Overall case length, how much to short?

I know that the overall case length can't exceed x.xxx or else the bullet will contact the rifling to soon, but how much tolerance is there?

My book shows a 40 cal to have a 1.135 case length, but how short can the overall case length be, or what is to short of a round?

Thanks.

Only if your weapon was over/under drilled by the company and............
went by the quality checking stations, with out being seen.
Maybe 1 in a million.

Minimum and maximum ammo and case lengths are set for every shooters safety.
Why load incorrect ammo that does not meet spec's.

Safety is the #1 rule in loading ammo.

Retired LTC said:

I know that the overall case length can't exceed x.xxx or else the bullet will contact the rifling to soon, but how much tolerance is there?

A cartridge's COL determines when the bullet will hit your rifle's lands. But it's important to note that case length has NOTHING to do with COL. Further, for any given OAL the case length has NOTHING to do with the volume available under the bullet.

For any given COL. the length of the case only affects how much of the bullet is in contact with the case, ie the bearing surface.

My book shows a 40 cal to have a 1.135 case length, but how short can the overall case length be, or what is to short of a round?

The max SAAMI COL (Cartridge Overall Length) for 40mm is 1.135. Since all factory-produced chambers must allow at least that length, how much longer it can be depends on your particular chamber. And it will vary from pistol to pistol.

How much shorter it can safely be depends on a number of factors, including the bullet which may demand a shorter COL. EG, hollow points will have shorter OALs than "ball" and will be shorter than the SAAMI max COL.

Too short a round may not feed well in your pistol or in others. The shorter a pistol round, the higher the peak pressure for any given powder charge. So while it's not possible to tell you what is safe and/or will function in your pistol, generally 1.125 (ie a 10 thousandths variation) will remain safe. And likely shorter can be workable with a reasonable powder charge.

Thanks.

Click to expand...

Hope the above helps some. If you tell us exactly what bullet and how short your COL is, those who actually shoot 40 cal might be able to help more. Online load data from your powder manufacturer may give you some insight, as might your reloading manual.

Retired LTC said:

I know that the overall case length can't exceed x.xxx or else the bullet will contact the rifling to soon, but how much tolerance is there?

My book shows a 40 cal to have a 1.135 case length, but how short can the overall case length be, or what is to short of a round?

Thanks.

Click to expand...

Too short of a round is when it physically won't feed in your gun, or you have driven the bullet is too far for the powder charge and have gone overpressure.
The term is expansion ratio, and the further in your push the bullet, the less room for the powder, and the higher the pressure.

So after reading the responses, I believe that I used incorrect terms.

If the overall round length is 1.135, what is the shortest the round can/should be?

Thanks.

The picture on the left shows a short case.
If short enough, the firing pin may not strike the primer.

Too short or too long of a case can cause extreme chamber pressures.

Stay safe.

Retired LTC said:

So after reading the responses, I believe that I used incorrect terms.

If the overall round length is 1.135, what is the shortest the round can/should be?

Thanks.

Click to expand...

Yes, you mixed terms. But the answer remains the same. We can't tell you with the info you provided.

- For pistol, the round must be of a length that allows consistent feeding in YOUR pistol.

- The bullet needs to be seated so the end of the case falls somewhere on the widest diameter of the bullet.

- And the powder charge may need to be adjusted smaller than for a 1.135 long cartridge using the same bullet to compensate for the decrease in volume inside the case.

If it meets those parameters, it will be safe to shoot. And it may shoot consistently.

That's all we can tell you.

Retired LTC said:

If the overall round length is 1.135, what is the shortest the round can/should be?

Click to expand...

I prefer to think of it the opposite way; how long can I load my cartridge and:

- still pass the plunk test in my pistol's barrel

- not exceed the SAAMI max. COAL" for that cartridge

- feed properly in/from my magazine

.

Perform a plunk test to determine the maximum Cartridge Overall Length (COAL) for the bullet you're handloading. Don't exceed the max SAAMI length, verify operation & record that length for the next time you load those same components.

Seating the bullet deeper, especially in a short round like the 40S&W, is only inviting troubles you don't want to explore.

There is no magic number either way.

.

Why are you concerned about how short a cartridge can be made? Usually, you get better results loading longer. For instance, IIRC, some NRA Hi-Power riflemen have two different loads for their AR match guns. One is for the long line, shot under relaxed time constraints, and it's loaded so long that cartridges must be chambered one at a time, by hand. They won't fit in the magazines.

Their short-line loads are loaded shorter. But only enough to get them into the mags.

