Lane

I finally pulled the trigger on all the parts for my first 7.62x39 AR build. I'll start with a list of what is has shipped already, or soon to be. I'm not in a rush to finish this build with the cold weather, but I am excited to break in the upper. GM 21" gunsmith's barrel with no gas port. BCA side charging upper/7.62x39 BCG combo (wanted the dual charging, but they aren't in stock/on sale; compromise for the price). Standard 80% lower with pistol grip. Debating on no hand guard at all with such a thick barrel; but 15" minimum length. No idea what buffer tube length, buffer weight, or stock. I want a light weight stock because of the barrel weight for sure. Standard Mil-Spec LPK; maybe sprinkle some sand in for a good AK-47 comparison gun. C Products Magazine. Upper warming up before the new year for sure. Build photos to follow.

From a functional standpoint; yes, you could easily turn the gas block upside down. From a legal perspective it wouldn't fly here in NY state. If the firearm were to come under the scrutiny of police, the examiner is allowed to disassemble and reassemble as they see fit; the catch is they aren't allowed to do any gunsmithing. Without a gas port drilled in the barrel it couldn't be assembled as a semi-auto, with the gas block upside down it could. Having a semi-auto capable firearm with a pistol grip would make it an unregistered assault weapon (same with any other attached "feature").

This is my next build actually. I purchased a Polymer 80% lower out of curiosity (and since Ceratac didn't have a sale on aluminum anymore). I will likely swap lowers around so that particular one isn't on a 7.62x39; but, I've been eyeballing my options for that build. I want an AR without a gas port drilled in the barrel so I can legally have a pistol grip installed in NY. I'm just now finishing the wood on a Traditions .50 cal muzzleloader, and slowly working through an AK build. Seems like you might have the building bug as well...

I've done a few of their AR-15s and have no complaints. What are your plans for those? Looks like the PA65 is a DPMS style lower with a curve at the receiver extension instead of a diagonal cut of the AR-10 style SR762 type lower that Ceratac sells. That will certainly limit, if not rule out interchangeability. There are a few threads around here with a comparison image of the two side by side, but I couldn't find one of them quickly.

I found the same information on the 5D tactical website and also asked them some pointed questions. Then with some help from this forum, I cut mine without the jig based on a measurements from an early Matrix Aerospace lower (Matrix Aerospace made the lowers for Ruger's SR762). The fire control group turns to be different in both vertical and horizontal position which is why standard 5D and other jigs are not compatible. I used the live chat to ask about the no fcg option. Turns out they omit all of those parts, no pins, hammer, trigger, disconnector, or associated springs.

I can try to answer at least some of your questions. You might want to search around the forum for answers on the barrel extension. My recollection is that only the nut and upper receiver threads are different, but I don't have anything to compare with myself. The no FCG option is new, but they have a live chat feature on the website that runs during business hours. Should be able to get that answer in a few minutes when they are open tomorrow. I will say the $10 savings is laughable regardless of how many parts are removed. I would gladly buy the trigger and hammer from you for $10 if there are too many other parts missing with that option. The barrel nut is not indexed for the gas tube; the gas tube passes over top of the nut entirely. When tightening the barrel nut you simply align the holes so the hand guard (when mounted) aligns with the upper receiver rail.

I went through this with a magazine that looks very similar to that one. Mine is marked as made by ACS, and not DPMS; but the construction appears the same. This magazine wouldn't latch no matter what I did; so I removed the magazine catch from the lower. Holding the magazine in tight and looking through the hole in the mag-well, it was clear that the catch hole in the magazine needed to be opened up on the top side. Yours could be left, right, or top of course; maybe even all of the above. I did all this with the upper installed and the bolt closed. Once I figured out what was going on; I slid out the floor plate and ground the catch hole in the magazine taller with a small flat file. Then I tested, cleaned the shavings, and put it back together. Even after that; the feed lips took some wear from the bolt carrier, so I cycled it with oil repeatedly. It is likely you could modify the feed lips to the same end, but I personally assumed it better to do that as a last resort. I don't think it took my more than ten minutes all told, but I did have the punch (to remove floor plate which was very tight) and flat file close at hand. I only removed the guts of the magazine to make sure it was clean inside when I was done.

Fixed this one for you; sorry I don't have any source material for this 3-ft purple tool everyone wants so bad. You may crop as you see fit.

Thank you, I'm quite happy with the way it turned out. I hope it does help someone else in the future as I got quite a bit of help from this forum along the way. So many great topics to read about here, and some things came up I hadn't even considered with previous builds. As nervous as I was to ruin a $10 part; my adjustable gas block conversion worked out, and has held up to my light shooting so far. I also had no idea the buffer weight could make such a difference, which is something I have yet to experiment with further as time goes on. For now though; I'm simply focused on getting it sighted in the best I can, and spraying bullets out the barrel before hunting season opens in less than a week. Yesterday I nailed six rounds through the same hole in a paper target, so I think I'm in good shape.

I think I figured out my initial problems with this. It seems like at some point during adjustment I would start squinting and adjust a focus to that. When my eye got too tired I would stop squinting, my eye would see something off, and I would start the process over again. I may be squinting into other scopes without thinking about it to compensate for my vision; I'll have to be more mindful when I shoot other things. I didn't need to make any adjustment at all shooting Monday after a careful setup on Sunday.

The DIY adjustable gas block was reinstalled with a stainless grub screw. I took it outside and adjusted the screw to fail to eject, then back out a bit after the new buffer body was filled with tungsten weights. It seems to be working alright; no longer marking the bolt carrier, ejecting at 4 o'clock, scope is adjusted close to accurate. I think I am finally finished with this build, at least until it comes time to play around with more buffer weight. Until then, I'll try to keep the barrel warm.

