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Posted: 2/11/2015 10:50:01 AM EDT
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I finished my build about a week. I used and AERO Precision upper and lower, Brownells .308 18inch barrel and a BCG from ARES armor. The buffer and spring is from heavybuffers.com. It is the standard CAR10 Heavy buffer kit from them.
I took it out shooting with some surplus Lake City FMJ. The rifle zeroed in quick but I noticed the primers were all cratered and then I got a few FTF with very light primer strikes. Towards the end of the zeroing in I started to get extraction issues etc. I took it home and started cleaning it and noticed the firing pin was bent and the bolt face had lots of brass marks on them. I have a set of .308 go/no go gauges coming to make sure the chamber is ok. Any thoughts? I am going to see if a round with seat fully by hand dropping into the chamber. Thank you |
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Is the firing pin bent, or the firing pin retaining pin?
These kinds of things are rules of the road when you frankenbuild a .308 AR, especially sourcing critical components from different sources who aren't on the same data sheet. Every build I have done, I used the receiver set and BCG from the same manufacturer, then sent the parts off to one of the most reputable rifle builders in the Nation, GA Precision, and got back working rifles that shoot better than most bolt guns. Any pics of your firing pin and bolt face? Brass shavings are just all the sharp surfaces shearing material from the rim and case head, and this is common on mass-produced, "we don't care" parts. |
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Quoted:
Is the firing pin bent, or the firing pin retaining pin? These kinds of things are rules of the road when you frankenbuild a .308 AR, especially sourcing critical components from different sources who aren't on the same data sheet. Every build I have done, I used the receiver set and BCG from the same manufacturer, then sent the parts off to one of the most reputable rifle builders in the Nation, GA Precision, and got back working rifles that shoot better than most bolt guns. Any pics of your firing pin and bolt face? Brass shavings are just all the sharp surfaces shearing material from the rim and case head, and this is common on mass-produced, "we don't care" parts. Yes the actual firing pin is bent. I will try to upload pictures and the video of the runout guage on the firing pin. |
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Your brass is getting thrashed.
Primers are flowing into the firing pin hole, and brass is flowing into the ejector channel, then being shorn by the primary extraction as the bolt rotates when still under pressure. You have symptoms of violent, early extraction, which is usually a shorter gas system and too large of a port, combined with a large firing pin hole. Keep in mind that Lake City brass is one of the strongest alloy brasses, and yet yours is flowing like Federal brass on a CLGS 16" barrel with too large of a port. Since this is an 18" barrel, may I ask what gas system length you have? This could also be signs of a short throat in the chamber. A fast-burning 147gr load should not be showing these signs. Something is seriously wrong. To compound matters, you have a heavy buffer from Slash, which should be stopping most of these things from happening since it uses static weight to keep lock time longer for the bolt. |
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Your brass is getting thrashed. Primers are flowing into the firing pin hole, and brass is flowing into the ejector channel, then being shorn by the primary extraction as the bolt rotates when still under pressure. You have symptoms of violent, early extraction, which is usually a shorter gas system and too large of a port, combined with a large firing pin hole. Keep in mind that Lake City brass is one of the strongest alloy brasses, and yet yours is flowing like Federal brass on a CLGS 16" barrel with too large of a port. Since this is an 18" barrel, may I ask what gas system length you have? This could also be signs of a short throat in the chamber. A fast-burning 147gr load should not be showing these signs. Something is seriously wrong. To compound matters, you have a heavy buffer from Slash, which should be stopping most of these things from happening since it uses static weight to keep lock time longer for the bolt. It is a mid length gas system. Its a Brownells branded barrel. There were no reviews on it when I purchased it. Now there is one review now and they were not happy. " i purchased 2 of these barrels awhile back and the chambers are so tight that the rounds will not chamber!the chambers can not be recut because of the nitride finish .... not happy!!" |
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let us know what you find out.
