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Mar 25th, 2012
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Seating Depth Test Before Ladder for Charge Wt? #7121111
03/23/18 11:44 PM
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Whoís tried load dev this way? Tech at Berger suggested I try it ó shooting groups at diff seating depths to see what jump groups best prior to doing ladder for charge weight.

Iíve been needing to accumulate some brass and break in my barrel on the 30 Nos before going up to Firemanís to do formal load dev with ladder... so I figured Iíd give it a try and see.

The results suprised me. Shooting 5 shot groups with both 180 Elite Hunters and 215 Hybrids with starting load of H1000 and varying jump in 0.030 increments from the lands gave me the same results. For both the 180 and 215 gr bergers, best groups were clearly at 0.090 jump.

Itíll be interesting to see if that same CBTO length holds true once I find node with ladder.

Re: Seating Depth Test Before Ladder for Charge Wt? [Re: RedSnake] #7121130
03/24/18 12:07 AM
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Never heard of that exact process. I've always been the other way around, seat close to the lands (giving the most powder capacity) find the right charge, then play with depth. But hey, it worked for you, so I won't argue with it.

I have seen Judd get a new barrel, of a cartridge he knew, go to his old load, and play with seating depth only. He was seating bullets at the range, and I was shooting two rounds. If two didn't group, we moved on. When two grouped, he would load a third. If it continued to group, he noted it. We went with more jump, and groups decayed. Went back to the good shooting jump, and he loaded 5. Those 5 shot, and we called it good.

Internal ballistics have some voo-doo going on sometimes.



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Re: Seating Depth Test Before Ladder for Charge Wt? [Re: RedSnake] #7121136
03/24/18 12:16 AM
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Yep. Wasnít sure what to make of it so I thought Iíd give it a go. Letís Mythbust it when I come out.

Btw. Itís a damn shooter. Even factory 180 accubonds group. Tony is the magicman.


Re: Seating Depth Test Before Ladder for Charge Wt? [Re: RedSnake] #7121160
03/24/18 12:41 AM
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Did you jump any further than .090Ē. Iím curious about this method. If that was your farthest jump it would make me think about it also being the highest pressure. If not Iím curious if you moved it back more creating a higher pressure would your results reflect a trend or deteriorate. Curious minds want to know. When you said starting load of H1000 did you mean book minimum or something similar? Iím always open to new methods. Iíve never messed with seating depth. I usually run at mag length or as the one Iím working on now as far as I can go without the bullet falling out of the case. Which happens to be jumping .080Ē

Re: Seating Depth Test Before Ladder for Charge Wt? [Re: RedSnake] #7121186
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Book min load on all

My OCD brass prep = Virgin brass - cases sorted by weight (all were within 0.2 gr same weight), then annealed, then FL sized with bushing for 0.002 neck tension, trimmed to uniform length.

Jumps = 0.00 / 0.030 / 0.060 / 0.090 / 0.120

Gr Size 1 moa / 1.5 moa / .75 moa / .5 moa / 1 moa

Groups for 180 and 215 looked similar for each seating depth.

Wish Iíd taken a pic


Last edited by RedSnake; 03/24/18 01:17 AM.
Re: Seating Depth Test Before Ladder for Charge Wt? [Re: RedSnake] #7121206
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Redsnake, thanks for sharing that. Something I will experiment with for sure.


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Re: Seating Depth Test Before Ladder for Charge Wt? [Re: RedSnake] #7121232
03/24/18 02:09 AM
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I never had a doubt it would shoot, Tony does excellent work. We just need to get it to shoot with a case full of powder. I wonder, with that .090" jump if we will find compression. That's Ok, and I hope we do, but I also hope it shoots there.



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Re: Seating Depth Test Before Ladder for Charge Wt? [Re: FiremanJG] #7121279
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Originally Posted By: FiremanJG
I never had a doubt it would shoot, Tony does excellent work. We just need to get it to shoot with a case full of powder. I wonder, with that .090" jump if we will find compression. That's Ok, and I hope we do, but I also hope it shoots there.


At .090 jump with the 215 I can fit 2 gr over book max (if I use a drop tube) before there is any compression on powder column from seating the bullet. We should hit pressure well before that as Iím running my can on this rifle.

Re: Seating Depth Test Before Ladder for Charge Wt? [Re: RedSnake] #7121398
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Originally Posted By: RedSnake
Originally Posted By: FiremanJG
I never had a doubt it would shoot, Tony does excellent work. We just need to get it to shoot with a case full of powder. I wonder, with that .090" jump if we will find compression. That's Ok, and I hope we do, but I also hope it shoots there.


At .090 jump with the 215 I can fit 2 gr over book max (if I use a drop tube) before there is any compression on powder column from seating the bullet. We should hit pressure well before that as Iím running my can on this rifle.


Book max is only a guideline. peep



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Re: Seating Depth Test Before Ladder for Charge Wt? [Re: RedSnake] #7121564
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Apparently this notion of playing with seating depth comes from Bryan Litz in the Berger reloading manual.

