BigBore77

You might consider Lilja. They hold numerous Olympic wins and records. I have two going now. One is 24" heavy contour fluted. I have just broken it in and it is grouping about 0.5" at 100 yds, with my reloads made for a different 308. I am confident it will be well below that when I get a load developed for it. I have not tried any factory match grade ammo yet, but might. My second is a 20" medium contour that is going into another gun, incomplete as yet. Lilja barrels are not cheap, but they give good results. Another data point js a CMMG upper I bought with 16" CMMG stainless barrel. It is grouping at 0.4" at 100 yds with my best loads tailored for it. It took a while to get the load developed, but it is sweet shooting. That shows you don't always need length to get accuracy. However, that won't be a long range gun. I dropped that upper on a CMMG lower and added a Giessele SSA Service Rifle 2-stage trigger. Total investment about $1625 to get sub 0.5 MOA at 100 yards. Good luck with your search.

I think 14.5" barrel makes it Class 3 unless the flash suppressor extends to16" and is welded. I'll buy US anyway. Price isn't that much lower than what you can get some US guns. Junk or quality, it's still from COMMUNIST China, the country that killed a bunch of US soldiers in the Korean war, just in case you youngsters didn't get the full version of American history in the "new" schooling. Just my two cents worth.

Finally the story ends. I received new headspace gages by Clymer and did the check using the NOGO from this set. The bolt would not turn on this NOGO. So my apologies to the rifle builder and the barrel maker. They were right and I had a faulty NOGO gage. I checked both of my NOGO gages in a RCBS Precision Mic for .308 WIN and found that the Forster was a full 0.001 shorter (maybe even a couple of tenths more) than the Clymer NOGO. I have had the Forster for over 30 years and used it on several bolt guns and a couple of M1-As. These were tight enough that it caused the bolts not to close, but the AR bolts headspace a little different I guess. The Forster gage has been re-marked as 1.633 since I can't bring myself to can it. I spoke with an engineer at JP and he said that the M-16/AR-15 specifications allowed the controlling dimension on the M-16 bolt to vary by a total of 0.003. The controlling dimension is from the rear of the bolt lugs to the plane of the bolt face recess. This dimension is not a Mil-Spec on the AR308s, but he thought most bolt makers probably used this allowance. JP does not. They hold their Enhanced Bolts to much tighter tolerances so the don't have this problem. So if you don't get a barrel chambered to your bolt or get a bolt supplied with the barrel, be prepared for the potential of swapping out bolts to get your headspace correct. When you buy a bolt by itself, check the lugs to see how close to 0.3125 they are and how close the face recess is to 0.125. Based on all I can find out, these are the theoretical dimensions that control the bolt's contribution to headspace. Subtracting the two gives 0.1875 or 3/16" as the theoretical distance between rear of lug and plane of recess for the controlling dimension. Since most folks cannot measure that directly, you have to measure the two dimensions and subtract. When you do, the farther you are from 0.1875, the more likely you will have headspace issues. Since there is only 0.004 between GO and NOGO, you can see why a bolt that uses up 0.003 might be a problem. I learned a lot on this go around. I guess the biggest thing to note is when there is no Mil-Spec you have to be very careful in mixing parts.

Very useful tool is Geissele Reaction Rod. It is $200 for 308 version, but worth it. You need a good vise to grab it, but once secure you can put great torque on a barrel nut with no chance of stressing or warping or even putting a scratch on your receiver. I'm particular about tools and usually wait and buy once. This is the way. If you are not familiar with this idea, it is a rod with very slick finish to fit inside receiver and has bolt lug spline to engage barrel extension. When you torque the nut the only force the receiver sees is the small amount of friction on the threads and the alignment pin. Nothing touches the exterior of the receiver so the only way to scratch it is for you to do something stupid. The rod can be clamped vertically or horizontally (or anywhere in between. It is also great for installing/removing flash hider/muzzle brake on barrels, either in the receiver of just the barrel (you will have to support a bare barrel to keep it secure). Geissele makes great stuff. Not cheap, but worth what you pay.

