Extractor Mark

NC1426 · 2024-11-01T13:26:59-0400

What would cause this?

New rifle. 6GT
Impact action
Alpha Brass
31.0 g Varget
CCI magnum primers
Berger LRHT 109gr
.08 jump

First 20-30 times firing it it was very smooth. Then about 75% had really heavy bolt lift on maybe 60-75% of shots. this happened to one round. I don’t think it’s pressure. Velocity was 2670.

NC1426 · 2024-11-01T15:02:55-0400

Also, it may be worth mentioning that I had a handful of instances where I pulled the trigger, the firing pin clicked, then it took another fraction of a second for the round to go off. I thought this might be related to the primer, but it looks like the Trigger Tech Diamond triggers have this issue. Maybe it's related to the above issue?

Im2bent · 2024-11-01T15:09:22-0400

Check for heavy copper fouling or a carbon ring. At 20-30 rounds would be extreme but who knows. That sure looks like pressure but greater minds then mine will chime in

Aftermath · 2024-11-01T15:12:10-0400

NC1426 said:
Also, it may be worth mentioning that I had a handful of instances where I pulled the trigger, the firing pin clicked, then it took another fraction of a second for the round to go off. I thought this might be related to the primer, but it looks like the Trigger Tech Diamond triggers have this issue. Maybe it's related to the above issue?

Double check your headspace and compare to unfired round.

NC1426 · 2024-11-01T15:41:02-0400

I used the hornady head space comparator...the fired casings were .004 larger than the unfired casings. Is that what you meant and what does that tell me?

Aftermath · 2024-11-01T18:48:12-0400

No. Measure the chamber and compare that to an unfired case.

I’m not saying this is the problem but my very first thought was your cases might be a bit under. They have too much room to move…so when the primer is struck, the case moves forward into the chamber.

If that is the deal, seat your bullets so there is a very slight jam and fireform the cases to your chamber….unless it’s so far off that it creates an unsafe situation.

ShtrRdy · 2024-11-01T22:28:24-0400

The primer looks fine but that brass burr is really something.

As for the hang fire, something else to check is the tip of the firing pin.

Dolomite · 2024-11-02T01:44:44-0400

is there enough neck clearance? Carbon ring? Verify seating depth bullet not in the lands? .004 seems about right for new brass to expand to chamber.

Do you have an alpha reamed chamber? Some people have luck with alpha brass in a non alpha chamber but some don’t.

NC1426 · 2024-11-02T05:43:08-0400

It’s a prefit barrel from Stutteville Precision. Not sure if it’s alpha reamed or not. I did reach out to them to see what they think.

All the primers looked fine.

I’ll check the brass dims and report back. I don’t have any way to check for a carbon ring.

What am I looking for on the firing pin?

I’m wondering if it also may be from wax left on the brass. I ran it through my resizing due before loading and just wiped off the wax instead of tumbling it.

Doom · 2024-11-02T08:00:03-0400

Here is what I would think from your post. The brass is seeing high pressure. Only way that it gets that messed up. If you hear a delay in firing after the click it is not a trigger issue as the click is the firing pin striking the primer. It is a delay in ignition of the primer or the powder. I'm guessing here but probably most likely issue is primer is not seated and compressing the anvil but it could be the primer is firing but powder ignition is being delayed. It is possible that the primer energy is dislodging the bullet and the powder is delayed in ignition. The bullet could be in the lands which would increase pressure.

You said the jump is 0.08". Is it that or 0.008"?

FWIW, GRT says 31 grains of Varget is only 80% case fill and a light load pressure wise. If that's the case then powder orientation may be an issue with the hang fires.

ShtrRdy · 2024-11-02T09:24:29-0400

NC1426 said:
What am I looking for on the firing pin?

When you remove the firing pin assembly is there any drag? Do you have to pull it out of the bolt body? Then carefully look at the tip for any damage.

NC1426 · 2024-11-02T15:01:53-0400

Firing pin was fine.

The primers were fairly hard to seat so that may make sense. I'll pay attention to that on my next reload. The jump is .08.

I measured a bunch of the fired cases and one thing I noticed is that the ones with the ejector pin marks were consistently .002 longer on the headspace than the ones without.

The only thing that doesn't make sense to me about the pressure is the velocity was very consistent. Wouldn't the velocity change significantly if sometimes it was over pressure and other times it wasn't?

spife7980 · 2024-11-02T15:03:37-0400

NC1426 said:
Wouldn't the velocity change significantly if sometimes it was over pressure and other times it wasn't?

Not necessarily.

I would clean the barrel. Clean it good.

Clean the brass, if you still have lube on them that will work to decrease the amount of grip the round has on the chamber walls under pressure which increases bolt thrust.

Measure your primer heights and the primer pocket depths. Pocket should be a couple though deeper than the primer. Seat until the primer is touching the bottom and then ~.003 more, just a slight crush.

Growing .004 in firing from virgin isn’t bad, pretty standard.

I’d take a sized case and seat the bullet long, see if you can chamber the round, see if that jammed bullet putting pressure back on the bolt face causes any sort of swiping on the case head, might just be a wicked sharp edges in the bolt face. It’s a hell of a deep scar in your pic so not out of the question.

Search

Search

Download Gravity Ballistics

Having trouble using the site?

Extractor Mark

NC1426

Private

Attachments

NC1426

Private

Im2bent

Two Star General

Aftermath

RECOIL FETISHIST

NC1426

Private

Aftermath

RECOIL FETISHIST

ShtrRdy

Gunny Sergeant

Dolomite

Private

NC1426

Private

Doom

Balding Eagle

ShtrRdy

Gunny Sergeant

NC1426

Private

spife7980

Luchador

Similar threads