Check My Load Development Proceedure

[treillw]

Pretty new to tuning rifles. Looking for a little advice on my plan. Would you do anything differently?

Would like to get this rifle down below half minute accuracy. Wouldn't be opposed to getting it to .1 or .2 - rifle shoots awesome without much trying, so I think it has a lot of potential.

I did pressure testing the other day. No hard bolt lift, no primer issues - only slight flattening, no extractor mark. I think I'm hitting case capacity of my creed before max pressure. 26" Kreiger barrel with a TBAC Ultra 9" can.

The bullets are jammed hard for this pressure test. I'm thinking of coming off the lands ~.010" and shooting two shots of 41-44 grains in half grain increments at 730 yards (could go further distance if advisable) and looking for the best vertical grouping (ladder test).

Hopefully that shows me a window with a good vertical. I will then take the charge at the center of the best grouping and try seating depths .010, .020, .030, and .040 off.

From there, fine tune powder charge in .2 grain increments.

Finally fine tune seating depths in .003" increments.

How does that plan sound?

 

[Bc'z]

I'd skip the big jumps in seating depth.
I only move in .003 increments from initial load charge weight testing.
You'll find seating tunes will repeat, coming into and going out of tune.

 

[Metal God]

I'd skip the big jumps in seating depth.
I only move in .003 increments from initial load charge weight testing.
You'll find seating tunes will repeat, coming into and going out of tune.

What is seating depth changes doing to change the accuracy ? Meaning what is happening at 3.310 that is not happening at 3.313 ?

Is it
internal start pressure ,
jump changing pressure ,
Time/amount of gas blow by the bullet before the bullet hits the lands ,

I ask because I've never been one to believe .003 makes a big difference unless the bullet is right up against the lands . In that case changing seating depth .003 to .006 either way can change things quite a bit . However do we really think a .123" jump accuracy will change that much with a .120 jump ? Do we really believe every .015 adjustment there are 3 or 4 nodes ? What if you start at 3.310 and the depth that actually shoots best is 3.290 and you are only moving in .003 increments . If shooting 5 shot groups . How is shooting 7 more 5 shot groups saving anything , components , time , barrel life etc .

I just have felt there is/has always been a whole lot of context and nuance being left out in these seating depth discussions . does anyone want to elaborate on what exactly is happening with such a small difference in seating depth ?

Not being snarky , I really would like to understand this better cus right now I'm not buying the .003 adjustment idea .

 

[Bc'z]

What is seating depth changes doing to change the accuracy ? Meaning what is happening at 3.310 that is not happening at 3.313 ?

Is it
internal start pressure ,
jump changing pressure ,
Time/amount of gas blow by the bullet before the bullet hits the lands ,

I ask because I've never been one to believe .003 makes a big difference unless the bullet is right up against the lands . In that case changing seating depth .003 to .006 either way can change things quite a bit . However do we really think a .123" jump accuracy will change that much with a .120 jump ? Do we really believe every .015 adjustment there are 3 or 4 nodes ? What if you start at 3.310 and the depth that actually shoots best is 3.290 and you are only moving in .003 increments . If shooting 5 shot groups . How is shooting 7 more 5 shot groups saving anything , components , time , barrel life etc .

I just have felt there is/has always been a whole lot of context and nuance being left out in these seating depth discussions . does anyone want to elaborate on what exactly is happening with such a small difference in seating depth ?

Not being snarky , I really would like to understand this better cus right now I'm not buying the .003 adjustment idea .

Its really above my pay grade as to WHY it works but it does.
When testing i only shoot 3 shot groups to find the seating window. I usually find it within 7, 3 shot groups.
This saves 14 rounds of components and barrel life by not shooting 5 shot groups. I always load on front side of seating window to maintain accuracy through barrel wear/erosion.
You can see how the the tune comes in and out in this seating depth test.
This seating test was using max magazine length as a starting point and work by moving bullet deeper into the case.

 

[Straightshooter1]

What is seating depth changes doing to change the accuracy ? Meaning what is happening at 3.310 that is not happening at 3.313 ?

