don't start head bump resizing till there is a chambering problem???

[flexible]

Hi everyone, flexible here. Been loading pistol for decades but new to rifle reloading.
This is a weird thought but in our pursuit of accuracy would it make sense to not start resizing FL till difficulties start when chambering?
This cropped up when I heard some Bench Rest shooters saying it takes 3 or 4 firings to 'really' fireform brass to the chamber?
So, I have some virgin brass. Is it sensible, after firing, to FL resize to the exact same length it came out of the chamber and NOT bumping the shoulder back by 1 to 3 thousandths until the brass became difficult to chamber. At that point (difficult chambering) would it be time to FL resize and shoulder bump back?????
Again, this is an oddball thought and would love to be proven wrong.
thanks
flexible

 

[CoalCrackerAl]

I always FL size.

 

[flexible]

I always FL size.

I'm not saying don't resize I'm saying would there be a benefit to FL resizing but NOT bumping the shoulder back?
You would be resizing the base of the case and the neck for tension but the shoulder bump would stay where it was after firing?
You would be getting closer each time you reloaded to a 100% match of the chamber. Then, only after the brass became too tight you would resize and bump the shoulder back.
thanks
flexible

 

[bihj]

If you're not a 'bench rester' or regularly shoot beyond 500 yards, full length resize every time. The juice isn't worth the squeeze.

If you don't bump the shoulder, you're 'neck sizing', which is what the 'bench rester' is doing.

 

[Pottimus]

I bump the shoulder on my British .303 hoping to get 3 or 4 firings from a case. It is a 2-3 MOA gun with a 3-4 MOA trigger jerker behind it. All other calibers get the full Monty.

 

[CoalCrackerAl]

I let my sizing dies set in one position. So far no negative effects.

 

[AJC1]

Your die should be set to the correct bump based on previous use. If your brass is still short keep the setting and just run them. As your case grows your necks get shorter if you trim by oal.

 

[JFrank]

I'm not saying don't resize I'm saying would there be a benefit to FL resizing but NOT bumping the shoulder back?
You would be resizing the base of the case and the neck for tension but the shoulder bump would stay where it was after firing?
You would be getting closer each time you reloaded to a 100% match of the chamber. Then, only after the brass became too tight you would resize and bump the shoulder back.
thanks
flexible

‘ if every set of dies came with a neck die included you would just use that until a fired case resisted chambering and from that point a case is sized back to just chamber freely -plus a couple thousandths of shoulder set back.

 

[Walkalong]

in our pursuit of accuracy would it make sense to not start resizing FL till difficulties start when chambering?

No.

 

[jmorris]

This is a weird thought but in our pursuit of accuracy would it make sense to not start resizing FL till difficulties start when chambering?

If you mean an interface fit and the case slightly compressed upon the bolt being fully closed like this, after FL sizing,



No, I think that is a sound technique.

 

[westernrover]

There is a good question in here.
If a case is still short, then you won't want to bump it until it gets more expanded.
Mind you, you will still size the body of the case every time, but if it's short, a properly adjusted die just won't be bumping it.
But how do you properly adjust the die, if you don't know when your brass is fully expanded?

Suppose you fire some new brass in a new rifle, and you were loading a ladder. You measure your cases with a comparator, but they're not all the same. Where do you set your die? To bump the shortest one? Probably not. Even if you set it to bump the longest one, you could still be bumping it four or five thou from the chamber dimension. It's hard to know when the brass is fully expanded into the chamber, until it starts to become difficult to chamber.

I"m not going as far as recommending that brass not be resized until it fails to chamber, but I will say that it might take several high-pressure firings before you can find where to set your sizing die so that it doesn't excessively bump the shoulder. It only takes one case to do this though. Also, if I was bumping cases a thou more than necessary, I don't think that would bother me too much -- it's a much better situation than having them not chamber.

 

[Theinkman]

I don't believe it is possible to FL resize without bumping the shoulder back somewhat. FL resizing dies aren't made to do that. If you envision the inside of a bottle-necked cartridge resizing die, the portion that resizes the case body is not separate from the portion of the die that bumps the shoulder back. They are all in one.

