Heat and velocity puzzle (140g absolute hammers and 180 ELDM)

[RockyMtnMT]

Sounds like you have accurate loads and dope that gets you to longer range. I think you are done. Ditch the Chrono and fine tune your ballistics data to match your drop data.

 

[Koda_]

Load B (eld/h4831) had been loaded for a long time, not annealed, and done when I knew less in general. so maybe there was some neck weld soaking up some pressure or something else. It was accurate at 500. Beer can accurate. But slower than before.

Load A (hammer/rl16) had been annealed, loaded, crimped, pulled, resized, reloaded, and recrimped with the same bullets and same powder. And it was 100fps or more different.

I would work on your reloading consistency before wondering if a temperature difference of 10 degrees over 2 weekends makes any velocity difference. Im curious what kind of scale are you using to measure your powder charges?

 

[300 Driver]

I also believe you are overthinking this. The chrono is an optional tool that gets you in the ballpark. Your DOPE and multiple groups are the real concern here. If DOPE is repeatable/good and groups are beer can at 500, ignore that chrono.

 

[JakeC]

I also believe you are overthinking this. The chrono is an optional tool that gets you in the ballpark. Your DOPE and multiple groups are the real concern here. If DOPE is repeatable/good and groups are beer can at 500, ignore that chrono.

Yeah, I know you're right I just worry that I'm missing a big hunk of the picture if I'm that far off.

But I don't think I am missing too much except some brakes on my imagination. I bought a magnetospeed and shot last Sunday and the original chronograph was way off as described by some guys above. My variations were identical across all 3 sessions, but in 85 degrees actual speeds are 2660 avg for the 180 and 3250 for the 140 AH. I was hitting high at 500 based on the calculators but that kind of truing is normal I bet. I'm fine with both of MVs, even though I'm a little sad I can't get 3400 with the hammer. No real reason for that, it was just a goal. I could monkey with powder and get roomier brass but that's pointless. I got to 3290 or so seating it long but I don't plan on hunting it like that. I need to remember to correct my data on the absolute hammer thread when I get home from hunting.

But anyway the animals aren't going to care, I just got irrationally thrilled by the fake numbers I had at first.

A scale is absolutely next on the shopping list, plus some other tweaks. My extreme spread over yen shots is 20 for the eld and 40 for the absolute hammer. I know I have consistency and tension to work on, and that's a max not tuned load for the hammer but I know for a fact the scale walks around. Not a ton, but some.

 

[JakeC]

As others have stated, could be chrono related but don't discount your initial suspicion….. temp. This past spring I worked up a CFE/51 gr Absolute load for my sporter weight CZ 223. Getting into the warmer summer months my Labradar has confirmed that speeds jump by 100fps when temp is over 75F and groups fell apart. Come back early in the cool of morning and the load returns to normal. Now trying to find the time to get a load that works in the summer. Will that load still work when it gets cold again? Only time will tell.

Thankfully I was able to rule that out, pressure was the same at the same charge weight. Which is good in terms of lack of sensitivity I guess