"In general, the seating depth of a particular bullet in a particular rifle tends to be more static than what powder charge will work best. In other words, it's probably best to start with a low to medium powder charge and find the best seating depth. Then, using that estabilished seating depth, start working on changes in powder charge."

I found that on the interweb, so take it for what itís worth.

Re: Seating Depth Test Before Ladder for Charge Wt? [Re: RedSnake] #7121877
03/24/18 11:56 PM
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Lots of good info on this thread. Thanks for detailing the work you did. I'm about to start working up a load for my 6.5 CM, so this should be helpful.

Re: Seating Depth Test Before Ladder for Charge Wt? [Re: FiremanJG] #7121908
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Originally Posted By: FiremanJG
Originally Posted By: RedSnake
Originally Posted By: FiremanJG
I never had a doubt it would shoot, Tony does excellent work. We just need to get it to shoot with a case full of powder. I wonder, with that .090" jump if we will find compression. That's Ok, and I hope we do, but I also hope it shoots there.


At .090 jump with the 215 I can fit 2 gr over book max (if I use a drop tube) before there is any compression on powder column from seating the bullet. We should hit pressure well before that as Iím running my can on this rifle.


Book max is only a guideline. peep

Good shooting RS, let's say I find a max load on a ladder testing, and find seating depth to tighten, if seating deeper will push my loads over max pressure correct? If so, is this the reason you start lower / medium loads? I assume you are a few thousands off the lands to start with

Re: Seating Depth Test Before Ladder for Charge Wt? [Re: RedSnake] #7122358
03/25/18 04:31 PM
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I am looking forward to what you guys figure out on this. This is an article I read a while back that has caused me to wonder about this as well. It is a paper on the "Optimal Barrel Time Concept".

http://www.the-long-family.com/OBT_paper.htm

Re: Seating Depth Test Before Ladder for Charge Wt? [Re: RedSnake] #7122403
03/25/18 05:48 PM
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In my own experience, loading to OBT has not really worked out well enough to conclude that it's an effective way to approach load workup. I get the concept and maybe it's valid, but I suspect based on my own experience that it works better when shooting rifles with heavy barrels. My best guess would be that lighter barrels are more influenced by other modes of vibration, or barrel whip. That's really all speculation on my part.




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Re: Seating Depth Test Before Ladder for Charge Wt? [Re: RiverRider] #7122406
03/25/18 05:52 PM
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The thinner, and longer the barrel, the more narrow the node, in my experience. So, on a short, heavy barrel, short action, it may shoot well in a 1.5 gr spread. On a long thin barrel, it may only shoot well on a .6 gr spread, or less, just as an example. Those are not hard numbers.



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Re: Seating Depth Test Before Ladder for Charge Wt? [Re: RedSnake] #7135565
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I have some results to share...

Short Version/Summaryó for 30 Nosler shooting Berger 180 gr Elite Hunter, I successfully found a 1/3 MOA load with a ES of 5 by finding best seating depth before finding charge weight with ladder test.

Background
Following the advice of a tech at Berger, I decided to find the seating depth at which my particular rifle shot the best before finding charge weight

Step I - Seating Depth Test
Groups in 0.030 increments at Book Min load of 75.5 gr H4831sc for 180 Berger Elite Hunters
Result: 0.090 jump shot smallest group ó approx 1/2 moa

Step II - Ladder Test
Eleven round ladder test loaded in 0.4 gr increments from book min to book max with all rounds seated with 0.090 jump per results of seating depth in Step I
Results: discrete node (velocity and vertical dispersion) between charges 76.3 and 76.7



Step III - Load Confirmation / Fine Tuning
Loaded 3-shot groups with seating depth from Step I (0.090) and +/- 0.010 on either side at charge weights from node found from Step II
Results. Groups with seating depth at 0.090 were most accurate


Re: Seating Depth Test Before Ladder for Charge Wt? [Re: RedSnake] #7135581
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Like the data. Also think it was smart to test the seating depth again after you found a node you liked


Any reason you didnít look at load 7 and 8? I image you are trying to create a hot rod with this gun.

Re: Seating Depth Test Before Ladder for Charge Wt? [Re: RedSnake] #7135722
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Very nice report RS. I may give this a try.


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Re: Seating Depth Test Before Ladder for Charge Wt? [Re: Cleric] #7135724
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Originally Posted By: Cleric
Like the data. Also think it was smart to test the seating depth again after you found a node you liked


Any reason you didnít look at load 7 and 8? I image you are trying to create a hot rod with this gun.


For Ladder loads #7 and #8, while velocity were similar, there was a large variation in the vertical dispersion from point of aim. For loads #3 and #4 both the velocity and vertical dispersion were nearly identical.

Re: Seating Depth Test Before Ladder for Charge Wt? [Re: RedSnake] #7136296
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That is some good work RedSnake. Thanks for letting the rest of us tag along.