 

[AJC1]

I don't believe it is possible to FL resize without bumping the shoulder back somewhat. FL resizing dies aren't made to do that. If you envision the inside of a bottle-necked cartridge resizing die, the portion that resizes the case body is not separate from the portion of the die that bumps the shoulder back. They are all in one.

Your not accounting for the opertunity to back the die off. Cases actually grow during sizing if your not pushing the shoulder back.

 

[Nature Boy]

I want my ammo the same from load to load, therefore I’m FL sizing to a consistent shoulder bump every time. A key to accuracy is eliminating variables.

Your suggestion would mean that the brass is changing dimensionally from load to load up to the point where you would need to size it properly.

Sure, you can get away with that but for what gain?

 

[JFrank]

Quote
m not going as far as recommending that brass not be resized until it fails to chamber, but I will say that it might take several high-pressure firings before you can find where to set your sizing die so that it doesn't excessively bump the shoulder. It only takes one case to do this though. Also, if I was bumping cases a thou more than necessary, I don't think that would bother me too much -- it's a much better situation than having them not chamber.

I think this is a fair point, a fella could take one case with a modest load and stuff a tissue in place of a bullet , shoot and reload three or four times you’ll have a dummy round fire formed to the chamber.

 

[AJC1]

Quote
m not going as far as recommending that brass not be resized until it fails to chamber, but I will say that it might take several high-pressure firings before you can find where to set your sizing die so that it doesn't excessively bump the shoulder. It only takes one case to do this though. Also, if I was bumping cases a thou more than necessary, I don't think that would bother me too much -- it's a much better situation than having them not chamber.

I think this is a fair point, a fella could take one case with a modest load and stuff a tissue in place of a bullet , shoot and reload three or four times you’ll have a dummy round fire formed to the chamber.

One could take any case fired in the gun partially deprime and use the bolt to seat the primer back to chamber length. One shot no fuss

 

[JFrank]

One could take any case fired in the gun partially deprime and use the bolt to seat the primer back to chamber length. One shot no fuss

That’s exactly right and great point.

 

[FROGO207]

I will always basically bump the shoulder back a couple thousands to assure it will chamber reliabily the next time. Some semiautos require a complete full length resize just to chamber. Had one of those in 308 once. Sold it off. Try it both ways and see what works the best for you. Proof will show on the target when all other factors are the same.

 

[Varminterror]

EVEN IF YOU ARE a 'bench rester' or regularly shoot beyond 500 yards, full length resize every time.

Fixed it for you.

It’s not 1995 any more. Nobody in their right mind is only neck sizing any more.

 

[Varminterror]

@flexible - yes, it is true that it generally takes 3-4 firings before a case will be fully fireformed to the chamber after firing. It’s actually pretty simple to test - try rechambering a fired case, it shouldn’t really want to close, as inserting and closing requires some clearance which properly fireformed brass won’t have (hence our 2thou bump…), so if it closes, you can be sure the brass isn’t giving a true indication of your chamber headspace length.

A couple tricks for virgin brass if you don’t want to wait for cases to actually grow to match your chamber after firing - add shim tape to the base of your virgin brass to find your headspace BEFORE your cases have stretched to actually fully fill the chamber and set your sizing die based on that length. You can also sacrifice one case and expand an oversized false shoulder and then use that to set your sizing die. Partially reseating a primer is another trick to MEASURE the chamber headspace - using the length from the datum to the primer to measure the headspace - but that requires some comparator to set the die, since the primer won’t offer proper reference when setting the seating die, and won’t offer sufficient resistance to enter the die anyway… AND it’s not an exact science - a guy kinda needs to be able to force the case into the chamber independently before using the bolt to seat the primer, because the case body may drag/wedge with enough resistance to allow the primer to be seated before the shoulder headspace (I’ve used an empty 9mm case to push cases into the chamber, spanning over the proud primer, then drop the 9mm case out and let the bolt seat the primer - it works well enough to repeat it here). With the shim tape and the false shoulder, you can directly set your sizing die. With the proud primer trick, you can really only capture a measurement. So I like the other two options better.