Working up my first load, Any advice?

[Ronincjn]

Alright so I finally found some time to sit down and get my first rounds loaded and fired these past two days. The load development and test method I used was "velocity node", just plain shooting at a berm over my magnetospeed sporter.

Here is load data:

Bullet - 85gr TREX tipped
Brass - once fired hornady
primer - CCI 450
powder - H335
brass length - 1.515

CBTO - avg 1.674 (had some slight fluctuation based on Ogive inconsistency, but only by a thousandth here or there)
COAL - avg 2.267 (min - 2.263/max - 2.270)
I measured my 10rd Durmag and figured I would be fine with a max 2.270, but did experience a feeding issue on one of the 2.269 cartridges. Think I may back down to 2.250 since this is where he designed the the bullet to seat. This will put me 0.073" off the lands.

Starting load 28.0gr increase by 0.2gr to a max of 31.8gr (20 rounds). Each charge will be accompanied by its velocity.

28.0 --- 2563
28.2 --- 2571
28.4 --- 2603
28.6 --- 2624
28.8 --- 2640
29.0 --- 2647
29.2 --- 2663
29.4 --- 2681
29.6 --- 2721
29.8 --- 2766
30.0 --- 2757
30.2 --- 2794
30.4 --- 2791
30.6 --- 2829
30.8 --- 2821
31.0 --- 2895
31.2 --- 2904
31.4 --- 2925
31.6 --- 2945
31.8 --- 2987 (only round I saw a pressure sign, light ejector mark)

Looks like I had a pressure spike between 30.8 and 31gr (74fps) ejected brass looked fine, no excessive pressure signs.

I don't see a super clear "node", although 30.2 and 30.4 caught my attention, looking at others data for similar testing method there seems to be a node of 3-rounds that have a similar FPS. All of the "nodes" that show similar fps (2-8 fps change) are 2-round based. There is only one exception that I found today, where he used a 2-round sample for their velocity node.
Any advice on the above data would be appreciated.

My next step is to potentially "redo" a smaller sample size since I know now that 31.6 is my max with no pressure signs and work backward. Load another 10-rounds start at 29.8gr, increase 0.2gr to reach 31.6gr. See if I can re-create the node at 30.2 and 30.4 but to see if the same pressure spike shows up between 30.8 and 31.0.

This all makes sense in my head, but would like some experienced opinions from the Horde. Please let me know if something looks off, dangerous, wrong, etc.

PS - I did recover more than half of the projectiles from the dirt berm I shot into at 100yrds+/- all opened up beautifully.

[A5BLASTER]

Having worked with this bullet a good bit.

I would do a 10 shot set at 28.8, 28.9 and 29 grains and see what the sd and es numbers look like.

Also 30.6, 30.7 and 30.8 as well.

You had a pressure spike at 31 grains.

Whatever 10 shot group gives you the best sd and es numbers would be the one I go with then I would play with seating depth to shrink the group up if need be.

[A5BLASTER]

Having worked with this bullet a good bit.

I would do a 10 shot set at 28.8, 28.9 and 29 grains and see what the sd and es numbers look like.

Also 30.6, 30.7 and 30.8 as well.

You had a pressure spike at 31 grains.

Whatever 10 shot group gives you the best sd and es numbers would be the one I go with then I would play with seating depth to shrink the group up if need be.

[Klem]

Ronin,

I would be cautious about using your velocity testing to infer anything more than what velocity you get for what amount of powder (for a particular bullet and cartridge length). I think there is a false belief that velocity variations across a range translate into accuracy on the target. It is a clumsy correlation at best and given shooting is a system of averages the fewer bullets you shoot the less meaningful and valid your findings are.

Here are your results graphed.


I have drawn a straight line through the wobbly results because again, it's a game of averages and at this stage you have fired only one round at each of those powder increments. If you were to repeat this test and the second wobbly line matched exactly the first; including sharp rises and plateaus in exactly the same spots then I would say you are on to something. Otherwise, you can infer the wobbles could also be indicators of vagaries in neck tension, brass volume, the unique way each powder column ignited, differences in primer function, and the inbuilt error in your Magnetospeed.Sometimes we also make errors when transcribing data...just saying.

Towards the end the velocity starts to climb above the straight line. This could be due to the powder starting to be compressed, although I do not have this bullet on Quickload to verify.

My thoughts are is that you pick a safe/max upper limit and go 5% low and shoot groups of 4 or 5 at the target in increasing increments of 1%. Precision on the target is the acid test, not velocity. Groups of meaningful numbers like 4 or 5 takes into account the statistical nature of shooting.

