Poor accuracy with new lot of 80.5

[Clancy]

In short, my old lot shot in the .2s with the occasional bad 3.

I got a new lot in, seated them the same 10 off, and things fell apart badly, hovering over an inch with the same and similar charge weights.

I did cross reference them with some leftover old lot bullets, and the old lot still shoots great.

I should probably start with seating depth, right?

 

[284winner]

Try jumping them .030-.050. See how they like it. The 80.5 bullets I've been using like the longer jump. Obviously your first or other lots shot well at only .010.

 

[RDavies]

In short, my old lot shot in the .2s with the occasional bad 3.

I got a new lot in, seated them the same 10 off, and things fell apart badly, hovering over an inch with the same and similar charge weights.

I did cross reference them with some leftover old lot bullets, and the old lot still shoots great.

I should probably start with seating depth, right?

Did you chronograph the old lot recently? Often different batches of the same bullet can vary in velocity, often by quite a bit. This could possibly due to slight differences in diameter, jacket hardness and ogive shape. The different ogive shape could also cause slightly different actual seating depths with the same seater setting. When I switch to a new batch of bullets I will always run a few of each batch over a crony, and use the switch as an excuse to recheck bullet jam/jump to keep up with possible throat movement as well as bullet shape change.

 

[Clancy]

I also check seating depth for each lot, and these were about .003 higher with the same die setting, but that had already been accounted for.

I made up some test loads with the low velocity node last night, from a hard jam (+.015) all the way to 35 off in 5 thou increments. I can’t go any lower than that without getting into a small donut at the base of the neck. I tried 50 off and BTO became very irregular.

Will report.

 

[barefooter56]

I also check seating depth for each lot, and these were about .003 higher with the same die setting, but that had already been accounted for.

I made up some test loads with the low velocity node last night, from a hard jam (+.015) all the way to 35 off in 5 thou increments. I can’t go any lower than that without getting into a small donut at the base of the neck. I tried 50 off and BTO became very irregular.

Will report.

Clancy,
I suggest you just drop the powder charge back a grain or so and work back up till you find your velocity accuracy node. It may just be the difference in how much of the bullet in the new lot is in the cartridge case neck changing pressure which changes velocity. The .003 CBTO variance between the lots should not make that big a difference. Please let me know what you find here Clancy!

 

[manitou210]

You might want to try kissing the lands with 24.7 Varget with new brass

 

[Clancy]

It’s not a 223, but good shooting anyway.

 

[Clancy]

Should be testing the loads this evening.

I’ve already tried a wide range of powder charges with no luck, so I’ll be trying seating depth now, with the original powder charge.

 

[Clancy]

Oook,

Fired some 5 shot groups from touch +15 all the way to 35 off as planned.

Accuracy was fantastic both 5 and 10 into the lands, and decent at 20 off.

Now that I’ve got a fairly obvious seating depth, I may backtrack and try a few different powder charges.

In short, the new batch shoots as well as the old batch, but required a new load development, which is unusual for quality bullets, but I’ll take it.