I have three Geissele Service Rifle SSAs and a Armalite two-stage in an AR-15 NM and i like the Geissele way better. Armalite feels great and I will not bash it, but Geissele is a step up. They provide great instructions and installation pins (great tools) with every trigger. Once sear engagement is adjusted (not hard) the second stage breaks so perfectly (I mean snaps) there is nothing but a surprise at the release. First stage is so smooth and will let off the same way. They are a fabulous company to deal with. My first Geissele trigger rubbed the front wall of my receiver trigger well, so they said send it all to them. They determined my receiver was a bit too tight and machined clearance to make trigger work. No charge to me. (I also bought both AR-15 and AR308 Geissele Reaction Rods to do barrel assembly and they are great. No clamping receivers and putting a bunch of stress on them when changing/installing barrels.) Those two trigger brands are my only two-stage experience, but I'm sold on Geissele.

Hey guy. I don't know if it's too late, but I bought a Troy Alpha rail (old style clamp) off CheaperthanDirt for a decent price and it fits DPMS low profile perfectly. They had both high and low versions a couple of months ago. I also have a 15" JP tube that does not fit. On top of that, I cannot use that tube with iron sights because the front end moves about enough to through off aim point. Just a slight bump, like rifle jumps on recoil, will move the end 0.030" to 0.040". At 100 yards even a slight front sight shift moves your hit. So I will have to put optics on this beast or trash the expensive JP tube. I have tightened the 6 tiny screws as tight as I feel I can without stripping them and it helped, but didn't eliminate problem. I have not finished build with the Troy tube, so cannot say how well it does. Bottom line is that I think the suggestion of a railed gas block is the way to go for iron sights. That way you know the sight stays put relative to barrel centerline.

The one thing they did not include in the testing was "confinement". Nothing like a GI ammo can was used. I and most of my shooting/reloading friends store ammo, powder, and primers in GI ammo cans, because we have been told that these air-tight cans are what these items need to be stored in. I am curious if anyone has any first hand experience with ammo cans, powder, and primers in a fire situation. I hope nobody has this experience, but chances are someone does. It's obvious that ammo on shelves, even stacked up in bunches, is not a terrible hazard, but I wonder about the ammo cans, powder, and primers. Do we need to take any special precautions? Any thoughts?

Guys, sorry for the delay in replying to thread, but I was babysitting for grandkids and got caught in the NC blizzard last week. Thank you all for your help, comments, and info. The following is long, but gives what I know about the issue to date. I have my upper back from the builder and the barrel is clearly marked .308 WIN. However, it could be chambered for 7.62x51 for all I know. If it is, it is tightly chambered on the 1.6355 GO dimension for 7.62x51, because it barely turns on the 1.634 308 WIN NOGO gage, with the builder supplied bolt (first one listed in the dimensions below). Note, the rifle builder and barrel company are not the same. I have ordered a new set of Clymer gages in 308 WIN from Brownells and will check with them when they arrive. When I first talked with the barrel company, I did not speak with the owner, but he called me back and we discussed the issue. He says he trys to get a 1.632 chamber (obviously a 308 WIN value), but he cannot tell me anything about the bolts he uses in the process. He also says if it just turns on the NOGO, it is safe to shoot and I should just shoot it. So what the hell is a NOGO gage for??? Now, if the bolt used by the barrel company was perfect, the chamber is 1.6325 or so, to turn on his 1.632 gage. Since there is no Mil Spec for a 308 bolt, and I still cannot find a dimensioned drawing, I don't know what the correct dimensions are, but I think the bolt face recess is nominal 0.125 and the lugs are are nominal 0.312 (my estimate and tolerances are anyone's guess). I have measured three bolts in my possession. The three actual recesses are 0.1255, 0.1265, and 0.1280 with lug lengths of 0.3110, 0.3115, and 0.312 respectively. I have used two different measuring tools (a Federal Spec depth micrometer and a Swiss made, Brown & Sharpe electronic caliper that has papers traceable to international standards), so my measurements are good to 0.0005 or better. There is 0.0025 difference in recess depth and 0.001 in lug length. This would mean an increased headspace of 0.0015 to 0.0030 for those bolts. So if the chamber made with a perfect bolt is 1.6325 or so, then adding 0.0015 to 0.0030 will make the headspace between 1.6340 and 1.6355 or more. I'm pretty sure this stack up is why the bolt turns on my headspace gage. Now I see why some of the best barrel companies supply the bolt actually used in chambering the barrel or ask you to send a bolt for the job. I have a sad feeling that many barrels not made to a specific bolt are not right with the bolt being used. I'm going to follow through and let everyone know how it all turns out, but my advise now is to only deal with a barrel company that supplies a bolt matched to the barrel or lets you send in your bolt for the chambering operation. I paid the builder about $900 for this barrel installed. It is over $600 straight out. This has been an expensive lesson in rifle building. So far I have not fired a shot from a rifle I have spent well over $3000 on.

