Ladder Test 6.5 CM

[Centerfire01]

Shot a ladder test with the following components Hornady Brass, 140gr, ELDM, H4350, and Fed GM210M. Velocties as follows (taken with a lab radar)
Grains Vel
40.3 2673
40.5 2678
40.7 2681
40.9 2715
41.1 2720
41.3 2734
41.5 2752
41.7 2769
41.9 2772
42.1 2788
42.3 2771
42.5 2820

The only node that stands out to me is 42.1-42.3 and maybe 40.3-40.5 was hoping for something in the 41 range. Found another node at 42.3-42.5 but worked up to pressure at 42.7 with a sticky bolt. What say you guys? What charge weight would yall settle with?

 

[acudaowner]

just to ask you what barrel length are you running ?
personally I choose to stick with 41.8 from my 26'' barrel getting me a 2777fps average but a 2.2 sd made me smile not terribly hot , but exactly what I was looking for I have not tried to go hotter than 42.gr as I really don't need anything faster for my local range best of luck choosing what ever load you choose .

 

[RegionRat]

If it were me, we would also plot the vertical shot fall at about 600 yards to see if there is a good node.

As often as not, velocity plots of single data points do not guide you well. They keep coming up when the rigs and recipes are well known and the authors are just verifying the next copy of an already well developed system.

To use a Creighton Audette Ladder method, you plot the shot fall and look for vertical clusters to identify potential nodes, then go back and investigate those with more samples. YMMV

 

[nn8734]

Pick whatever cw from your ladder that has a minimal acceptable velocity for you and start seating depth trials to dial in your group size.

I wouldn’t go beyond 42.3 for a .4g “pressure buffer”.

You should have no problem developing a high performance load with those components

 

[Centerfire01]

just to ask you what barrel length are you running ?
personally I choose to stick with 41.8 from my 26'' barrel getting me a 2777fps average but a 2.2 sd made me smile not terribly hot , but exactly what I was looking for I have not tried to go hotter than 42.gr as I really don't need anything faster for my local range best of luck choosing what ever load you choose .

just to ask you what barrel length are you running ?
personally I choose to stick with 41.8 from my 26'' barrel getting me a 2777fps average but a 2.2 sd made me smile not terribly hot , but exactly what I was looking for I have not tried to go hotter than 42.gr as I really don't need anything faster for my local range best of luck choosing what ever load you choose .

24"

 

[Centerfire01]

View attachment 7880442

If it were me, we would also plot the vertical shot fall at about 600 yards to see if there is a good node.

As often as not, velocity plots of single data points do not guide you well. They keep coming up when the rigs and recipes are well known and the authors are just verifying the next copy of an already well developed system.

To use a Creighton Audette Ladder method, you plot the shot fall and look for vertical clusters to identify potential nodes, then go back and investigate those with more samples. YMMV

What charge weight would you choose prior to that? If it were me and what I did with my 260 was pick where I saw a reduction in velocity. So in this particular example I'd pick 42.2.

 

[Rob01]

That reduction was an anomaly. You don't lose velocity with the higher loads. I would bet you load that again you would get a higher velocity.

From what you have I would stay in the 41.7-41.9 area. Good velocity and no need to push it harder.

 

[Doom]

One shot chronograph data is worthless. Ladder test without target is worthless. Flat spots are an anomaly not and not representative of the loads. They are due to normal variations in the shot to shot loads and the errors in testing.

 

[TheOfficeT-Rex]

Plot a regression line in excel then pick a speed you're happy with.

Or just pick 41,5 and move to seating depth. 2750 aint a bad spot to be.

 

[Doom]

Plot a regression line in excel then pick a speed you're happy with.

Or just pick 41,5 and move to seating depth. 2750 aint a bad spot to be.

I have not tested this theory but I believe it is valid. I personally use Newberry's OCW but it picks a charge based on a given seating depth and can sometimes be refined by seating depth adjustment. I did have occasion to arrive at the same charge weights for two radically different seating depths. This was with the 53 SMK in 223 where the same charge worked with 8208XBR at 2.22" and and 2.25" COL (I don't have the CBTO handy).

 

[RegionRat]

What charge weight would you choose prior to that? If it were me and what I did with my 260 was pick where I saw a reduction in velocity. So in this particular example I'd pick 42.2.

