Dealing with 2 variables: Seating Depth and Charge Load

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Gobc

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For all you precision shooters out there (the reason I posted in this forum, and not the reloading forum), how do you deal with determining the seating depth and charge load when determining a handload? Theoretically the best way would be to compare every possible charge value at every possible seating depth, but that would amount an an exponential amount of shooting just to determine your best load. Do people generally just start their handload development with the bullets some arbitrary distance off the lands?

I'm development a new load for my FNAR and I want to consider seating depth instead of just using the standard 2.8" COAL. So what I'm planning on doing is seating the bullets 20 thou off the lands, and then doing my load development.
 
Mystic Precision said:
Look in the Tech section of my website and I have several load tuning articles that will help answer your question.
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^^^This. Very helpful info.

For bolt guns where single round feeding was an option I have been taught to try and do charge weight first with the bullet just touching the lands, and then play with seating depth from there. If you know how far off the lands you want or need to be then you can use that as your constant and vary your charge weight, just be sure the bullet you are shooting is jump tolerant.

Certainly you want to try and limit your variables if possible, because as I was told by a very accomplished TR shooter who has been helpful to me "if you change one thing you change everything".
 
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FTRRookie said:
"if you change one thing you change everything".
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THIS, even a simple primer change can effect your groups/speeds/es everything, only change one thing at a time so you can see the relationship of the change to your groups.

I prefer a 10 thou jump, remember that ogives can vary +/_ 3 thou so when you change your jump or jamb it is pointless to move in less then 5 thou incriments.
 
With the very little bit of load testing that I've done (getting powder/ into fly in only communities is a B!), I decided there is only one acronym that I would follow. KISS, keep it simple stupid. I used only one seating depth and the same neck tension with varied charges.
Reasons? Lets say little johnny found a load that worked at near max pressures at 10 thou short of lands and decided to play with his seating depth and went into the lands. Instant over pressure! Same thing would happen if he decided to try more neck tension... KISS
 
clatartar said:
With the very little bit of load testing that I've done (getting powder/ into fly in only communities is a B!), I decided there is only one acronym that I would follow. KISS, keep it simple stupid. I used only one seating depth and the same neck tension with varied charges.
Reasons? Lets say little johnny found a load that worked at near max pressures at 10 thou short of lands and decided to play with his seating depth and went into the lands. Instant over pressure! Same thing would happen if he decided to try more neck tension... KISS
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Hence, why I'm generally leaning to do an entire charge development everytime you change the seating depth.

Thanks for the replies guys.
 
depends on the bullets you are going to use. Since most 308 bullets are tangent ogives, I'd do your load development at 10 thou off the lands and get a speed node. Then work on a seathing depth node statring from 20 thou in though to 5 thou jammed. If you see a trend from or towards one end or the other, carry it further in or out as needed. you may need to tweak the powder load one more time as seating depth alters case pressure.
 
paperslayer said:
dI'd do your load development at 10 thou off the lands and get a speed node. Then work on a seathing depth node statring from 20 thou in though to 5 thou jammed.
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Not criticizing this man as he knows more than me. However, I have one rifle that I can stick bullets well into the lands and exceed max charges with no sign of pressure. I have another I can touch the lands at minimum charge and I get brass flow.

Finding a speed node and then going from 10 thou jump to 20 thou into the lands may cause a significant pressure increase.

Just wanted to be sure thats understood.
 
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Interesting, so you guys are essentually suggesting to:

1) start at some distance close to the lands, say 10-20 thou.
2) Do my charge development, IE shoot groups at different powder charges with the seating depth from 1
3) Pick a charge, and then go back to varying the seating depth. If I decrease the distance to the lands, be prepared to decrease the charge to compensate for pressure increase. If I increase distance from the lands, do the reverse.
 
Gobc said:
Interesting, so you guys are essentually suggesting to:

1) start at some distance close to the lands, say 10-20 thou.
2) Do my charge development, IE shoot groups at different powder charges with the seating depth from 1
3) Pick a charge, and then go back to varying the seating depth. If I decrease the distance to the lands, be prepared to decrease the charge to compensate for pressure increase. If I increase distance from the lands, do the reverse.
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I start with my bullets jammed into the lands 5 thou and work up my load to find the speed node with either a ladder test or a OCW test. Once the charge weight is found I start moving my bullet seating in. With this method you will be moving in the direction that decreases pressure instead of ending up in the situation where you want to seat closer to the lands but you need to decrease your charge weight because you will run into pressure.
 
thunderstruck said:
I start with my bullets jammed into the lands 5 thou and work up my load to find the speed node with either a ladder test or a OCW test. Once the charge weight is found I start moving my bullet seating in. With this method you will be moving in the direction that decreases pressure instead of ending up in the situation where you want to seat closer to the lands but you need to decrease your charge weight because you will run into pressure.
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I do this process as well only difference being because all of my rifles are mag fed, my start COAL is max magazine lenght.
 
Allot of us shooters are inclined to constantly load develop, and try to improve to nausim! Been there, done/still do that LOL!

QUALITY Load development is about establishing a repeatable,consistant,traceable/trackable method. Easier said than done at times.

I know more than a few shooters that load develop constantly, so much so, that you can tell that they lack the condfidence to use ANY of thier loads at any distance past the "comfort zone". They wind up severely limiting themselves. They dont allow themselves enough trigger time to really learn to shoot at longer distances.

I found that at some point a shooter needs to relax, accept what they have for a load, and shoot it. More times than not, they are suprised at how well thier loads shoot. Its all about confidence in your load and gear.
 
dthunter said:
Allot of us shooters are inclined to constantly load develop, and try to improve to nausim! Been there, done/still do that LOL!

QUALITY Load development is about establishing a repeatable,consistant,traceable/trackable method. Easier said than done at times.

I know more than a few shooters that load develop constantly, so much so, that you can tell that they lack the condfidence to use ANY of thier loads at any distance past the "comfort zone". They wind up severely limiting themselves. They dont allow themselves enough trigger time to really learn to shoot at longer distances.

I found that at some point a shooter needs to relax, accept what they have for a load, and shoot it. More times than not, they are suprised at how well thier loads shoot. Its all about confidence in your load and gear.
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I couldn't agree more. Been in that rut before!
 
do your homework on where certain bullets like to sit. Secant (VLD) bullets generally prefer jamming as much as 20 thou (I start VLD load development stuck 10 thou into the lands and only usually have to tweak to 15)

Tangent ogives are not seating depth sensitive as a rule and most sling and iron shooters jump 10-20 thou.

Unless you are using a bullet comparator to make your measurements, you are wasting your time. COAL is a very imprecise measurement.
 
paperslayer said:
depends on the bullets you are going to use. Since most 308 bullets are tangent ogives, I'd do your load development at 10 thou off the lands and get a speed node. Then work on a seathing depth node statring from 20 thou in though to 5 thou jammed. If you see a trend from or towards one end or the other, carry it further in or out as needed. you may need to tweak the powder load one more time as seating depth alters case pressure.
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I would disagree with jumping to find the speed node and then adjusting the seating depth from jumping to jamming.

Jamming bullets typically has a 5,000 psi greater difference then jumping. So if you were to max out on speed while jumping bullets then started to jam them you would most likely blow primers.

If you run quickloads their computer model show a pressure increase when jamming.

I always start my ladder test with the bullets jammed not jumping and not touching (not touching for fear that one bullet will be jumping while the next will be harder into the lands)

Start low and work up

Trevor
 
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