After reading and studying on bullet seating depth, I was going after some more accuracy from my 270, not that it really needs it. I've always understood that seating as close to the lands as safely possible should make for the best accuracy. It made my accuracy suffer miserably! Anyone have an explanation on this? I was shooting 90 grain Sierra HP bullets.

I'm trying to attach a pic of one target to this post. If it doesn't work then the rest of this post won't make sense, so forgive me. The upper right is with seating depth a bit deeper. The other's are with bullet seated out as far as safely possible. All shots were from bench at 100 yard range. I burned 40 rounds in all, each target group is about the same, poor accuracy from longer length.

My answer will sound flippant, but honesty, every gun likes different things. While one rifle might like seated to touch the lands, another may not. I usually start at .030 off for normal bullets, .050 off for X bullets and adjust in and out a bit if mag length will allow. Lead, I try to get as close to the lands as possible but mag length also plays a part. If your gun shoots the bullet accurately, it doesn't matter where it is. One can always try different seating depths to really fine tune it, but finding a gun that doesn't like the bullets close to the lands is not at all uncommon, especially with bullets like the X bullet. They seem to like a running start. Different seating depths equals different pressures and different barrel harmonics so changing the seating depth can quite often have good, and bad affects on group size.

My answer will sound flippant, but honesty, every gun likes different things. While one rifle might like seated to touch the lands, another may not. I usually start at .030 off for normal bullets, .050 off for X bullets and adjust in and out a bit if mag length will allow. Lead, I try to get as close to the lands as possible but mag length also plays a part. If your gun shoots the bullet accurately, it doesn't matter where it is. One can always try different seating depths to really fine tune it, but finding a gun that doesn't like the bullets close to the lands is not at all uncommon, especially with bullets like the X bullet. They seem to like a running start. Different seating depths equals different pressures and different barrel harmonics so changing the seating depth can quite often have good, and bad affects on group size.

Not at all flippant, Big Bore. This makes sense and I'll be leaving the depth alone for these bullets. I was curious and the note about pressure differences and different harmonics are a great explanation. Thanks!

All the above on what Big Bore says -

Since most of my reloads go into bolt action magazine rifles, the mag length pretty much dictates OAL. They are seated to give it a little clearnance and then left at that. The bullet type, weight, powder type and primer types then get tweaked for the best possible accuracy for that rifle. This designates the cartridge load for that rifle and nothing else is loaded for it. Boring, eh?

I can't say what causes it, but we found the same thing with Jr's 270 using the 90 gr Speer. Seated nearly to the rifling, groups were about 1.5", give or take. Seating deeper has given groups under an inch, and one group that was just over 1/4". Big Bore said it- you just have to try them to see what depth works best!

Ran into the same thing with a Ruger M-77 Target .243, the rifle will do 1/4" all day with Sierra 80gr BTSP's @ .018" off the lands. Wanting to try a lighter load,(60gr V-Max), the groups were all over the place. A shooting friend and long time reloader, reminded me of seating depth from a different view. Suggested that whenever possible, to try and seat at least one caliber in the case neck. It worked out fine for the SHORTER 60gr bullets, but when I tried it with the 80gr Sierras, the grouping was consistant, but also back up around an inch. AIN'T THIS FUN ? I love this hobby... :D :D