Is it
internal start pressure ,
jump changing pressure ,
Time/amount of gas blow by the bullet before the bullet hits the lands ,

I ask because I've never been one to believe .003 makes a big difference unless the bullet is right up against the lands . In that case changing seating depth .003 to .006 either way can change things quite a bit . However do we really think a .123" jump accuracy will change that much with a .120 jump ? Do we really believe every .015 adjustment there are 3 or 4 nodes ? What if you start at 3.310 and the depth that actually shoots best is 3.290 and you are only moving in .003 increments . If shooting 5 shot groups . How is shooting 7 more 5 shot groups saving anything , components , time , barrel life etc .

I just have felt there is/has always been a whole lot of context and nuance being left out in these seating depth discussions . does anyone want to elaborate on what exactly is happening with such a small difference in seating depth ?

Not being snarky , I really would like to understand this better cus right now I'm not buying the .003 adjustment idea .

It's not the change in the jump distance that's the big deal, it's the change in case volume, which effects both the pressure curve (see Pmax in illustration below) as well as the Barrel Time as your are apparently thinking. Take a close look at the two QuickLoad pics below where I've only changed the seating depth (as measured by the COAL highlighted in blue) by .003. Compare the two and you can see the various changes that occurred, which effects how the charge fits in a node or not.

 

[Metal God]

This seating test was using max magazine length as a starting point and work by moving bullet deeper into the case.

Ok thats actually .0155 from good to better with a bunch of wasted shots in between . I'd think if you were seeing a difference in .003 increments , you would see noticeable differences on paper inside of .009

It's not the change in the jump distance that's the big deal, it's the change in case volume, which effects both the pressure curve (see Pmax in illustration below) as well as the Barrel Time as your are apparently thinking. Take a close look at the two QuickLoad pics below where I've only changed the seating depth (as measured by the COAL highlighted in blue) by .003. Compare the two and you can see the various changes that occurred, which effects how the charge fits in a node or not.

That's good info thanks and somewhat backs up what I was getting at above .

Yes I was thinking barrel timing and harmonics and at .3gr I'm not seeing much as far as returning to point of flip ( my term just made up hha ) I mean I actually have no idea but it seems .003 could cause a bigger issue then less . My thinking is a .3 increment would not allow the barrel to whip back which Bc'z target seems to show . I don't think we are seeing the barrel whip returning to optimal position until at least .006 to .009 seating depth differences .

I don't know I'm still soaking all this in , it will take me a bit more time to process what I think I'm seeing . I can now see if you're increments are to much , lets say .015 depending on the cartridge . You could literally be jumping right past the sweat spot .

I guess my overall point is I'm still ok adjusting in .005 to .010 increments based on the info I've seen so far .

 

[Bc'z]

Ok thats actually .0155 from good to better with a bunch of wasted shots in between . I'd think if you were seeing a difference in .003 increments , you would see noticeable differences on paper inside of .009


That's good info thanks and somewhat backs up what I was getting at above .

Yes I was thinking barrel timing and harmonics and at .3gr I'm not seeing much as far as returning to point of flip ( my term just made up hha ) I mean I actually have no idea but it seems .003 would cause a gigger issue the less . My thinking is a .3 increment would not allow the barrel to whip back which Bc'z target seems to show . I don't think we are seeing the barrel whip returning to optimal position until at least .006 to .009 seating depth differences .

I don't know I'm still soaking all this in , it will take me a bit more time to process what I think I'm seeing . I can now see if you're increments are to much , lets say .015 depending on the cartridge . You could literally be jumping right past the sweat spot .

I guess my overall point is I'm still ok adjusting in .005 to .010 increments based on the info I've seen so far .

Study the target a little more.
You can see by the 2nd group it shot smaller than the 1st by .24" but then groupings opened up on 3,4,5 but came back in on targets 6&7 with 7 being the sweet spot in this test.
I'm really not seeing the waste in shots/components when I already saved 14 rounds by not shooting 5 shot groups. Lol
Also look at the size differences in 1st and last group.
Next pick out any 3 spots in a row and reference the size of groups to see the benefits in the .009 you've mentioned.
Its my belief that if you're seating in .010 increments you very well may skip over a good seating window, as I found 2 windows in .015 of seating depth changes with one window standing out.

