COL tolerance for 9mm?

[walter62]

I've just started reloading 9mm on a Dillon 750 (w/ Lee carbide dies and separate crimp die).

The book want 1.160" in COL. Using mixed brass

Some questions:

How much (in 0.001's) variation on COL would you expect from a 750?
Should I compensate for the small amount of setback during the crimp? (I've seen this a few times)
Is the 1.160 the *minimum* so then variation should be accounted for by biasing the length a little.
A couple of them are 1.158, are those safe?
What do *YOU* accept as amount of reloading variation in COL?

 

[Eric H]

For 9mm you are thinking way too hard about it. You'll find more variation than that from projectile to projectile, or more variation in your powder charges than .002" of an inch in overall length.

Do these rounds pass the "plunk test" in your barrels and your powder charge is within the range specified in your manuals? If both yes, then you're going to be fine.

 

[Jim Poulette]

*fixed typo*

Here's the SAAMI spec. I keep mine at 1.115 +/- .003 - they pass the plunk test and seem to chamber fine in a P226 as well as revolvers.

The only issues I've had is resizing - some cases "blow out" easy, and won't pass plunk.

Good luck !

 

[mac1911]

For 9mm you are thinking way too hard about it. You'll find more variation than that from projectile to projectile, or more variation in your powder charges than .002" of an inch in overall length.

Do these rounds pass the "plunk test" in your barrels and your powder charge is within the range specified in your manuals? If both yes, then you're going to be fine.

Exactly
OP measure some bullets Base to tip and see what you have. Then if you have a bullet comparator measure some bullets base to ogive, whats your plus minus there?
where does tour seating die touch the bullet? Dead on the tip or at the ogive?
I would not sweat over .002” unless your flirting with absolute minimum seating depth and max loads!
I wonder if Dillon had a +/- spec on cartridges and powder drops on their machines?

 

[nstassel]

A book doesn't determine your oal, the chamber does. You do a push test to get the oal then subtract .1 inch.

 

[TrashcanDan]

I've just started reloading 9mm on a Dillon 750 (w/ Lee carbide dies and separate crimp die).

The book want 1.160" in COL. Using mixed brass

Some questions:

How much (in 0.001's) variation on COL would you expect from a 750?
Should I compensate for the small amount of setback during the crimp? (I've seen this a few times)
Is the 1.160 the *minimum* so then variation should be accounted for by biasing the length a little.
A couple of them are 1.158, are those safe?
What do *YOU* accept as amount of reloading variation in COL?

1- You'll get more variation from the dies and brass than the press. Most presses will stop at the same spot every time. Different headstamps, die-slop, different projectile manufacturers, you'll always get variance. Not a huge deal for handgun loads unless you're bullseye shooting. For games you're more concerned with power factor.
2- It won't hurt. Some chambers are less tolerant of variations than others, I.E.- A C.Z. chamber is less tolerant than say a 929 or M&P.
3- 1.160 could be the minimum, could be the maximum. Play around with it (start long) and see what it chambers at, then subtract from there.
Dud loads for the win!
4- What I accept and what someone else accepts are 2 totally different things. If I'm bulk loading say .45 acp, and I know 1.235 works with every 230 gr design across 4 handguns, then I'm running that. For 250-255 gr, It'll only work in the 625 even though it has the same o.a.l.
If measurement X for 9mm only works in 2 of 4, then I'm adjusting so it runs in all.

 

[eisenhow]

A book doesn't determine your oal, the chamber does. You do a push test to get the oal then subtract .1 inch.

The minimum of you chamber AND your mags: On my Glock 40's the Dawson mag extension limits the length.

 

[nstassel]

The minimum of you chamber AND your mags: On my Glock 40's the Dawson mag extension limits the length.

Good point

 

[eyeman56]

A book doesn't determine your oal, the chamber does. You do a push test to get the oal then subtract .1 inch.

Please explain. Thanks
Bruce
[email protected]

 

[nstassel]

Please explain. Thanks
Bruce
[email protected]

The push test is a way to find max oal for your exact chamber. You take a fired case and lightly press in your bullet just to hold it in place. Then you gently press it into the chamber as far as it goes and pull the case out. Measure the length. That's the total length. You should subtract .1 inch. That's the best oal for your gun. Then you make up a few empty dummy rounds to see if they cycle into the gun from the mag.

 

[gerrycaruso]

I load to the longest that will fit in the magazine. If you do this, make sure they'll fit in the magazines of ALL the guns in that caliber.

 

[240Geezer]

A book doesn't determine your oal, the chamber does. You do a push test to get the oal then subtract .1 inch.

.010 but these things do matter.

 

[Rick O'Shea]

My COL is what my chamber tolerates,..

 

[cookiecutter]

A book doesn't determine your oal, the chamber does. You do a push test to get the oal then subtract .1 inch.

With all due respect, the push test (or some other functional test) will determine your MAX coal ... but the book definitely tells you what coal you should not go below. You may know this, but the OP is asking so I will explain:

• Seating too long will cause the projectile to engage the rifling as it is chambered. The gun may or may not go into battery, but it is a bad condition even if it does go into battery because being pushed all the way to the rifling will cause the pressure in the chamber to peak faster and higher.
• Seating too short will reduce the effective volume of the case and this will cause the pressure to peak faster and higher than otherwise.

I don't tend to run my pistol loads to max length, so I know that +0.005" won't cause a failure to feed or go into battery. I also don't run nuclear loads, so I also know that -0.005" won't cause my pressure to spike to unsafe levels. I run Lee presses, but I don't have any issues at all staying within those tolerances. 0.002" is a non-issue, though.

CC

 

[nstassel]

.010 but these things do matter.

I actually thought it was .1. This explains alot.