My.260 has a 1/9" bbl (Rem M7) and dosen't like a 140gr or heavier boat-tail bullets. it shoots 2-3" groups with the blunt-lightly boat-tailed Prvi-Partisan 139gr BTSpt, and shoots "patterns" with the 140gr Hornady SST and clone, the 140gr Remington Accu-tips. (4-5" 5-shot groups with yawing bullet holes).
It does however shoot very, very well with the 140gr Speer Hot-Cor and Hornady 140gr Interlok (also a flat-base bullet).
Please note that though these are extreamly accurate, they are also MAXIMUM loads in my rifle. This rifle likes to be "spanked" pretty hard to shoot well.
120gr Speer and Prvi-Partisan BTHP: Reloader 17; start at 42.5gr (2,700fps) max (best; see above disclaimer) 44.0gr @ 2,875fps (20" bbl @ 15'). Shoots 5/8-3/4" groups 5-shots @ 100yds. 2.815" lightly into lands. Brass "partially full length sized for easy chambering- hunting loads. All are using Federal 210 GoldMedal match primers. Just cause thats what I've got. Winchester LR seem to shoot just as well from this cartridge, however.
129gr Hornady Interlok; 42.5gr RL17, 43.0gr IMR4350. 2,750fps. Groups under 1" with either @ 2.810"oal. My first load to try on deer this coming year.
Is only less than 100fps behind a friends .270wcf that has killed over 500deer and 10+ elk in past 35yrs. (130gr Sierra "Pro-Hunter" over 52.5gr IMR4350). I told him that there were "better" bullets and powders. He said, so what!!! He still has close to 1,000 Sierra 130's he bought in 1974 at about $5/100...... And is still using range pick-up brass from late 60's (all "Win" however....).
140gr Hornady, or Speer @ 2.810" (lightly into lands).
42.0gr IMR4350. There is simply no comparison with other powders with this bullet weight in my gun (RL17, RL19, RL22, IMR4831, IMR7828, H414-"yech!", tried.... H414 "might" be better with a "magnum" primer, but I refuse to buy any more to find out.....
Some factory ammo, I'm told is loaded with 41.5gr of H4350 (Nosler Custom).
This 42.0gr load of "IMR"gets 2,655fps from my 20" bbl and is my #2 hunting load. The 41.5gr load is similar accurate but at 2,570fps. About like factory ammo w/140gr bullets. 42.5 is also accurate but flattens/craters primers at 90degF temps. and gives "sticky" extraction. May be "ok" at 32degF. however.....
160gr Sierra Semi-Pt soft point. 2.740" oal (lightly into lands).
44.0gr RL22 @ 2,430fps -20" bbl and Fed210 primers.
43.0gr RL22 @ 2,370fps. Both are very insanely accurate, (two 3-shot groups were 1-hole, but the 44.0gr load gives me a POI same as 140gr bullet above. Bullet is discontinued. I however am very, very impressed by this bullet. Has a better b.c. than the similar Hornady 160gr RN. I'm saving these for something BIG !!! Maybe some hogs if I find another "hot spot" as I had in '03 and '04....
I gave the remaining (140gr SST's and AccuTips) bullets to an aquaintance who shot them through his Remington M700 w/26" Shilen bbl with 1/7.7" twist in 6.5x55Swede). He stated they shot ~1/3moa at 300yds through his rifle (1" 5-shots!). So, it was my rifle/barrel, not the bullets. (He uses RL22, btw).