Seating Depth Increments?

[Wind Gypsy]

Chasing unicorns.

To elaborate - Overlay all 3 of those groups with the POA aligned and you get one bigger group with the same general POI. The average of those 3 groups is 1.15 MOA. A gun/load/shooter that averages 1.15 MOA 5 shot MOA should shoot occasional groups smaller and larger than those shown so you don't really know if one is best from this seating depth test.

I wouldn't be surprised if breaking and then rebuilding positions to let the barrel cool caused more POI shift and group opening than any changes in seating depth. A 30-06 shouldn't need time for the barrel to cool on a 5 shot group.

 

[ImBillT]

With less modern bullets the be at thing to do was to test jumping and jamming. How much wasn’t of huge importance. Whichever shot better was good enough.

Today a lot more bullets have secant ogives than in the past. Secant ogive bullets usually shoot well jammed, and will usually shoot well within some narrow band of seating depths. Berger recommends testing VLDs jammed .010”, and jumped .040”, .080”, and .120”.

Smaller seating depth adjustments are relegated mostly to benchrest shooters shooting be set accurate rifles and they’re perhaps shrinking groups from .250” to .150”, maybe, if everything else goes perfectly.

Adjusting seating depth is unlikely to cause a rifle to go from shooting 1.5” to .5”. Also, most hunting bullets still use a tangent ogive, which is generally considered to be tolerant of a wide range of seating depths. Minor or major adjustment may make a small difference that a short range benchrest competitor might be able to take advantage of, but which most hunters would not even see on target.

So to answer the question, if you’re not shooting a bullet advertised as having a high BC, or if you are, but you know it has a tangent ogive, I would not even worry about seating depth beyond functionality in my rifle. If the bullet might have a secant ogive, I would test at something close to 040”, .080”, and .120” jump if possible, but I would not expect a rifle that has been disappointing you to suddenly become a tac driver.

 

[ImBillT]

To elaborate - Overlay all 3 of those groups with the POA aligned and you get one bigger group with the same general POI. The average of those 3 groups is 1.15 MOA. A gun/load/shooter that averages 1.15 MOA 5 shot MOA should shoot occasional groups smaller and larger than those shown so you don't really know if one is best from this seating depth test.

I wouldn't be surprised if breaking and then rebuilding positions to let the barrel cool caused more POI shift and group opening than any changes in seating depth. A 30-06 shouldn't need time for the barrel to cool on a 5 shot group.

I never owned a rifle with a light contoured barrel that was custom until a few years ago, so I have never attempted to get high levels of accuracy from a sporter barrel before. At the range I was having fits with two new rifles. With each rifle, I had 10-20 shot ladder tests with two different powders, all of which were about the size of a nickel. So four groups of at least ten shots, spanning a range of 5+ grains of powder and all around .5ish MOA. But my 5-shot groups were over 1 MOA. Usually I could put three in one hole, and then fall apart. In the reloading room a gunsmith and benchrest competitor says “so why not just shoot a three shot group with each rifle and see what happens?”. I said “I don’t know, I guess I’d just feel better evaluating a rifle with five shots.” And he says “those skinny barrels aren’t gonna hold up to five shots without letting them cool. You shot those ladder tests coming back in here and loading one round at a time”. So I loaded three, shot three, repeated it with the other rifle, giving the first rifle time to cool down, then repeated the process, and each rifle produced a three shot group at 100yds, and again at 200yds that was .5-.75 MOA. I can’t say I’ve done it enough to prove it beyond a shadow of a doubt, but it seemed to be what cured the “problem”. One was a 30-06AI and the other a 280AI. Both of those will run a little hotter than a 30-06, but it seems it’s possible that a barrel could heat up enough to matter in fewer than five shots.

 

[Wind Gypsy]

I never owned a rifle with a light contoured barrel that was custom until a few years ago, so I have never attempted to get high levels of accuracy from a sporter barrel before. At the range I was having fits with two new rifles. With each rifle, I had 10-20 shot ladder tests with two different powders, all of which were about the size of a nickel. So four groups of at least ten shots, spanning a range of 5+ grains of powder and all around .5ish MOA. But my 5-shot groups were over 1 MOA. Usually I could put three in one hole, and then fall apart. In the reloading room a gunsmith and benchrest competitor says “so why not just shoot a three shot group with each rifle and see what happens?”. I said “I don’t know, I guess I’d just feel better evaluating a rifle with five shots.” And he says “those skinny barrels aren’t gonna hold up to five shots without letting them cool. You shot those ladder tests coming back in here and loading one round at a time”. So I loaded three, shot three, repeated it with the other rifle, giving the first rifle time to cool down, then repeated the process, and each rifle produced a three shot group at 100yds, and again at 200yds that was .5-.75 MOA. I can’t say I’ve done it enough to prove it beyond a shadow of a doubt, but it seemed to be what cured the “problem”. One was a 30-06AI and the other a 280AI. Both of those will run a little hotter than a 30-06, but it seems it’s possible that a barrel could heat up enough to matter in fewer than five shots.

I'm positive you're right and that it happens at times. But 5 rounds of 30-06 aint that much and a barrel shouldn't get that hot and if it's properly stress relieved it shouldn't be throwing shots. I'm of the opinion that people blame hot barrels for lots of issues that aren't because of a barrel getting hot. Much of the time the "issue" being that groups get bigger when more shots are in them.

 

[USAF Ret]

I'm positive you're right and that it happens at times. But 5 rounds of 30-06 aint that much and a barrel shouldn't get that hot and if it's properly stress relieved it shouldn't be throwing shots. I'm of the opinion that people blame hot barrels for lots of issues that aren't because of a barrel getting hot. Much of the time the "issue" being that groups get bigger when more shots are in them.

My barrel is a sporter and I am in the better safe than sorry camp. When it heats up to where I can't hold it for 10 seconds, I stop and wait.