finally learning the importance of seating depth

[dsculley]

I test all new bullet/powder/rifle combinations with the Berger seating depth test before I start powder testing. I use that seating depth for powder charge testing. Once I find the node I want to shoot, I will test again in smaller steps on each side to see if the group will tighten up some more.

Many times you can pick an arbitrary seating depth to start testing powder charge and find a combination that shoots very good. The problem with that load is that it is usually very sensitive to any changes so you are walking a very narrow line trying to make sure everything is perfect.

 

[DUSTY NOGGIN]

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I had a, well, "discussion" with a supposed tech guy at Hornady who told me seating depth had "no affect on group size" I couldn't believe what I was hearing. After that I didn't believe a thing he said because he proved he had no idea what he was talking about.

i think their advice is altered by liability deflection ..depending on your question, you may never get the right answer .. even if , im my opinion they know

i bet they suggested another one of their bullets though

.

 

[vancewalker007]

started reloading about a year ago and have never really messed with the seating depth of bullets, i typically just left them 20 thou off the lands and if it I did not find a good load would assume did not like that bullet. Yesterday I was doing the same for my 6.5 sherman short and for fun decided to try bergers suggestion on seating depth with the 140 vld bullet. glad i did. this particular barrel like the .150 off the lands. No telling how much time I have wasted as I would have never pushed the bullet in that far in the past.



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My questions would be are most bullets this sensative to seating or are the vld's that much more extreme?

What I have found in a 300 WSM, 7mm LRM and 6.5 PRC is those VLDs either like being close to the lands, ie. 0.005-0.010 or way off like 0.100. They never seem happy in the .030-0.050 range. Once I find a good powder node, stable velocity, I load bullets are various jump distances with about 2 thou neck tension. Seems to work pretty fast to land on a good recipe.

 

[BasilPascali]

Lets be sure we get our decimal places correct, 0.150 or 0.0150. I think we all know what you meant. A friend reloader likes 0.010 off the lands for his Hornady bullets in his RPR.

 

[ajkellerusmc]

Can someone clarify what the following is regards to bullets. #1 Hybrids #2 Secant #3 Tangent

Thanks

 

[FURMAN]

started reloading about a year ago and have never really messed with the seating depth of bullets, i typically just left them 20 thou off the lands and if it I did not find a good load would assume did not like that bullet. Yesterday I was doing the same for my 6.5 sherman short and for fun decided to try bergers suggestion on seating depth with the 140 vld bullet. glad i did. this particular barrel like the .150 off the lands. No telling how much time I have wasted as I would have never pushed the bullet in that far in the past.



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My questions would be are most bullets this sensative to seating or are the vld's that much more extreme?

Glad you figured it out. Some still refuse to believe. It is NOT SOME bullets. It is NOT SOME barrels. I have done load development in 60 ish barrels with more bullets than I can count and every single one of them has seen relatively huge accuracy changes with seating depth. I am almost to the point of not even bothering telling people. Bergers test does not always work because most seating depth tunes are not as gross as they suggest. I can not even figure out why some don't believe it. I guess if you are ok with 1 moa it might not matter?

As far as seating depth testing before powder. I have done it several times. It is a waste of time. Several times I have found the bullet does not have a seating depth preference. The bullet has a seating depth preference at a certain powder charge(velocity). Meaning it may like 40 off at 2950fps but prefer a different seating depth at 3050fps. Powder charge is a gross adjustment while seating depth testing is fine tuning. You can argue this until you are blue in the face. I have targets that prove it.

 

[FURMAN]

Can someone clarify what the following is regards to bullets. #1 Hybrids #2 Secant #3 Tangent

Thanks

Are you just asking the difference? This is a great description.
http://bulletin.accurateshooter.com...how-to-load-hybrid-bullets-for-best-accuracy/

 

[Varmint Hunter]

Most shooters seem to think that accuracy is generally enhanced by getting bullets close to the lands, .015-.030" off.

My experience tells me that you are just as likely to find an accurate combination when bullets are well off the rifling. I have found some very accurate loads while testing with cartridges that fit into magazines and had bullets that were .150" or more off the rifling.

My buddy shoots Weatherby MarkV rifles exclusively. With the ridiculously long freebore in those rifles he has still been able to make accurate ammo with bullets that are literally 1/4" off the rifling.

