Excess pressure

[bboswell]

Do these look over pressured to y'all?



To me some if these loads look hot but all are about mid range in book charge weight.

All new in-fired SSA 6.8 SPC brass, 110 Accu Bond, CCI 41 primers and 27-28g of A2200 & H322. Both powders show a 29g max.

27.5g of A2200 shot under 1/2".

[DarrellS]

Appears that some (due to angle of pic) have excessive pressure signs.

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[Phillip Fields]

I can see pressure signs in some of them. I see flattened primers on some, and ejector marks on some.

[Outbreaker]

Were you shooting a ladder?

[bboswell]

Were you shooting a ladder?

27, 27.5 & 28 grains of each powder. 3 shots of each. Dang Ammo box got dropped and fired brass got mixed up.

Gun really likes 27.5g of A2200 which should be a conservative load but...

[Mike D]

Flattened primers don't concern me much. Ejector swipes start to concern me.


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[Outbreaker]

Were you shooting over a chronograph? That will tell alot about a pressure spike.

I do not like ejector marks as well. Was the bolt sticking at all?

[bboswell]

Flattened primers don't concern me much. Ejector swipes start to concern me.


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I'm the same on bolt guns but there I can add ease of bolt lift to gauge pressure.

[Outbreaker]

I just noticed that this was a 6.8 SPC. Is this in an AR?

6.8 are notorious for 2 things.

1. Pressure spikes out of nowhere. (no solution other than watch for it)

2. Over gassing where the bolt tries to remove the round before the pressure falls (solution here is an adjustable gas block).

[bboswell]

Excess pressure

I just noticed that this was a 6.8 SPC. Is this in an AR?

6.8 are notorious for 2 things.

1. Pressure spikes out of nowhere. (no solution other than watch for it)

2. Over gassing where the bolt tries to remove the round before the pressure falls (solution here is an adjustable gas block).

Yes AR which is why I had to ask, I can't fall back on bolt lift for an additional indicator.

[Outbreaker]

My first guess would be that it is over gassed. What does the rim look like? How violent was the throw of the shell?

[Outbreaker]

Suppressor?

[bboswell]

Suppressor?

No suppressor.

16" ARP rifle

[Outbreaker]

Does it have an adjustable gas block? If so I would try to turn down the gas so that it barely locks the bolt back and try again.

You will get these marks if the barrel is still pressurized when it tries to extract.

I had these issues on my Grendel until I got an adjustable gas block. 6.8 are far more sensitive to pressure issues than the Grendel is......and the Grendel is chronically over gassed.

[bboswell]

Does it have an adjustable gas block? If so I would try to turn down the gas so that it barely locks the bolt back and try again.

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No

Or not yet...