Huge Drop In Velocity Going To Jacketed

[Shepard]

I generally load lead 180 over clays. It is accurate with an extreme spread of 15 - 16 fps. But, on hot humid days the smoke can completely obscure the targets. So I decided to give jacket bullets a try. I loaded 180 grn Zeros and MG over my usual powder charge. I expected some drop but I lost a full 100 fps and the extreme spread went to between 90 and 100 on both bullets. Is this normal? If not, what is wrong?

Thanx, Shepard

[EricW]

I generally load lead 180 over clays. It is accurate with an extreme spread of 15 - 16 fps. But, on hot humid days the smoke can completely obscure the targets. So I decided to give jacket bullets a try. I loaded 180 grn Zeros and MG over my usual powder charge. I expected some drop but I lost a full 100 fps and the extreme spread went to between 90 and 100 on both bullets. Is this normal? If not, what is wrong?

Thanx, Shepard

<{POST_SNAPBACK}>

Totally normal. Most cast bullets are .0005" TO .001" larger than jacketed. There's a huge difference in velocity because there's a huge difference in how the bullet fits in the barrel. I really have to pump up my MG loads over my lead loads.

[Larry White]

What you saw is about right. On average I find the difference of about .3 grains in powder chg between lead and jacketed.-----Larry

[Shepard]

How about the extreme spread? Is 90 to 100 fps what I should expect from jacketed?

[MstngLX50]

I got an extreme spread of 22 with zero 180jhp. Load was TiteGroup with Win SP. Loaded on 650. Sample size was 50 rounds in 5 round strings, with about a minute between each string. CED chrono.

[Shepard]

Mine was 10 rounds each bullet over a ced loaded on a 1050.

[Harmon]

high es is probably from pressure spikes associated with that powder

[MstngLX50]

Mixed brass maybe, I'm just getting set up so all I've got so far is the factory stuff I shot. It was all once fired UMC. But then I guess you'd have seen that with lead as well.

I'd have thought that the deviation would remain constant with just a switch to jacketed bullets.

[Shepard]

Yea, the extreme spread is really throwing me. I expected a FPS drop but not the large ES, and with both types of bullets. Guess I gotta try them through my back-up gun and see if I get the same results.

[MoNsTeR]

Try Master Blaster, Bear Creek, and/or Precision to cut down on the smoking without having to jack up your charges.

[Larry White]

Check your crimp, you may need to change it. Bullets are diffrent dia. and you may have to increase crimp to get a constient bullet pull.-----Larry

[ErikW]

Blame the spread on Clays.

I think I need .3 gr more Clays with a jacketed 180 than with a coated 180.

[wide45]

When switching from lead to jacketed, I'm guessing that you should fire a bunch of rounds to condition the barrel to the new load before going to the chrono.