[email protected] it looks like your chamber is out of spec and the brass is expanding into the firing pin hole. |
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let us know what you find out. [email protected] it looks like your chamber is out of spec and the brass is expanding into the firing pin hole. I will. I sent you guys the video of the firing pin and pictures as well. |
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And....now Im terrified to start my 308 build.  Tagged for info.It could just be an out of spec barrel from brownells. When I get the headspace gauges I will let everyone know. Looks like someone else had issues with the brownells branded barrels as well. |
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Quoted:
It could just be an out of spec barrel from brownells. When I get the headspace gauges I will let everyone know. Looks like someone else had issues with the brownells branded barrels as well. Quoted:
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And....now Im terrified to start my 308 build. Tagged for info.It could just be an out of spec barrel from brownells. When I get the headspace gauges I will let everyone know. Looks like someone else had issues with the brownells branded barrels as well. My Brownells barrel was out of spec. I had to send it back. I tried 4 different bolts and only one would pass a GO gauge. Even then, it would not chamber any mil-spec 7.62 ammo (Malaysian surplus). I sent it back and bought a Rainier Arms barrel. That barrel passed the GO and NO-GO on ever bolt that I checked. If you find that it does properly pass the gauges, I'd recommend getting an adjustable gas block to turn the gas down a bunch. Hell, I'd recommend that anyway. It makes for a nice, soft shooting 308. It worked wonders for mine. |
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My Brownells barrel was out of spec. I had to send it back. I tried 4 different bolts and only one would pass a GO gauge. Even then, it would not chamber any mil-spec 7.62 ammo (Malaysian surplus). I sent it back and bought a Rainier Arms barrel. That barrel passed the GO and NO-GO on ever bolt that I checked. If you find that it does properly pass the gauges, I'd recommend getting an adjustable gas block to turn the gas down a bunch. Hell, I'd recommend that anyway. It makes for a nice, soft shooting 308. It worked wonders for mine. Quoted:
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And....now Im terrified to start my 308 build. Tagged for info.It could just be an out of spec barrel from brownells. When I get the headspace gauges I will let everyone know. Looks like someone else had issues with the brownells branded barrels as well. My Brownells barrel was out of spec. I had to send it back. I tried 4 different bolts and only one would pass a GO gauge. Even then, it would not chamber any mil-spec 7.62 ammo (Malaysian surplus). I sent it back and bought a Rainier Arms barrel. That barrel passed the GO and NO-GO on ever bolt that I checked. If you find that it does properly pass the gauges, I'd recommend getting an adjustable gas block to turn the gas down a bunch. Hell, I'd recommend that anyway. It makes for a nice, soft shooting 308. It worked wonders for mine. I have heard a lot of people talking about the Rainier Arms barrel. Nice piece? |
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Quoted: And....now Im terrified to start my 308 build. Tagged for info.No need for terror. Many of these problems could be avoided with a set of go/no-go gauges and sticking with known-good combinations. Too many people, myself included, didn't want to pay the $70 for a set of gauges. Finally I decided it's good insurance to avoid some very bad outcomes. Plus look at what we spend on the stinkin rifle parts! I went with a Mega receiver set, Mega barrel and an RCA BCG because that's what Jason@Mega recommends. Guess what? It headspaces and shoots fine. You just can't expect the same bargain basement set up to work with .308 as it does with 556, yes, partly because there isn't a "standard." I went with DPMS compatible stuff which is about as standard as it gets in the 308 world. -Stooxie |
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Quoted:
No need for terror. Many of these problems could be avoided with a set of go/no-go gauges and sticking with known-good combinations. Too many people, myself included, didn't want to pay the $70 for a set of gauges. Finally I decided it's good insurance to avoid some very bad outcomes. Plus look at what we spend on the stinkin rifle parts! I went with a Mega receiver set, Mega barrel and an RCA BCG because that's what Jason@Mega recommends. Guess what? It headspaces and shoots fine. You just can't expect the same bargain basement set up to work with .308 as it does with 556, yes, partly because there isn't a "standard." I went with DPMS compatible stuff which is about as standard as it gets in the 308 world. -Stooxie Quoted:
Quoted:
And....now Im terrified to start my 308 build. Tagged for info.No need for terror. Many of these problems could be avoided with a set of go/no-go gauges and sticking with known-good combinations. Too many people, myself included, didn't want to pay the $70 for a set of gauges. Finally I decided it's good insurance to avoid some very bad outcomes. Plus look at what we spend on the stinkin rifle parts! I went with a Mega receiver set, Mega barrel and an RCA BCG because that's what Jason@Mega recommends. Guess what? It headspaces and shoots fine. You just can't expect the same bargain basement set up to work with .308 as it does with 556, yes, partly because there isn't a "standard." I went with DPMS compatible stuff which is about as standard as it gets in the 308 world. -Stooxie I've got my upper and lower and am piecing together a DPMS compatible gun. I'll definitely check out each part before ordering. I've gotten complacent because milspec is milspec. 308s are more work. 
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