6.5 TCU rifle build quick load help !!!!

[Silver Bullet]

Hello all,
Long time viewer. learned a ton of knowledge even after loading and shooting since 1970.

Need some help please,going to build a 6.5tcu 1 and 8 twist rifle
Bullet 120 a max bc .465, and 123 a max bc .510 / .264 dia.
powder h-4895 and imr 8208.
what velocities can I expect? approx.
trying to determine varmint barrel length 20" - 26" which one?

thank you very much!!!
Dave

 

[FCS]

Re: 6.5 TCU rifle build quick load help !!!!

Will depend somewhat on how much freebore you have but I'd guestimate 2600ish from a 24" barrel.

Figure about 15-20 fps/in of barrel length as you go longer/shorter.

 

[bohem]

Re: 6.5 TCU rifle build quick load help !!!!

Skip the 120 Amax, the 123's true BC is about 0.49 as I've run it. The bearing surface length on the 120 and 123 are very similar and I've shot both from my 260, the load data is virtually identical.

I would not expect 2600 from a 120gr bullet in that case, more in the mid 24's for a reasonable barrel length.

You don't need an 8 twist for those bullets, a 9 or even 10 would work better as you're wasting less of the energy in the powder to spin the bullet as it transits down the bore. This will help preserve the useful energy in the small powder capacity as much as possible.

Also, I think that 8208 is going to be too slow for you, take a look at H335 and H322 burn rates, look at your overbore ratio, it's going to be in the low 400's, even the 223 is in the mid 500's. You should be matching it to something like the powders used in 6TCU with medium bullets.