot the 60gr sierra at 3600. Even shot some 80gr bergers at 3200. NO, it definitely wont keep up with a 6BR on a level playing field, but its about as good as you can do on a small BF receiver with UNLIMITED brass availability, and the ability to magazine feed. I shoot fast twist barrels now and have pushed the 95mk to almost 3100 but the brass didnt like it. I settled on 2950 and all is well. Cant wait to try the new 95 TMK. I have been doing all of my varmint, predator, and deer hunting with a TCU for the last 3 years. 2 big WT bucks, a good muley, and countless hogs and coyotes didnt know the TCU wasnt as good as the BR!

80gr sierra blitz at 3050. Shot was 250yds and a complete pass through.

 

[GrocMax]

Yup, gotta love mil 223 brass. Split neck? Looks funny? primer loose? Into the bucket it goes, never a 2nd thought. 20 Prac, 20 Tac, 6x45/AI/TCU. Finally saw a print of a 6x45AI reamer its gotta be close to 1.5g better capacity than TCU. Necks shorter by .040". How 'bout a 257 Practical? Hrmmm.....

I'm a poor boy, still love the 6BR for PDs, as long as I don't have to invest in 1000 cases.

 

[fredo]

Groc, here's a print of my 6x5AI reamer, for comparison.

.267" neck, .050"FB. I have to skim turn Lapua .223 necks to make 'em fit. Winny & milsurp stuff seem to be just right, no need to turn them...

Great little round! Bet ya could throw a hat and cover the 6x47, 6TCU and 6x45AI, maybe even the 6PPC. But the 6BR is simply a larger case, and on a larger boltface for that matter. IE, no comparison, the larger case will always perform better (faster), assuming a 'fair' comparison done with the same bullet, at same pressure, same barrel length, etc...

The 6x45AI, TCU, and 6x47 can all beat the 6x45 for the same reason. More case capacity = more performance. Its really as simple as that. One really only needs to look as far as measured case capacity to determine which case can "beat" another by pushing the same bullet, faster. The only way the smaller case "beats" the larger one, is to operate at a higher chamber pressure...

Ergo, there are no magic cartridges. Only subjective comparisons that make it appear that way...

 

[GrocMax]

Here's the 6TCU with a bit shorter throat (I never intend on shooting anything over about a 65vmax) for comparison. I went .270" neck usually use LC brass, gives ~.004" neck clearance and the std non-bushing Redding die is perfect. Looks like the necks are .029" longer in my TCU print. TCU is not like a 'standard' AI that is like .004" longer neck and the parent round chambers with a slight crush, you have to bump the necks down before it will chamber. By geometry a 6x45AI has a very slight capacity advantage, around .02 cc's or .31 grains of water. 1 cc = 1 gram water. 1 gram = 15.43 grains.