So, shoot one or two groups of four rounds with the following powders loads:
31.6
31.3
31.0
30.7
30.4
30.1
It's the tightest average group size you want at the highest velocity, in the safe range.

You won't see meaningful variations in velocity with powder increments less than 1%. 1% is 0.3 grains in your case.

Unfortunately with an AR, because it is so minimalistic (fragile) relative to other actions using typical overpressure signs as benchmarks is often too late. That swipe mark on the base is probably already three increments too hot.

[Ronincjn]

Having worked with this bullet a good bit.

I would do a 10 shot set at 28.8, 28.9 and 29 grains and see what the sd and es numbers look like.

Also 30.6, 30.7 and 30.8 as well.

You had a pressure spike at 31 grains.

Whatever 10 shot group gives you the best sd and es numbers would be the one I go with then I would play with seating depth to shrink the group up if need be.

Ronin,

I would be cautious about using your velocity testing to infer anything more than what velocity you get for what amount of powder (for a particular bullet and cartridge length). I think there is a false belief that velocity variations across a range translate into accuracy on the target. It is a clumsy correlation at best and given shooting is a system of averages the fewer bullets you shoot the less meaningful and valid your findings are.

Here are your results graphed.
[ATTACH=CONFIG]16028[/ATTACH]

I have drawn a straight line through the wobbly results because again, it's a game of averages and at this stage you have fired only one round at each of those powder increments. If you were to repeat this test and the second wobbly line matched exactly the first; including sharp rises and plateaus in exactly the same spots then I would say you are on to something. Otherwise, you can infer the wobbles could also be indicators of vagaries in neck tension, brass volume, the unique way each powder column ignited, differences in primer function, and the inbuilt error in your Magnetospeed.Sometimes we also make errors when transcribing data...just saying.

Towards the end the velocity starts to climb above the straight line. This could be due to the powder starting to be compressed, although I do not have this bullet on Quickload to verify.

My thoughts are is that you pick a safe/max upper limit and go 5% low and shoot groups of 4 or 5 at the target in increasing increments of 1%. Precision on the target is the acid test, not velocity. Groups of meaningful numbers like 4 or 5 takes into account the statistical nature of shooting.

So, shoot one or two groups of four rounds with the following powders loads:
31.6
31.3
31.0
30.7
30.4
30.1
It's the tightest average group size you want at the highest velocity, in the safe range.

You won't see meaningful variations in velocity with powder increments less than 1%. 1% is 0.3 grains in your case.

Unfortunately with an AR, because it is so minimalistic (fragile) relative to other actions using typical overpressure signs as benchmarks is often too late. That swipe mark on the base is probably already three increments too hot.

Thank you both for the advice, unfortunately I'm a hard headed fool and decided the best thing to do was to start all over again knowing that I had a pretty decent spike at 31 grains. I did acquire a new RCBS ultraflow powder measure and Dillon Precision Terminator digital scale. I felt my vintage lyman beam scale and #55 powder measure were unreliable and difficult to get consistent throws and readings. So new equipment, plus the fact I changed from 0.2 to 0.3gr increments might be contributing to the change in velocity or the fact I shot these in the morning vs the afternoon last time. All this lends credence to what Klem had to say about velocities. The one thing I will say is I still had a similar "node" in the 28.6 - 29.2 range between both test.


So I did this instead:

11 rounds using same components but adjusting COAL/CBTO - to give me 2.260/1.663. Starting at 28gr and increasing at 0.3gr to 31.0.

28.0 - 2488
28.3 - 2532
28.6 - 2608
28.9 - 2600
29.2 - 2625
29.5 - 2662
29.8 - 2674
30.1 - 2699
30.4 - 2750
30.7 - 2797
31.0 - 2785

Not really sure what I was expecting to see between the two test since I changed quite a few variables. The one thing that seemed to remain the same was the "node" i mentioned above.

Test #1
rounds:
4 - 28.6gr - 2624
5 - 28.8gr - 2640
6 - 29.0gr - 2647

SD - 11.8
ES - 23

Test #2

Rounds:

3 - 28.6gr - 2608
4 - 28.9gr - 2600
5 - 29.2gr - 2625

SD - 12.8
ES - 25

I only have 18 projectiles left and plan to give A5Blaster suggestion a try, while I wait for another order to arrive of projectiles to give Klem advice a try.
I'm trying to not get discouraged, this is a learning experience for me and sometimes you have to make a few wrong decisions to finally arrive at the right one. I blew thru 50 projectiles with no load developed, but I like to think I learned a lot from the experience of both loading and gathering data.