 

[JEFFPPC]

Study the target a little more.
You can see by the 2nd group it shot smaller than the 1st by .24" but then groupings opened up on 3,4,5 but came back in on targets 6&7 with 7 being the sweet spot in this test.
I'm really not seeing the waste in shots/components when I already saved 14 rounds by not shooting 5 shot groups. Lol
Also look at the size differences in 1st and last group.
Next pick out any 3 spots in a row and reference the size of groups to see the benefits in the .009 you've mentioned.
Its my belief that if you're seating in .010 increments you very well may skip over a good seating window, as I found 2 windows in .015 of seating depth changes with one window standing out.

I do it all with 2 shot groups until I have it narrowed down. If you compete, remember every extra shot in development will come back to haunt you especially if it's a really good barrel as it come to life's end.

 

[Ccrider]

What is seating depth changes doing to change the accuracy ? Meaning what is happening at 3.310 that is not happening at 3.313 ?

Is it
internal start pressure ,
jump changing pressure ,
Time/amount of gas blow by the bullet before the bullet hits the lands ,

I ask because I've never been one to believe .003 makes a big difference unless the bullet is right up against the lands . In that case changing seating depth .003 to .006 either way can change things quite a bit . However do we really think a .123" jump accuracy will change that much with a .120 jump ? Do we really believe every .015 adjustment there are 3 or 4 nodes ? What if you start at 3.310 and the depth that actually shoots best is 3.290 and you are only moving in .003 increments . If shooting 5 shot groups . How is shooting 7 more 5 shot groups saving anything , components , time , barrel life etc .

I just have felt there is/has always been a whole lot of context and nuance being left out in these seating depth discussions . does anyone want to elaborate on what exactly is happening with such a small difference in seating depth ?

Not being snarky , I really would like to understand this better cus right now I'm not buying the .003 adjustment idea .

Get a 6ppc, Dasher or Bra and actually test it. You will become a believer. Can’t say about a Creed.

 

[Bc'z]

Get a 6ppc, Dasher or Bra and actually test it. You will become a believer. Can’t say about a Creed.

It was the creed that made me a believer. Lol

 

[JFrank]

At this point in my journey I’m fairly comfortable saying that I see combustion as number one including powder, primers, neck tension etc.
followed by seating under the sub catagory of harmonics and for myself i may start a bit course at .005 increments I will eventually narrow down to .001 increments, where at a greater distance these small changes make bigger differences in group shape although they don’t seem to change the point of impact thus the catagory placement… Harmonics
Jim

 

[tsyarnall]

I have seen it to where a person would go right past a major change by doing .01 changes (or .009) in seating depth. Going by small changes will help a person see the width of the seating depth window.

 

[powderbrake]

Treillw:
Tuning is for accuracy. Where are the targets from your tests?
Every test for seating depth, powder levels etc, should be done on a target so that you can measure the group size.

How does your plan sound, you asked. I think it has put the cart before the horse. I suggest you start with a moderate load with bullet just touching the lands, and observe the group sizes as you adjust powder for best group. Then adjust (in small increments) the seating depth.
Look for pressure signs as you get into the higher loads, but you only need to go there if you dont get good groups at lower levels.

 

[Ironman308]

A little off topic but does the group feel jump incriminate is for all bullets or if you are dealing with a 6 mm would the incriminate be different than a 338?

 

[treillw]

Treillw:
Tuning is for accuracy. Where are the targets from your tests?
Every test for seating depth, powder levels etc, should be done on a target so that you can measure the group size.

How does your plan sound, you asked. I think it has put the cart before the horse. I suggest you start with a moderate load with bullet just touching the lands, and observe the group sizes as you adjust powder for best group. Then adjust (in small increments) the seating depth.
Look for pressure signs as you get into the higher loads, but you only need to go there if you dont get good groups at lower levels.

My target is currently outside in the rain. It's incomplete anyway. I was having trouble with getting my Labradar to read a couple shots with a suppressor -it's new to me. So there are multiples of the same powder charge mixed in with some shots from another powder that I had laying around to try to get the Chrono to work.

