the only bdc i have is on the AR i use for 2 & 3 gun matches that shoot out to 500yds. of course the hash marks don't line up perfectly for me, but with testing/dope i know where to hold at the various distances. never dial.
ditto for altus if you bought all the components from them. they did the tl3 build i mentioned above as well as two similar builds for my bil.
https://www.altusshooting.com/
just "built" this one last week. tikka t3x action, proof carbon 24" prefit 6.5 prc, mesa precision altitude stock. have an almost identical one in 6.5 creed. also doing one in 7 prc, have the action; another mesa stock is on order as is barrel from carbon six. at least with the mesa stock...
yeah it's weird, factory ammo variety and selection was up there with 300wm just a few years ago, now on ammoseek there are very, very, very few options for 300wsm. my ignorant guess is it will come back and perhaps production capacity is being used for the current hotties like 6.5 and 7 prc.
get a limbsaver recoil pad for that bad boy! the t3 in 300wm i had a while back kicked like a friggin mule, or two or three! you never feel it in the field of course. congrats and good luck!
haven't measured anything yet, but shot five more today, aggressively slamming the bolt all the way got them in there no problem, and no problem ejecting after firing.
and could be 18" or more... field wobble vs steady position at the range. buck fever. altitude/breathing. and the wind out there may not be the wind you're measuring 600yds back. obviously folks do it, so it is doable. but not as simple and easy as falling off a log.
yeah if you can shoot other stuff accurately, and a buddy also cannot shoot your rifle accurately, and you've tried various ammo, does sound like it's the gun or something loose. if you haven't verified the scope in another rifle, and another scope on your rifle, maybe it's the scope.
yeah that is a sweetazz scope, if you can live with 10x max. it is sfp but being that you'll prob be at 10x for any distance shots, no issues holding over and certainly no issues if you dial.
also i generally prefer 50mm objectives just for more light, but at 10x max mag, it's still very...
just rebarreled my tikka t3x with a proof carbon 6.5 prc prefit. first three shots with factory hornady 143 eldx no problem, smooth as butter. same with next three shots. cleaned after each group (barrel break in).
then did another three with the factory berger 156 ammo and it was very hard...
did they tell you what ammo they used? was your scope on it when they tested? have you shot other rifles that shot way better? have you had another good shooter shoot your rifle with the same results? agree with expensive ammo i hate chasing problems.
the downside to second focal plane scopes is that the hashmarks generally only match their stated values at max magnification, such as in the nf 2.5-10x series. the good news is this scope only goes to 10x, so chances are at any distances where you'd need to hold over, you will be at the max of...
I did what you are thinking, and took it a little further. Started with a lefty tikka t3x 300wsm. having had a t3 in 300wm that kicked like a friggin mule (or two or three), i immediately had it threaded for a brake. that, and putting it into a mesa altitude stock, really made it a pussycat...
yeah 300wsm ammo availability went to hell quickly. not even a full page on ammoseek and it's all 150g. 300wm has way more availability and variety now, when they were pretty even just a few years back.
i'd look for ammo identified as big game/elk in the 180 - 215g range.
but do yourself a favor and don't just go off the box's ballistics, or even a ballistics program, or a cds label etc. actually shoot your rifle with your ammo out to distances you might encounter and see where you are...
https://www.altusshooting.com/
these guys will def take the time to help you put together a nice rifle. if you buy the components they'll generally assemble it for you, or they can also do full custom.
i will say the whole 'shouldered prefit barrel' thing is pretty cool. i just did my 3rd...
https://grabagun.com/firearms/rifles/bolt-action-rifles/tikka-t3x-lite-black-300-wsm-24-3-inch-left-handed-stainless.html
got two elk a few years back with basically this lefty gun. can't speak to your other options.
and btw that vortex 4.5-27 is an awesome scope, have that on my PRS rifle...