Reloading FPS oddities

[moxford]

Hi all,

Loaded up 10 cartridges in increments of 0.2, trying for the "Scott Satterlee method" of working up the load.

I noticed some interesting chrono drops (Magnetospeed) and no really good "flat spots" / nodes.

30-06 with 150gr TTSX, H4895 loaded to OAL of 3.2500" in Lapua brass and Fed 210 primers. Nothing exotic.

This is an old Husqvarna 30-06 from the 50s (Mauser 98 action) with a very (very) long magazine and freebore. I've free-floated the barrel, but it did have the Mag off the front (so accuracy might suck from harmonics, but shouldn't affect velocity.) Barrel twist is a fast 1:9.5" (not that it should matter here.)

No pressure signs seen, and loaded 0.010" long I could push up above the book slightly ... might be worth a look next trip out.

49.0 2934
49.2 ????? <-- misadjustment of chrono
49.4 2936
49.6 2959
49.8 2945 <-- dip
50.0 2978
50.2 2968 <-- dip
50.4 2990
50.6 3005
50.8 3025
51.0 3015 <-- dip

1) Any clue what causes the dips? Inconsistent neck-tension maybe?
2) I don't see any obvious "really great" flat-spots, but lacking data from 49.2 hurts but could show a potential "light" node. Nothing really obvious to my eye.
3) Velocity over 3k is pushing pressure limits according to the book, but bolt handle, primers, etc all seemed okay. I've yet to measure case expansion at the head, but that will happen before next trip.

I usually use OCW, but thought I'd try something new.

Same type of workup with TTSX 130s (same brass, primers, powder) right after that one gave great data, decent groups, and couple good nodes to explore (the slower being a 3-shot ES of 4!) ... but that 150 data feels like it's just all over the place.

Thanks in advance!
-mox

[Cheep]

One cartridge at each charge weight is not enough data to rely on. Make a few at each charge weight, shoot one of each then start over and see if the data is consistent.

[JackEllis]

I usually shoot two cartridges at each charge weight, but I also start with the minimum and work up in half grain increments.

Based on the test data you provided, I’d try 50.5 grains and load them really short so long as you aren’t seeing any pressure signs.

I load Hornady GMX and found they tend to fly faster out of my rifle than Hornday’s load data said they would for a given powder charge. I get some primer cratering at about 75% of the difference between min and max recommended charge weights.

[NapalmCheese]

49.0 2934
49.2 ????? <-- misadjustment of chrono
49.4 2936
49.6 2959
49.8 2945 <-- dip
50.0 2978
50.2 2968 <-- dip
50.4 2990
50.6 3005
50.8 3025
51.0 3015 <-- dip

I'm not the most seasoned reloader here, but here's my take:

By shooting only one round at each charge weight your data is practically useless. You've got one significant digit of precision, so what happens if you load a round at 50.04 grains and then load the next one at 50.15 grains? Your scale reads a 0.2 grain difference in charge weight, but the actual difference is 0.11 grains, that could effect velocity by a few feet per second. Those inconsistencies mean that with a sample size of only one round your data just isn't reliable. Combine that with inconsistencies in your chrono (I'm not familiar with with the magneto speed, but with my chrony shifting light levels, cloud cover, etc. are potential causes for variations in reading) and inconsistent chamber temperatures and you really need to shoot more than 1 load at each charge.

That being said, I imagine the dips in velocity you're seeing are statistically irrelevant and if you loaded up more than 1 cartridge at each charge weight and averaged your velocities at each weight you'd come up with something more consistent.

At any rate, 49.0-49.4 looks like it's probably a flat spot. 49.4-49.8 might be, and 50.6-51.0 looks like another one to me, but there isn't enough data to actually say.

edit to add: Looking at the Scott Satterlee method it's clear that it's as much a reloading method as a load development method. That is he's trying to control all of the variables to ensure consistency as a replacement for loading multiple rounds at each charge weight and averaging them. If you are a good enough loader, and you can keep everything under control, and make sure everything is accounted for between steps I suppose it could work. I am not that good of a reloader and so prefer to load more than one cartridge at each charge weight.