Seating from lands...

[std7mag]

Ok, so working up loads for the 7mm-08. Found 41.4 grains of Reloader 17 for powder charge with 139 grain Hornady cheap fodder for consistent vertical grouping. (I know, not a power house charge)

Next loaded up several batches of 3 rounds each different distances off of the lands. Starting at touching(or 0) and increasing in 0.003 increments up to 0.015 off of the lands.
0.009 worked best with groups of just under 3/4" at 100 yards.

Since the 140 Grain, Nosler Ballistic Tip has a much better BC than the Hornady's I was shooting, I thought I would try different distances off of the lands with them.

All shot within 1". (except for the 2 fliers I called to myself)
There is not descernable difference in group size.

Does the gun just love these?
Does it not make a difference with these?
Is my barrel ready to explode into millions of pieces????

Just looking for some sort of possible reasoning, as with other bullets, the distances off of the lands has made a huge difference in group size.

Thanks

Std7mag

 

[trigger643]

I think you're splitting hairs and the variation you're using is fairly insignificant, but I'm glad you found a range off lands that works for you.

When I'm working up the best COAL I run it this way:

Six rounds each/
0.010 into lands (touching/jam)
0.030 off lands (jump)
0.070 off lands (jump)
0.110 off lands (jump)

I'll then shoot 2 separate 3 round groups. Using the best group, then I'll load 6 each in +/- 0.005 increments until I've nailed it.

If you're not wanting to drive it into the lands, then use these measurements:

0.010 off lands (jump)
0.050 off lands
0.090 off lands
0.130 off lands

Since I'm in no position to beat the world record BR 1,000 yard either with skill or equipment, the above system works pretty well for me.

Hope this helps.

 

[Bart B.]

In wearing out several. 308 Win barrels, I've not seen any significant difference in accuracy with a 1/10" spread in bullet jump to the rifling starting with 1/100" or mote to let rounds feed from magazines. As the leade eroded away 1/10" over 3000 rounds, accuracy stayed at 1/2 MOA through 300 yards. Same thing for 7-08 use in competition I got from their users. For use at longer ranges, bullets touching the lands for single round loading produced a little bit better accuracy.

 

[nemesiss45]

A single 3 shot group is not enough to even start to indicate a sweet spot. Any one of those could be a fluke either smaller or larger than your average would be shooting more groups of that depth.

Second, are you measuring your seating depth at the ogive or bullet tip? Because even the best bullets wil vary by .003 or so at the tip, meaning your groups would actually be made from slightly different seating depths.

But to get to the point... if every group of the nosler was good, then shoot that and dont fret over the seating depth. If you must find the best seating depth, shoot more groups over each depth, and make them 5-10 shot groups.... it gets expensive, and the payoff is probably not going to be big... but if you only do 1 3 shot group of each, you are just throwing money down range without any real payoff

 

[Slamfire]

I had bud's who were using one brand of bullet at long range, they were shooting excellent scores, and of course, we would ask what they were shooting. Then, months later, those buds had dropped those bullets. The reason was the bullets were jump sensitive and when the throat wore enough, there they would be at 600 or 1000 yards, no forewarning, and their rifle was shooting like a shotgun.

If you find a bullet that is jump insensitive, go with that bullet. It is better to use bullets that will jump a country mile, and still shoot good, than have a schizophrenic bullet that goes crazy with a little jump distance.

 

[Bart B.]

Sierra's bullets are typically not jump distance sensitive. Berger's VLD's are for the most part. In any evaluation, shoot enough shots per test to be significant. 15 shots per setting.

 

[RC20]

Oddly, the Sierras I shoot in the 1917 did have quite a change.

I tried the standard 3.290 and they were 1.5 inch or so groups at 50 yds (I can see a good black dot there)

I had a batch at 3.265 that I got a 1/2 inch group at 50 yds out of (5 shot).

Keeping in mind the bullet hit the lands on the 1917 at 3.005

They did seem to like the longer jump.

Consistency being difficult with old eyes and sight picture and changing light conditions but three tests seem to indicate that.

