"Shrinking" bullets

S

simonrichter

New member
I recently discovered that some rounds out of my 9mm cache were seemingly "shrunk", say the bullet has sunk a little deeper into the cartridge. Is there any potential concern firing these rounds in respect of weapon function / pressure?
 
simonrichter I recently discovered that some rounds out of my 9mm cache were seemingly "shrunk", say the bullet has sunk a little deeper into the cartridge. Is there any potential concern firing these rounds in respect of weapon function / pressure?
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Definitely. Bullet setback increases pressure.
 
Bullet setback will increase pressure, sometimes dangerously. Are these commercially manufactured rounds, purchased reloads, or hand loads of your own? Have they been chambered? Multiple times? Do you have any sort of caliper to measure them and compare the length to other rounds of the same manufacturer or batch?
 
How about some more details : exactly how much have they shrunk...moved deeper into the case. What bullets were used, were the bullets crimped into place , what kind of crimp , heavy or light .
When were they loaded, on what equipment were they loaded. how were they stored,
In what conditions were they stored. Did the loaded rounds have anything pressing down on the bullets.
I've been a handgun ammo reloader for 50 years, done a lot of it and I have never had my bullets recede deeper into the case. There must be an explanation.

I have witnessed just the opposite , a few bullets easing forward..... it was traced to primers seated into tight pockets, .357 diameter sized cast bullets when seated into the case it created some pressure, not quite enough crimp and over time the bullets moved forward just enough to stop them from fully chambering . Not all of the mixed cases were the same length, the shorter ones got less crimp ! Once all the facts were looked at then it became apparent what happened.

Give us some more to go on and lets see if we can figure it out....the details matter.
Gary
 
Anytime you can easily see that a bullet has been pushed deeper into the case than it was originally loaded, that is a potential danger sign.
 
TailGator said:
Bullet setback will increase pressure, sometimes dangerously.
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Especially in small case capacity rounds like 9mm.


simonrichter said:
I recently discovered that some rounds out of my 9mm cache were seemingly "shrunk", say the bullet has sunk a little deeper into the cartridge.
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"a little" is a relative term. Any amount of setback will increase pressure as it reduces case capacity. How much depends on how "little" the setback is and how large the powder charge is.
 
There are dangers from excessive pressure, but the main danger is "Second round stoppage".

When law enforcement began moving to the auto pistol there was a spate of problems with the guns jamming during the feed cycle on the second round.
The officer would fire the first shot, then the gun would jam on the second, often during a gun fight.

This was traced to how the police inspected their pistols.
They'd remove the magazine, then eject the chambered round.
After inspection they'd inset the magazine and chamber the top round, remove the magazine and load the first round back in the mag.

This meant that the same two cartridges were being chambered over and over, pushing the bullet back in the case.
At some point the cartridge was so short it would fail to feed the round.

This was solved by changing the way of inspecting pistols so the same rounds weren't chambered more then a couple of times , and by the police ammo makers manufacturing law enforcement ammo so that it could withstand 3 to 4 chamberings before the bullet started being pushed back into the case.

One technique I've always used is to segregate one cartridge out of a box of new ammo.
I use that cartridge to visually compare to cartridges in use to insure the bullets aren't moving back.
After chambering rounds more then a couple of times I use them for practice.
 
It's cheap Sellier & Bellot bulk ammo, but fresh from the box, never chambered. The setback is clearly visible, the bullet is set approx 1/3 deeper than normal
 
It's cheap Sellier & Bellot bulk ammo, but fresh from the box, never chambered. The setback is clearly visible, the bullet is set approx 1/3 deeper than normal
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S&B is generally quality ammo.

Bullet setback can be measured by measuring the over all length of a number of rounds and seeing the average. Then deciding that something is out of spec by a particular amount. "1/3" less doesn't actually tell us much as we don't know the average OAL to begin with.

One bullet is set back. That happens at times. Sometimes a box is dropped, a round is dropped etc. Toss that one round out as it may be over pressure.

A few thousands usually does not make much of a difference .005-.010 but much beyond that becomes questionable and can be discarded. This is especially the case if it's +P or +P+ ammo.

