Air trapped under bullet

[Flashman929]

This must surely have come up before, but I can't find anything that relates?

I'm loading the Lee 405 gr HB into Starline cases. Bullets mic at .460 just like they should. Case is .457 neck. 1/5 of the bullets pop back up .01 or so, and I can compress them with finger pressure against the air pressure under them. What's the solution? That neck tension should be fine, and short of getting a custom die I can't make it tighter...

No such issue with Lyman 535 Postells, also measuring . 460

[country gent]

Neck tension is actually set by the expander belling die the sizing die sizes small and the expander opens it up to the right size. You need to break the air seal the lube is producing to stop this. (On grease cookies a pin is pushed thru the center to allow air to escape) your wad may be producing an air seal also. .003 tension is a lot for these rounds and you may be compressing the hollow base some also. If you feel you need the extra size 1/2" -3/4" down from the case mouth in a 45 acp die These are set up to size for .451 dia bullets. Not deep enough to full length size though. I leave cases as fired and load them using the sizing die to set tension on the bullet after its seated in place by hand. Usually setting the sizing die .400-.450 high is about right to do this. My boolits can be pulled by hand and will turn in the cases with a little finger tension. But they don't fall out or change a lot. Another thing to try is to hold ram at top of stroke for a 10 count to allow air to bleed off.

[Lumpy grits]

Hold the case in the seat die for a 10 count.
Have you used an inside mic to measure the case mouth after expanding?
How far down the case does that .457 stay in place?
LG

[Flashman929]

Thank you sirs...

I realized I omitted a lot of detail there... I'm using a Lee loader, all my presses and dies are 1000 miles away in my old province.
Neck ID was determined by measuring case neck brass thickness and subtracting from the OD of a sized case. Using a .457 expander die in a hand press to bell and expand.
It's not the wad, checked that and they're hard against the powder after compression.
I figured it was the lube causing it, but I don't have the problem with 535 Postells pan lubed the exact same way the exact same lube?
Seating depth for the 405s is .600, the offenders sit about .100 high, so there's .500 in the case.
3 thou tension sure seems like a lot to me too? That's .001 more than I use for jacketed rounds.

I give the loaded rounds a quick spin & wipe with a drill using a case trimmer lock stud, to remove excess lube. This seems to help - spinning the bullet in the case then reseating helps, but there's still a few stubborn ones. I'll try seating normally then clamping the Lee loader in a vice for 10 seconds to see if that helps.

[Lumpy grits]

Wipe the bullets 'butt' on a towel before seating into the case.
LG

[Flashman929]

I do, make sure there's no lube on the base before seating, those hollow bases sure like to pick it up.

[Flashman929]

Here's a pulled one out of the melt box...
https://preview.ibb.co/nco5e5/20170821_211319.jpg (https://ibb.co/gxJhRk)

[Lumpy grits]

You really need to measure the case mouth ID. At this point you're guess'n what the ID of the case mouth is. Case wall thickness can and does vary a good bit.
LG

[Wayne Smith]

I think it's a boolit weight issue. I have the same problem intermittently with the Gould boolit, but not with the 457125. Remember the Army crimped the 405 boolit to allow more complete powder combustion while not doing this with the 457125. Mass matters.

[Lumpy grits]

Neck tension is the answer. The 405 was a fighting load and the crimp was insurance.
There is no need to crimp a target round.
This is all SWAG'n till the case mouth is measured.
You're run'n a bit of a fat bullet(most folks run .458-.459 dia)and it won't stay seated. The only place it can be is the expander die, which is either marked wrong or adjusted wrong.
Are you FL sizing or Neck only?
LG

[Flashman929]

Lumpy, I'm not tracking there brother... Measuring case wall thickness, x2, then subtracting from OD, and using pin gauges are the only two accurate methods of measurement. Using a case mouth dial gauge is nice to visualize the variations in thickness, but mine is 1000 miles away, and you can get the same accuracy by just taking a bunch of measurements at different points on different cases. I've been shooting precision rifle competition for 15 years, and never met a shooter that does it any other way other than OD minus thickness x2... even the Canadian national champions who have also won at Bisley do it like that. How are you suggesting to measure it?

