Chicken or The Egg... Again

[Michael J. Spangler]

alright guys.

i've seem some pretty good arguments in either direction. but i lack the knowledge to figure out if the arguments are based off of facts or total B.S.

when working up a load, to get to an accurate load which should be adjusted first, seating depth in relation to the lands (assuming you're going to seat over max magazine length if it proves accurate) or powder charge.

seems like you would want to determine the length first. from what i've read, the OAL has a big effect on chamber pressure, in finding your optimum max length it should really determine the max pressure right?

seating depth effects barrel harmonics right? that's why you tweek to find a an accurate node. does the powder charge effect harmonics also? or is it more of a SD, ES type of thing?

if powder and depth effect harmonics, which one effects it more? shouldn't that be the one that would be adjust first? and use the latter as a fine adjustment?

thanks for the help guys. just trying to figure a nice load before i burn through a barrel with the .300 RUM

 

[Mikecr]

Well, it's been my belief that seating depth is dominate given that regular powder charge changes don't affect grouping as much as seating.
So I find the seating that the bullet/barrel likes, before changing powder & primers.

Alot of people just jam bullets to begin & vary powder. THEN they tweak seating.
I see no particular reason that jammed would be predicted as best(it isn't on any of my guns).
So why would I check charges with less that optimum seating, mucking up the grouping -across the board.

I wish I understood why seating affects accuracy.
In my experience seating is the single largest factor in accuracy, because nothing else can cause a 1/4" group gun to suddenly jump to 3/4" grouping like seating. And with this, I don't think seating has anything to do with timing. Yet I'm told that there are 'seating nodes'.
OK, if timing, it's still NOT a tweak, but a prerequisite.

 

[Michael J. Spangler]

does anyone else have any information on thus subject? i would love to learn more about it..

Thanks for the input Mikecr

 

[fj40mojo]

You gotta start somewhere. I pick a seating depth, usually .005 off the lands and do my ladder testing. When I find an accuracy node and a load I want to further test, then I start playing with seating depth. If and when I notice a change in group size I may do a mini ladder test dropping and adding .2-.3grns below and above in .1grn increments at the new seating depth to see what my groups do. Then again I may just run with it if I don't think I can improve the groups any more.

Read this.
http://optimalchargeweight.embarqspace.com/

 

[justgoto]

I have been using bullets with a cannelure lately, I'll seat those bullets for a crimp. I'll preform an Audette Ladder Test usually getting sub-moa accuracy using 10 or so cartridges, simply finding the optimum powder weight. Then if I want to tweak the load a bit more, (bullets without a cannelure,) I'll mess with seating depth.

Many long rangers use bullets that need seated at a specific point from the lands or they suffer from poor accuracy. With my 30-30 I need to seat the 110gr V-max right on the lands before I preform the ladder test.

Check this article out.
Optimizing Precision And Accuracy From VLD Bullets By Eric Stecker

Background
VLD bullets are designed with a secant ogive. This ogive shape allows bullets to be more efficient in flight (retain more velocity = less drop and wind deflection). While this result is desirable for many rifle shooters the secant ogive on the VLD bullets produces another result in many rifles. It can be difficult to get the VLD to group well (poor accuracy).

 

[BountyHunter]

I am one for seating into the jam (for VLDs) and then adjusting powder and then seating. I have tried the other way and it is by far easier to get the most accurate load by adjusting powder first and then seating.

IMO powder and charge plays the bigger role, then seating, neck tension and then primer.

Now that is for a single shot gun IK BR guns for max accuracy, if a magazine gun, sinply start at max COAL for the magazine and then work powder and then seating.

BH

 

[Michael J. Spangler]

thanks for all of the input guys. anyone else care to help out with another in depth explanation? thanks.

 

[BillR]

A lot of it depends on the gun's magazine OAL and the length of the throat. I have some guns that have throats long enough that the bullet will drop out of the case before they touch and some that are very short throats. The short ones are east and I usually start those touching and then work back as needed and when I find a OAL the gun likes I will then play with the powder etc. to wring out the best accuracy I can.
The ones with the long throats I just load to the longest length I can for the magazine and work on load. My 700 VSF in .308 is like that. With the 175 SMK's though it does not seem to matter much where I load the bullet as it shoots great using the mag length even if the throat is long. What does seems to make a difference with it is neck tension.

 

[flashhole]

Once I select a powder to use I always try and find the optimum charge range where minor deviations in powder charge weight have mimimal to zero impact on point of impact. I try and key in on a charge weight that lets me use my Lee Dipper Cups instead of an adjustable powder measure (I find it faster and easier). I do this using COL data from the loading manuals. Then I tweak my seating depth. Once I find the seating depth I make a dummy round that I use to adjust the seat die between loading sessions.

It doesn't always work cleanly because if you start with a bullet your gun just doesn't like you burned a bunch of components. But, when it does work, it is very repeatable over long periods of time. As an example, I couldn't get 55 grain bullets to shoot worth a darn in my 223 no matter what powder charge I was using. Switched to 40 and 63 grain bullets and all was good. I burned through a bit of powder and primers before I found the better (for my gun) bullets.