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Re: Seating Depth Test Before Ladder for Charge Wt? [Re: RedSnake] #7160328
05/04/18 06:58 PM
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Hmm...going to try this over the weekend if the weather permits...thanks RedSnake.


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Re: Seating Depth Test Before Ladder for Charge Wt? [Re: RedSnake] #7160383
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Very interesting. Can you post the speeds of your Groups on the 76.3, 76.5, and 76.7 loads? I would bet that your Group 4 and Group 8 are near identical in speed.

IMO, playing with the seating depth first, then the powder charge is backwards. If you have a powder charge that the rifle doesn't like, IMO, playing with the seating depth will only marginally improve the groups, if at all. (I would truly love to test this)

Here's also some info on accuracy nodes. When a rifle starts stringing groups in a line (if everything else is good), you are approaching a node. Groups will go in a line, then the next group or two will be it. So, if I shoot a load with say 65 grains of powder and it strings, I know my next load at 65.3 or 65.6, should be it. In your example, some of the groups strung, then the next one was tight.

Another thing to think about, and this holds true for almost all rounds. There is always multiple accuracy nodes for a given caliber and bullet combination. Take your 30 Nosler. 4831 powder is a good medium burning powder for magnum rounds. But, paired with a 180 grain bullet in the 30 Nosler, it's a fairly fast burning powder choice, when loaded up near max. Anytime you reduce a load (or minimum load in this case), you want to lean more towards a faster burning powder, like this. What this does, is it increases the sweet spot, or accuracy node window for what shoots good across the course. Meaning, if I wanted to load the most accurate round possible that shot the best in many 30 nosler rifles, I would select a fast burning powder for the powder and bullet combination, and work it on the lighter powder charges. You can easily get it to shoot good doing this. But, it's not a full power load that takes advantage of the full powder capacity and velocity of the cartridge. For a full power load with this combo, I would select H1000 as the fastest burn rate I would go, and probably use Retumbo for that combo. But the sweet spot is a smaller node when you go to a slower burning powder.



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Re: Seating Depth Test Before Ladder for Charge Wt? [Re: ChadTRG42] #7160426
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Originally Posted By: ChadTRG42
Very interesting. Can you post the speeds of your Groups on the 76.3, 76.5, and 76.7 loads? I would bet that your Group 4 and Group 8 are near identical in speed.

IMO, playing with the seating depth first, then the powder charge is backwards. If you have a powder charge that the rifle doesn't like, IMO, playing with the seating depth will only marginally improve the groups, if at all. (I would truly love to test this)

Here's also some info on accuracy nodes. When a rifle starts stringing groups in a line (if everything else is good), you are approaching a node. Groups will go in a line, then the next group or two will be it. So, if I shoot a load with say 65 grains of powder and it strings, I know my next load at 65.3 or 65.6, should be it. In your example, some of the groups strung, then the next one was tight.

Another thing to think about, and this holds true for almost all rounds. There is always multiple accuracy nodes for a given caliber and bullet combination. Take your 30 Nosler. 4831 powder is a good medium burning powder for magnum rounds. But, paired with a 180 grain bullet in the 30 Nosler, it's a fairly fast burning powder choice, when loaded up near max. Anytime you reduce a load (or minimum load in this case), you want to lean more towards a faster burning powder, like this. What this does, is it increases the sweet spot, or accuracy node window for what shoots good across the course. Meaning, if I wanted to load the most accurate round possible that shot the best in many 30 nosler rifles, I would select a fast burning powder for the powder and bullet combination, and work it on the lighter powder charges. You can easily get it to shoot good doing this. But, it's not a full power load that takes advantage of the full powder capacity and velocity of the cartridge. For a full power load with this combo, I would select H1000 as the fastest burn rate I would go, and probably use Retumbo for that combo. But the sweet spot is a smaller node when you go to a slower burning powder.

Man that's some great info & wisdom. Thanks!

Awesome thread all-around. Good work RS.

Re: Seating Depth Test Before Ladder for Charge Wt? [Re: ChadTRG42] #7160435
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Originally Posted By: ChadTRG42
IMO, playing with the seating depth first, then the powder charge is backwards. If you have a powder charge that the rifle doesn't like, IMO, playing with the seating depth will only marginally improve the groups, if at all. (I would truly love to test this)


In his first test it showed a swing from 1.5 MOA to .5 MOA on seating depth alone with the same charge no?


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Re: Seating Depth Test Before Ladder for Charge Wt? [Re: redchevy] #7160451
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Originally Posted By: redchevy
Originally Posted By: ChadTRG42
IMO, playing with the seating depth first, then the powder charge is backwards. If you have a powder charge that the rifle doesn't like, IMO, playing with the seating depth will only marginally improve the groups, if at all. (I would truly love to test this)


In his first test it showed a swing from 1.5 MOA to .5 MOA on seating depth alone with the same charge no?


Yes it did.

We ladder tested H-1000 and a completely different bullet from his initial seating depth jump test. And the new bullet, and new powder still liked a .090" jump.



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