 

[reynolds357]

My most accurate .308 loads are done with a bushing sizing die. I use a bushing that allows the bullet to slide in the neck with finger pressure. I long seat the bullets and the rifling actually pushes them slightly back into the case. Definitely not a hunting load. You can do the same thing with an inside reamer.

 

[44 AMP]

Since the OP doesn't mention the rifle, this is being moved to the Handloading forum.

 

[T. O'Heir]

Seating from lands really only mater in a target rifle. Doesn't make much difference for a hunting rifle. Makes no difference at all in a battle rifle or a civilian copy of one. If you're getting consistent 3 or 5 shot groups out of your rifle, you're done.
Not seeing any RL 17 data for 7mm-08 on-line. 41.4 is a minimum load for a 145 though. If you're using a minimum load you'd best work it up more, but don't worry about the OAL. Load at 2.800".

 

[Bart B.]

If you're getting consistent 3 or 5 shot groups out of your rifle, you're done.

What is "consistant?" All the same size? All centered at the same place?

I've shot thousands of such groups. They ranged from very small to quite large. And their group center's are not all in the same place relative to the point of aim. A composite of a few or several of them with a dozen or two shots always had a larger extreme spread than the biggest single 3- or 5-shot group.

 

[tobnpr]

A couple of months ago, finished building my son's .260 Match and loaded a bunch of 140 VLD's for it. I failed to account for mag length feeding- it's in an AICS

So, he single-loaded for the first trip- short range, only to chrono the loads and check groupings at 100 yards.

Last weekend we stretched it's legs after loading up boxes of drastically shortened loads (don't have the measurement handy) to the 3.89 max mag length.

We didn't have the chrono, and he didn't put any groups to paper, but he was still hitting a 4" gong at 565 yards...

Needless to say, I was really surprised. VLD's aren't supposed to like jump- and his Match chamber is throated .04 longer than the standard SAAMI chamber. More testing to follow to see if we really need different mags to allow for longer OAL.

 

[BumbleBug]

Second, are you measuring your seating depth at the ogive or bullet tip? Because even the best bullets wil vary by .003 or so at the tip, meaning your groups would actually be made from slightly different seating depths.

Good point - no pun intended! The first thing I noticed is the very small increments the OP mentions in varying off the lands. I don't have any 139gr Hornadys, but using a comparator, I have measured a number of hunting bullets, ogive to base, & the variation is significant. Obviously trying to control the jump less than the bullet's variance doesn't seem worthwhile.

FWIW...

...bug

 

[Bart B.]

Regardless of what point on the bullet its reference for cartridge length to the case head is, if all roundsare the same, the distance bullets jump to the rifling will still vary a few thousandths. The 7-08 case headspaces on its shoulder. A case with 1.632" headspace will position its bullet .003" further back from the rifling than one with 1.629" headspace. Cases shorter from head to shoulder than longer ones position bullets furter forward in the chamber.

 

[tobnpr]

Which is also why using "factory" LNL modified cases will produce different results than those that make their own using fire-formed brass.

Perhaps, this might make some sort of difference in the case of a very "jump sensitive" round, but it's still a very small amount.

 

[std7mag]

1) Gun is Stevens 200 in 7mm-08. Yup, a hunting gun.
2) using fired brass that has been collet sized.
3) Was following instructions given by Sierra's website.
4) No, there is no load data for Reloader 17 with a 140gr. bullet. Was using data from the 145 Gr. When using Sierra's recommended process, this was the loading that gave me the least vertical stringing. aka .3gr up or down didn't move vertically.
5) measurements where from tip. Yes I know that they will sometimes(most times) vary, but it is what I have to measure by.
6) those distances, while small compared to a VLD bullet jump, did give rather dramatic differences in group sizes for the other bullets tested.
7) I like to shoot. I didn't leave it to just one set of 3 bullets for each distance. just what I had for that one batch. Didn't have much time during the week for the reloading that I usually do.

Thanks all for your responses!!

Std7mag

 

[green_MTman]

I would try .010 first and if you have accuracy problems back off by .005 slowly,if you have pressure problems back off to .035.if pressure probs persist back off to .050 and that should not cause pressure problems