Much lower than expected max charge

[DTF370]

So I have been in load development for my 308. Here are my rifle specs:

Armalite ar-10
Rainier ultramatch 16”
Match precision bcg
Sig tango4
Timney drop on trigger


I have been playing around with various bullets and Varget. I have found that my rifle strongly prefers the 178 eld-x. Today I attempted to find some accuracy nodes by increasing charge weights by .2 grains. I found a very broad node that shot very well from 40.9 grains to 41.7. My potential pet load is as follows:

178 ELD-x
Lapua brass trimmed 2.010
41.7 grains Varget
Fed GM large primer
COL of 2.805

Here’s what I personally found odd... I started seeing very consistent ejector swipes after 41.7 grains of Varget. By my source, I anticipated a max charge to be quite a bit higher than 41.7 grains.

Should I be worried about pressure signs at such a low charge?

 

[spife7980]

Over gassed?
New brass or previously fired?
How do the primers look?
I know you’re at mag length basically but you’re not jamming bullets?

If that’s your max then load them at 41.1 and stay away from the upper end. That’s a wide ass node though.

 

[DTF370]

I have not noticed any overgassing. This was the third round of firing with the Lapua brass. The primers weren’t noticeably flat or cratered.

 

[DTF370]

Not sure how well this will show up

 

[D2junky]

Thems getting fairly flat. Buffer and spring? Adjustable gas block?

 

[DTF370]

The buffer system is a stock Armalite. The rifle was originally a AR-10 Tactical 20”. They may look a bit flat in the photos, but in person they don’t appear to me to be any more flat than an unfired primer.

 

[DTF370]

I just loaded a dummy round and saw some slightly scratched surface on the ogive of the projectile. Maybe my barrel has too short of a throat?

 

[D2junky]

Color it with sharpie and place it in chamber and ease the bolt into battery. Only half the pic shows on this phone so I cant really see any land marks. If you see marks at regular intervals ur in the lands.
Would be nice to know some speeds as well.
Lapua brass is thicker but it’ll still usually swallow 45grains of Varget. I wouldn’t go there at this point.
I see the occasional ejector mark.

 

[D2junky]

Was the bolt matched with that barrel and is it compatible with the Armalite bcg? I finally got the whole picture and those don’t look like land marks. More like a lead that wasn’t properly cut.

 

[DTF370]

Color it with sharpie and place it in chamber and ease the bolt into battery. Only half the pic shows on this phone so I cant really see any land marks. If you see marks at regular intervals ur in the lands.
Would be nice to know some speeds as well.
Lapua brass is thicker but it’ll still usually swallow 45grains of Varget. I wouldn’t go there at this point.
I see the occasional ejector mark.

I would love to chrono these, but I don’t have one yet.... probably time to invest. The marks on the ogive are more like tiny scratch marks rather than deliberate lands and groves. Good idea with the sharpie. I just tried it and again I just get what I would describe as small “scratches” on the ogive.

Was the bolt matched with that barrel and is it compatible with the Armalite bcg? I finally got the whole picture and those don’t look like land marks. More like a lead that wasn’t properly cut.

The bolt was matched when I placed my order with rainier. Their barrels are DPMS pattern, therefore I replaced the bcg with a compatible one with the barrel.