Bullet depth vs powder charge, which first?

[Toby Bradshaw]

major edit - I think the light just came on. What you guys are doing is using the Boyer method as step 1 such as the one in post #33 then fine tuning the best group from the test with a ladder style test looking for a flat velocity node and perhaps even tweaking the seating depth even finer. Or am I still missing something?

Here's a Boyer-type test for one of my 30BR barrels. If any followup testing were done I might fiddle with neck bushings, but there's nothing more to be done with charge weight or seating depth.

 

[Richard Coody]

well in revisiting tony's method he really is only changing one thing at a time. he is doing seating depth testing over a range of powder charges. if there is a node in that range you should find it. 12 3 or 5 shot groups. now if the node is outside those charge weights or seating depths i guess you start over.

not so different then finding a charge weight and then doing seating depth test.

 

[JimSC]

ok it is starting to make sense now, thanks to all for putting up with my density.

The way I am doing it now is shooting 20 to get me in the ballpark seating wise, then shooting 30 or so to look for a flat velocity node, then doing a final tuning for depth.

I did a lot of woodworking in the 90's and found out that there might be 10 ways to accomplish the same thing and none were really wrong as long as they provided acceptable results

 

[Richard Coody]

like i always say whatever works for you. lots of ways to skin this cat.

 

[mikecr]

Whatever Boyers' doing is with an underbore and 300yds inward, right?

 

[DngBat7]

Seating depth first. There will be seating depth that shoots better at all powder charges.

So if seating depth first, what powder charge are you doing your testing with? Are you just picking a middle of the road powder charge?

 

[Dusty Stevens]

Whatever Boyers' doing is with an underbore and 300yds inward, right?

Yes he shoots 100/200yd but it applies to any rifle

 

[urbanrifleman]

So if seating depth first, what powder charge are you doing your testing with? Are you just picking a middle of the road powder charge?

Yes. You could pick a starting load and do it right there.

 

[dcali]

If you're shooting a grid of seating depth and charge weight, you *are* only changing one variable at a time. This is the preferred way to do it (by me at least). With some experience, you can narrow down your grid to some likely good spots, but to really fine tune it you've got to shoot some groups in the area of interest.

 

[Roach]

So I've been needing to rework my load in the 6.5CM. I think messing with the seating depth, having changed case capacity, threw a monkey wrench into the equation and not my groups are averaging around 1MOA.

From this thread it seems like the consensus is start with seating depth as that will work with a wide variety of charges. So after that when moving to charge weight what are you looking for a particular velocity or will the groups tighten up even further with the right charge weight? How about doing a 10 round ladder test to find the flat spot in velocity and use that?

 

[mikecr]

Yes he shoots 100/200yd but it applies to any rifle

It might apply to any underbore which is competitive at 100/200yds then.

 

[Dusty Stevens]

It might apply to any underbore which is competitive at 100/200yds then.

It still applies to any rifle, but to everybody has their own ways

 

[JimSC]

To me it seems as if that method would only be efficient where velocity variations between charges would not affect the vertical. Like mikecr said 100 , 200, even 300. But at 500 or greater velocity SD and ES will makes or break a load, a teensy group at 100 may can give 2 MOA or more vertical spread at 800. My routine has evolved to where I go with a finer resolution on the charge weight and courser on the initial seating test. I basically research the charge, pick what seems to be a safe and sufficiently fast charge shot at 4 widely spaced depths then after that is analyzed go back and do a ladder chronograph style to find a velocity node. If I want to tune it further I may fine tune the seating depth doing development at the range.

Gets me to the same place just taking a different road

 

[GSPV]

You should have a decent idea of what works from the results of others. Don’t try to blaze a new trail if you don’t need to...time is a very precious commodity.

From there, I start with by shooting a graph to find the place where increasing powder charge produces a *lower* POI on the graph with the same POA. Then, I park the powder charge in the middle of that half of the sine wave and start fiddling with seating depth. Then back to powder charge to make see the new graph. Then perhaps fine tune the seating dept again, etc etc.

 

[garandman]

IME...

Charge weight first, cuz it determines velocity.

Then seating depth. I do ladder test at 0.010 off the lands. Once I find a good node, then I tweak seating depth.

YMMV.

Objects in mirror are closer than they appear.

 

[mikecr]

I do ladder test at 0.010 off the lands. Once I find a good node, then I tweak seating depth.

Why 10thou off? Was there any actual seating testing leading to that?
'Tweaking' seating after powder amounts to no more than group shaping.

Personally, I don't want my bullets spraying all over hell during ladder testing. So I do coarse seating testing before powder testing, to be sure I'm not in a bad seated condition for it.

 

[garandman]

Why 10thou off? Was there any actual seating testing leading to that?
.

(1) ya gotta start somewhere

(2) its always worked.

 

[mikecr]

ya gotta start somewhere

You skipped seating testing. This thread is about when to DO seating testing.

 

[Lucky Shooter]

I'm looking at this thread, another thread on this forum----Neck Tension, and the
book by Tony Boyer.

BartsBullets writes on the Neck Tension thread about the importance of knowing
his good seating depth before he leaves for a match.

After reading Mr. Boyer's chapter on tuning-----several times----my interpretration
is that seating depth is a barrel-specific factor. He writes about maintaining the same
bullet/barrel relationship by altering seating depth to compensate for throat erosion.

Do you guys have the same interpretation about-----"the seating depth for this barrel" ?

It appears ti me that if "seating depth follows the barrel", our load tuning and maintenance
might be simplified a bit.

Comments and opinions ?

A. Weldy

 

[JFrank]

I’m going with Bart.

I’ll rephrase this- Bart’s comment (IMO)is towards fine tuning whereas the original poster x-47B started asking about establishing a load.
So for fine tune , Seating is King!