How much shrinkage is okay?

[Glennp]

I've ventured onto loading .38 HBWC rounds. Since ive heard how easy it is, and how bad it is, to shrink down the round by not expanding or crimpping properly I went ahead and pulled a loaded round to measure the bullet. Sure enough, it measures out to about .355/.3555"

Im sure some shrinkage is par for the course, BUT, how much is normal, and how much is too much? This is using a .358 expander plug, should I bump it up to my .361 plug? Or should I leave it be as its totally fine? The outside dimensions if they matter are: right at the mouth, the loaded and crimped round is approx .375 diameter. midway down where the bullet is, its about .3765/.377 (varies).

Im using a lee FCD but it isnt sizing it down at all so that isnt a problem


Thanks!

 

[ditrina]

How much shrinkage is okay? ??

It all depends on how cold the water is

 

[Dan Cash]

Shoot it and fergedaboudit. That hollow base will bump up as big as the barrel will let it.

 

[Dale53]

GlennP;
Pulling a bullet from a crimped case will nearly always show you an undersize bullet. However, fire that same loaded round and the gas opens up the crimp without "downsizing" the bullet.

If we are talking of soft, HBWC's exclusively, the expanding stem should not be more than one or two thousandths smaller than the bullet. This will insure that the bullets will not be undersized when seating in a sized case.

FWIW
Dale53

 

[nicky4968]

I always understood the HBWC to be slightly undersize from the get-go. That's why they won't obdurate when loaded backwards in the case, unless you put a gascheck on what used to be the nose and is now the base.
But I don't have any right at hand. What do they mic at in the box, before you load them?

 

[Glennp]

out of the box they are dead on .358

 

[Dragon88]

You have another factor to be concerned about which is your cylinder throats. The bullet is likely reduced a thousandth or two by seating and crimping. Then if your throats are undersized it will be swaged down even more. Finally when it hits the forcing cone and bore it will begin to obturate. However, HBWCs are often loaded light in target loads, so pressure may not be high enough to fully seal the base against the bore and rifling. The result is reduced accuracy and leading.

Your best option here is not to worry about it. Shoot a bunch of them and see how accuracy is. If it's fine, don't bother with it. If you really want to get serious about this though, you will need to slug your bore and all your cylinder throats, measure all your components, then make everything match. That's going to be costly depending on how much they are off.

 

[Glennp]

You have another factor to be concerned about which is your cylinder throats. The bullet is likely reduced a thousandth or two by seating and crimping. Then if your throats are undersized it will be swaged down even more. Finally when it hits the forcing cone and bore it will begin to obturate. However, HBWCs are often loaded light in target loads, so pressure may not be high enough to fully seal the base against the bore and rifling. The result is reduced accuracy and leading.

Your best option here is not to worry about it. Shoot a bunch of them and see how accuracy is. If it's fine, don't bother with it. If you really want to get serious about this though, you will need to slug your bore and all your cylinder throats, measure all your components, then make everything match. That's going to be costly depending on how much they are off.

So basically, unless i want to get really really into it, I have nothing to worry about, and without gun work, a bit of shrinking is a moot point.

 

[WR Moore]

If I understand your question, you're worried about crushing the bullet during seating/crimping. The case has to be a wee bit undersized with respect to the bullet in order to properly grip the bullet-it's why you resize the case. (BTW-I've never seen an undersized HBWC)

Over expanding the case neck can shorten the life of the brass by overworking it.

Finally, don't worry overmuch about accuracy. I once pulled some leftover factory .222 to get the bullets. The crimp was so tight the bullets were wasp waisted and they'd still been shooting one ragged hole.