Why are my reloads "growing"

[woody2]

Yesterday I loaded 100 rounds of 9mm. Bullets were seated to an OAL of 1.142” plus or minus 0.002”. The gun has a very tight chamber so anything longer than 1.146” won’t allow the slide to lock. I seat the bullet and crimp in 2 separate operations, using a taper crimp die for the last stage, and spot check length with a caliper during seating. After seating bullets in all 100 rounds I noticed that some of the rounds appeared long, and the lube groove was visible above the case on a few of them. That prompted me to measure about 40 additional rounds and many of them ranged in length up to 1.157”.
At that point I reseated all 100 rounds, measuring each round individually immediately after reseating, to make sure lengths were in the acceptable range. I then spot checked length and found that many had “grown” to lengths up to 1.154”. Decided to let them sit overnight to see what would happen.
Meanwhile I checked the lengths on rounds I had loaded in January, March, April, and June of this year. All were 1.142” plus or minus 0.002”.
This afternoon I remeasured all 100 rounds. Forty three are within tolerance. Fifty seven have grown to lengths up to 1.154”. I reseated them and already some have started to grow. I put one in the calipers and watched it increase in length from 1.142” to 1.146” in less than a minute.
I’m loading a Lee 125 gr RN #356-125-RN over 3.6 grs of Bullseye. Cases are Remington, some once fired, some fired several times.
I’ve been reloading for over 55 years and this is the first time anything like this has happened. If anyone has any ideas about what’s happening I’d really like your input.

[reddog81]

1.14 inches to over 2 inches? That can't be right.

[BK7saum]

Sounds like you don't have enough neck tension and the air pressure inside the case is pushing the boolits back out. Also sounds like they are coming out after seating and before they are crimped.

What are you using for an expander and how close in size is it to your boolits?

[MBTcustom]

The only time I have had this happen was with a compressed load. Better check that load data.

[mongoose33]

1.14 inches to over 2 inches? That can't be right.

The boolit is floating over the casemouth.

The only time I have had this happen was with a compressed load. Better check that load data.

The 3.6 grains of bullseye isn't sound out of bounds; makes me wonder if it's 13.6 grains.

[Yodogsandman]

What have you changed since loading those in January, March, April, and June?

[country gent]

Are bullets tight in cases when seated and after being crimped? Hold one bullet down and tap your hand against bench top 2 -3 times and see if it grows then. I have seen compressed loads grow especially Black powder that is compressed alot more than smokeless normally is. 1.140 to 2.005 is .060 growth thats alot for air or even powder compression push back. Are your dies still thight in the press. nothing shifting or moving around?

[Bzcraig]

The only time I have had this happen was with a compressed load. Better check that load data.

This is was also my first thought and strongly suggest pulling some of those and checking your powder weight.

[country gent]

Yep it is .865 I didnt get it right in my head. At that much bullets should be falling out of cases. Cases arnt getting sized down enough or over expanded for some reason.

[bedbugbilly]

You say they are growing "after" crimping . . . but is there any chance . . . if your neck tension isn't enough . . . as in not sizing down or over expanding . . . . that your seating and or your crimp die is crudded up with lube, etc.? You don't mention how your boolits are lubed but if you neck tension isn't enough and your dies are dirty, it could "pull" on the boolit. But it seems like you would notice it when you pull the finished cartridge from the holder and put it in your tray. It might be worth cleaning your dies anyway?

I haven't had it happen with 9mm but I have had it happen with some other calibers when I was setting up my dies initially or ran across a case with very thin wall thickness at the mouth. Check your head stamps on the ones that are "growing" . . are they all the same or different?

[w5pv]

I would check the load and then check your calipers I think there may be a problem with your measuring that giving you a false reading.

[Tatume]

...1.140 to 2.005 is .060 growth thats a lot...

It appears that you were thinking correctly, but in your mind you were seeing what the OP meant, not what the OP said. You are probably correct to assume that he MEANT 1.140" to 1.200" of growth.

As others have pointed out, it is impossible for a 9mmP cartridge to attain 2.0" length.

Take care, Tom

[Tatume]

P.s., +1 on checking the charge. If in fact there is 13.6 grains of Bullseye in there, serious injury will almost certainly be the outcome if one is fired.

[MBTcustom]

P.s., +1 on checking the charge. If in fact there is 13.6 grains of Bullseye in there, serious injury will almost certainly be the outcome if one is fired.

My thought exactly. If the OP has a tendency to move decimal points and devisions, it's a good thing the only bad that has happened is the powder pushing the bullets out.
Dyslexia and reloading do not mix!
It is obvious that the OP was mixing up the numbers somehow, because there is no way a 9mm is the same length as a 308.
Misstating the length of the cartridges is a benign error, but considering the subject of this thread, I have a very real concern that his missing "1" found it's way from the OAL of the cartridge to the powder charge, and that is a very dangerous mistake.
Remember fellers, Kabooms are caused by a very small error that results in catastrophic consequences.

[dondiego]

Smokeless powder is made of nitrates, a natural fertilizer that makes things grow!

[country gent]

The OP has offered none of the asked for imformation thats been asked for as of yet. There is a definate issue here as loaded ammo doesnt normally "grow" like this. Has he change lots of brass ? Thinner brass produces less neck tension when sized in the normal dies. Changed expanders to a diffrent dia? Changed bullets a load set up for .357 dia then going to .355 loses tension also. Another issue that isnt seen alot anymore is a carbide sizing ring thats been pulled out then the case no longer gets sized down for the expander to open up. This is very obvious when looking at the die from the bottom. Also is there any chance of an alloy that has more shrinkage was used and bullets are undersized now? There is alot of questions raised here.

[Echo]

OP, what say?

[.22-10-45]

Woody..you didn't happen to add Viagara to your lube did you?

[303Guy]

Didn't anyone notice? We have a new member here! Welcome aboard, reddog8.

Remember fellers, Kabooms are caused by a very small error that results in catastrophic consequences.

Yup.

The thing about errors is that they can and do happen and they can be hard to detect.

[woody2]

Thanks for all the responses. Many of you caught the obviously incorrect "2.004" and 2.007" dimensions. Don't know why I used those numbers instead of the correct "1.154" etc. I've edited the original post to reflect the correct lengths.

Many asked what has changed since my loadings earlier in the year. The answer is nothing has changed. I prepare components for pistol cartridges in 1000 piece lots so all of the cases that I've loaded this year were sized at the same time last January using an RCBS carbide die set. They were all primed, using CCI small pistol primers, at the same time, and bagged in 100 case lots. All of the bullets were cast, sized, and lubricated at the same time last December using the same alloy and the same lube. All of the powder came from the same one pound container purchased last summer.

When loading I charge 100 cases at a time using two 50 round loading blocks. After charging the first 50 cases I visually inspect every case to assure that each case has been charged and the powder level in each case is about the same. After inspecting the first 50 cases I set them aside and charge the next 50 cases, repeating the visual inspection of each case. I set the second 50 cases aside and then perform a second visual inspection of the first 50 cases before seating bullets. After seating the first 50 cases I perform a second visual inspection of the second 50 cases before seating bullets in them.

A double charge is pretty unlikely using that method.

Nothing has changed except that some of the bullets are backing out of the cases, and that has never happened to me before. Just wondering if anyone else has had a similar experience and looking for possible causes.