A strange thing happend...suggestions?

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BanditsRoost

BanditsRoost

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I need another opinion....yea I know, everybody has one.
Reloading 380 auto for the first time. I'm not new to reloading at all, just first time reloading 380 auto and something strange is happening.
Reloading once fired brass with 88 grain Remington Hollow Points and 90 grain Hornady XTP.
The Remington measures .3555" to .356"
The XTP measures .355"
By the book C.O.L is .955" and .965" respectively. ( I've tried down to .950" and up to .970")

Now, I load the rounds, check it on a Lyman case gauge and then do my normal "plunk" test.
All goes well. Fifteen minutes later it no longer passes plunk test but passes Lyman gauge test!! huh?
Load another 5 rounds from different brass, same thing. Works great out of the press, 15 minutes later fails plunk test but passes Lyman gauge test.
Case mouth of loaded round measures .371" to a max of .373". Varies with different brass head stamps and XTP vs Remington.
The Gun is my daughters Sig P238 Legion. Over the years I've never experienced this. I don't do exotic loading. Always stay within min and max listed in various reloading manuals.
Is this something unique to 380? I can't find anything on the web saying so.
Is the small brass springing back out after reloading and resting? ( my favorite thought so far)
How about some of you really smart guys giving me some imput.
 
Only thing I can think of is the brass rebounding? Do you store your brass in a different location than the rest of your components? Particularly, is the location of your brass significantly cooler than where you load your ammo? That is just a shot in the dark (no pun intended).
 
Rebound or springback would be instant. To confirm your theory of growth, measure fresh out of the press, then again after a few minutes. I would do this both with loaded and simply with resized cases.
 
Is it a compressed load? If it plunks right out of the press and won't 15 min later maybe they are decompressing. It's a weird thing for sure...
 
WestKentucky said:
Rebound or springback would be instant. To confirm your theory of growth, measure fresh out of the press, then again after a few minutes. I would do this both with loaded and simply with resized cases.
Click to expand...

Agreed. Hence the query about temp differences. Otherwise, I have no clue.
 
I have glued up boards with wood dowels, these dowels had a spiral groove in them to give the excess glue somewhere to go. I have not experienced decompression of a seated bullet if the load was not compressed.
 
docbrown said:
Only thing I can think of is the brass rebounding? Do you store your brass in a different location than the rest of your components? Particularly, is the location of your brass significantly cooler than where you load your ammo? That is just a shot in the dark (no pun intended).
Click to expand...
It is cooler where I reload. Haven't turned on the heat yet and the room is about 58 to 62 degrees F. But all of this happened in the reloading room.
 
adcoch1 said:
Is it a compressed load? If it plunks right out of the press and won't 15 min later maybe they are decompressing. It's a weird thing for sure...
Click to expand...
Not a compressed load, plenty of free space. My intentions were to try and find a load using Universal powder.
 
WestKentucky said:
Rebound or springback would be instant. To confirm your theory of growth, measure fresh out of the press, then again after a few minutes. I would do this both with loaded and simply with resized cases.
Click to expand...
Good point, I only measured the case mouth "after" it failed the plunk test which was 10 or 15 minutes after reloading. I'll give that a shot ( no pun there either) when I get back in town Sunday.
 
BanditsRoost said:
380 ... 88 grain Remington Hollow Points and 90 grain Hornady XTP ... [OAL] .950" and up to .970". Remington measures .3555" to .356" The XTP measures .355"

Fifteen minutes later it no longer passes plunk test but passes Lyman gauge test!! huh? Load another 5 rounds from different brass, same thing. Works great out of the press, 15 minutes later fails plunk test but passes Lyman gauge test.

Case mouth of loaded round measures .371" to a max of .373"
Click to expand...
Welcome to THR.

You may be over crimping and causing the brass to bulge. I would suggest the following:
  • Resize 10-20 offending headstamp brass and ensure they pass the barrel and case gage. If any fail, adjust the resizing die to ensure brass are being full-length resized (Keep in mind, resizing die reshapes down to case base and don't touch the case rim, which the case gage checks)
  • Add .022" to the bullet diameter for taper crimp at case mouth. So for .355" bullet, use .377" taper crimp and for .3555"-.356" bullet, use .378" taper crimp
  • Check the finished rounds in the barrel and cage gage. If you see bulge on one side of the case neck, you may be tilting the bullet during seating. If that's the case, increase the flare and/or be careful to ensure straight bullet seating and even bulge around the case neck.
If the finished rounds pass the barrel but not the case gage, mark the case to see where it rubs. If you don't see any rub mark on the case, inspect the case rim for damage as plunk test only check down to case base, not the case rim.
 
