It depends on how much the die sizes the neck down. I had a set off lee 300WSM dies that you wouldn't have been able to seat a bullet without crushing the neck if you removed the expander. I went to Redding full length bushing dies for it with the expander removed and couldn't be happier, they don't overwork the necks and cases just go on an on. I wish they made them in bigger calibers.

I've often read the recommendation of forum members that cases be f/l resized without the expander ball in the die.
Will this not cause the case to grip the bullet more tightly and cause an increase in pressure?.
Thanks in advance.
rob

The change in chamber pressure (due to neck tension) would probably not be measurable.

i resize with out expander ball,it makes it easier to see when the size die is adjusted to touch shoulder. i use a lyman "M" die to expand the neck. i use the short plug and reduce the diameter slightly so that the bullet slightly expands the neck when it is seated. bullet pull appears to be more consistant also.

Good point Saline. I will have to try that one myself.

Answer:

Yes , it will increase pressure. But probably not enough to worry about with safe loading practices. The total grip of the neck on the bullet will cause the pressure to rise quicker, and may help with powder burn consistency. ( lower FPS spread )

how small are you squeezing the neck ? Any squeeze past .004 will stretch the neck to fit the bullet.
Bullets suck as expanders.

You will also notice concentricity improves when you delete the expander, when measuring runout on the neck. This is an illusion, the hole in the middle of the neck will be offset an amount more or less equal to the difference between the thickest and thinnest parts of the neck wall.

Lots of variance in neck walls and no expander will give you ammo that, when measured at the neck seems straighter than before. ( it ain't )

The hole in the middle is the important part.

Travis F.

I feel the same as TBF--a bullet doesn't make a good expander. I would think the likelyhood of scratching the base of the bullet during seating would be increase alot too. And I agree--without an expander the hole "inside" is now not going to be perfect. If expanders weren't a good idea maybe die makers wouldn't bother putting them in their dies??
I really think some of us are getting "crazy" worrying about a little bit of runnout. A piece of typing paper is .003" thick---now you see people in the forums that are going crazy because the total wobble of their loaded ammo is .003". It's almost like people have this vision that with that little tiny imperfection the bullet is slamming into the rifling sideways and now is forever distorted and doomed to flying crazy on it's way to the target!! I "tune" my dies for as little runnout as possible but I'm now beyond all the hype about runnout.

My concentricity gauge tell me that pushing bullets makes MUCH better expanders than pulling expander balls.



Brass yields after .002" change in diameter.



The more neck tension the better, but you can only get .002".



Eccentricity .000" up to ~.004" for a typical 30 cal chamber makes an additional 0 moa up to a 1 moa error at the target in a linear progression. After .004" Eccentricity, the throat forces concentricity to .004", and there is no increase in error at the target.



Those getting 5 moa, concentricity is not your problem.



But if your groups are stuck at 1.5 moa....

Look at someone's ammo that gets .2 to .4 moa 5 shot groups in a concentricity gauge.

Now look at YOUR ammo with a concentricity gauge.



--

A society that teaches evolution as fact will breed a generation of atheists that will destroy the society. It is Darwinian.

Kevin has the right idea. Find a bushing that will have sized the diameter of the neck down say .002" from what it would be after the bullet is seated. Bushings are fairly expensive when you get all you need, but bushing dies are a great piece of engineering in my opinion.