Seating Depth + Powder Charge Ladder

Yosemite Steve · February 11, 2018, 06:02 PM

Today I was going to just do a quick work up of IMR4350 behind Hornady's 180 gr. SST. I decided to kill two birds with one stone and got three as a bonus.

I was shooting my Savage 30-06.
I decided to try three seating depths to see what differences they would bring.
Because I had some big pressure issues the last time I did this with my shorter chamber and cartridges I started low and finished upper mid range.

The loads were as follows: IMR 4350 - 180 grain SST - CCI 200
Winchester brass weight sorted within .2 grains, 69.2 grains H2O
3 seating depths: 3.310", 3.320" and 3.330" - lands at 3.338"
Charges: 49.0, 50.0, 51.0, 51.5, 52.0, 52.5, 53.0, 53.5, 54.0, 54.5 for each seating depth.

You will see that I did not adjust my scope for any of the shots. My aiming point was the target at top left. I was shooting at 100 yards. Yes, it's just a 32 year old hunting rifle, not a 6.5 Creedmore.

We will start with 3.320":

3.320"

3.330"

I see that I put the velocity data sheets on the wrong pictures for 3.320 and 3.330...

The best grouping for certain was the longest of the three cartridges with the limitation that pressure was starting to appear on the primers and higher charges would be more than I want to go.

The COL of 3.320" had a nice three in one hole that put a smile on my face as I was hoping to find some glory in a safer seating depth.

The 3.310" seating depth was as bad as I care to see as far as grouping. But each shot was a different charge and I never got down to .3 grain increments.

What is most interesting is shots 3 and 4. At all three seating depths those two shots are nearly in identical positions! with the two longer seating depths shots 3 and 4 make one hole! Another two shots are 6 and 7, particularly 7, which is in the same exact spot on both longer cartridges. Now I have solid evidence backing the method so many people have told me... Start with a powder charge! Or... I might just do it this way again. In 30 rounds I found about where I want to seat my bullets. .020" off the lands...(somebody kept suggesting that!) and a powder charge of 51 or 53 grains.

Std7mag, you said it. This proved what you said! Thanks!

T. O'Heir · February 12, 2018, 02:55 PM

The ladder test tells you nothing about the accuracy out of your rifle for a particular load. Only the POI in relation to other loads.
"...did not adjust my scope..." That'd be how load testing is done. You shoot for group only. Off a solid rest on a solid bench.

Yosemite Steve · February 12, 2018, 03:58 PM

Do you think that shots 3, 4 and 7 were coincidentally in the same place on the targets? I don't understand how you can't see the significance. This was three ladder tests so I can undetstand how together they create groups, but...in the longer cartridges 2, 3 and 4 were all next to eachother as well... another coincidence? I think not. A node, it was.

std7mag · February 13, 2018, 04:23 PM

Yup, those are indeed accuracy nodes!!

I would load up some at 51.0gr. and shoot some groups.

Next is to tune your action.

Do you have an inch pound touque wrench?
I use the Fat Wrench that i also torque my scopes with.

Yosemite Steve · February 13, 2018, 04:32 PM

I don't. That is another can of worms. Sunday I had to loosen my rear action screw because the trigger was sticking in the fired position. I need to find out what was binding up. I hope to find a little higher node too. I want to try 52.7, 53.0, 53.3 to see if shot #7 was a node.

std7mag · February 13, 2018, 04:53 PM

I would ask Unclenick, Taylorce, or Mr. Guffey about shot #7.

Otherwise it would appear that your rifle only really has one node. At least with that bullet and that powder.
Sometimes there will be 2 nodes, sometimes not.

Fat Wrench is is $45 on Amazon right now. Not sure if Harbor Freight has one or how much.

Yosemite Steve · February 13, 2018, 05:20 PM

Shot #7 is in the same hole on the second two targets and 1/2" high and left at 30 fps faster in the top target. My increments were .5 grain so it may have been the middle of the node. Shot #6 is not too far away. I am wondering if I mixed up 5 and 6 on the top target. There is what appears to be a pattern.

