.260 OAL question

[cp3head]

I am having a .260 built. I am looking at what OAL I should be going with. I am going to be using lapua brass and sierra matchking 142 grain bullets. The load will be for target shooting and possibly competition. The Sierra reloading manual has them listed to reload to 2.765". I have been doing a lot of reading and have read that you can load this round longer and that the boat tail can be below the neck of the brass. This would make the round well over 2.900" if my calculations are correct. I am having the barrel chambered to whatever OAL I come up with. I would like my rounds to feed from my AICS magazine, so that would be my only limiting factor. My questions to the group are:
A: Is what I am reading about loading longer applicable in this situation?
B: Is there a sweet spot somewhere between 2.765 and 2.9??" that will fit in my magazine but still optimize case capacity, BC, etc? Or should I just single load?
C. What have you found to work for you in your setups?

Thanks in advance for any and all input.

 

[427Cobra]

I have found
139 Scenars shoot best at the lands to about .010 off
140 Amax shoot best at .010-.020 from the lands
142 SMK like a .030-.060 from the lands

my advice is seat bullets by there ojive length, if the bullet is too long to fit in a mag switch bullets

 

[cp3head]

Thanks for the reply 427Cobra. I guess in my scenario then I should seat the bullet to its ogive length and then have the barrel made to conform to that? Seating the bullet off of the lands does not help for my situation because I don't have the barrel chambered yet.

 

[2clicks]

GAP 260 Match chamber works great for 142 SMK, 139 Scenar, and 140 Bergers just make sure to mention your using Lapua brass some reamers are kinda tight on the neck for the Lapua brass. Not so with Remington 260 & Winchester 7mm-08 brass necked down to 260 Rem. My over all loaded length is 2.790 my estimates are that's .010 off the lands. I had my action notched out on the bottom for long Loading but it wasn't necessary. I get excellent results with H4350 right around 42.8-43.3 grains behind these bullets. Best of Luck to you.

 

[BusterB]

I ordered a reamer with .100 free bore so that I could feed the long bullets from ai mag. Just call up dave kiff at ptg, let him know what components you will be using and you want mag fed and he will fix you up with just what you need.
Ps, fwiw unless you just have the sierra bullets on hand the lapua 139 and bergers have done better in my rifle.

 

[cp3head]

I do have the sierra 142's; however, I can get something else. The barrel is a 8.5 twist, and range shooting will be 400-1000 yards. Thanks for all of the input, please keep it coming.

 

[2clicks]

I forgot to mention that 2.790 oal was with 142 SMK's sub Moa at 600 with a sling. No bipod 2820-2850 fps 26 inch Bartlein barrel 1-8.5 twist. It takes 12 moa from 100-600 yards exactly with a scope. Bergers and Scenars shot well too but for the $ the 142 SMK is getting the results I need I still have a couple hundred Bergers they are better than the Sierra's. 139 Scenars shot great too. I rate them in order Bergers, Scenars, Sierra's. Mine feed flawlesly out of Alpha Industries 10 round mags even the Bergers do since the bottom of the action is notched out.