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  #1  
Old 11-26-2022, 11:41 AM
Northern Northern is offline
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Default 6TCU vs 6BR... velocity?

How is a 6TCU compared to a 6BR.

6TCU advantage is easy feeding.
6BR a bit more speed, but usually finicky feeding.

Does anybody know how these compare in a 18-22" barrel, velocity wise with the regular 6mm bullet weights?

ca weights
55 grain
65 grain
75 grain
85 grain

.
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  #2  
Old 11-26-2022, 03:01 PM
Spook Spook is offline
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TCU all day at that weight/length restriction.

6BR at 30" with 103 bullets is what I shoot at 1000yd competitions.
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  #3  
Old 11-26-2022, 03:12 PM
Hotshot Hotshot is offline
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Spook has it right. The two cartridges are not in the same category. Handy little carry rifle go 6tcu. Longer range performance go 6br with more barrel weight and length.
I built a carry rifle with 22 inch light varmint contour in 6cm. Feeds great, fine accuracy, slightly heavy for carry.
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  #4  
Old 11-26-2022, 03:48 PM
Johnly Johnly is offline
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To answer this question properly, one needs to know the magazine length restrictions. The standard ogive length of a 6mm bullet in a 2.235" length magazine can be problematic as the bullets start limiting the powder volume.
When I wanted a light, small bolt action rifle using a CZ527 action, the choices I considered were: 6x45, 6mm TCU, or 6mm AR(Grendel). I opted for the 6mm AR and have zero regrets. I can generate 3000 fps with a 85 gr. bullet, mimicking the original 250/3000 Savage ballistics. My 6x47mm KoO is about 200 fps short of that, as the bullet seating depth reduces the effective case capacity. However, if your plan is to shoot the short 55-58gr. 6mm bullets, the velocity difference will be negligible.
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  #5  
Old 11-27-2022, 10:41 AM
Spook Spook is offline
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Quote:
Originally Posted by Johnly View Post
To answer this question properly, one needs to know the magazine length restrictions. The standard ogive length of a 6mm bullet in a 2.235" length magazine can be problematic as the bullets start limiting the powder volume.
When I wanted a light, small bolt action rifle using a CZ527 action, the choices I considered were: 6x45, 6mm TCU, or 6mm AR(Grendel). I opted for the 6mm AR and have zero regrets. I can generate 3000 fps with a 85 gr. bullet, mimicking the original 250/3000 Savage ballistics. My 6x47mm KoO is about 200 fps short of that, as the bullet seating depth reduces the effective case capacity. However, if your plan is to shoot the short 55-58gr. 6mm bullets, the velocity difference will be negligible.
Had it been spec'd as as option...
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  #6  
Old 11-27-2022, 02:04 PM
Oso Polaris Oso Polaris is offline
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The 6TCU modestly improves performance over a 6x45, and has added benefit of increased safety with its case profile eliminating risk of loading into standard 223 chamber.

As others have mentioned the 6BR is a different beast and more comparable to performance to a mid-sized cartridge 6x47 Lapua or 243 Win or 6mm Creedmoor. The 6BR is better suited for a short action receiver (Rem 700 footprint or similar), and just a bit too much for a micro action.

I think the best answer for top performance while staying within the micro-actions footprint is a Grendel derivative, either 6mm AR (aka 6mm Grendel) or the newer, slightly modified version (6mm ARC). I would be tempted to go 6ARC for the simple convenience of store bought ammo (when needed) and abundance of factory brass. I know... converting 6.5mm Grendel brass into 6mm Grendel is easy, but not everyone wants to do it.

Last edited by Oso Polaris; 11-27-2022 at 02:07 PM.
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  #7  
Old 11-27-2022, 03:04 PM
barretcreek barretcreek is offline
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Good question. Have gathered all the bits and pieces to build a 24" 6BR on a 788 and have dies to convert my M7 to 6TCU. Accurate Shooter has threads about the 6BR and derivatives (BRX,Dasher...) which may interest you.
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  #8  
Old 11-27-2022, 04:01 PM
Bill K Bill K is offline
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I think, if I read your wants correctly, you would have an easier project and be happier with the 6 TCU overall.
Forming brass and obtaining dies, etc. The old K.I.S.S. idea comes into play, in my opinion.
But it will be your choice, when you decide which was to go. Enjoy.
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  #9  
Old 11-28-2022, 12:39 AM
barretcreek barretcreek is offline
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Not mine. LGS has Rem 660 6BR. Had half dozen bench rest guns, think this came in with them.
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  #10  
Old 11-29-2022, 04:03 PM
Johnly Johnly is offline
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Quote:
Originally Posted by barretcreek View Post
Not mine. LGS has Rem 660 6BR. Had half dozen bench rest guns, think this came in with them.
That's close to how I came into my 6mm BR. The local benchrest crowd years ago would "dump" their 6PPC barrels that "quit shooting" which were threaded for Stolle Panda actions. Panda actions are threaded the same as Winchester M70, but with a longer tenon. I would just shorten the tenon and run a 6mm BR reamer into the short 6ppc chamber and spin it on to my waiting action. It was the simple and cheap way to make an accurate varmint rifle.
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