Lowlander

Here's a good reference on correlation between barrel length and velocity in 308: https://rifleshooter.com/2014/12/308-winchester-7-62x51mm-nato-barrel-length-versus-velocity-28-to-16-5/ The difference really isn't much between 16" & 18", the barrel tested above was cut to 16.5" actually, I'm not sure if that 0.5" makes any difference at all, but velocity was 2466 & 2523 respectively, on the 168SMK. It's also worth noting that "stiffer" barrels are usually more accurate. Shorter = Stiffer... A 16" or 18" barrel will make hits at longer ranges, the difference between the two is minimal. Plus every barrel is different, some shoot faster than others. You are going to have to work up "dope" no matter what length you have, out to the range you wish to shoot it too. All that said, most factory barrels are going to be a little more frustrating to get dope for. Because they just aren't made to the same tolerances a lot of aftermarket/custom barrels are. There's always an exception, I've seen factory 700 barrels shoot on par with a custom job. They are rare, but some do. It depends on what you are wanting to do with it, do you just want to ring steel at longer range? Hunting? Match shooting? That will determine a lot of what you want out of a replacement barrel. It all depends on what your intended purpose is for this rig. I think that will help everyone point you in the right direction, if your looking for recommendations?

No problem, if you end up swapping barrels try to get a headspaced bolt with it. A lot of places will do this for you free of charge, just the cost of the barrel/bolt. All they do is disassemble a bolt, verify it is properly headspaced to the chamber of "that" barrel, reassemble and ship it if it checks out. Then I always check it myself when it arrives. If you don't have headspace gauges for it, I would order a set too. All you really need is GO and NO-GO guages. Take the ejector out of the bolt prior to checking. I like my 18" 308, it strikes a pretty nice balance and isn't terribly wieldy in the brush. Are you re-barreling it to try to get better accuracy? If so, the quality of whichever barrel you choose will be important. Quality large frame barrels are spendy, I have had good luck with Criterion 308 barrels, they are a little more than a Ballistic Advantage and they are a better barrel in my expierince, they also make 6.5CM barrels for the large frame if your wanting to go that route. Rainer Arms makes good 308 AR barrels, ready to order. If your wanting a full custom job on a Bartlein, Kreiger, etc blank, Craddick Precision turns some nice tubes too...

I second this, headspace gauges are of paramount importance. I can't even imagine how many people are out there today, assembling ARs from a market saturated with parts that just go together too easily... I've seen this happen first hand, on a 5.56 small frame AR, home build. The guy brought the gun to the range where we were shooting after having just assembled it. I can't say for sure what the exact cause was, but something was out of spec: barrel nut loose, improper chamber, etc... I was down on the 100yd side, he was down on the 25yd. I watched him chamber the first round and the bolt wasn't closing right. He was messing and fighting with it and it caught my attention. It hit me, I thought: poop I better say something. Before I could get a word out, he finally got a round to chamber after popping the forward assist over and over. He threw the gun up on target and pow!! Looked like a frag going off in his face. I knew he was hurt, he was still in shock, standing there dazed holding the rifle in his left hand, right hand shaking and just starting to drip a good stream of blood. He says: What happened? I can't see anything... I told him to lay the rifle down pointing away from anyone. I took cover behind a berm til he kneeled and laid it down. It shredded his firing hand pretty bad, looked like a hit from about a 20ga shotgun. It blew the bolt carrier sideways out of the ejection port. It blew the mag out of the lower and the spring, floorplate and live rounds just scattered. He took some shrapnel, to his right hand and a piece or two in his forehead. Damn he was lucky, to be honest. We got him out of there via ambulance. I will never forget it. The moral here is, these rifles are WAY too easy to assemble. They are dangerous as hell if everything isn't built exactly right. Headspace gauges are a requirement in my opinion, I have a set for every cartridge I use. For the price of a box of ammo or two, they are worth every penny. With all the AR barrels and parts on the market, I know there's tons of parts out of spec out there. It's easy to get excited about a new build and rush into firing it. We all get it... I will not fire a ANY firearm without it, period. Even if it's a factory new rifle, the tolerances are so small, they must be checked prior. Buy them, don't take that chance. Buy them from a reputable manufacturer too: Forster, Clymer, Manson... I own Forster and Manson. I'm sure there's many of us here, myself included, that would be more than happy to help you out like Anderson3754 has offered to do. Every round fired without checking headspace is pure luck. It also needs to be recorded, from prior to shot #1, through the life of the firearm. Because there are a myriad of ways it can change, a $30-$40 gauge beats a trip to the ER or worse, every time...

