[Durby]

Loading for a 338 win mag, attempting to load a long range target round with 250 grain Sierra Matchkings. I have loaded a few different hunting rounds, including a 225 grain Hornaday Interbond that shoots 3 shot groups .350" center to center, so I know the gun is capable of decent accuracy.
I get all sorts of different advice on where to seat the bullet. Some people suggest close to the rifling (.010" off), some people suggest kissing the lands, and some others say that bullet is actually designed to have some jump and to seat it further away from the lands. So which way is the bullet designed to be loaded? Magazine length is long enough for any of the above.
Also, some people have advised me not too even bother shooting it at 100 yards, saying the bullet takes so long to stabilize that i need to shoot it at least at 200 yards. I plan on shooting this gun at 600 yrds plus, but dont have good access to a long range at the moment. Any input on how 100 yard groups will compare to 2 or 300 yard groups would be great.

[WNTFW]

Check the Sierra website. SMKs are supposed to be pretty tolerant of jump. I seat 1x the bullet diameter as a general rule of thumb.

In my experience groups open up MOA wise as range increases. I would not expect a group to tighten up @200 vs 100yds in MOA.

[Durby]

By 1x the diameter, you mean you would seat a .338 bullet .338 inches from the lands? I've called the Sierra tech line, they are great to talk to, and i forgot to ask them this question. i have some loaded with RL19 to try, if I dont see anything promising I will try more jump.

[Afy]

Durby 0.338 from the lands may be difficult to achieve.

What WNTFW means, is that the bullet must have at least .338 inches inside of the case. Or at least that is what I think he means.

I normally jam my bullets into the lands, but I do not have a .338 Win Mag.
Personally am not familliar enough with the caliber to make a judgement on how it might perform at 600. It certainly isnt a typical target round, that is for sure.

[WNTFW]

Durby,
Afy explained better than I did. I shoot factory stock rifles and they have generous leade. The rifling can hardly be touched so seating long doesn't help much. By the time the bullet contat the lands precious little is in the case. I do get the brass to fit the chamber, which may be more important. The 1X method has the benefit of being easy to remember. I do make sure the round looks sensible. I have never varied from my seating depth and have not had reason to. I use the OCW method and have found good loads fairly quickly. Just food for thought, my way is not the only way.

Is .338 an acceptable caliber for competition rules wise? I was just curious.