For sure neck thickness varies; but unless you neck turn you have to average it out, because it's going to be present in your loaded rounds. I will say the Starline brass is remarkably consistent, as good as the best Lapua brass I've ever measured. They come out at .010 with a half thou variation. That's so good I wouldn't bother neck turning except for the most demanding application.

It's a Lee loader, so it'd be FL sized.

I get .477 on a sized and expanded case, .480 on a loaded round. That's 3 thou neck tension. You don't even need to know ID if you measure it that way. Subtract. 020 and you get .457 and .460, respectively, which is exactly what the plug and the bullets measure, so it all adds up. I would have expected a bit of springback to .456 or so after expansion, but the cases are freshly annealed so that probably explains it.

[Lumpy grits]

Brass is elastic and just because a expander is marked a give'n dia, doesn't mean this will be the dia you have after real usage. Same is true in sizing, due to case mouth 'springback'.
Forget the expanders nose-What does it measure before it steps up to the 'V'?
Have seen some with crazy taper because of poor QC.
S/L is very good brass-hard as a rock and needs annealing before loading.
How often do you check bullet dia?
Try this-Confirm the dia of 25 bullets before loading them. See if you have any issues with these.
LG

[Flashman929]

Sorry, when I say "on the nose" I mean precisely. As in not .4565 or .4575, etc. It's. 457 all the way to the bell section.

I definitely found the Starline hard out of the bag, they annealed beautifully before the first loading.

Probably measured about 50% of what I cast after cooling. A bit OCD like that.

Measuring the loaded rounds tells me I have 3 thou tension, I'm sure you're right and it just needs time to bleed out. Just bizarre I don't have the same issue with the 535s, cast in the same session from the same alloy, dropping at the same size and lubed exactly the same way.

[Lumpy grits]

Try it with bullets you have measured and confirmed dia.
You'll be surprised.
Are you using any OPW in this load?
How are you compressing the powder?
LG

[Silver Jack Hammer]

Why not just let the boolits sit for a day in the loading block, the weight of the boolit should force any air out.

Your placing your boolits in the case with your fingers right? No using a seater die.

[Flashman929]

I'll try that Lumpy. Yes, a .030 card. Tried a thin paper card over the primer and between bullet and over powder card, but there was no noticeable difference so I discontinued. Compression is on a hand press, verified with the depth measurement on my caliper. Set my seating depth so the bullet is hard against the card, then verify the OAL which it pretty easy, if it's not right on the end of the last driving band I have a problem.

SJ, that's a good idea too. I'll give it a go. The only issue is I usually get back from the range one day, reload that night and repeat the next morning.

What do you mean about the die? I place it on the case mouth then slide the chamber die down over it all and seat. Same way I've always loaded my precision rifle rounds. Just like at 1:10 here, but using a Lee loader which is really just a chamber die, essentially. https://youtu.be/YbkYet59g7E

[Tom Myers]

What works for me is to place all the loaded rounds in a loading block, put a flat board on the bullets and gently press them all down on the wads and then place a weight on the board.
The next morning, about 99% of them will stay down.

[Silver Jack Hammer]

.45-70 lead boolits should be seated by placing the boolit in the brass all the way to the wad with finger pressure. J-words can be seated with a seating die and a press. A J-word can be placed on top a case mouth and jammed down into the brass. The lead .45-70 boolit needs to be placed down into brass that is expanded enough that the boolit bottoms out on the wad with finger pressure. Otherwise the lead boolit will be distorted by forcing the brass to expand.

[Chill Wills]

.45-70 lead boolits should be seated by placing the boolit in the brass all the way to the wad with finger pressure. The lead .45-70 boolit needs to be placed down into brass that is expanded enough that the boolit bottoms out on the wad with finger pressure. Otherwise the lead boolit will be distorted by forcing the brass to expand.

What you are describing is slip fit bullet seating.

Some of us like to use a little neck tension or pressure to grip the bullet. I seat them with match bullet seaters. My bullets are tight enough that not only do they not fall out, but you can not even pull them out of the case by hand.

