9mm Question?

[jst1tym]

Though I'm not totally new to reloading, I reloaded in the 80's for my .357 and .44 mags. I'm now strictly a 9mm reloader..or at least when I get finally set up. I've bought several manuals and have read in a couple that " this cartridge headspaces from the case mouth"....Just what exactly does this mean?? Thanks for any help!

[BayouSlide]

Though I'm not totally new to reloading, I reloaded in the 80's for my .357 and .44 mags. I'm now strictly a 9mm reloader..or at least when I get finally set up. I've bought several manuals and have read in a couple that " this cartridge headspaces from the case mouth"....Just what exactly does this mean?? Thanks for any help!

As I understand it, the mouth of the cartridge rim butts up to the end of the chamber, thereby controlling how deep the round goes into the chamber...sort of an awkward way to describe it. Somebody brighter than me, please feel free to chime in

Curtis

EDITED: because I hate typos!

Edited August 5, 2008 by BayouSlide

[GentlemanJim]

That is correct

The mouth of the case stops on the lip at the end of the chamber...this is why TOO much crimp can create problems

Rimmed cases (like revo) stop on the rim.

Rifle cases stop on the shoulder.

Jim

[wide45]

The mouth of the case stops on the lip at the end of the chamber...this is why TOO much crimp can create problems

Yes, and no. Too much crimp can cause problems, but headspace is rarely an issue.

Modern dies are designed so that they can not size the case so much that it will not headspace. Try it on an empty case. Run your crimp die down a few extra turns, and abuse one case with it. See how far it drops into your barrel.

I have seen some frightening crimps done with old dies, where excessive headspace could occur.

Edited August 6, 2008 by wide45

[JimInFL]

Very interesting thread. So since the chamber lip stops the brass, then the length of the brass actually determines how deep the cartridge actually seats (the whole cartridge oal) in the chamber. Now when the breech face comes up to it, what effect does the brass being a bit too long or short have ?

JimInFL

[GentlemanJim]

If the brass is too short it results in excessive headspace...in a pistol its not an extinction level event..the brass will batter the breachface

and can cause other issues

If its too long..1 it may not go all the way into battery..in some firearms it may be possible to fire with out lockup...(bad thing)

2 it may be pressed into the chamber and create excessive pressures...(bad thing)

In rifles ...Too much or too little...CAN be an extinction level event

Jim

[G-ManBart]

Rifle cases stop on the shoulder.

Jim

Yeah, but manly rifle cases stop on the belt!

My Win Model 70 Supergrade is so old is just says ".300 Magnum" on the barrel, 'cause there was only one in 1941 (300 H&H Mag)

[Hi-Power Jack]

When I switched from reloading for my .41 Revolver

to 9mm (semi-automatic), there were some very

surprising differences for me:

1. the cases have to be much cleaner so they feed

2. the OAL is more important

3. the powder charge is more important (too little

and the gun won't cycle).

4. the crimping is important

5. sizing the cartridge case is important (it wasn't

in my revolver)

6. no lubrication on the cases

7. squib loads are more important if you're going to

shoot rapidly

Almost anything I put together fired in my .41, or it

wouldn't go into the cylinder - to make the semiauto

work without malfunctioning, much more attention to

detail is necessary.

Good luck.

[buddy_fuentes]

Reloading for the nine, or anything else, is not rocket science. It is a very simple procedure to follow. Get a good loading manual (or go to the web site of the powder manufacturers) and it will have the specifications for different loads. Decide which bullet you want to use and then pick a powder and charge from the manual. Follow the procedure and check everything twice. Shoot what you loaded and see if it meets your needs.

As you load and gain confidence you will try other powder/bullet combinations and may or may not find something you like better. I really like WW 231 for the nine, but there are many good powders out there.

Winchester has a free pamphlet that has a list of their powders and loads for each caliber they are compatible with. It also has the measurements for each case at the start of loading data for each cartridge. If you don't have a micrometer, you need to invest in one. A digital is easier and faster to read, but the dial works fine, too.

The nine is fun to shoot, enjoy.

Buddy

[JimInFL]

[jstitym - I swear I'm not hi-jacking ! But this is interesting]

Making sure I understand. The bullet seating depth of course affects pressure, velocity etc, and ability to feed from a mag properly. But the OAL (a product of the seating) really has nothing to do with how the cartridge sits in the chamber, once it's in there - correct ? So if I could load one of my 9mm rounds to 1.500 (which of course is silly) it would drop into the barrel just the same as a 1.160.

The reason I ask is that someone at a match once told me something about the the bullet actually touching the rifling and that oal can affect how deep the cartridge sits in the chamber. What's being explained here makes much more sense to me.

[bruce282]

I do believe it's a combination of the 2. If I tried to load a 1.5 OAL into one of my Glocks by just dropping it in it would hit the rifling and stop. I might be able to press on the end and force it in further but that's where the problems start. When the round goes off there is very very small slice of time where the bullet is passing through the part of the barrel that has no rifling. Then it hits the rifling and starts to spin. If the bullet is already touching the rifling, it takes more pressure to get it both moving and spinning at the same time. Could lead to a KB if it gets bad enough.

Hope this helps and if I'm totally off base, someone will enlighten both of us.

Bruce

[JKSNIPER]

As I understand it there should be at least a small "jump" of the projectile out of the case and to the rifling.

Its measured in thousandths of inches.

If its already touching the rifling the pressure can spike because the powder has not burned to the point of being able to overcome the resistance of the projectile vs the rifling and the projectile acts like a plug.

Not an experienced reloader here so I will not say what you should do to overcome this problem.

I would ful length resize and trim the case and load it to specs and not fool around with touching the rifling until I had a lot more experience/knowledge.

JK

[jst1tym]

Thanks for all the replies. A little background, I shoot mainly all 9mm consisting mostly all Sig's except my SA EMP. I purchased a dillion RL550B w/most goodies. I've purchased MG 115gr CMJ, new Winchester brass all 1k's worth. Two different powders, Blue Dot #5 and VV320#4 and winchester small pistol primers. Once I get setup I plan on loading to OAL for the 9mm and start working up loads for both different powders. I have the Lymans 48th handbook, a Speer manual, and a Sierra 50th Anniversary relaoding manual, and a VihtaVouri manual and that one came with another manual as a bonus.....So, I'm basically equipped and ready to go.

The information presented has helped me understand the idea and it's importaqnce to the relaoding of the 9mm. I have read that it needs just a small taper crimp, just enough to take the bell out from resizing aqnd opening up the casemouth for bullet seating. I think all this will make more sense when I actually start to reload. I'm glad to see that I wasn't the only one that had interest in this question....and please any further comments, keep em coming