A lil more headspace sizing?

[R2BRO]

So I have headspace gauge for rounds, lets say Go=0.
the fired rounds from new JP barrel show +2.

the factory Hornady SST measures -4.

some of the new cases after sizing i measure -6.
question: is it still OK to load them with 31.2gr CFE223? (my guts telling me OK, although -6 is 2 mils more than factory -4). Your opinion?


on another note...i found 1 round of hornady HP which measures -5/-6 depending on how i screw in the gauge...but i have only 1 sample of that ammo round.

[Yondering]

[Klem]

BRO,

Unsure what convention of measurement you are referring to with whole numbers and "mils". Does +2 mean + ,002"?

What sort of headspace gauge are you using. Is there a link or photo?

[LR1955]

So I have headspace gauge for rounds, lets say Go=0.
the fired rounds from new JP barrel show +2.

the factory Hornady SST measures -4.

some of the new cases after sizing i measure -6.
question: is it still OK to load them with 31.2gr CFE223? (my guts telling me OK, although -6 is 2 mils more than factory -4). Your opinion?


on another note...i found 1 round of hornady HP which measures -5/-6 depending on how i screw in the gauge...but i have only 1 sample of that ammo round.

R2:

Factory ammo is normally made with the brass at a minimum or even below minimum for headspace. Companies do this so their brass will safely fit into chambers made by dozens of different companies. It is common for new brass to be small so you should not be surprised that your Hornady is under the gauge zero.

Never heard of a gauge calibrated in mils before.

LR55

[Happy2Shoot]

R2BRO,

You are fine.

What you describe is completely normal.

When resizing brass, I push it back 2 mils.

Factory ammo is like a hotdog down a hallway.

Not sure why people had a hard time understanding what you wrote with the +/- 1, or mills. That is how I say it in my head.


Equal to 1 / 1000 of an inch, it is normally referred to as a thou, a thousandth, or (particularly in the United States) a mil. The plural of thou is also thou (thus one hundredth of an inch is "10 thou"), while the plural of mil is mils (thus "10 mils").

[mtnlvr]

A mil is one thousandth of an inch (0.001"). I isn't used in many areas. Even in the engineering world it is hardly used.

It sounds like the OP is measuring a GO headspace gauge (as a fixed reference point) and comparing it to factory and fired rounds. Fred rounds are +0.002, sized rounds are - 0.006, so he's bumping the shoulder back 0.008". If he wants to continue using that method, he should size the cases to - 0.001" to - 0.002" from his guage.

Personally that's adding more opportunity for measurement error so he should skip the guage.

He's asking if it's OK to continue usung 31.2 gr of CFE in the cases. Im not sure we have enough data to answer. It's surprising that he's suggesting factory rounds are only 0.006" shorter than his chamber. I thought factory was more like ~0.013".

[R2BRO]

gentlemen...of course I meant 0.002" when I say 2 mil. 1 MIL = 0.001", instead of hitting keyboard 5 times to enter 0.001 I do it once by typing 1.

back to the question, I will restate it now in terms of diagrams of my headspace which is shown here:


GREEN: where it measures after firing a round in my chamber
BLUE: measure of factory Hornady 123gr SST round
RED: where it measures after me resizing a case

so my concern is now understood I hope: typically, you do not want to resize more than the factory round does, in my case I resized 2 mils more than what factory round measures. is it OK to shoot it with 31.2gr of CFE223 or not?
or think of it another way: I pushed back 8 mils from measured fired round.

that is all I asked!

and then I said that on another note, I found 1 more round at home which is factory HP round, and that (depending on high I screw the cap of gauge in) sometimes measures -6 mil as well.

thats it.

[R2BRO]

A mil is one thousandth of an inch (0.001"). I isn't used in many areas. Even in the engineering world it is hardly used.

really? I think it is used every second all over the US in engineering. I use it every day during the PCB design (where people put constraint in CAD in mils "6 mil trace/space between traces" etc.

[mtnlvr]

I'd say that if you worked up your load for a normal 0.003" bump and this time you bumped the shoulder 0.008", (0.005" more than the usual) the load will most likely be safe, just may not be the same accuracy wise. Probably not a huge difference.

[R2BRO]

honestly... I was measuring from "worked load" fired cases, so each load was different.. On a next batch it will be more consistent.

so when I was measuring the samples of fired rounds in my chamber I was getting these results:
+1 mil (some...30% or so)
+2 mil (MOSTLY)
0 (10% of measurements)

^
so above is what I measured... since most of the time I measured +2, that is what I decided to go with.

basically... backing up 8 mils down (or 0.008" down) is it SAFE or not?

thanks.

[biodsl]

The US customary mil can be confused with the millimeter, which is the standard meaning for "mil" or "mils" (plural) in British English and European engineering circles.

Communication is hard.

https://en.wikipedia.org/wiki/Thousandth_of_an_inch

[R2BRO]

alright, just feel free to answer my question so the topic can be finalized, and I'll use inches on this website from now on.

[Klem]

R2,

Yes, it will be fine.

You only need to bump a fired case .003". Anything more is wasted case life.

[Happy2Shoot]

Too little headspace and your case won't chamber.

Too much headspace and your case will split in two, mid-case.

A mid load vs a max load in the 6.5 Grendel will not make much difference when a case will split due to excessive headspace.

When you fire a max 6.5 Grendel load the case expands to fill the chamber, then shrinks a little when the pressure is released.

If you can hand chamber your fired load I would only size the headspace 0.002 inches or 0.003 inches.

If your load is listed in a reloading manual, shoot it.

[kmon]

The chamber of your rifle with that brass is in reality the same if your bump the shoulder .002 or .005 you still have the chamber walls which allow the case to expand and seal the chamber to the same dimensions for the burning powder. Just will work the brass more the more you size it.

After firing in your chamber with new brass, measure your brass and bump .002 from the longest piece of brass has worked well for me with several rounds. At the lower pressures of the Grendel compared to higher intensity rounds that run 10 to 15k higher PSI, it might take a couple firings for the brass to fit your chamber tighter to really have that .002 gap for headspace. I have seen that on several different cartridges.