Flashman - you seam pretty savvy to me. So, I do not doubt you in the least. Having said that; in my experience, having 0.003" neck tension on the bullet would not only hold place against any trapped, but would resist all efforts to move the bullet in the case unless by press or tools. I like to use about 0.001+ neck tension. Once seated, air and all, it is seated.

All, think about it. The bullet is the piston. The case is the cylinder. If you have a larger bullet than case neck, you will be compressing air every time. It does not take much neck tension to keep the bullet from popping up.

Flashman - I think there must be something else going on that you, and or, we don't know. I am not doubting you or your measurements, you sound like you have a GOOD handle on the facts, it is just that something else is present here you have not accounted for. I say this because, bullets with three thousands neck tension don't slip back out.
All the best - let me know what you come up with.

-Michael Rix

[Silver Jack Hammer]

CW, My boolits don't fall out or can they be pulled out by hand. I'd probably use a different method if I were loading for week long elk hunt here in the land of constant precipitation.

Boolits that are seated by force will have distortion, I use 20:1. 20:1 is a very common alloy. What are you using to seat your boolits?

[greenjoytj]

1/5 of the bullets pop back up .01 or so, and I can compress them with finger pressure against the air pressure under them. What's the solution?

If you can bob the bullet with finger pressure you don't have the .003" of case grip. Ether the case grip has squeezed the bullet smaller or the case has lost all it elasticity and was stretch out during bullet seating. Or your measurements are off, fine measurements are tricky to get accurately.
How to get the trapped air out? Pin through the wad colum trick. Bronze brush case interior to make air escape scratches in the brass. Powder and or wad colum adequately pre-compressed.

[aspangler]

I may be way off but the thought just hit me, the postal flat base boolit has less air under it that the hollow base Lee. Could it be that there is more air and therefore more air pressure under the hollow base?

[Lumpy grits]

Try a 'wad' of white coffee filter paper over the primer at the bottom of the case.
The targets of both my .45-70 and .45-90 Shiloh's say this helps.
LG

[Chill Wills]

CW, My boolits don't fall out or can they be pulled out by hand. I'd probably use a different method if I were loading for week long elk hunt here in the land of constant precipitation.

Boolits that are seated by force will have distortion, I use 20:1. 20:1 is a very common alloy. What are you using to seat your boolits?

I have read your post a few times but I am not sure I get it. If you finger seat the bullets you can most likely finger un-seat your bullets too. Or did I miss your point?

I hope not to distort the bullets to any degree when seating them in a case that provides a little neck tension.
Yes, 20-1 is common -Okay?
Is your point that bullets seated into neck tension cases can not be accurate as slip-fit bullets?

I think we are slipping off topic of trapped air. Maybe a different thread, seating bullets for making accurate ammo could be the way to go.

[Flashman929]

What you are describing is slip fit bullet seating.

Some of us like to use a little neck tension or pressure to grip the bullet. I seat them with match bullet seaters. My bullets are tight enough that not only do they not fall out, but you can not even pull them out of the case by hand.

Flashman - you seam pretty savvy to me. So, I do not doubt you in the least. Having said that; in my experience, having 0.003" neck tension on the bullet would not only hold place against any trapped, but would resist all efforts to move the bullet in the case unless by press or tools. I like to use about 0.001+ neck tension. Once seated, air and all, it is seated.

All, think about it. The bullet is the piston. The case is the cylinder. If you have a larger bullet than case neck, you will be compressing air every time. It does not take much neck tension to keep the bullet from popping up.

Flashman - I think there must be something else going on that you, and or, we don't know. I am not doubting you or your measurements, you sound like you have a GOOD handle on the facts, it is just that something else is present here you have not accounted for. I say this because, bullets with three thousands neck tension don't slip back out.
All the best - let me know what you come up with.

-Michael Rix

Michael, that was my thought exactly. .003 is .001 more than I use for j words and they take a fair whack to unseat with an inertia puller. It just doesn't make any sense they could have any play at that tension.

