Donuts suck

So short story my ES went up to the 40-50 FPS range and sd 18-24 FPS. I figured out I had donuts. So I ran a few batches through the expander and shot them. Results below.

First group atip
30.80g varget
Expanded neck
5 rounds .4”
Sd4 es11 avg2768


Second group atip
30.98g varg
Expanded neck
9 rounds .74” two fliers
Sd8 es26 avg 2786

Two fliers were 2775 2771 rest of group was 2783-2797 Es14


Third group jlk
30.98g varg
Expanded neck
12 rounds .7”
Sd11 es40 avg2830
2837
2842
2829
2834
2834
2829
2829
2842
2818. ?
2802. ?
2837
2828

Groups are a little bigger than I’d like but I had a very large POA so I prob wasn’t too consistent. I’m pretty curious why the two I marked with ? Are so far out of the rest of the group. I’m keeping track of the brass and will load it again tonight and shoot it and see if those two are still out of the group.

Attached pics are of the electronic target screen for the two groups. The 9 round group was on the x. The 12 round was aiming at the number 9 in the 9 ring right side. The 5 round group poa was bottom left corner of the target center. Poi slightly low right of corner of paper. As seen through 40x spotter.

So anyways. Where it used to be all over the place now it’s just sort of a couple fliers but still too many to shoot a match.

I obviously don’t want to neck turn all this brass. So all I did above was expand it after resizing. So my question is does that work long term? Just moving the donut tonthe outside ?

no i have the forster but that looks like what i need.

Legionnaire said:

You use the Forsters on fired cases, correct?

Click to expand...

I just have the trimmer.

Yeah those look bad. Mine are much less pronounced. Not even affecting accuracy just velocity

ok, so the purpose of this exercise was to figure out if i have a problem with my brass. this is after i discovered the donuts, and each of the cases involved has been run through the expander mandrel. also, each case has been fired an unknown number of times, but potentially quite a few. annealed right before this test.

the exercise is to shoot the same 12 cases twice, keeping track of them, and to see if some cases shot fast every time or slow every time. and especially to see if cases that were much higher or lower than average would repeat. (with the implication that either i have a few bad apples that need to be culled before a match, or maybe the whole lot is just a little goofy and i need all new brass)

the first table is the raw data, two strings, one friday and one today, with the difference to the right.
so.... as you can see from the blue line which i fired friday, two cases (9 and 10) were way below avg velocity while the rest was reasonably tight given the age of the brass and the fact that it's been a while since i cleaned my barrel. because of this, i made a copy of the table on the far right, but zero'd out those two outliers just to see what the SD and ES would look like if i had culled them as bad brass. as you can see, without those two culprits, the SD of 5 is not too shabby. ES is a bit higher than i like but prob wouldn't drop many points in a match because of it.

i had expected those two cases to be way below avg again today. but i was very surprised to see them ABOVE the average today.

if i take those two cases out, my 10 shot average is 2834 day 1 and 2833 day 2. The averages are pretty much the same. So going with that in my calculator i'm 8.2 mils at 1000. The four bad shots are 16, 17, 24, 32 fps off the average, which are either .1 or .2 mils off both high and low. that's roughly 4 and 7" off, which could easily put me off a plate at that distance.

anyways, it seems likely that i need to go through all my brass and cull some of them. but the low one day and high the next bit has me completely baffled. any theories on what sort of defect in the case or prep could cause such a result? what features on the brass would you look at?

same as always, acculab scale, weighing to the kernel. seating primers with forester hand tool. if it had been low both times or high both times, flash hole or brass weight might be culprit. but i can't imagine anything that would cause it to go up AND down

Blue68f100 said:

Try use a bushing die and only size the top portion (like a neck sizer), leaving the donut section untouched. Not sizing as far should eliminate the donut depending on thickness.

Click to expand...

that's a good idea too. i'll try it. when i shot 260AI, i only resized half the neck as a way of controlling neck tension. but i stopped doing that on dasher and 6.5x47L brass because i needed more neck tension to get low SDs. idk why. worth a shot though