If more than one or two rounds is involved than return the box of ammo to where you got it and ask for a replacement.

tipoc
 
S&B Factory Ammo ! Have no idea why this happened. I looked the last box of S&B 9 mm Luger and all look normal....at a total loss.
Gary
 
SR, others differ, but I prefer to not use ammo which has the bullet set back in the case. Both due to the potential for increased pressure, and the second round stoppage Defariswheel mentioned. FWIW, for years I was issued Remington .45 ACP standard pressure, and 9mm +P, that one had to be careful with as regards bullet set back. If I chambered this ammo more than once, the bullet would often demonstrate measurable set back. I guess I shouldn't be surprised. It is my understanding that manufacturers only intend their pistol ammo to be chambered once.

BTW, Just out of curiosity, I once ordered some Remington 9mm +P+ from a police supply to test. I was interested in chronographing it to see how much velocity might differ from our issued +P ammo. The ammo I received had bullets obviously seated to different overall lengths, no precise measuring with a dial caliper required to see this. In the interest of science, I decided to chronograph it anyway. Velocities were erratic as expected. It's been a while, but I did mic it, IIRC, bullet seating depths varied as much as .050" or so. I suspect the ammo I received had been declined, or returned, by a LE organization as being out of spec., due to the bullet seating issue I mentioned. I was not tempted to purchase more of that particular ammo....
 
I realize that "setback" is an easy term to use for the condition, but I must point out that if the round hasn't been previously chambered, then its not actually "setback".

Too deeply seated, too little neck tension, but not exactly setback from feeding.

It is my understanding that manufacturers only intend their pistol ammo to be chambered once.
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I would agree that seems to be the case, today. But it was not always true, for all ammo makers. Ammo can be made so setback doesn't happen. It used to be commonly done. Today (and for some time now) ammo makers don't take the extra steps needed due to the added cost for what is now considered no useful benefit.
 
I have witnessed just the opposite , a few bullets easing forward..... it was traced to primers seated into tight pockets, .357 diameter sized cast bullets when seated into the case it created some pressure, not quite enough crimp and over time the bullets moved forward just enough to stop them from fully chambering . Not all of the mixed cases were the same length, the shorter ones got less crimp ! Once all the facts were looked at then it became apparent what happened.
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I do not understand that one at all. (But it is early and maybe I am missing something).
I have seen bullets moved forward when seated over a compressed charge and crimped lightly. Nothing to do, however, with primer seating.
 
I had a problem like that with hollow point bullets in my M1911. It was a bear of a problem to figure out but I tracked the problem to the shooting Star mags that came with my Springfield Armory 1911. When loaded with 8 rounds, the top round in a full mag would tip down a little and slam straight into feed ramp.

The top 2 rounds were beat seriously deeper into the case. The top 2 would get swapped back and forth from unloading, reloading and then topping up the mag. My solution was to go to a more typical 7 round mag and only use the SS mags with round nose bullets.

I carried this gun day in and day out for years before I decided it was getting too heavy for that purpose..

Tony
 
Geezerbiker said:
I had a problem like that with hollow point bullets in my M1911. It was a bear of a problem to figure out but I tracked the problem to the shooting Star mags that came with my Springfield Armory 1911. When loaded with 8 rounds, the top round in a full mag would tip down a little and slam straight into feed ramp.

The top 2 rounds were beat seriously deeper into the case. The top 2 would get swapped back and forth from unloading, reloading and then topping up the mag. My solution was to go to a more typical 7 round mag and only use the SS mags with round nose bullets.

I carried this gun day in and day out for years before I decided it was getting too heavy for that purpose..

Tony
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Nosedive is normal in single column magazines. More rounds in the magazine means more nosedive. Readers might find this article of interest: https://americanhandgunner.com/nosedive-and-feed-angle-in-the-1911-45-acp/
 
Most handgun ammunition, especialy auto pistol calibers, has a cannelure in the case at the base of the seated bullet. Seen in revolvers cartridges at times ttoo. The purpose of this is to restrict bullet set back in handling, shipping, or carrying in cartridge belts.

Note the two WW I vintage cartridges have this cannelure, plus the stab points to hold the bullet under recoil when fired in M1917 revolvers. This was "bullet pull."





Here's two M-1909 .45s with the cannelure:



Bob Wright
 
Most handgun ammunition, especialy auto pistol calibers, has a cannelure in the case at the base of the seated bullet.
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Are you seeing that in ammo and/or cases that you buy nowadays? I'm not.
 
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