Your last paragraph got me thinking again, perhaps it is the annealing... these cases are brand new, and were annealed just before loading. There's no doubt the tension is 3 thou, I've measured a large sample of the loaded rounds with my mic and with calipers, getting the same measurement every time. And the measurements add up, .460 bullet into a .457 neck is. 003.

But... measuring neck tension is only indirect. You're only measuring the expansion, not the actual gripping force. E.G. hard brass will grip the bullet much harder than annealed brass, even if both measure the same loaded diameter. That's the whole purpose of annealing, to ensure consistent neck tension. Now you have me thinking that the fresh annealing just isn't providing the tension required on some of the rounds.

I've got a .458 and .459 expansion die on the way, I'll play around with them too and see what happens, though I don't expect that would solve it. But you never know, I've been surprised before.

[Flashman929]

If you can bob the bullet with finger pressure you don't have the .003" of case grip. Ether the case grip has squeezed the bullet smaller or the case has lost all it elasticity and was stretch out during bullet seating. Or your measurements are off, fine measurements are tricky to get accurately.
How to get the trapped air out? Pin through the wad colum trick. Bronze brush case interior to make air escape scratches in the brass. Powder and or wad colum adequately pre-compressed.

And I'm thinking that's it. The annealing is right on the edge of being too soft, and some cases it's just a bit too annealed.

Will poking the wad allow the air to escape from under the bullet into the powder charge? I always thought it was to allow air under the wad to escape up. But now that you've said it, that sure makes sense, it'll allow the air under the bullet to vent into the much larger space where the charge is. D'oh.

Cases are brushed clean after a good soak before loading again, quick spin with a brush chucked in a drill.

I can rule out wad and powder compression, it's like a brick in there and the wad is hard against it. Depths are all consistent too.

But poking that wad to allow the air to vent down into the rest of the case sure would increase the volume it has to go into... thanks.

[Flashman929]

Try a 'wad' of white coffee filter paper over the primer at the bottom of the case.
The targets of both my .45-70 and .45-90 Shiloh's say this helps.
LG

I tried it with thin airmail paper, and got no difference. Maybe it was too thin. I'll give the filter media a try!

[Flashman929]

.45-70 lead boolits should be seated by placing the boolit in the brass all the way to the wad with finger pressure. J-words can be seated with a seating die and a press. A J-word can be placed on top a case mouth and jammed down into the brass. The lead .45-70 boolit needs to be placed down into brass that is expanded enough that the boolit bottoms out on the wad with finger pressure. Otherwise the lead boolit will be distorted by forcing the brass to expand.

Slip fitting won't work for me unfortunately, these rounds are mainly for hunting use.

I'm not getting any bullet distortion either, pulled bullets measure exactly the same as fresh ones, .460, and there's not so much as a mark on the nose from the seating punch, nor any lead shaving.

[Silver Jack Hammer]

OK Flashman929, slip fitting would probably fix your air trapping problem but it's no solution when your trying to build hunting boolits.

CW, I apply a slight crimp after slip fitting, just enough to fold the bell in enough to get the case to chamber. This way the base of the boolit is absolutely prestine for match shooting.

[ryan28]

Could be the cases are annealed a bit too soft. Maybe try shooting a few rounds, then see how they are.

[Shasta]

When I have this trapped air problem, I simply give the air a means to escape by using an X-Acto knife to put a light scratch along the length of the bullet before seating it. Works for me.

[Lumpy grits]

When I have this trapped air problem, I simply give the air a means to escape by using an X-Acto knife to put a light scratch along the length of the bullet before seating it. Works for me.

That cut mark may let gas pass by when you fire it. Good way to lead up a bbl.
LG

[Bent Ramrod]

When mine used to do that, I just cut a piece of Styrofoam sheet or thick cardboard, put it over the cartridges and closed the lid of the Case-Gard 50- or 60-round plastic box (or put a weight on the telescoping covers of the 20-rounders) to press everything down properly. In a few hours, the air had escaped and the boolits were in the shells to the proper depth. Then there was a slight vacuum seal from the lubricant to keep the boolits in the shells, if carefully handled.