I need to know if a case is only .002-.004 short, is the pressures going to spike enough to hurt someone shooting the fiream? Let us say the cartridge trim length is .750 but the cartridge only measures .746 to .748 and all the oals are the same, what could happen? Could the pressure increase that much? Seems to me it wouldn't matter THAT much but tell me if I am that wrong!!
SHORT CARTRIDGE CASE QUESTION?????
- Thread starter 74man
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CQB45ACP
Member
This should prove to be a very interesting thread. Might be even more so as a poll
I’ll vote—it depends
I’ll vote—it depends
Yamifrk
Member
That is a loaded question…seriously it depends on what you’re loading for. For instance a small case (380-9mm) will have more pressure in a “short” case compared to say a 308 or larger rifle case. It’s also the case length, unless you are talking about coal. Most case measurements have a min and a max
If the cases is just a little short & you reload to over all length it should lower the case pressures because you will have less neck tension. But if you load the projectiles to the same line on the bullet it will increase the pressures.
Yes, the caliber is always helpful when answering questions.
Blue68f100
Member
It's the volume that's below the bullet that impacts the pressure. Case length variations do not impact this, OAL (like @Walkalong ) said is what you need to be concern with.
conan32120
Member
I would also think that on ignition the case would expand to fill the chamber thereby instantly removing any concerns of pressure spike. Think dent in case, never seems to make any difference that I've noticed
Charlie98
Member
...all of that... ^^^
OP, you mentioned a trim-to length of .75"... a COL difference of .002-.004 with a midrange load of Unique, for example, wouldn't worry me too much, but a COL difference with a max load of something like TiteGroup would. It really depends on the actual cartridge you are loading, and the actual components used with what data.
Measure some once fired factory brass. I'd be willing to bet the brass lengths are all over the place.
@Walkalong has it right in post #5
@Walkalong has it right in post #5
Archie
Member
One of the measurements affecting chamber pressure is chamber volume. The danger of seating a bullet too deep crowds the chamber size and increases pressure. Typically that will cause heavier recoil, a louder than usual report, perhaps counter that constipation problem and not do any serious harm. Except might retire that particular cartridge.
That is the danger of a slightly shortened case.
However, if the bullet is seated to the normal length, then the internal volume is 'normal' as well. And the pressure should be 'normal'.
As I read it, the couple thousandths shorter should not matter, IF, the bullet is seated to the same over all length.
Bullet seating depth affects internal volume.
That is the danger of a slightly shortened case.
However, if the bullet is seated to the normal length, then the internal volume is 'normal' as well. And the pressure should be 'normal'.
As I read it, the couple thousandths shorter should not matter, IF, the bullet is seated to the same over all length.
Bullet seating depth affects internal volume.
Jim Watson
Member
At .750” the OP’s secret cartridge is probably 9mm P.
If the case is short but the OAL remains the same then the working volume is no less.
There are a lot of press, seating die, bullet shape combinations that will not keep OAL within 4 thou, working volume is not significantly different.
I think another case of making stuff up to worry about.
If the case is short but the OAL remains the same then the working volume is no less.
There are a lot of press, seating die, bullet shape combinations that will not keep OAL within 4 thou, working volume is not significantly different.
I think another case of making stuff up to worry about.
N555
Member
The danger is being too long, usually. A rifle case jams into the rifling when the shot is fired or if it's way too long the gun won't go into battery.
If a pistol case is too long the gun won't go into battery, too short and the extractor is only holding the case when the firing pin hit it, you get light primer hits.
For revolvers they head space off the rim, too short is no problem. 38spl are like 0.14'' shorter than 357mag, running the shorter ones in a 357 won't cause any problems.
If a pistol case is too long the gun won't go into battery, too short and the extractor is only holding the case when the firing pin hit it, you get light primer hits.
For revolvers they head space off the rim, too short is no problem. 38spl are like 0.14'' shorter than 357mag, running the shorter ones in a 357 won't cause any problems.
bigpower491
Member
A human hair measures .005..........
