FL sizing question for rifle brass?

[Jasper1573]

Tell me, is it true that if I FL size .308 Win cases that have been reloaded 5 or 6 times, should I get a little more velocity than with just neck sizing? That is, because I am sizing the body of the casing, does that bring the interior volume down a smidge and provide 20 or so fps more velocity than a case that is neck sized 5 times?

 

[rcmodel]

No.

Internal pressure will expand the case to fit & seal the rifles chamber before peak pressure is reached, no matter what size it starts out at.

rc

 

[kingmt]

I agree with RC. Besides what difference does 20 fps make?

 

[gamestalker]

Neck or FL length makes no difference in velocity. I have doubles of certain chamberigs with the same barrels, and same model actions, and for some reason one will shoot 100 fps faster or slower than the other with both using the same brass and load specs? Who knows what happens in the chamber / barrel that produces such significant variances in fps?
GS

 

[Jasper1573]

Thanks for your wisdom. No, 20 fps probably makes little difference if any at all...I am simply trying to quantify what is going on with brass volume and neck vs FL sizing....apparently not much.

Again, thanks for the inputs. If all three of you say the same thing, I accept your advice and have learned.

Jasper

 

[kingmt]

All of this is theory because there isn't enough room to make a measurable difference. If your brass is already formed to the chamber it should hold a few more grainuals which should increase pressure if it is a compressed load. People over think things tho.

 

[Slamfire]

If you shoot your loads over a chronograph you will see just how meaningless an extra 20 fps is when the extreme spreads are often close to 100 fps.

A very good extreme spread is around 20 fps, but it will take a lot of experimenting to get there.

 

[popper]

Is your powder drop method accurate enough to adjust for the miniscule difference? Seating depth will make more difference as will neck tension.

 

[Jasper1573]

Will I get more consistent neck tension from FL sizing than neck sizing with a Lee Collet neck sizing die?

 

[rcmodel]

You will if you don't have the collet die adjusted exactly right.

Lots of new reloaders on this board have had their share of problems with them.

rc

 

[kingmt]

That & your sizing your brass about .004" smaller with the bullet where if the die is adjusted right it is .002 at most. If you don't get it adjusted right it will bee all over the place but still no more the .002" less.

 

[ranger335v]

Lee's excellant collet neck die is not a simple 'push the case in, pull the case out' device like all others. Lee's has a moving part (the collet) that seems to baffle some users, especially those who ignore instructions..