Seating depth advice

[CastIronSkillet]

I actually started at 65 grains and then worked up by 0.3 grains until I found a velocity node. I believe Nosler lists 66 grains of IMR 4831 as the most accurate load. With Nosler's recommended COAL of 3.600", that load didn't impress me. The accuracy was never better than 1--1.25 MOA until I started messing with the seating depths.

A velocity node has little to do with accuracy. A velocity node is when you have low SD/ES. Group sizes can cloud your judgment when you are finding your velocity node.

This is why you rarely see selected loads at this stage shoot constantly time after time. Yes you can get lucky and find your load with this. You can also waste components and chase your tail wondering why it shot yesterday and not today.

Good ignition = low SD/ES
Seating depth = small groups

There is little overlap between the two.

 

[Vern400]

Seating depth test tunes your group sizes. I would bet that over a larger sample size all of those seating depths would produce similar ES #'s. If you were to graph your seating depth group sizes you would see that they follow a perfect wave. I would call 3.608-3.614 your seating node and use a final depth of 3.610 and leave it. You will see that your rifle will shoot well over time even as the rifling wears.

Ignition tunes your ES...ie your powder charge and primer selection. You have two choices. Do an OCW test around 67.5 grains in .2 grain increments. Start with 66.9, 67.1, 67.3, 67.5, 67.7, 67.9 and see which one has the best SD/ES. Or you could stay with 67.5 and shoot as many different primers as you can find for better SD/ ES.

You are almost to your final load. Don't give up. May the force be with you.

This is the best comment I've seen yet. First I find a powder/primer/case capacity/ bullet weight that like each other. ie low ES on velocity. That can suck and still get bugholes at 100 yards. But it falls apart farther out.

THEN dork around with exact seating depth. If you start close to the right jump distance for your gun, adjustments aren't likely to mess up ES.

THIS is how I load for unknown rifles people bring me. I might shoot for a group with the first handoads but trust me I'm looking at the Chrony for consistent ignition and velocity. Without that I'm not loading for any kind of long shots.

I have a box of most high quality primers for that purpose. I switched once from F210 to F215 primers with H380 in a 308/165 gr load in a heavy rifle and took velocity ES from 55 to 19. Don't know why and don't care. That momma shoots.

 

[CastIronSkillet]

Seating depth test tunes your group sizes. I would bet that over a larger sample size all of those seating depths would produce similar ES #'s. If you were to graph your seating depth group sizes you would see that they follow a perfect wave. I would call 3.608-3.614 your seating node and use a final depth of 3.610 and leave it. You will see that your rifle will shoot well over time even as the rifling wears.

Ignition tunes your ES...ie your powder charge and primer selection. You have two choices. Do an OCW test around 67.5 grains in .2 grain increments. Start with 66.9, 67.1, 67.3, 67.5, 67.7, 67.9 and see which one has the best SD/ES. Or you could stay with 67.5 and shoot as many different primers as you can find for better SD/ ES.

You are almost to your final load. Don't give up. May the force be with you.

Yes, I know I'm quoting myself. I don't load for 300 H&H but I do load for 300 win mag and your charge weights seem to be on the low % case fill. In my experience with magnums they like to be near full to show low ES. A case with a lot of empty air has the chance of powder shifting and will cause erratic ignition. The ignition from a load with the powder sitting on the flash hole will be vastly different from one that has the powder sitting against the base of the bullet... ie shooting up hill vs down hill.

My suggestion to do an OCW test and/or primer test will only show results if the load density is near 100%. I am not saying to stuff your case with a lot more powder. You need to work up to it until you reach pressure and back off before you do the finer OCW and/or primer test.

Another point. Your seating depth test increments didn't follow a pattern. I dont think you need to retest this part but for future ones make sure you stick to a consistent incremental movement. Somebody else noted a comparator tool, I will second that and test off of CBTO.

The more tools and knowledge you gain from all of this the more you move into handloading and away from reloading.