I don't think don't the pressure test to get a max powder charge before hand is a bad thing. What's the harm in exploring accuracy nodes in the upper charge realms to start with? If it doesn't work, I can always go lower.

 

[Straightshooter1]

I do it all with 2 shot groups until I have it narrowed down. If you compete, remember every extra shot in development will come back to haunt you especially if it's a really good barrel as it come to life's end.

Similarly . . . I'm all for not wearing out a barrel with load development and so though I set up to shoot 3 shot groups, if the first two shots are significantly apart, I won't shoot a 3rd shot. As I've heard on this forum, a 3rd shot with an unacceptable 2 shot group isn't going to make that group any better. When 2 shots look decent, I'll shoot a 3rd to essentially confirm the group. All left over cartridges that were loaded and not fired are taken home and reloaded. . . or sometimes I'll fire them over my chrono to get velocity data.

 

[Metal God]

What's the harm in exploring accuracy nodes in the upper charge realms to start with? If it doesn't work, I can always go lower.

If you've already tested charges leading up to and through the upper charge range then there is no harm . However you don't start there with you bullet engaging the lands . No published data has the bullet on or into the lands . Starting there puts a variable in play the component manufacturers did not test when coming up with there safe load data .

If you are experienced with the component combo in "that" rifle . Maybe you can play around with starting in the mid to upper levels . Don't start there if you've not tested those exact components in that rifle before .

 

[Straightshooter1]

That's good info thanks and somewhat backs up what I was getting at above .

Yes I was thinking barrel timing and harmonics and at .3gr I'm not seeing much as far as returning to point of flip ( my term just made up hha ) I mean I actually have no idea but it seems .003 could cause a bigger issue then less . My thinking is a .3 increment would not allow the barrel to whip back which Bc'z target seems to show . I don't think we are seeing the barrel whip returning to optimal position until at least .006 to .009 seating depth differences .

I don't know I'm still soaking all this in , it will take me a bit more time to process what I think I'm seeing . I can now see if you're increments are to much , lets say .015 depending on the cartridge . You could literally be jumping right past the sweat spot .

I guess my overall point is I'm still ok adjusting in .005 to .010 increments based on the info I've seen so far .

Hmmm??? I don't like to think in terms of barrel "whip" as in the flex of the barrel after the bullet as left the muzzle. I've come to think more in terms of a barrel's resonance and the amplitude of the resonance. If you strike your barrel with a rubber mallet and lay your fingers on the barrel, you can feel that resonance like one can with a tuning fork. It's that resonance we're trying to deal with in our effort to sync Barrel Time to the right spot (like the node of the frequency).

Physics Tutorial: Nodes and Anti-nodes

One characteristic of every standing wave pattern is that there are points along the medium that appear to be standing still. These points, sometimes described as points of no displacement, are referred to as nodes. There are other points along the medium that undergo vibrations between a large...

www.physicsclassroom.com

As you suggest, the increments used is relative to the size of the cartridge. Large magnum like cartridges can better utilize a little larger increments. Though my 6.5 PRC has substantially larger volume than my .308, I still use .003 increments. But I feel any larger cases that that, I'd probably do well to use .004 or .005. The whole point, as I see it, is to be able to read what's happening on the target without skipping over a node and without using up any more my stock than necessary or wearing out the barrel more than need be.

 

[Metal God]

I did not mean after the bullet has left the barrel . Haha that would have been a huge faceplant . Everything I spoke of was in the realm of internal ballistics . I may have used the wrong common wording but think we are on the ssme page

 

[treillw]

If you've already tested charges leading up to and through the upper charge range then there is no harm . However you don't start there with you bullet engaging the lands . No published data has the bullet on or into the lands . Starting there puts a variable in play the component manufacturers did not test when coming up with there safe load data .

If you are experienced with the component combo in "that" rifle . Maybe you can play around with starting in the mid to upper levels . Don't start there if you've not tested those exact components in that rifle before .

It creates more pressure when you seat the bullet into the lands, correct?

Initial pressure spike at least.