curious question on cases

[bmortell]

i was lookin at some of my 38 wadcutter loads beside some buffalo bore factory ammo and i noticed the factory ammo you couldnt see the case taper down at all below the point where the base of the bullet is in the case. so question is how do they achieve neck tension if case id is already bullet diameter

[bhn22]

Are you expecting taper at the inside of the case, or the outside?

[rockshooter]

Why would you expect the case ID to be bullet diameter? It should be a couple of thousands smaller.
Loren

[pal82]

Are you talking about the bulging of a case neck in some reloaded ammo vs. never see a bulge in factory ammo. Maybe someone here has ammo manufacturer knowledge and could shed light on how new ammo is made.

As for reloading, the first thing that comes to mind is the amount of interference fit between the case mouth ID and the boolit OD. I believe at least .003 - .004" interference fit is required for proper neck tension (probably not true for small calibers or rifles). The other factors may be the brass thickness and temper.

I measured my 45 cal neck expander dies.
Dillon 45acp = .446 I use this one for 45ACP, boolits sized to .452
RCBS 45acp = .449 I use this one for 45 Colt, boolits sized to .452
Lee 45Colt = .450 I don't use this one. Maybe someday I'll have an old SAA that shoots .454 slugs.


My guess is that factory ammo uses a minimum amount of interference fit to create neck tension or they resize after the bullet has been seated, like a lee factory crimp die. Heck, I'm probably just dreaming.........
Pal

[pal82]

And another thing. Most factory ammo is jacketed. Jacketed bullets probably require less interference fit due to higher coefficient of friction created between the jacket and the brass case, vs a slippery lead boolit to case.

Again, probably just dreaming. My dad would say that to me, "your just dreaming", instead of saying what he really meant, "your just making s**t up!".

I've got an old Machinery's Handbook around here somewhere. It has a section on press fits.......stop, now I am in over my head.

[bhn22]

If a bulge shows in the outside of a 38 Spl case, it's likely caused by the sizing die being a bit too tight, leaving the O.D. of the case (& I.D.) under spec. That's what causes the odd "the snake ate a pig" look seen on most reloads.

[NSB]

Might not even be the case dia being under spec. Lots of cast bullets are over sized on purpose and they do that when put in the case. Either way, it doesn't hurt a thing.

[pal82]

Could somebody measure some samples of factory ammo to confirm that it has no bulge. The last time a had factory center fire ammo was in the 90's.

[bmortell]

the particular factory loads i was lookin at had a crimp that bottlenecked down to fill the length of the crimp grove but what i was sayin is the bullet didnt appear to strech the case as it was seated. so perhaps with the super crimp they get the same resistance of bullet leaving case as does bullet stretching case couple thousandths and regular crimp. but i rarely buy factory except these ones cause there for ccw so maybe others are different?

[.22-10-45]

Factory .38 wadcutter brass is formed with less taper inside so as not to deform the soft hollow-based bullets...there was quite a discussion on this very topic oven on the CBA site.

[Airman Basic]

Elmer said it was a good thing. Indicated sufficient neck tension.

[TXGunNut]

Folks who buy factory ammo find bulges unsightly so factories size their bullets and cases accordingly. Many resizing dies are a bit undersize but that's better than oversized, IMHO.