Model 12 F T/R modify to shoot 80gr ?

[Bob Link]

I have a model 12 F T/R chambered in .223, can i shoot 80 gr without changing the bolt head or anything else? Or must I make changes? I guess you realize I am not an expert like many of you. I am shooting black hills and federal gold 77 gr SMK right now and would like to shoot to 500yds.

Thanks bob

[foxx]

No need to change anything if the throat is cut deep enough for the longer bullet. You'll know if you have trouble closing the bolt on a chambered cartridge.

My first question, however, would be what is the barrel's twist rate? Unless it's a 1:7 or 1:8, POSSIBLY 1:9, I would not bother. Anything slower will not stabilize that long of a bullet. You would be better off shooting shorter bullets, even at longer range.

[nhkuehl]

If you have the F T/R the twist should be 1:7. 1:8 would stabilize an 80 gr bullet. 1:9 will stabilize the 69 and 77 SMK, though a 1:8 is recommended for the 77 SMK. Here is a twist rate calculator http://www.bergerbullets.com/twist-rate-calculator/

[GaCop]

I have a 1 in 8 twist barrel on my 223AI and can shoot up to the 90 grain bullet. My best accuracy has been with the 80 grain VLD though.

[earl39]

Bob that 77gr bullet will go well past 500 yard easily. I shoot them to 1000 but i do reload and drive them harder than factory ammo.

[darkker]

77gr SMK's will safely cross the Trans-sonic threashold. we shoot them long past 1200 with 9-twists.
Remember in all of this that weight is irrelevant. LENGTH is what you need twist for, and that is based upon Muzzle Velocity.
MV * 720 / Twist = RPM

As an example: the 75gr Amax is quite a bit Longer than the 77gr SMK. So WHICH 80gr bullet makes a big difference.
I am not home, so can't give you my bookmark. But google search "JBM Stability Calc" that will allow you to look up the bullet lengths, then input your specifics and tell you if there is any chance of Stability.