Seating depth and accuracy

[FOTIS]

What increments do you seat bullets to test for accuracy nodes? Also are the increments the same for big and small cased rounds?

By the way, I can not even remotely get to the lands. Way too much throat.

 

[Billyram]

I've found seating depth in most rifles to make the least difference accuracy. It does make a small difference but not as much as bullets or powder. Some rifles with very loose throats may want the bullet very close to the lands and may not shoot as well with boat tail bullets. If you're loading for a Weatherby Magnum I experimented with seating depth with out any change in accuracy.
Billy

 

[Dwh7271]

Fotis,
Not very original but I use the "hunting" recommendations from Berger to find a spot.

http://www.bergerbullets.com/getting-the-best-precision-and-accuracy-from-vld-bullets-in-your-rifle/

Just reread your post. Maybe use mag length as the start then their jumps from there?

 

[Richracer1]

I start out with .020 off the lands or what will function through the magazine. After finding what powder & charge works the best, I start seating the bullet .005 deeper and see if the groups can be improved upon.

 

[SJB358]

Fotis,
Not very original but I use the "hunting" recommendations from Berger to find a spot.

http://www.bergerbullets.com/getting-the-best-precision-and-accuracy-from-vld-bullets-in-your-rifle/

Just reread your post. Maybe use mag length as the start then their jumps from there?

Same as Dewey.

I also have found excellent results with systematic changes in seating depth. Cup and core Bullets get micro adjustments while Bonded Bullets get larger increments.

 

[Darkhorse]

I consider seating depth to be very important in rifles where the bullet can touch the lands, allowing seating depths from touching the lands out as far as practical. Attached are 2 targets shot while testing loads observe how the center of the group shifts with .010 seating depth changes, and how the group size changes. All seating depths listed are distance from the ogive to the lands, ignore any OAL I might have written on a target.
I start out with .010 changes and start fine tuning when I find a node.
My Browning .300 mag. only allows seating depths of .100" or more due to the clip length. But I found using the BOSS it didn't matter as I could adjust it to average 1/2" groups anyway.

 

[DrMike]

My initial tests will find the best standard deviation. Then, I will adjust by 0.020 inches to find the best accuracy, if there is a significant change. After this, I may (or may not) adjust by 0.005 inches to fine tune the load. Monolithic and bonded core bullets almost always are started at 0.100 inches off the lands. Cup and core bullets are almost always started at 0.010 inches off the lands. There may be exceptions, but I would need a pretty good reason to vary this procedure.

 

[ShadeTree]

Provided magazine length and the throat will allow it that close, for a hunting rifle with cup and core bullets I usually start at .030 off the lands, work up the powder charge until I find the best load, then if it's plugging them in there I leave it alone, if I think there's room for improvement with that charge I'll try .010 or so on either side. I really don't like to get closer than .015 for a hunting round. Just my method, no real right or wrong way in my opinion.

 

[Billyram]

I had a .284 HESAM built with a heavy 26" barrel on a short action 700 action that I worked up loads for 150gr BTs and partitions .010" from the lands that wouldn't fit the magazine. Seating them to 2.820" LOA to fit the magazine made no measurable difference in accuracy or velocity. I'm showing 5 shot groups with 150 gr BTs in the .400"s. I also had a Rem varmint special in 6mm Rem. that was recrowned and pillar bedded that I worked up a load with 105gr Speer spitzers just off the lands. When seated to fit the magazine I couldn't measure any difference in accuracy but had to reduce the powder charge a bit. This rifle had a long throat and you couldn't seat shorter bullets to touch the lands but it didn't care where the bullets were seated. This rifle would shoot in the .300"s with Watson 75gr which was remarkable for a factory barrel.
Billy

 

[salmonchaser]

My experience has been rifle specific. My Jarrett a difference of 05 made a huge difference. Significant enough I had a Wyatt magazine box installed.
My Ruger #1 375 just doesn't care. The groups are identical at factory length or long enough to touch the lands.
My 3006, she is sensitive to overall length but in the 50 years I've loaded for her, powder/ load is what really changes things.
The others seem to fall somewhere in between.

Kinda like dealing with the woman in our lives. Maybe this is why we give them names like Old Betsy.


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[icallitmaize]

I have very little add that hasn't already been said but had this exact conversation with a buddy this morning before work.

Seating depth affects pressure rise, barrel time(if you subscribe), neck tension(if not uniform) and possibly ignition uniformity if compressed....and probably a several more variables.

My experience is the longer the ogive, the more distance to lands matter. YMMV.

Below is from this weekend. Loaded for the first time some 75VLD. First group is loaded at modified magazine length of 2.350" and other is loaded at 2.400" and must be single fed.

Could I find a load that shoots the 2.350" better...probably so, but you can see the huge difference that 50/1000 made with the VLD.


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