Case Length

[runningfree]

With all things being equal will case lengh change over all pressure?

I have been loading 9mm with a case length of .750 if I start loading a case of say .744 will the pressure increase?

Thanks.

[Westwindmike]

I don't think so. If you load to the same OAL, there will still be the exact same space for the powder.

[R_Bert]

.744" is the "trim-to" length for 9x19mm

You should be just fine.

[DWARREN123]

I would not worry unless you are making nuke loads. Anything else should be okay.

[Jonnin]

How hot the loads are has no effect. Pressure is changed by modification of the distance between the back of the bullet and the primer. If that distance is decreased (seated deeper), pressure rises (and in a straight walled case, it rises FAST). That is all there is to it. When making ammo, your seat depth should be the same (virtually, with a margin of error of course) for every round -- and there WILL be minor variation in case length unless you trimmed the brass first and discarded the ones too short to trim.

[dlm37015]

i lose 9mm cases before they strech and have to be trimed

[Dolomite_supafly]

Actually case length can have an effect on pressures in pistol or rifle calibers. Not so much in revolvers.

If the case grows enough to cause the barrel throat to pinch closed the case mouth upon chambering or if the crimp is so heavy it allows the case mouth to pass into the throat area.

In either instance the case mouth can't open and release the bullet. And if the bullet can't be released then pressures can spike.

Dolomite

[runningfree]

Thanks guys

[LngRngShtr]

only bottlenecked casings stretch,.. straight walled cases shrink mouths get thinner and then they split..

try it sometime,.. measure a case say a .357 MAG then load and shoot it say 5 times then measure it...

the only pistol cases I ever trim other than making a wildcat like the .401 Herters (from either .41 MAG or .30-30 Win cases) are for my S&W M-52 ammo in .38SPL because the crimp will be affected by case length and that is the one pistol I have found that will show any variance in handloads .

My IPSC guns in .38 Super and 10mm and my .45ACP Series 70 Gold Cup could care less but the 52 is heads above most any pistol in the fussy about ammo category to get it to shoot to its potential ( they were gauranteed by S&W to hold less than 3" at 50 yds. with quality ammo in a machine rest )

My S&W 586 and my K-38 also don't respond to case trimming so as long as they aren't above MAX length to where they would jam into the chamber end and cause problems with pressure just load them and shoot them

you can experiment with trimming say 20 and loading them to compare with 20 un trimmed keeping them separate and shooting a few groups to see if you can have any measurable differences or if it was just a mental excersise.

the joys of reloading is that you can experiment with wheter something works or doesn't work in your individual pistol to see if it is worth the effort to trim,weigh each case,trickle the powder,weigh the bullets,weigh the primers ..or just load and shoot them

Most of my pistols I just load and shoot except for that one fussy one, using loads I worked up for each of them and keeping lots of notes to duplicate when I run low

the 10mm and Super and Gold Cup will all hold 4" or so at 25 yds. from sandbags, the revolvers a tad tighter.. better than I can shoot these days sucks getting old...

John

[ArmyBrat61]

A question along those lines.....as far as .308 brass goes, what is the max OAL that will chamber safely? My book gives an AOL of 2.015......would 2.040 be too long? I can't find my Dillon case guide so I thought I'd ask here.

[ArmyBrat61]

I did not realize this thread was over a year old..... :stunned:

[deadeye111]

A question along those lines.....as far as .308 brass goes, what is the max OAL that will chamber safely? My book gives an AOL of 2.015......would 2.040 be too long? I can't find my Dillon case guide so I thought I'd ask here.

The Lyman 49th Edition Manual as you stated above shows 2.015 and the trim to length of 2.005.  If it were my brass and I planned to reload the cases I would trim them.  Without a chamber cast I couldn't answer whether the cases are too long to cause excess pressure.