After the builder told me I was wrong and basically screwed up, he stated he used "special tactical headspace gages for SR type rifles", whatever that means. I have searched a hundred or more headspace references on the web and only found a reference to differences in gages for pure bolt guns and autoloaders…however it was a passing reference and i could find no more info. Autoloaders do stretch brass a bit more than bolt guns, but that only means you have to work the case a little harder in the resizing die. It seems to me a .308 WIN chamber is a just that…a 308 WIN chamber???? Also found a caution to always use the same brand of gages…don't mix Forstner and Clymer or others. Explanation is that Forstner gages tend toward the minimum end of SAMMI tolerances and Clymer tend towards the maximum end of SAMMI tolerances. I guess I should buy a set of Clymer gages and check with them. Maybe that's the difference. Anyone have other info??

I will not name builder or barrel manufacturer, but I checked recent .308 WIN upper purchase for headspace and found the combination of barrel and provided bolt would turn on my Forster NOGO gage. Also tried a buddy's NOGO (same brand) and two other bolts with same result. Sent upper back to builder and he checked with his .308 "tactical" NOGO for AR type rifles and says the build is fine. Has anyone ever heard of "tactical" headspace gages for AR type rifles? I cannot find any reference on web search. Is this guy pulling my leg or have I missed a chapter in the book? ??? Any help with this issue would be great. THANKS!!

Sorry to be so slow to respond. I'm new to working in the forum environment. Lost my way on site…still not sure if this was right forum/topic to start asking help with with my problem. Very glad to hear there are dimensions on site somewhere, but how to find may be beyond me at the moment. Can anyone give me a pointer? THANKS

Hi, I found this forum while searching for detailed info on DPMS platform .308 bolt. I'm an old M1-A guy, just starting out in the AR .308 world. I am experienced in assembly/disassembly of firearms and have all the right tools recently purchased from Brownells and Geissele, but I am not a gunsmith. I just like to tinker and build. If you can get quality parts, building an AR style rifle seems fairly straight-forward. I've had a completed new rifle for several months, waiting for the company that sold me the completed upper to send the scope and mount I ordered. Finally, I got fed up waiting and decided to just go shoot it with some iron sights I picked up. Long story short, I checked headspace before taking it to shoot and it swallows the NOGO gage. It has a Lilja barrel, 24" heavy contour and fluted. Lilja has the best reputation, so I don't suspect the barrel. I think the brand-X bolt may be the culprit. I can find no name on the bolt, so cannot call that mfr. Either of two dimensions could be the problem (bolt face recess depth from front of lugs; or the length of lugs) so I am trying to find spec dimensions on the bolt, to no avail. I'd rather not name the seller, as I am still waiting for help; still waiting for response after a week. Does anyone have solid info like a drawing with dimensions and tolerances. Any other suggestions would be good as well. Thanks!!