Now, let's see if we can dissect this a little.

The "Min OAL" listed with load data is simply the minimum OAL they tested. In other words, they didn't care about how the cartridge would function or what it looked like--they simply jammed it in that deep. And it's bullet-specific. So if they tested the exact bullet design you're using--say, the H&G #68--then great. If they simply list "200-grain LSWC", then you just don't know. And if they say "200-grain lead", then the listed Min OAL is completely without context.

So what you do is apply common sense. If you're loading some random 200-grain LSWC, don't go seating the bullet past the shoulder. If you're concerned about maximizing performance and function, your best option is to spend some time with a handful of dummy rounds, plunk-testing in your barrel and hand-cycling with the recoil spring removed. Again, there's nothing really to be gained by making the cartridge any shorter than it has to be. With revolvers, the crimp groove is your friend. On autos, you don't want the bullet contacting the rifling prematurely, and you don't want excessive headspace (seat a roundnose too deep, then crimp it, and all of a sudden the cartridge doesn't headspace off the case mouth like God intended).

Now, the pretty drawings at the start of every cartridge's section in the manual are just that--pretty drawings made with whatever the nominal bullet design is. They may or may not be relevant to what you're doing, but likely not.

All this is complicated by the fact that, as standardized as things are these days, guns have chambers of different lengths. This is because nothing is ever easy, and happens for all sorts of reasons. In this instance, you may choose to load ammunition specific to a particular gun, or load for the shortest- and tightest-chamber'd gun, or a combination of both.

Load data

People who create load data are engineers. The data listed is only accurate depending upon the person using the load data exactly as tested. If you expect to obtain the same results as the data you must copy the conditions they list. powder type and brand, primers used, brass trim length, COLA, bullet type etc. There are some safety built into the data, and loaders learn what they can to safely change the "load." but Just starting, follow the data for safety.

SAAMI publishes min/max..

Look up SAAMI on the web.

The shortest for a .40 S&W case is .640"

I have to disagree a bit with the statement.
"the listed oal is compleatly without context" although in some ways it is true. what is important is bullet depth in the case. and volume of the case.
most bullet makers use some standard for bullet length so if you use min. oal you should be safe on allowed volume. but not always.
where this could be a problem is. Using data for one type of bullet or weight bullet for another type or weight.

I have to disagree a bit with the statement.
"the listed oal is compleatly without context" although in some ways it is true. what is important is bullet depth in the case. and volume of the case.
most bullet makers use some standard for bullet length so if you use min. oal you should be safe on allowed volume. but not always.
where this could be a problem is. Using data for one type of bullet or weight bullet for another type or weight.

I have to apologize......

.....it was late and I guess I wasn't reading closely.

SAAMI sez about overall length of the .40 S&W

max = 1.135"

min = 1.085"

And I believe that this is a legitimate question. As long as the reloader knows that deeper bullet seating increases pressure rapidly in short, high pressure semi auto cases and works out a good length that works in his guns and realizing to err on the side of a slightly longer cartridge than a shorter one.

I had some daggum 'small ball' ammo in 9mm that had to be seated to 1.060" or shorter when the minimum OAL was 1" even. It really threw me for a while.

The round is too short when it no longer functions(i.e. feeds) in the pistol or the bullet is seated too deep and causes an over pressure issue.

There are too many variables to give an accurate answer. The answer depends on the bullet, the gun and the powder charge. Change any one of those items and the answer changes. You have given none of those variables and have only mentioned 40 Cal which could apply to any number of different cartridges. Everyone is assuming you mean 40 Smith & Wesson.

As mentioned the length of the actual brass case is not related to the COL (cartridge overal length)

You can have a short piece of brass and still seat the bullet to the correct COL.

What happens is if a piece of brass is too short instead of head spacing on the case mouth in the chamber, it will space on the extractor. Which over time will screw up the gun

Just like some dim wits shoot 40 SW ammo out of a 10mm handgun. Yes, it will work but not advised.

Retired LTC said:

So after reading the responses, I believe that I used incorrect terms.

If the overall round length is 1.135, what is the shortest the round can/should be?

Thanks.

Click to expand...

depends on the specific bullet
I'm seeing a 175 grain lead bullet with an OAL of 1.100"

here's a sketch I made awhile back that shows what others are talking about - with the length of the brass not related to OAL

hope it helps

Lyman has the 40 S&W case trim length at .845"

It also has the shortest OAL at 1.085"
and the longest OAL at 1.135"

OAL depends on the length of the bullet and the spec's for it in
the manuals and from the maker.

Good loading.