PS
In the latest 'Rifle' magazine Terry Wieland writes that 48gr of IMR-4350 under 140gr Nosler partition is outstanding in the Swede....
Are you sure that 140/48 grain data is for IMR 4350?.
That powder is indeed a fine one for accuracy in many 6.5x55 rifles, however, pressures get up to primer flattening/light cratering, and with close to 1/2 a thou. of case head expansion(Lapua brass) at 45+ grains or so .... in my experience.
IMR 4350 can sometimes "hit the wall" quite suddenly with minor charge increases, in a cartridge with high S.D. bullets.
I have dared 43 grains of IMR 4350 and 140 Hornady Interlocks with superb groups.
As have I 'looky, .... 44.5 grains/IMR4350, sings, with that bullet in my M96 rifles. And, it is as max. as I want to go.
Vviking: that's interesting regarding the mag primers. I have read some guys promoting mag primers with RE22, others say no need with 6.5x55 size charges. I currently use RE22 with 140gr bullets in my Tikka 6.5x55 but want to work up some loads with 120TTSX which will be used in cool-cold fall weather. Have you tried CCI 250's? I might give this a try to ensure good ignition and just work up slowly.
kayaker: Mag primers keep the groups tight and consistent(for me)when it gets really cold ... minus 15 to minus 30C(that
is Ont. style cold

)
A switch from LR to MAG LR primer seems to add a half grain of powder's worth of pressure to a 6.5x55's sized case capacity, and that is with a close to max. R22/140 load.
I find that that half a grain reduction, plus, the switch to non-magnum LR match primers, is what it takes to maintain similar results when yer camo-cap brow is getting damp in the summer sun.
Yes, I have tried CCI 250's ... very good primers for hunting purposes(MOA, no problem), My 6.5's are aimed at LR steel though, and those Match primers do shoot noticably tighter for me .... so ...
Yer on yer own with the 120's, ... however, in the past I've got many, many, tiny bughole groups with 120 grn. Nos. Ballistic tip and IMR/H4350(.3's MOA type tiny). They lack BC compared to 139/142's, so limited use for LR.
Much 6.5x55 load data is based on the M96/94 Swede rifle. All mil. spec. barrels that I have slugged, even many brand new M38 barrels, are somewhat oversize. .365" to .366" grooves are typical. This lowers pressure.
Typical comm. barrels measure .264", requiring less powder for higher vels., at higher pressures too.
My tight-bored 6.5/06 shoots 140's to 2950fps., with barely a grain more R25 than the Mil. 96 6.5x55 takes to hit 2700fps, with the same components.. Both 23.5" barrels.
My Tikka Varmint stainless likes 49gr of R-22, a Fed 210 primer, and Lapua brass behind the 142gr Matchking. Velocity is right at 2750fps. Five shot groups are sub 1/2moa.
Nice.
That 49 grains R22/140 is the max load listed in some of my older loading manuals.