Don't worry about it
Don't worry about it
CQB45ACP
Member
Told ya it'd be an interesting thread. I still vote, "it depends."
tightgroup tiger
Member
He said case length, that means nothing if the COAL is still the same length as the recipe dictates. A shorter case doesn't change the volume unless the seating depth has been changed. Internal volume is still the same.
^^^ Tiger Beat me ("tuit") ^^^
Then the usable internal case volume is the same -- regardless of case length.
No pressure effect at all
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johnjohn
Member
I think you're "overthinking"this. Drop back to the start load.
small town life
Member
Case length vs coal will change pressures. How it changes (higher or lower with neck tension being equal) is by seating depth changing along with case length.
If coal (example) 1.125" and case length .980 from known safe (even @ max psi) will decrease in psi due to less neck tension if the case only is shortened and same charge weight of same powder (example, unique).
Now if, the case is longer creating more case to bullet contact the psi will increase without the bullet being seated the extra 2-4thou to meet case length extension.
If, it's in a straight wall cartridge it can/could be an issue with it not sealing more at the mouth
Bottle neck will not be affected by this due to sealing at the shoulder where headspace is.
Now if, you're asking about bottleneck cases pressure will decrease if the neck is shortened and increase if the neck longer/increased the psi will be more.
Think of it like changing seating depths.
If coal (example) 1.125" and case length .980 from known safe (even @ max psi) will decrease in psi due to less neck tension if the case only is shortened and same charge weight of same powder (example, unique).
Now if, the case is longer creating more case to bullet contact the psi will increase without the bullet being seated the extra 2-4thou to meet case length extension.
If, it's in a straight wall cartridge it can/could be an issue with it not sealing more at the mouth
Bottle neck will not be affected by this due to sealing at the shoulder where headspace is.
Now if, you're asking about bottleneck cases pressure will decrease if the neck is shortened and increase if the neck longer/increased the psi will be more.
Think of it like changing seating depths.
CQB45ACP
Member
Knew this would be an interesting thread.
So, OP, if you haven't already read this article about 45acp case longevity give it a try.
A key finding of the author's test is the relentless shortening of the cases from a beginning .894" to under the SAAMI minimum of .888"
Yet despite this shortening (far more than difference in your example), no change in the load was made nor was it mentioned nor even hinted at. One might conclude there were no noticeable changes to pressure. And the loads were on the high end.
Since May 2023, I have been running a similar test and posting updates here. My results are essentially the same as in this article. I've never made a load adjustment nor noticed a reason to do so and like the author, my case lengths have shortened far more than the spread you mentioned. All loads are the same and COL a consistent and precise 1.260".
www.floridareloading.com
So, OP, if you haven't already read this article about 45acp case longevity give it a try.
A key finding of the author's test is the relentless shortening of the cases from a beginning .894" to under the SAAMI minimum of .888"
Yet despite this shortening (far more than difference in your example), no change in the load was made nor was it mentioned nor even hinted at. One might conclude there were no noticeable changes to pressure. And the loads were on the high end.
Since May 2023, I have been running a similar test and posting updates here. My results are essentially the same as in this article. I've never made a load adjustment nor noticed a reason to do so and like the author, my case lengths have shortened far more than the spread you mentioned. All loads are the same and COL a consistent and precise 1.260".
How many times can I reload 45 ACP brass? – Florida Reloading
IWAC
Member
Generally, a human hair measures about .003/inch. That much variation or more is not unusual in factory-new brass, so, in my never-humble opinion, it will make very little to no difference.
lordpaxman
Member
- Joined
- Jun 4, 2011
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Don’t panic!!! Have you got your towel?
Chances are your COL tolerances won’t even be within that range.
Unless you’re roll crimping some really heavy caliber like .460, most trim jobs output +- a few thou. Now, if you’re +- in the hundredths range, then you need to correct the process.
Chances are your COL tolerances won’t even be within that range.
Unless you’re roll crimping some really heavy caliber like .460, most trim jobs output +- a few thou. Now, if you’re +- in the hundredths range, then you need to correct the process.