What ends up happening with the tests that run while only observing velocity, is that the results are confused by under-sampling.

So if you run that same test several more times, the data tends to smooth out and "flat spots" can evaporate. The method would then require many more rounds to fill out where the ES may in fact narrow. However, not every rig gives a simultaneous low SD/ES where it gives the best accuracy at distance.

What we want to find early, are the vertical nodes, and "acceptable" velocity stats. I am not one to say that you ignore one or the other, but I am saying you need to emphasize the shot fall first, and then the seating depth, and lastly examine the velocity. However, it would be rare to see very poor velocity stats where the shot fall and group at range is best, even though you may see better velocity stats nearby. At distances past 600 yards, you don't get away with anything. But if you chase velocity flat spots, you waste more rounds while passing by group nodes.

If you want to design a load development test on a completely unknown rig, one without any known history, you run an Audette Ladder at an arbitrary safe seating depth, then investigate the potential vertical nodes of those results with follow up tests, and then optimize the group with seating depth testing. That first test should be at enough distance to get at or near your maximum interest without going too close to sonic transition. YMMV

 

[Centerfire01]

What ends up happening with the tests that run while only observing velocity, is that the results are confused by under-sampling.

So if you run that same test several more times, the data tends to smooth out and "flat spots" can evaporate. The method would then require many more rounds to fill out where the ES may in fact narrow. However, not every rig gives a simultaneous low SD/ES where it gives the best accuracy at distance.

What we want to find early, are the vertical nodes, and "acceptable" velocity stats. I am not one to say that you ignore one or the other, but I am saying you need to emphasize the shot fall first, and then the seating depth, and lastly examine the velocity. However, it would be rare to see very poor velocity stats where the shot fall and group at range is best, even though you may see better velocity stats nearby. At distances past 600 yards, you don't get away with anything. But if you chase velocity flat spots, you waste more rounds while passing by group nodes.

If you want to design a load development test on a completely unknown rig, one without any known history, you run an Audette Ladder at an arbitrary safe seating depth, then investigate the potential vertical nodes of those results with follow up tests, and then optimize the group with seating depth testing. That first test should be at enough distance to get at or near your maximum interest without going too close to sonic transition. YMMV

So I have leisure access to a mile with berms at varying distances. I'm going to make 10 rounds at 40.5 and ten rounds at 41.8 and post the results up.

THANK YOU EVERYONE for the feedback advice. I think I got lucky with my 260 as I left this step out and shot that rifle to a mile making consistent hits. My ES was 12 for the load. Like I said I think I got lucky.

 

[RegionRat]

@Centerfire01 Any time you fall off a log and get a tight and accurate group, and a simultaneous great velocity stat, you take it an run.

Just like with known good ammo, the closer the rig stays to a known good recipe that you can copy when it comes time to replace the barrel, the more likely you will learn to shoot well as compared to spending resources and time chasing load development.

If you have a rig that suits your shooting style, and it has a good quality barrel chambered by a good smith, you should stock up on what works and spend your time learning to shoot and dope wind instead of chasing the latest greatest wonder caliber.

If and when all this ammo shortage eases up, try and budget some ammo and time for that Audette Ladder test out at 600 - 1000 yards. Pick one aim point and shoot the whole ladder with as many fine steps as you can stand while spanning the charge weights well above and below where you expect to shoot (within safe limits).

You should find vertical nodes and plan how to stay in the middle of the one you like based on temperature conditions of the day you tested. Play with a ballistic program in advance to anticipate the total vertical range you should expect from the whole span of the ladder. Shoot far enough away that your shot fall spread is way bigger than your typical group scatter to make it easy to read. When you are lucky, you see more than one node, but find one in the top half that is wide enough to forgive tolerances in components and loading methods.

You can then tune it further with seating depth to shape the group by arriving at the range with a bunch of pre-loaded long rounds and the ability to adjust depth at the range. You take as many shots at the depth settings as it takes to know your limits and you leave the range with confidence.


Good Luck and in for the range report.

 

[Centerfire01]

So I have settled with the 41.8 as it yields an acceptable velocity and accuracy. If I actually focused shooting these groups and took my time I can imagine I could tighten then up quite a bit. They were shot with relatively quick to stay in the wind the ES for 11 shots of 41.8 was 33. Here are the ladder results at 500m