 

[Mikecr]

As far as seating depth testing before powder. I have done it several times. It is a waste of time. Several times I have found the bullet does not have a seating depth preference. The bullet has a seating depth preference at a certain powder charge(velocity). Meaning it may like 40 off at 2950fps but prefer a different seating depth at 3050fps. Powder charge is a gross adjustment while seating depth testing is fine tuning. You can argue this until you are blue in the face. I have targets that prove it.

Absolutely opposite of truths.
I can take well built gun and run through many charges with several powders and never break 1/2moa in the testing. But with seating alone, any load, the same gun can be taken beyond 1moa and back. SEATING IS COARSE, POWDER IS FINE.
With anything calibrated, coarse is adjusted before fine.
And best seating does not change with powder.
Seating is independent of powder

 

[Shootin4fun]

started reloading about a year ago and have never really messed with the seating depth of bullets, i typically just left them 20 thou off the lands and if it I did not find a good load would assume did not like that bullet. Yesterday I was doing the same for my 6.5 sherman short and for fun decided to try bergers suggestion on seating depth with the 140 vld bullet. glad i did. this particular barrel like the .150 off the lands. No telling how much time I have wasted as I would have never pushed the bullet in that far in the past.



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My questions would be are most bullets this sensative to seating or are the vld's that much more extreme?

Seating depth is really the 2nd most important factor after charge weight! You learned the hard way but now you know. Reloading is an experiment game, probably why a lot of us reloaders are engineers of some kind.

VLDs are more sensitive that VLD Classic Hunters. Berger has articles on this.
Other bullets from other manufacturers may or may not be as sensitive as VLDs.

Barnes seem to like .050 off the lands, just as Barnes recommends. Amazing. That works across the board of calibers and weights within a given caliber for me.

 

[Shootin4fun]

Absolutely opposite of truths.
I can take well built gun and run through many charges with several powders and never break 1/2moa in the testing. But with seating alone, any load, the same gun can be taken beyond 1moa and back. SEATING IS COARSE, POWDER IS FINE.
With anything calibrated, coarse is adjusted before fine.
And best seating does not change with powder.
Seating is independent of powder

Interesting interpretation. Actually, many say it is best to find a consistent powder node if you have a chrono, the OCW, first. Then adjust depth. Bottom line though is that as you say, seating makes a huge difference. It's aboslutely the opposite of truth to say that you can have unstable (meaning different pressure peaks measured over the time of detonation to bullet leaving the barrel and wide ES and SDs) and get stable results.

 

[Shootin4fun]

I test all new bullet/powder/rifle combinations with the Berger seating depth test before I start powder testing. I use that seating depth for powder charge testing. Once I find the node I want to shoot, I will test again in smaller steps on each side to see if the group will tighten up some more.

Many times you can pick an arbitrary seating depth to start testing powder charge and find a combination that shoots very good. The problem with that load is that it is usually very sensitive to any changes so you are walking a very narrow line trying to make sure everything is perfect.

To refine my previous posting, I DO find that after I find a good depth, I can then tune the powder charge. When I get a new batch of powder, or even switch to a different powder I already know my depth is correct and work up the charge to a stable node.

But when I first start out, I find a stable velocity powder node first, then tune the depth for group size and shape. You have to start somewhere. Which do do first is a matter of a lot of debate. ALSO, barrel contour matters because a very heavy barrel has less harmonic distortion than a sporter barrel.

 

[Alex Wheeler]

Seating depth goes in nodes like powder charge. .005" is a coarse move, once you get close work in .002" steps. You will find multiple places in and off the lands a rifle will shoot. Heres a very typical example of a seating depth test I shot at 1008yds with my 300 Norma Imp. Small changes show up big at that distance.

 

[Mikecr]

Since the fine seating adjustment provides shaping, and grouping at a powder node will have some shape to it, people assume that fine seating adjustments are all there is to seating (that seating is fine). These people have not engaged in full seating testing, just very limited tweaking.
And if you do coarse seating testing from a powder node, then that node will collapse on top of the already huge seating affects. This leads folks to the utterly ridiculous assumption that whatever seating they pulled out of their butts for powder testing -must have been best..
To prevent this, do coarse seating testing first, away from any powder nodes. Then move to powder. Then move to fine seating (for best group shaping).
This is a calibration in order of coarse, fine, and finer.