Looks like it is standard DPMS pattern bolt/barrel combo. Found this on BARF.com, here's a link: https://www.ar15.com/forums/AR-15/SA-Saint-Victor-308-/121-745624/

Finally got a free minute to update... I tested out the new hammer spring on the RRA trigger Sunday. Everything functioned perfectly, no FTFs and no pierced primers. So looks like the light hammer spring was the culprit. I have a Rem 700 I'm in the middle of building right now. After I get it all sorted I'll be back to finding a decent optic for my Stag 10. I haven't gotten into high end optics yet, just hasn't been a priority yet. I am running an old Simmons 2-10x on it just as a basic hunting scope. It is reliable so it's better than irons I suppose. I am excited to see how this rifle does out to 600yds. That's basically the limit of what I built it for. It really loves FGMM 185gr Juggernauts which should be a good bullet in 308 for the wind. My DA is low where I live, 800'-1100' ASL on average so I need every advantage I can get. I'm really liking the looks of the Arken 4-14x: https://arkenopticsusa.com/SH4-4-14X44-FFP-MIL-SHR-Reticle-with-Zero-Stop-30mm-Tube-p139429111 It has a lot of features I'm looking for and the price is pretty good. Still about 4-6 week lead time, they are pretty new. I already have a Sig Alpha 2 30mm 20MOA one piece mount for whatever glass I end up with. I'm hoping this will get me out to 600yds and be a tough scope. My rifles get a lot of use. I shoot a lot of inclined shots so a cosine indicator may be in store for it after I get glass for it.

It is a locking detent that keeps the end from threading its way off during firing. They made 2 versions, the one pictured is the Gen 2 CQB. I actually had the Gen 1 CQB but they are functionally identical. The Gen 1 has a "Krinkov" looking front end vs. the Gen 2 has full squared prongs. The purpose of the threaded end cap is so that you can disassemble and clean the carbon out of the inside of the brake. The detent keeps it locked in place. You can time the brake via shims or a crush washer. A trick I use is, I'll take a crush washer and lay it flat on a flat file and just slide it back and forth, removing material from the chamfered side until the brake/flash hider times into the correct position once torqued. It's a little time consuming and tedious, but using this method I can time just about any muzzle device with a crush washer in 30min or less without shims. You just remove material from the back of the crush washer until the muzzle device is properly timed. My CQB brake was definitely the most effective brake I used on any of my 7.5" builds. The design of it acts similar to the blast chamber of a suppressor. While not fully sealed as a suppressor would be, my thought was it would be the closest I could get to that without running an actual suppressor. Most cans aren't going to handle the abuse of that 7.5" blast and risks a baffle strike from bullets that don't fully stabilize in the short barrel...

I've been down the 7.5", 5.56 road before, they are a pretty cool little set up. But yes, they will jar your head without something to direct the concussion forward. With an A2 you'll feel like yours eyebrows may get burnt off, lol... I ran a KAK flash can on a 7.5" 300blk. It did ok directing the blast forward. Your gas port seems to be about right. You'll want it to be small as possible by the time your done tuning most likely. I do recommend a pigtail gas tube. As far as muzzle devices go, I went this route: https://www.primaryweapons.com/product-url-5232 The CQB was the best muzzle device hands down on my best running 7.5" 5.56. It was a Pac-Nor barrel spec'd to Noveske Diplomat specs, I can't remember the gas port size but it was definitely on the small side. If you want, I can contact the gentleman I sold it to and get the dia. Out of 3 7.5" 5.56 barrels I've owned over the years that Pac-Nor ran better than any other hands down. Another good muzzle device option I meant to try was a Surefire Brake with a Surefire QD Warden attached. Pricey but I imagine it would help. The direct thread Surefire Warden may also. I sold my 7.5" off and now the shortest I run is a 10.5" 5.56. 11.5" is the sweet spot for SBR.

Thats my back up plan. I have the PNT Trigger in another lower so swapping it back would be no big deal... Hopefully I'll be able to get out tomorrow and test it out.

I do hunt whitetail for the most part. I also take every opportunity to tag a coyote with it when I can. Every once in a while we will have a rash of feral hogs. They are really destructive and are fun to hunt, the 308 does a good job of dispatching them.

I guess I'll throw in here too... I love AR's first off. I've owned a bunch in small frame platform. Secondly I hunt, while my 6.8 SPC's are great for hunting, the 308 gives me more range and its easier to come by 308 ammo vs. specialty small frame rounds like the 6.8. Years later I have tons of 6.8 ammo and reloading components, but my 308 is my favorite hands down. I guess it boils down to the confidence the 308 gives me when hunting and I just prefer to shoot AR's.

Looking forward to the 308 thread PaddyMac. I've machined several small frame lowers, Matrix was the brand iirc. I'm going to be going down the 308 80% lower rabbit hole soon too. I've got to get one ordered to check if it's going to fit my upper. My set up is slant cut so I'm limited to just a few options for 80% lowers. Great thread by the way. Pics are great and it looks like you have been baptized into the world of 80% fitment issues, lol. Good work...

