I note that several of you folks who load for this round report large variations in velocity. I have a Rem Model & with the 18in bbl. I already was using IMR 4831 so I pleased to find that it's one of the two best powders for the 120 gr. bullet as far as velocity is concerned. When I first bought the rifle I inquired of Reminton as to how much velocity loss I could expect from my 18in. bbl as compared to the 24in test bbls that all the loading info was based on. They replied that I could expect to lose 30fps. I was very confident therefore that I could obtain a minimum of 2950fps using 46 1/2 grs (almost compressed load) of IMR 4831 with a 120gr reminton PSP with new Rem. brass and Rem 9 1/2 primers. Off I went to the range, Chrony in handbut to my dissapointment I was only able to achieve 2554 fps ave. I asked reminton why but they ducked their heads ! I then read an article on the effect of temperature on cartridges. The day I went to the range, it was about 35 F with a cold wind. On my second trip the temp was about 55f and I averaged 2664fps ! that's 110 fps ! I live in central Canada and by the time rifle season rolls around the temp can be anywhere from plus 10 to minus 25F
I shot a 6point White tail this year at 80 paced yards  using a frontal neck shot. The temp was -5F but it stopped him dead in his tracks so the rifle, lower velocity or not did the job. I still admit however to wanting a max. velocity with best accuracy for my handloads so I plan to try the new Barnes Triple Shock X bullet. They advertise greater velocity at lower pressue and in their email return they say I can load 1 to 2grs. higher than listed ! As standard length 4831 is all but compressed at 46 1/2 grains, i may consider another powder taht would give me some extra oomph in the same case. The problem in the Model 7 is magazine length. I'm almost required to stay at the factory O.A.L. to work the rounds through the action. Anybody out there with a model 7. pre 2000 with the 18bbl that has any ideas. I'd be very happy at 2700 to 2750 fps vel with the 120gr at 70F

You will get variations in velocity from temperature and altitude. I live in Colorado and shoot usually at 5000 feet but may hunt at 11,000 feet. Some powders and cartridge combinations are worse than others but I got from 2 to 3 inches vertical drop when going up high where it's also usually cold too. Switching to Hodgdon's powders helped and using winchester primers which are hotter helped. I settled on the 270 winchester as my hunting rifle. I use cci magnum primers, 62 grains of H1000 powder in winchester cases and any 140 grain bullet. Pressures seem mild and accuracy is good. This load gives little vertical dispersion from temperature or altitude. I use it to shoot prarie dogs in 100 degree heat and don't have to resight daily like I used to. I like the 260 remington and had one when they first came out. I was dissapointed with the velocity and the trajectory. It shot well and stayed zeroed with H4831SC. You can find loading data on hodgdon"s website. The 140 grain Speer Spitzer bullets gave best results, loads are in there handbook.

Thanks for the quick reply. It's amazing but I found a real difference in Win Primers vs Rem. I ave. almost 40fps faster with Win. I asked suppossedly experts on the net if they saw a difference and all said no. I also asked if I could use magnum primers in cold weather and all advised against it. Glad to talk to some one who has had experience. I see that IMR 4320 is a natural fit for the 260 so i may try that . Do you know if that is a shorter stick powder than IMR 4831 as reg 4831 makes for compressed loads in order to get the velocity I want from my 18'bbl Model 7.  I'm not comfortable with compressed loading so I may try the Hodgdon's 4831 S.C.
Thanks again
Dave

H 4831 SC is a shorter stick that will meter through a powder measure very well. As for barrel lenght, the 18 inch barrel gave as much as 150 fps slower velocities. The original 140 grain remington load gave about 2250 if I remember corectly. Not a barn burner. If you're lucky you may get 2600 fps in the short barrel and the H4831SC is slightly compressed.