Headspace

Moderators: gds, bakerjw, renegade

Post Reply
Srt4ever
Member
Posts: 19
Joined: Sat Nov 07, 2020 2:33 pm

Headspace

Post by Srt4ever » Sat Dec 19, 2020 11:47 pm

So I am attempting to reload some 300 blackout, once fired cases from my rifle in a LE Wilson case gauge show the headspace to be negative 0.007, shouldn’t it be positive since it was once fired form my rifle ?

In that case if it’s negative should I back out my die to bring it within SAMMI spec of the gauge when reloading ?

BulletFlight for Android
User avatar
dellet
Silent But Deadly
Posts: 6536
Joined: Fri Nov 30, 2012 1:25 pm

Re: Headspace

Post by dellet » Sun Dec 20, 2020 1:46 am

Do you have a case gauge, or a headspace gauge? Wilson makes both.

One is for checking fired cases, the other is for sized cases.

If it is the case gauge, for sized brass, then yes I would back the die off a half turn and check again.

if it is the gauge for fired brass, it depends on what length it started at, and what the load was.

Compare to some unfired cases if you have some and then you will know how much it grew on a single firing.

Not uncommon for supers to take 2-3 firings to quit growing, subs maybe 5 firings until the brass expands the full chamber size
300 Blackout, not just for sub-sonics.

Srt4ever
Member
Posts: 19
Joined: Sat Nov 07, 2020 2:33 pm

Re: Headspace

Post by Srt4ever » Sun Dec 20, 2020 11:37 am

It’s just the plain case gauge. I didn’t think they made one for fired and new brass, simply because I have there trimmer as well and the holder is for both fired and new brass.

I primarily only shoot subs and that brass I measured was once fired maybe it does need those 5 firing to make a shoulder extend into the chamber.

Some of the other brass are even at -0.009 when the fired brass was only -0.007.

User avatar
dellet
Silent But Deadly
Posts: 6536
Joined: Fri Nov 30, 2012 1:25 pm

Re: Headspace

Post by dellet » Sun Dec 20, 2020 1:27 pm

New brass/ammo is always shipped at minimum headspace length, honestly a lot is sometimes shorter, to work chambers that might be set at minimum length.

Yes, Wilson makes a minimum chamber style gauge for sized brass or loaded rounds and a gauge to check fired length. The big difference is that the “headspace gauge” has a larger diameter to allow the fired case to fit. Generally fired brass will not fit a chamber style gauge. The exception is low pressure loads, like many sub loads.

If you back your sizing die off a half turn, you might notice something interesting. The shoulder should not be touched and the sized brass will actually measure longer in the gauge. Squeezing the diameter smaller, will push the shoulder forward.

The opposite can also happen when firing a low pressure load. The case will expand to fit the chamber, before it will stretch. Very low pressure loads can measure shorter and fatter after firing.

Often dies set up to touch the shell holder, then turn down whatever the manufacturer suggest, will size the brass to minimum length. If you want your brass to grow to chamber length, it does no good to keep pushing the shoulder back. Find the place where the die just touches the shoulder and back off.

Shooting a few supers would make it a lot easier to find max length.
300 Blackout, not just for sub-sonics.

Srt4ever
Member
Posts: 19
Joined: Sat Nov 07, 2020 2:33 pm

Re: Headspace

Post by Srt4ever » Sun Dec 20, 2020 2:18 pm

I figured it could’ve been since it was subs and not having much pressure to fire form. I might shoot a few supers to see. But over all if it falls below minimum it should still be ok to reload ?

noname
Silent Operator
Posts: 72
Joined: Tue Aug 27, 2019 8:55 pm

Re: Headspace

Post by noname » Sat Jan 09, 2021 7:20 pm

The slotted Sheridan gauge is the way to go. Measures all critical size issues. I have not used my Wilson gauge since I got it.
Previously known as hardcase. Moved lost internet connection for 1+ years.

Post Reply