52degF that day.

It's all good, I've got thick skin so no worries... I appreciate all the welcomes so far. Definitely a good knowledge base here.

Hey everyone, I'm new here on the forum. I've posted a few odds and ends around the site. But I thought I would post up an issue I had recently with my 308 build. I have gotten tons of great info from here over the years just from people posting similar issues to what I was having. So I figured I would contribute one. Fair warning, I do tend to ramble on and on and on sometimes. I do try to break it up into paragraphs at least and use the best grammar and punctuation that my WV public school education can afford me. So... Apologies if the thread gets unbearably long. Here's a breakdown of my rifle. It is a home build and one I researched a lot prior to building: - Stag 10 Receiver Set. - Seekins SP10 Barrel, 1:11.25, 5R, 18", Intermediate Gas System, Smith Vortex. (Rock Creek Button Blank). - Toolcraft Nitride Carrier, JP Bolt (NiB). - RRA 2 Stage Chrome NM Trigger. - Troy Carbon Fiber 15" M-Lok HG. - Magpul UBR, running standard small frame carbine length H2 Buffer. (UBR = A5 Length Buffer Tube with Spacer Removed). - Seekins Adjustable Gas Block. That pretty much sums up the build. I run either Magpul or ASC mags. It mostly consumes the following ammo: - Federal Gold Medal Match: 185gr Juggernauts. (Best Groups) - Federal Gold Medal Match: 175gr SMK. - PPU 168gr Match. - IMI 147gr FMJ. (Plinking Ammo) - Handload: 168gr ELD over 39.5gr H4895, LC Brass, Federal 210 Primer. From day one, this rifle has ran flawlessly, I've recorded 426 rounds so far of all the above ammo mixed. I originally had a BCM PNT Trigger in this rifle for the first 420 rounds. I replaced the PNT Trigger a little while back with the RRA 2 Stage. When I did this, I also swapped in a bit lighter hammer spring. So I take my rifle out to shoot, try out the new RRA trigger. I had dry fired it over 100 times prior to this and everything was properly lubed and ready to roll. I hit the ground (prone), lined up behind the rifle and started firing a 5 round group at 100yds. Ammo being used was the (cheap) PPU 168gr Match. I figured since its a new trigger and I'm just function testing, just shoot the PPU until I have confirmed everything is running properly. I fire 3 shots, on shot number 4 I get a "click"... So I stop and run the charging handle, a live round ejects. I look it over and there isn't so much as a mark on the primer. So I go check put the brass from the previous 3 shots and one of them had a pierced primer. I pulled the bolt carrier group and found that a tiny "cup" had been punched out of the PPU primer and had stuck on the tip if my JP firing pin. This is turn jammed the firing pin back into the bolt face and wouldn't allow it to protrude. So I cleared everything, and thought maybe it was a fluke? Soft PPU primer? I got down and tried one more time. Shot#1 fired and cycled fine, shot #2: "click" FTF again... At this point I assumed it was the trigger since its the only thing that had changed. This rifle normally eats any of the ammo I listed above, including 80rds of the PPU, prior to the trigger upgrade without a single issue. No cratering on the primers either, the JP has a smaller firing pin tip and tighter opening in the bolt face. Which is one of the reasons I'm running it. So... at that point I pack my 308 in for the day. My thought was, lighter hammer spring and possibly lighter hammer on the RRA 2 Stage? I ordered a couple heavy hammer springs, installed the spring and tuned the RRA disconnector (polished the surfaces) so it would reset a little more crisply. The heavier hammer spring made the RRA reset a little sluggish at first. Many dry firings and a little light polishing the contact surfaces and its resetting perfectly. The heavy hammer spring didn't affect pull weight much if any. It did give the first stage a little different feel, but still a nice trigger pull. I'm going to give it whirl this weekend and see if that heavy hammer spring solves my pierced primer issues. That was my thought anyways seeing as the trigger was the only change made. A lighter hammer spring not applying sufficient force on the firing pin would allow this to happen was my thought on it. I suppose it could possibly be unlocking a bit too soon also? Gas is adjusted right on the money, not running hot or anything. Brass is being ejected to 3-4 O'clock with all ammo listed. Thanks for reading my gigantic post. I like to try to be thorough and thought maybe some of you guys have seen this before?...

Well I guess I'll bump this thread up for you guys since I'm new here... Slow day at work so I figure what the hell. I've actually used this site more times than I can count along my 308 journey. I've gotten tons of great advice and info just from Google searches where this forum would have posts that were related to my searches. I figured now is as good a time as any to join up and try to return the favor. I'm no guru by any means, but I'm a large frame AR fanboy and I've picked some stuff up along the way. If nothing else, I can answer some noob questions for a while that I figure you guys get tired of answering, lol. I pretty much eat, sleep and live guns and long range shooting and if I survive long enough, hope to retire with a little custom rifle shop that I'm slowly piecing together little by little. So until I have the dinero to make that a reality, I figure I should learn what I can. Diagnosing problems and custom rifle builds are something I see a lot of on this forum. It's also something I'll need to be knowledgeable about so, getting some practice and looking to learn...