Last edited:
LiveLife said:
Welcome to THR.

You may be over crimping and causing the brass to bulge. I would suggest the following:
  • Resize 10-20 offending headstamp brass and ensure they pass the barrel and case gage. If any fail, adjust the resizing die to ensure brass are being full-length resized (Keep in mind, resizing die reshapes down to case base and don't touch the case rim, which the case gage checks)
  • Add .022" to the bullet diameter for taper crimp at case mouth. So for .355" bullet, use .377" taper crimp and for .3555"-.356" bullet, use .378" taper crimp
  • Check the finished rounds in the barrel and cage gage. If you see bulge on one side of the case neck, you may be tilting the bullet during seating. If that's the case, increase the flare and/or be careful to ensure straight bullet seating and even bulge around the case neck.
If the finished rounds pass the barrel but not the case gage, mark the case to see where it rubs. If you don't see any rub mark on the case, inspect the case rim for damage as plunk test only check down to case base, not the case rim.
Click to expand...

Thanks LL,
I did consider over crimping. I used the same as I normally do on my 9mm. (1/4 turn after touching case mouth) "However" I didn't check it after it failed. Maybe the 380 die (Lee Factory Crimp) is set differently. Thanks!
I did resize some empties of the same headstamp and all passed the gauge and barrel. So that does kinda point to over crimp. I'll check it.
That would aggravate me though since it passed the Lyman gauge...meaning I can't trust that gauge on the 380's...rats!
You may have won the cigar...
 
BTW, I did load them in the magazine and cycle them through the little P238. All cycled fine going fully into battery with not failure to feed and no failure to eject. Just another bit of info.
 
BanditsRoost said:
BTW, I did load them in the magazine and cycle them through the little P238. All cycled fine going fully into battery with not failure to feed and no failure to eject. Just another bit of info.
Click to expand...
If they cycle through your pistol, I'm not sure you have any problems at all. Go to your range and if you don't have any problems with they cycle through while shooting then you're golden and I wouldn't worry about what your gages are telling you.
 
BanditsRoost said:
fails plunk test but passes Lyman gauge test.
Click to expand...
OP, as I mentioned in my post, this could happen if the bullet tilts during seating and bulges one side of case neck.

Another factor that I did not mention in my post is varying case wall thickness and out-of-round bullet diameter. Case wall thickness can vary from 12/3/6/9 O'Clock positions for the same case and if bullet is out-of-round (Yes, trucking companies/US postal service do rough handle the heavy boxes of bullets and can drop them which can damage the roundness of bullets), these two factors along with brass spring back can result in oblong case neck and taper crimp die only contacts the top of the case neck/mouth area.
 
Sounds similar to a situation I've encountered. I like to do my handgun caliber loading in batches. I will resize and deprime a large quantity of brass(maybe 500-1000 of the same caliber). I then will load 100-200 cases at a time. Sometimes I will just prep brass when there's nuttin' else to do. When I flare cases, I flare a little as possible to reduce working it and to extend the life of the brass. While bullets will start easily in the flared brass the immediately after I flare it, sometimes, if I don't get to all the cases that have been flared right away, the next day, bullets that stated easily before, will not start without re-flaring.
 
Are you mixed headstamped cases? Different brands can vary by as much as .004" in 380 Auto, from what I have seen.
 
Ok, I'm gonna call this one closed. It gets stranger but I believe @LiveLife may have been closest to revealing an issue. Got home today and loaded one each of the same rounds with no crimp and everything worked well. (even 15m later). The .355" bullets show .373" at mouth and the .376" bullets show .374" at mouth after "very" light crimp. So I was thinking maybe over crimped on the first rounds that failed after 10 minutes. Went back to check measurement and they were a tiny bit tighter at .371" and .372"....BUT now they all pass the plunk test and the gauge test again!!
My only thought is, in addition to a slight over crimp a piece of trash or powder flake got in the chamber somewhere. The lesson learned though is with the little 380's a "very" light to no crimp is the way to go. So, Thanks for all the help and suggestions. It really did bring to light the over crimp issue. Now it's off to he range to do some chrono and workups to see if this Universal powder will do any good on the baby bullets. Thanks again and Happy New Year to the lot of ya.
 
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