Bbear · February 16, 2018, 12:54 PM

Harbor Freight has a decent torque wrench. It's the one I use. https://www.harborfreight.com/14-in-...nch-61277.html

Looking at the targets, it appears that the best of all of the nodes available are on the last picture. Loads 1-6 are all about level with each other. Load 7 begins the 'climb' towards a possible second node above where you topped out.
I'd try from 50 gr to 52 gr in .3 increments and try and tie it down some more. Might shoot 3 or 5 shot groups and see how they do.

Yosemite Steve · February 16, 2018, 04:17 PM

6 shot groups - round robin

#1 - 50.3 grains - 24006 fps-SD 26.2 - 1.9" group

#2 - 50.7 grains - 2426.6 fps-SD 17.9 - 1.6 " group

#3 - 51.1 grains - 2446.4 fps-SD 11.3 - .6" group - damn good for this gun!

#4 - 51.5 grains - 2466.6 fps-SD 13.0 - 2.2" group

#5 - 51.9 grains - 2488.0 fps-SD 12.1 - 2.1" group

My pic vanished...Now it's back and now my groups are measured...

I don't know why #2 and #4 crapped out they looked good on the ladders.

std7mag · February 16, 2018, 04:48 PM

Shcweet!!

February 12, 2018, 02:55 PM	#2
T. O'Heir Senior Member Join Date: February 13, 2002 Location: Canada Posts: 12,453	The ladder test tells you nothing about the accuracy out of your rifle for a particular load. Only the POI in relation to other loads. "...did not adjust my scope..." That'd be how load testing is done. You shoot for group only. Off a solid rest on a solid bench. __________________ Spelling and grammar count!

February 12, 2018, 03:58 PM	#3
Yosemite Steve Senior Member Join Date: December 27, 2017 Posts: 460	Do you think that shots 3, 4 and 7 were coincidentally in the same place on the targets? I don't understand how you can't see the significance. This was three ladder tests so I can undetstand how together they create groups, but...in the longer cartridges 2, 3 and 4 were all next to eachother as well... another coincidence? I think not. A node, it was. Last edited by Yosemite Steve; February 12, 2018 at 04:32 PM.

February 13, 2018, 04:23 PM	#4
std7mag Senior Member Join Date: June 23, 2013 Location: Central Taxylvania.. Posts: 3,609	Yup, those are indeed accuracy nodes!! I would load up some at 51.0gr. and shoot some groups. Next is to tune your action. Do you have an inch pound touque wrench? I use the Fat Wrench that i also torque my scopes with.

February 13, 2018, 04:32 PM	#5
Yosemite Steve Senior Member Join Date: December 27, 2017 Posts: 460	I don't. That is another can of worms. Sunday I had to loosen my rear action screw because the trigger was sticking in the fired position. I need to find out what was binding up. I hope to find a little higher node too. I want to try 52.7, 53.0, 53.3 to see if shot #7 was a node.

February 13, 2018, 04:53 PM	#6
std7mag Senior Member Join Date: June 23, 2013 Location: Central Taxylvania.. Posts: 3,609	I would ask Unclenick, Taylorce, or Mr. Guffey about shot #7. Otherwise it would appear that your rifle only really has one node. At least with that bullet and that powder. Sometimes there will be 2 nodes, sometimes not. Fat Wrench is is $45 on Amazon right now. Not sure if Harbor Freight has one or how much.

February 13, 2018, 05:20 PM	#7
Yosemite Steve Senior Member Join Date: December 27, 2017 Posts: 460	Shot #7 is in the same hole on the second two targets and 1/2" high and left at 30 fps faster in the top target. My increments were .5 grain so it may have been the middle of the node. Shot #6 is not too far away. I am wondering if I mixed up 5 and 6 on the top target. There is what appears to be a pattern.

February 16, 2018, 12:54 PM	#8
Bbear Junior Member Join Date: May 30, 2017 Posts: 10	Harbor Freight has a decent torque wrench. It's the one I use. https://www.harborfreight.com/14-in-...nch-61277.html Looking at the targets, it appears that the best of all of the nodes available are on the last picture. Loads 1-6 are all about level with each other. Load 7 begins the 'climb' towards a possible second node above where you topped out. I'd try from 50 gr to 52 gr in .3 increments and try and tie it down some more. Might shoot 3 or 5 shot groups and see how they do.

February 16, 2018, 04:48 PM	#10
std7mag Senior Member Join Date: June 23, 2013 Location: Central Taxylvania.. Posts: 3,609	Shcweet!!