Swipe on brass

[Dt219]

I was doing load development with varget and 120 eldm, and the brass is brand new starline. Anyways this weekend just a rough trial to check how it would group. I was not checking speeds or sd/es. When I got to 26.6 I noticed a swipe on the 3 pieces and at 26.9 the swipe was there again on all 3 but one had a decent stamp, no burrs was created on the case head. My setup is a 18” Lilja with A5 buffer system H0 buffer non adjustable gas block. Would an adjustable gas block help with the swipes ? 26.9 is not near the max load. Thanks guys

[VASCAR2]

The ejector pin can leave marks on the brass prior to significant pressure. If the primer edges are still rounded and not flattened I suspect there is a stout spring under the ejector. With hotter loads the primer fills the void around the edge of the brass case primer pocket and the edge of the primer is less distinct. If the velocities are in line with the published data I’d chalk it up to a strong ejector spring. You can clip a couple of coils off the ejector spring and see if the swipes are diminished.

[Dt219]

Yes the primers appear still rounded to me definitely not flattened like I’m used to with a warm bolt gun load

[Dt219]

It’s a maxim bolt I bought from Lilja with the barrel. Should the outter edge of the ejector be slightly rounded or squared off ? Thanks

[Old Bob]

It’s a maxim bolt I bought from Lilja with the barrel. Should the outter edge of the ejector be slightly rounded or squared off ? Thanks

Over the years I've been playing with ARs most ejectors I've seen have a small radius. Some were flat-faced & some had a sort of a truncated cone shape. As I said, a large majority have the small radius. I've put my own radius on those that were flat-faced. Squared off ejectors will definitely cut into your cartridge rims. I remember seeing a You Tube video where the presenter ground a bevel on the side of the ejector nearest the cartridge rim to cure a feeding problem he was having.

[lazyengineer]

Im not convinced headswipe is automatically a sign of overpressure, though overpressure often has headswipes.
But it could just mean the plunger has a strong spring and the bolt is rotating more quickly due to higher pressure of the warmer load. Fast rotation due to increasing port pressure, doesn't necessarily mean overpressure.

Flattened primers and extrusion into extractor and plunger area is another matter! That takes closer to 60k+ psi levels

[Dt219]

Ok I disassembled the bolt, and lightly rounded the ejector and ground a couple coils off the spring so that should help with the swipe

[muvef]

Nothing was wrong with your Maxim bolt.

I would start with a ajustable gas block, standard carbine spring and H1 or H2 buffer.

It's probably unlocking early while pressure is still building.