5.56 Primers

[poke5353]

What do you all think about these primers? I am shooting this out of a 5.56 noveske upper that is 14.5". This is 2 different 5rd loads. These are loaded at 23.4gr and 23.7gr of AR Comp under 75gr Hornady BTHP. The load data on Alliants site states 22.1 for 77gr SMK. Average velocity is 2703 at 23.4 and 2774 for 23.7. These are seated at mag length. Do these primers look OK or do I need to back it down?

 

[noahmercy]

Re: 5.56 Primers

They look cratered a little bit to me, and some of the case heads have shiny spots on them. These indicators generally point towards high pressures, but without mic'ing the case just ahead of the extractor groove and comparing it to the case of a factory load fired in the same firearm, I couldn't say for sure if they are too hot. Also, since those are reloaded cases, the shiny spots could be from previous loadings.

That being said, the max load on Alliant's site for the 75 grain bullet (an A Max) is 23.3 grains. Both of your loads are above that. You should be starting at about 21 grains or so and working up.

 

[poke5353]

Re: 5.56 Primers

Yeah I saw the a max data but it is not at mag length. That's why I used the 77gr smk load data. I feel I am a bit too hot so I think I am going to start all over and go from there. I started at 21.5 and worked up to this point. Also can you specify where I would need to measure to check the case for over pressure

 

[gunsnjeeps]

Re: 5.56 Primers

They don't look flat but they are cratered. What was the load before tey cratered?

 

[poke5353]

Re: 5.56 Primers

I was at 23.1 before these and didn't notice any issues

 

[Beef82]

Re: 5.56 Primers

They're not flattened, tryin to read primers is kinda pointless, its not neccesarily indicative of anything.
The circle spots where brass is flowing into the ejector on the cases on the left and on the bottom, well that's a pretty good indication of pressure.
Also a couple of those have nice straight lines directly across from the ejector marks, look like your extractor was trying to pull the rims off which is caused by too much pressure, a pressure curve that doesn't match port location/size, and/or too light of a buffer causing the bolt to unlock before the case contracts.

 

[poke5353]

Re: 5.56 Primers

So I am assuming I should back it down a bit and go from there huh?

 

[Beef82]

Re: 5.56 Primers

Yep, pronounced ejector marks like the ones that appear on some of your cases are bad.

Also check your case rims, if the extractor is pulling them so they're no longer flat either the loads are hot, the chamber extremely fouled/rough or the rifle is in need of some tuning. A ripped rim and brass pieces floating around in the chamber can cause one hell of a jam.