.260 Remington in the AR-10 Platform — A Smart Solution
The AR-10 was designed to handle the 7.62×51/.308 Winchester and other .308 “family” cartridges such as the .243 Win and .260 Remington. Our friend Dennis Santiago recently put together an AR-10 to shoot the accurate .260 Rem cartridge. Here is his initial report:
AR-10 Platform Chambered for .260 Remington by Dennis Santiago
I was very curious to see how the .260 works in the AR-10 compared to a .308. I’ve always thought about chambering a bolt gun in .260 but before doing so I thought it’d be good to try it using a less expensive entry point. With an AR platform’s easy interchanging of barrels, it seem like the best way to test out the .260 Rem chambering. So far, it’s most impressive.
DPMS LR-308 in .260 Remington getting function cycle tuned and zeroed
I took the AR-10-type .260 Rem a step closer to being ready for matches yesterday. The first order of business was to confirm which buffer spring to use with both the 123 grain and 140 grain bullet loads. My .260 Rem loads, on average, are using 4-5 grains less powder than the .308 loads. In a semi-automatic action that means less gas/energy to work the mechanics. The solution in an AR-10 platform is to either cut coils in the .308 spring or use a weaker AR-15 buffer spring; yup they are not the same. In this case, a CS flat spring for the AR-15 did the trick.
I also put a very nice NightForce Benchrest 12-42x56mm scope that came via friend Mark Gravitt on it and got zeros. This scope’s 1/8th MOA clicks are nice. The AR-10 had previously mounted a NightForce F1, a more “field tactical” 3-15X system. This 12-42X scope now sets this gun up as more of a target cannon. Field of view is limited when your minimum magnification is twelve. Maybe I’ll put an auxiliary red dot on it just to find the target.
Pet Loads: H4350 and Lapua 123gr Scenars
Comment by Daily Bulletin Editor
Over a two-year period, this Editor put a lot of rounds through a .260 Remington. I did a ton of load testing with that Savage-actioned rifle (before it was rebarreled as a 6mmBR Norma). I tried two dozen load recipes with five different powders and bullets ranging from 100 grains to 142 grains. Hodgdon H4350 was my “go-to” powder. As many 260 Rem shooters have discovered, H4350 is a winner in the .260 Rem. This propellant delivered the lowest ES in my rifle and nothing beat H4350 for consistent accuracy with bullets in the 120-140 grain range. My most accurate load was with Lapua 123gr Scenars, pushed by H4350 and CCI 250 primers. The 123gr Scenars worked well jumped as well as seated into the lands. Best accuracy, in my 24″-barreled .260 Rem, was right about 2950 fps. Other powders work well, but H4350 is a very good choice for the .260 Remington (as well as the smaller 6.5×47 Lapua cartridge).
How long will a barrel last before the accuracy “goes south”? There are so many variables involved (powder type, bore diameter, bullet coatings etc.) that it’s hard to predict. You might say “Well, my buddy has a .243 and he got 1500 rounds before the throat was shot out” — those kind of comparisons can be useful, but they’re not very scientific, and they won’t help much if you’ve got a gun in a new chambering (such as the 6.5×47) for which long-term test results are lacking.
