10mm load data for 220 gr. bullets?

[Objekt]

Yes, I was happy to see no cratering of the firing pin strikes. However, I found some of the flattening rather extreme and alarming, particularly the following examples:

Far left on the bottom row of #1
Second from the left on the middle row in #2
Second & third from left on bottom row in #5

Flattening wasn't consistent even within batches of the same load. For example, look at the leftmost brass on both rows in #6. The top one looks fine, but the bottom one looks squashed.

I'll spill the beans a little by telling you that picture #4 matches up with my recipe #2 above, 8.0 grains of Blue Dot with a "normal" seating length (between 1.260" and 1.270"). #4 is also the only set of brass that looks entirely "normal" to me in how much the primers were squashed.

 

[RhinoDefense]

Never go by visuals. Always measure the web expansion.

 

[Clark]

I have worked up enough 10mm 200 gr loads.

The primer is likely not the weak spot with a good firing pin to firing pin hole fit.
It will more likely be the guppy belly in a poorly supported chamber.
It will more likely be the primer pocket gets loose in a very hot load in a well supported chamber.

800X can be measured with the little Lee dippers.

 

[Objekt]

Some data on web expansion

Never go by visuals. Always measure the web expansion.

My brass and I just spent some time with my dial caliper. Here's what I found. Averages are based on measuring 10 cases of each type.

Starline brass from my "normal" 10mm reloads (mostly 6.0 grains Bullseye under a 170 grain cast lead bullet): average diameter @ web = 0.428".

Mixed-brand brass from the reloads w/220 gr. plated bullet, 8.0 grains Blue Dot: average diameter @ web = 0.429".

Mixed-brand brass from the reloads w/220 gr. plated bullet, 9.0 grains Accurate #9: average diameter @ web = 0.428".

Mixed-brand brass from the reloads w/220 gr. plated bullet, 10.0 grains Accurate #9: average diameter @ web = 0.429".

For reference: brand-new Winchester Silvertips measure between 0.420" and 0.421" at the web, as one would expect with new, unfired ammunition. I don't have any once-fired Silvertips brass, but it would be interesting to measure some. How much web expansion should one get with a standard factory load? Is the dimension any different with insanely hot 10mm, like Buffalo Bore's 220 grain cast lead offering?

The variations in case diameter at the web are not significant between batches. So perhaps all my loads were well within the realm of safe pressures, despite the appearance of some primers.

My next few test batches will explore the following variables:
-bumping up the Blue Dot charge by 0.2 grains;
-use of Federal magnum large pistol (#150) primers with Accurate #9;
-use of Federal magnum large pistol (#150) primers with 8.0 and 8.2 grains Blue Dot.

FWIW: I use an Evolution Gun Works U-die to size, which mostly irons out any bulges at the web. Typically, my many-times-fired 10mm brass will go from 0.429" at the web to 0.425". It won't ever go back to the original 0.420" dimension. The only tool I know of which may do that is Redding's "Rx" push-through size die, but I haven't tried it.