The Firing Line Forums - View Single Post - I would like a Hot Rod 6mm.....so which one?

FrankenMauser · March 8, 2014, 01:18 AM

Eppie, I suspect you're thinking of 6mm Remington AI, when referring to .243 AI (.243 Winchester Ackley Improved).
The actual .243 AI runs the same basic OAL as .243 Win, and works with any 'standard' short action. The 6mm AI, however, is based on the 7x57mm case, which is notably longer (and requires an intermediate or long action).

And, don't let barrel length get into your head, too much. The bore and groove finish will have more impact on velocity than the actual length.

I have owned a 22" and a 25.5" .243 Winchester.
One of my brothers owns 18" and 22" .243 Winchesters.
And, my father just jumped on the bandwagon with a 24" .243 Win.
We have all shot the same Remington 100 gr factory load, as well as a Federal 100 gr load, and a Winchester 100 gr load. The difference between the barrel lengths only differs 33 to 140 fps. With a difference of 7.5" .... only 33-140 fps.

And with handloaded Hornady 95 gr SSTs on top of IMR 4064?... 40 fps.

Unless you drop some serious change for a high end barrel, or have someone hand-lap a decent quality barrel, anything over 20" is a crapshoot. It might get you a little more velocity ... or it might not.

March 8, 2014, 01:18 AM	#22
FrankenMauser Senior Member Join Date: August 25, 2008 Location: In the valley above the plain Posts: 13,424	Eppie, I suspect you're thinking of 6mm Remington AI, when referring to .243 AI (.243 Winchester Ackley Improved). The actual .243 AI runs the same basic OAL as .243 Win, and works with any 'standard' short action. The 6mm AI, however, is based on the 7x57mm case, which is notably longer (and requires an intermediate or long action). And, don't let barrel length get into your head, too much. The bore and groove finish will have more impact on velocity than the actual length. I have owned a 22" and a 25.5" .243 Winchester. One of my brothers owns 18" and 22" .243 Winchesters. And, my father just jumped on the bandwagon with a 24" .243 Win. We have all shot the same Remington 100 gr factory load, as well as a Federal 100 gr load, and a Winchester 100 gr load. The difference between the barrel lengths only differs 33 to 140 fps. With a difference of 7.5" .... only 33-140 fps. And with handloaded Hornady 95 gr SSTs on top of IMR 4064?... 40 fps. Unless you drop some serious change for a high end barrel, or have someone hand-lap a decent quality barrel, anything over 20" is a crapshoot. It might get you a little more velocity ... or it might not. __________________ Don't even try it. It's even worse than the internet would lead you to believe. Last edited by FrankenMauser; March 8, 2014 at 01:27 AM.