I'm so confused- data not jiving with targets

[bearintex]

So I'm working up loads for my 6.5MB RAP (in an MDT chassis). I finally got a hold of 8 pounds of H4350. Federal Gold Medal primers. Brass is 2x fired Hornady which has been trimmed to 1.910", primer pockets uniformed, flash holes deburred in and out. Neck sized only, with 0.002" tension using a Lee sizing die.

Shot 5 loads from 42.4 to 43.2 grains, all measured and trickled up to weight. I had previously seen this as a "flat" spot in the velocity curve when I had done pressure checks in half grain increments. I didn't see any pressure signs whatsoever at 43.5 grains, which is where I stopped.

My SD is worse than a Hillary presidency. The best I got with those loads was a measly 18.2, the worst was 33. Velocity was measured with a cheap Shooting Chrony. I was shooting at 300 yards. Wind was negligible until about halfway through, then it started gusting from 4 oclock up to about 6 mph. I wasn't as worried about overall group size as I was the vertical grouping. Bipod on the front and a heavy sock bag in the back.

Charge 42.4 42.6 42.8 43 43.2
Average 2774 2752.4 2798.2 2787.6 2789.8
Std Dev 22.2 25.3 18.2 33.0 22.7
Overall grp 4 2 5 5.75 5.5
Vertical grp 2.75 2 2.25 1 4.25

So which do I believe, the raw data or the groups on the paper?

[Radar]

I'm gonna go with the data. My I ask why you are dead set on H4350? I have been working on load development for my 6.5 CM and have discovered two things: RL26 and RP 7.5 primers.

Now I am using Lapua brass with the small flash hole, so we aint apples to apples on that. SD for my current load is 8 and velocity avg is 2904 with Berger 135gr Classic Hunter. Sub moa with 5 shot groups. I am changing seating depth to see what happens, I will tinker with loads till I think its as good as it gets.

I have another load with Sierra 140gr SPBT. SD is 11 and avg velocity is 2874.

I did not catch what bullet you are using, and when you are seating bullets in your brass does the neck tension feel the same on every round?

[xman59]

something I learned a long time ago,,,,

if the group is right it does not matter what the numbers are,,,, as long as it is a safe load...

shoot it a few more times at different distances and let that be the deciding factor....

the standard deviation will not cause as much elevation change as you saw either

[McClain]

You don't say how much jump to the lands with the bullets you are using. If only a couple tho, and if you are not sorting your bullets (by weight or length) then it might be possible that there is enough variation in bullets such that some are off the lands and some are touching when chambered. This could lead in variations in pressure/velocity, thus causing high SDs. Also, you might want to try weight sorting your brass.

Also, even though H4350 is supposed to be temperature stable, extreme heat differences during your strings could still be causing some increased SDs.

[bearintex]

Bullet is 143 eldx. Seated at 2.247 to the ogive measured with calipers and Hornady tool. That’s my max mag length, it’s at least 20 thou off the lands. Neck tension feels similar on everything.

[Radar]

Well if neck tension is good and seating depth is good, you aint got but three things left. Chrony, Primers or powder

I would not change anything but primers and load only 5 rounds and shoot them across the chrony. See what you got.

If it aint primers then its powder,powder charge or your chrony.

Sunlight can play tricks on a chronograph, especially the older chronys. I had one and I know that to be true. Did you have it shaded good?

If it aint the chrony, then it is only one thing left.

Someone else mentioned go by the target and sometimes that is true, but your reloading a precision round and that means they must all be the same.

[bearintex]

I’m thinking it’s the chrono. I am trying to convince the CFO I need a magnetospeed. What is the difference between the $150 and $300 versions?

[diamond10x]

something I learned a long time ago,,,,

if the group is right it does not matter what the numbers are,,,, as long as it is a safe load...

shoot it a few more times at different distances and let that be the deciding factor....

the standard deviation will not cause as much elevation change as you saw either

To me this is what it all comes down to... reloading has been a thing in our family for 3 generations and this is what i have learned through all of it. Let the target show the results and all the other stuff with numbers is just to make sure you get each round exactly like the one before or next up.

[Radar]

I’m thinking it’s the chrono. I am trying to convince the CFO I need a magnetospeed. What is the difference between the $150 and $300 versions?

I don’t have a magnetospeed. I ain’t sold on one yet. The one I got now has done a real good job and I can use it with my arrows, pistols or rifles.

[Rem40x]

Hornady brass sux. Change brass

[Radar]

Hornady brass sux. Change brass

sometimes and sometimes federal primers too

[bearintex]

sometimes and sometimes federal primers too

Even the match primers?

Got 1k of them.

[Rem40x]

Yep I m now shooting Peterson srp didn't help my sd as everyone said but I can push it harder without the primers falling out now . Also how many rounds and he you checked for carbon ring?

[bboswell]

1. I don’t trust your chrono.

2. You didn’t mention neck turning which makes me wonder how you are so sure on neck tension.

[kck]

1. I don’t trust your chrono.

2. You didn’t mention neck turning which makes me wonder how you are so sure on neck tension.

This. Turn your necks (I shoot only Lapua and I turn them) as you'll have thickness variations. Is the brass annealed? I'm not a fan of shooting more than a few rounds through worked brass but that's personal (and I love using my AMP annealer ). You may also want to bum a magnetospeed to verify velocities as well if you know someone with one as that's what I did. I used to shoot through a cheap chrono and upgraded a couple years ago.