.380's Deep-Seating

Gun: Glock 42

Load:
Mixed headstamps, mostly one fired.
COAL is .950", same as Freedom Munitions ammo that uses the same bullet.
Winchester small pistol primers.
Powder is 3.4 gr of WW231.
Bullets are X-treme 100 gr plated flat point, .3551 diameter.
Crimp is just enough to remove the flare, both my micrometer and my magnifying glass say the loaded case mouth is neither belled out nor crimped in, though it does leave a moderate ring on pulled bullets but definitely not through the plating.
10 rds average 845 fps with an ES of 45 fps from my G42.

Loading Eqpt: Dillon 650, Dillon dies. Expander die mics .3530

I've fired over a thousand of these loads through several G42's and they work well. Recoil and accuracy is about equal to various factory loads I've tried, not a sniper rifle but can stay on a silhouette out to 50 yds.

When I first got the .380 conversion from Dillon, I loaded up a few rds with different headstamps and hand-cycled them through the gun, then measured bullet setback which was minimal- maybe one or two thou for each trip up the feed ramp into the chamber.

But after loading a bunch more, for some reason I re-did the setback test. This time the results were not so good. Each time hand-cycled set the bullet back by an average of .005, so three loadings would set back about .015".

I'm not sure what to make of that. Obviously, the ammo works well in normal firing. Since this is range practice ammo, I don't usually re-chamber any one cartridge more than once. By coincidence, it might get re-chambered twice.
Bullet setback can raise pressures drastically in 9mm, but the tests I can recall seemed to start with .020" setback and go more (well, less) from there. And the .380 is a relatively low pressure round. So perhaps I don't really have a problem here. Just remembering to avoid re-chambering any individual round more than once might be enough to keep things safe.

OTOH, I'm not sure what to do differently even if I'm determined to eliminate the "problem".
Crimping is not the way to prevent setback, and anyway with plated pullets that have no channelure it would probably make things worse instead of better.
The expander plug could be polished down a couple of thou, but that might cause the plated bullets to get "swaged" down by the cartridge case and destroy accuracy. And it might not solve the problem, since the length of the bullet that is actually gripped by the case mouth is so short.

Comments and suggestions?
Thanks.

I tested 5 different headstamps (out of a dozen in my pile), and Winchester gave me the most setback. PMC and Blazer Brass gave the least.

But I didn't do enough repeats to know if those are valid comparisons.

I'm saving my Winchester .380 brass reloads for "lost brass" matches or practice in deep grass/snow, because my Win .380 (from new ammo I bought a couple of years ago) has shallow primer pockets. Out a 100 Win reloads, I'll get about 5 with high primers and a dozen more that are just barely flush and require careful inspection. Same primers (Win) are fine in any other brass.

Winchester 9mm brass has been fine for me, I've got many thousands once-fired but they are all from 10-20 years ago, haven't reloaded any of their new 9mm.

"Jim, I'm not getting past the expander measuring .353". I'm not familiar with the Dillon dies, but do they taper out larger to bell the mouth? "

Yes, the powder drop die gets bigger at the top to bell the case. It's fairly abrupt, so does not change the normal expander dimensions.

The sizing die is set to just be kissed by the shellplate, per Dillon instructions; and it sizes the cases down enough that sized cases or loaded rounds will easily drop into my L.E. Wilson "max cartridge" gauge.

I have two Dillon .380 sizing dies, one got some grit embedded and I ordered another to keep loading while the first one was back at Dillon being polished. Results are the same with either die.

A sized Federal case has an OD near the mouth of .368, a loaded round is .371-.372 in the same area.

A sized case does not slip onto the expander plug easily, I would have to force it (which is correct).

It looks like I may have found the "secret"-

Factory ammo deep-seats about as much as my reloads.

I took 2 rds of Winchester FMJ-FP and 2 rds of Blazer Brass FMJ, and hand cycled them three times through the same gun in the same way as my reloads. There is some statistical "scatter" in the results, but all 4 of the factory rds had deep-seated similar to what my handloads did.
I'll try to post some numbers tomorrow.

Here's some numbers on my testing:

After three trips hand-cycled through the G42, my reloads in five different headstamps had "shrunk" from .006" (R-P brass) to .022" (Win brass).

Not having a lot of different factory-fresh .380 laying around, I tested two rds of Win 95 gr FMJ-FP, two rds of Blazer Brass 95 gr FMJ-RN, and finally two Speer Gold Dot.
The two rds of Winchester, after the three hand-cycles, had shrunk .012" and .013".
The two rds of Blazer Brass shrunk .007" and .012".
The two rds of Gold Dot each shrunk only .001" total by the third cycle. Outstanding.

So, the factory range ammo resisted deep-seating a bit better than the reloads but not a huge difference, two cycles on the reloads averaged less setback than three cycles on the factory ammo.

I'm not aware of any industry standards on how much setback is acceptable on a low pressure round like the .380, but I've never heard of setback causing serious problems in the little round. 9mm is a whole 'nuther story.

My plan is to save any .380 round that has been into the chamber twice without being fired, and measure it later.
If the setback is less than .010" (which would probably be anything except Winchester brass reloads), it's good to be loaded again and fired.

EDIT:
Added two rds of Speer 90 gr Gold Dot JHP to test.

"Due to deeper bullet seating, I tested 2.6, 2.8 and 3.0 gr of W231/HP-38 which produced acceptable accuracy shown below.

3.4 gr at .950" COL? Hodgdon lists 3.1 gr as max charge for 100 gr Hornady FMJ at .980" - http://www.hodgdonreloading.com/data/pistol"

Loading manuals for .380 are all over the map.

Were you able to chronograph your loads (understanding that the Taurus would produce different velocities than my G42)?
My Hornady manual shows a max of 3.5 gr WW231 for a 100 gr bullet, and my Speer manual shows the starting load for a 95 gr bullet as 3.6 gr with a max of 4.0 gr.

Freedom Munitions reloads, with my same bullet and same COAL, chronograph over 100 fps faster than my reloads. Might be a different powder, but I don't see them safely getting an additional 100 fps with any powder, if the 3.4/231 is marginal.

1,000+ rds through four Glock 42's with no problems so far. Ejection pattern and distance are similar to normal factory ammo, recoil feels identical.

Thanks.
My club range is snowed in right now and may remain that way until March.
Ugh.

Gamestalker-
Your idea sounds good, I'll try that to see if anything changes.

EDIT:
I tried a few samples using Gamestalker's technique (post #12)- size, chamfer, and seat. No expander, no crimp.
That produced a noticeable reduction in the setback test.
The one Winchester case in my new test had total .012" setback after three cycles compared to .020" & .022" for the first batch. PMC now .01" and .003" vs .010" and .008" first batch. Fed and Remington cases had setback reduced by about 50% too.

That's a significant improvement, my expander plug is about to go on a diet. Even if accuracy suffers some, the convenience/safety of not having to worry about setback after 2 or 3 chamberings is worth it.

Thanks!