Seating Depth effects on ES and SD?

[Lonewolf74]

So I'm curious what sort of effects you all have seen the seating depth have on ES and SD?

I ask because over the wknd I did a short seating depth test with a charge weight that I believe is in a node. .010 and .030 off both shot well for me but what really caught my attention was the .030 off had an ES of 0, all 3 shots where 2930 fps. The other depths had 15-20 ES. So it could of been coincidence or the seating depth really helped my ES.

So has anyone else experienced the seating depth having a fair impact on your velocity spreads?

 

[djfriesen]

I'll be curious to read others' experience. I don't have any personal experience, but intuitively, I would think, other than jammed into the lands and an associated pressure spike, seating depth wouldn't have an effect.

I may be way off but, like I said, I'm curious to see what others say.

 

[Clucknmoan]

Tag

 

[Mikecr]

What is your neck sizing amount/length?

 

[Rich Coyle]

tag for a fun question.

 

[R.Morehouse]

Repeat the .030 with 10 shots. Pay very close attention to your "feel" when seating and be sure not to clean the carbon out of your necks.....

 

[Lonewolf74]

What is your neck sizing amount/length?

I full length resize with Forster dies. If I recall my measurements the neck tension is .003

 

[J E Custom]

Normally SDs and ESs are a function of powder type and charge, primer and case capacity. with changing seating depth, you also change the case volume and this can effect SDs and ESs in some cases. at this point you have to look at the accuracy change also.

If the .30 off shoots best you can adjust the powder charge by .01 tenth or less or more and normally you will find good accuracy and SDs because you obviously have a good load with the case volume you had.

I always start with the load first to get the best SDs and then adjust the seating depth for best accuracy. If the SDs change, I try to compensate for the case volume change by tweaking the powder charge. (Very slightly). Don't worry about the slight velocity change ether way but it
is not unusual for it to go up slightly with more clearance between the bullet and the lands

Just the way I work up loads to save time and components.

J E CUSTOM

 

[Lonewolf74]

Repeat the .030 with 10 shots. Pay very close attention to your "feel" when seating and be sure not to clean the carbon out of your necks.....

I use the Imperial dry neck lube on the case necks before I seat bullets. I use an ultrasonic cleaner to clean my brass

 

[Lonewolf74]

JE, always appreciate your input. The powder charge I'm at is one I found while doing load development that I believed to be a good node. I was surprised to see the velocity spread I did while doing this test, then on the other hand all 3 at .030 off had the same velocity.

Definitely gonna load more to further test but man it be nice to get that lucky!

 

[Lonewolf74]

JE, I forgot in my previous post but what I wanted to ask is did you mean 1 tenth powder charge increase or decrease to further test my load development?

I don't have a scale that has accuracy better than 1 tenth. I use the rcbs charge master and scale combo to throw the charge then verify with a beam scale and trickler.

 

[J E Custom]

JE, I forgot in my previous post but what I wanted to ask is did you mean 1 tenth powder charge increase or decrease to further test my load development?

I don't have a scale that has accuracy better than 1 tenth. I use the rcbs charge master and scale combo to throw the charge then verify with a beam scale and trickler.

Yes = 1 tenth of a grain or less. (My scale divides tenths by 10 if necessary after I calculate the volume change that .020 or .030 makes) I know that seems picky, but I don't want to go buy the best powder charge and miss that sweet spot. And if I find the absolute best charge (SDs of 0 to 3 or 4) I change powder lots and the impact is normally not noticeable. I normally work up loads in 5 tenths increments until indications are that I have passed the "Node" then I go with 2 tenths changes and refine it with 1 tenth changes. unless I have to change even less.

I have seen some bullets seat as deep as .110 of the lands before they really shoot (These are normally the secant Ojive bullets that don't have a very long body and therefore need more neck contact with the bullet). In many cases this type of bullet requires more load testing because of the extreme seating depth requirements and often the good powder charge has to be adjusted because of the decrease in case capacity.

J E CUSTOM

 

[Clucknmoan]

I always thought consistent neck tension had a lot to do with ES and SD? My ES went way down when started annealing after every firing and expanding out with a mandrel for my final size. Don't know that annealing after every firing is necessary, but I have the machine so I may as well be consistent.

ES still isn't where I would like to see it, so I'm real curious as to how eveeyone is getting the best results.

 

[TwoMore]

I seem to get a stable ES when I get inside .010 even with elite hunters, the best when I get -.005 to +.005 to the lands, I run into trouble when I loosen up my neck tension also but I run slower burning powders. I run .003 neck tension on 4 different rifles, but different seat depth on one, I have an edge that I run .005 off(300 OTM) a 7wsm .005 jammed 168 VLD and a 7mm RUMAI .005 jammed 195 EOL , the only rifle I have that shoots with a bigger jump is a 338 rum with a 200 grain AB, I jump .090. the other rifles I shoot bergers but the bergers are longer bullets. I have been shooting my RUM AI alot this year, I started at .020 off the lands worked my ladder for my nodes and pressure, and was around 40 to 50 fps ES sometimes worse ,started to seat to the lands and ended up .005 jammed with a 12 fps es best and under 20 for the most part. My edge and wsm both will hit the same velocity time after time sometimes three in a row quite often