I live pretty much smack dab in the middle of the state between Charleston and Clarksburg... I do work down that way from time to time. We have a coal sampling system at a mine near there. Anytime there's a breakdown or rebuild I get to spend a little time there. It's definitely a "country" place, lol. Thanks for all the welcomes...

Looks like an Anderson AM10 upper to me. So it appears to be the same make/model as your lower. It also appears that your handguard is not an Anderson handguard. If I am thinking right, the Anderson AM10 has a bit different rail height than anyone else, so to get the upper and handguard top rails to match up properly, you'll have to go with an Anderson handguard. That's why there is a height difference between your upper rail and the handguard rail. But your upper does appear to be the matching AM10 upper that goes with your AM10 lower. If the height difference between the upper rail and handguard rail doesn't bother you, then it's not that big of a deal. I'm not a huge fan of the Anderson handguard, so you may have a more functional rail with what you have on there despite the height difference. Also I'm pretty sure the dimensions on the AM10 upper/lower are proprietary. So they really will only mate up with other AM10 uppers/lowers. I'm new here so some of the other guys here may have different info than I do? Back when I was looking at builders kits that was one of the things that steered me away from Anderson... Other than that, you should be able to swap in any DPMS/SR25 pattern barrel onto the upper as I understand it. Most 308 AR barrels are this pattern so you should have no issues finding what you want there. Hope this helps and feel free to correct anything that's incorrect, I'm new here too like I said... ETA: As Belt Fed posted, the keyhole is just a forge mark. Cerro Forge is pretty common marking, the machining is done by each manufacturer.

On AR barrels, large or small frame, the gas port won't line up if you make any adjustments to the barrel/extension interface. On most bolt actions you can cut the shoulder back which in turn allows the barrel to screw in further. Decreasing headspace and allows some adjustment. Once a gas port is drilled into an AR barrel and a barrel extension installed, it is pretty much permanent. Hopefully your KAK barrel will headspace properly with a 308 bolt. I do agree with 98Z5V that you should check it with headspace gauges once it's built and the barrel is torqued properly. Just remember to pull the ejector out of the bolt so it doesn't give a false measurement. I'm a big proponent of headspace gauges for any cartridge you run. They are worth the money to ensure your rifle is safe to fire. Most ARs are chambered so that headspace is within spec to a standard bolt dimension. But there's always an exception, better to err on the side of caution especially with a more uncommon chambering like the .358Win. Best of luck and let us know how it goes...

Hey everyone, glad to be part of the forum. I've gotten some great info from this site and figured it's time I join up. I've gotta say, I'm a big 308AR fan. It was something that started years ago when I got an Armalite AR10A2. 20" barrel and I really loved it. But ended up parting with it due to the A2 upper being difficult to mount optics. This was back in the day when AR10 parts were pretty much nonexistent and as simple as it would have been to swap out to an A4 upper, I didn't want to separate the original A2 upper from its original lower. Plus, I never found an A4 upper, lol. Anyways, I went several years going through a HK phase. Built a couple 91's and a pretty nice heavy barreled 91 on a PSG1 receiver. The HK91 is a great battle rifle, but after much $$ the precision I wanted wasn't there. The more recent flood of 308 AR parts and rifles on the market allowed me to finally build what I wanted. I built on a Stag 10 receiver set. Rock Creek 18", 1:11.25, Intermediate Gas, stainless 5R barrel. Toolcraft Nitride Carrier with JP bolt. RRA Chrome 2 Stage Trigger, UBR stock running a H2 buffer, Troy Carbon Fiber 15" M-Lok rail and a Seekins Adjustable Gas Block. I love the rifle, I have a hard time shooting anything else sometimes. I'm getting ready to figure out a decent optic for it. I've got a cheap place holder 2-10x hunting scope on it now just to be able to shoot it. I have a Liberty Mystic X can in NFA jail that will reside on this rifle most the time. I've got 2 spare Stag 10 uppers that I'm going to start building soon. One will be short at 14.5" and the other will be a 20"+ most likely in 308. I may go 6.5CM, though I hate to stock another cartridge in the ammo pile, I may just try it out. Anyways, sorry for the huge post, lol. Since I'm going to be building these 2 uppers soon I figured now's a good time to join. I need to source a couple 80% lowers for this set up too. The Stag 10 being pretty much SR25 spec, DPMS High and slant cut. I wouldn't mind having a couple spare lowers. I already have a nice 308 jig and all the tooling ready to roll. Thanks for reading and I'm looking forward to being here on the forum...