Gouge on Case?

[quig]

Anyone notice this marking? Cause?

R-P Brass. From my 60gr V-Max, Varget powder 25.0gr.

[rsrocket1]

Looks like an extractor mark on the case and cratering on the primer. Signs of reaching or exceeding max pressure.
Hodgon's website says that 25.0g is the start load for that bullet, but Quickload says you are at 55.3 kpsi which is 300 over SAAMI max pressure at 2.26" COL. Do you have chrony data for this? I would back off at least 10% or 2.5g and slowly work up a load that gives you the best groups.

[bruceflinch]

^

[r3dn3ck]

yep,

also look in the bolt face for debris or bad machining. I had a similar problem on my AA grendel bolt but it turned out they left .005" in the bolt in a ring (looks like the mill had a busted bit) which they shouldn't have and it was messing up my brass. Had to replace the bolt head.

Also make sure your bullets aren't jammed into the lands. I got similar pressure signs once from the extractor cutout on my brass when my bullets were jammed into the rifling just a bit instead of having a couple thousandths to jump (those loads were near max).

[huckberry668]

that's 'ejector' mark, not extractor. extractor marks look like damages to the case head rim and deformed case head. your load was hot enough to slam the case back into the bolt face fast enough to create that.

a 60gr bullet over 25 grs of Varget shouldn't cause that. are you sure it's 25gr? Were you at a high altitude when you shoot this load?

[scarville]

Check that your OAL is not too long for the chamber. The NATO chamber has a longer distance from the case mouth to the start of the rifling (called the "leade"). A load that is perfectly safe in a NATO chamber can cause a dangerous pressure spike in a SAMMI chamber.

[Pete1979]

How far are you bumping the shoulder back? I get extractor marks with my 308 sometimes with mild charges if the shoulder has been bumped back too much. sends the case back hard against the bolt...

[quig]

WTF.

Here I am, slowly working up a load and starting low (24.7gr, 25.0gr, & 25.3gr), and I am getting pressure signs.

I have to admit, I didn't recognize the pressure signs I was having. I was looking for craters and flattened primers.

I am using a BCM 5.56 16" Midlength. I guess I gotta check for the OAL of the chamber. I just assumed that I was with-in normal limits.

Explain to me about the shoulder? I did a full length size of the case.

[jameshenry]

Huckberry is right ejector marks, and it looks like cratering and flattening.

[Hoop]

Any oil in your chamber or on the bolt face?

[quig]

I'm pretty sure it is isolated to these rounds.

Nothing out of the ordinary as far as the oil goes. I'll take a look, but I only oil as necessary and not in excess.

[Sunwolf]

Use a case gage,make sure your brass fits.

[Munk]

Is ejector mark.

Is this just a discoloration/grime? It could be from a dirty boltface.
If it's an indentation, it could be a result of soft brass or overpressure.

[quig]

Well, I think I got my answer and was educated as well.

I called up Hodgdons and went through my load.

He said that in their testing, they use Winchester brass. This is important, because Win brass has the greatest volume compared to all other brass. Where as "Remington" has the least amount of volume (figures, that is the one I chose). All other fall somewhere in between.

He suspected that 25.0gr of Varget was at the case capacity and near max load. He suggested backing down to 22.5gr.

Actually, I have Winchester brass on hand and will try it again.

Thanks for all the help.