I spent some more time with it yesterday and today. I thought I was getting next to nothing useful out of the parallax adjustment until I finally figured out that 1/64th of a turn is all I need from fully closed. I had been riding past that point every time and thought it must be my eye because the rest of the range was useless for me. The ocular adjustment seems roughly accurate distance-wise. I guess I really did just need to play with it a bit more. Having had the parallax adjustment off, the blur was causing me to get tired quickly. Still not quite sighted in but I'll get to that in time.

I am able to adjust the focus on the scope to get a clear sight picture, but at that setting the distance numbers are way off. I aim at something roughly 50 yards away and have a focus setting around 150. My eye does get tired very quickly, and I did notice I can get a clear reticle image early on. When my eye gets tired I can barely see it well enough to aim magnified to anything less than 8x.

I have not spent a lot of time with this scope yet, but I think I might need some secondary optics. I've recently remembered that I do have an astigmatism in my right eye, which is very much noticeable with 1x holographic scopes. I have not owned, or worn glasses in many years as they got destroyed long ago. I hadn't considered how an FFP scope might give me similar problems. I do drive just fine with my current vision; the left eye is nearly perfect. I searched around and couldn't find qualified information about this particular problem. I'm open to any suggestions, but at this moment I think I'm going to need proper glasses for hunting with this scope. Is that common for FFP vs SFP, or have I not explored all the settings in detail?

Nearly finished with the second bronze buffer. I took my time with this one, and measured everything very carefully. I also took the time to cut out enough of the tail end so I could mill it through for weights on my existing drill press. The hole for the weights is cut all the way to depth, and true to diameter. The last thing to do is weld up the face hole because that was just how this particular bronze stock came. I think if I take my time with the right filler, it will be fine. I also ordered a stainless buffer body with two steel weights which will be here on Monday. That way I have the bumper pads, and some steel weights to try in combination; and another body to work with. Unfortunately no adjustable gas block yet so I decided to drill and tap the one I have. I drilled and tapped for 8-32 but it looks like I can cut to 10-32 pretty easily. I'm going to pick up grub screws in both sizes tomorrow so I can try it out. I'm not sure how soon to expect the one I ordered; no reply from the seller who sent a shipping notice more than a week ago. Might as well throw it on an AR-15 if it ever does arrive. Primary Arms 4x14x44mm scope showed up, but I haven't really had a chance to do much with it. I also had to fully neuter my gun after learning that you can't truly fix a magazine here, given the way the law is written. I don't really like this Boar grip, but it was cheap, available, and very much legal.

txdo_msk: Can't say as I know anything at all about the jig. I presume it works just fine if you want to buy one. Personally I did the milling from measurements off what the Ceratac kit appears to be based off of. The upper assembly in the kit might work with any of the compatible lowers based on the measurements, though I don't know anyone that has tried. I am reasonably sure the hammer should line up to hit the firing pin; I can't swear that the takedown pins will though. I'm currently working out some issues with an 18" kit being a bit over-gassed, but it's a reasonable assumption that the 16" kit might be ok. There is another Ceratac thread in "Building a .308" where I outlined a few things I ran into; but it's no longer a complete list. There was some break-in; not everything came perfect from the factory. They also don't check the headspace on the builder kit (if you don't pay for an assembled upper). Hope this helps.

Thanks for that total buffer breakdown 98Z5V. I hadn't fully considered how the weights should be banging around in there before you mentioned it. How much worse is a solid buffer (like the one that came with the Ceratac kit)? I presume if the adjustable gas block shows up I can simply turn the gas down a little extra to get it running ok while I work out a heavy buffer solution? I didn't actually drill through the buffer face; it's just that my starting material already had a hole in it. Planning to weld that up nice and solid, but that's how I messed up the first one. I had welded up some scrap and it looked great; went to do the real thing and it got out of control. Now I remember that "Low Fume Bronze" welding rod is really brass, it spit and burned and gave off a ton of smoke when I got the buffer really hot. I've got some actual bronze rod around here that should work fine to seal it up solid, then I'll just mill it back flat again. I was able to get welds deep enough inside that hole on the first one to have extra to drill out later. I've also left a bit of extra material on each end of the buffer to be sure I have room to mill everything up clean and flat in the end. As a result of my cowboy welding attempt I have turned out another one. I plan to use my first one for more welding practice before I go ahead with the new one. The first one isn't a total lost as it didn't deform and lose anything, I just don't see it being a nice finished product. Turning a second one was required to get a center hole cut correctly anyway since I couldn't remount the old one in the Unimat's small chuck (buffer face is too big around). I need to maintain the mounting tail while I'm doing all the lathe work and then cut it off and mill it flat before the welding. I have just enough of this particular stock to make one more; but if I mess this up again I'm very likely to just buy something. Honestly, I was thinking earlier today that I could cast one in bronze almost as fast as all these other steps. I would need to get a propane tank filled though, and I can't find that particular crucible at the moment. That sounds more like a project to take on when I get all this done. If I'm going to cast a single one; I might as well cast 10 or 20 at the same time.

Hijack away. I hijacked the first Ceratac thread. I'm as interested as you in how the spacers play a role. I don't have any spacers so I'm going to have to improvise those in the short term. I'm currently digesting options to mill out the center hole for weights. I'm still stuck with a drill press I can't break down to put long bits in. The compound table and vise are centered and bolted down. I'm a hair shy on a half inch end mill. Seems like I'm going to have to use the lathe to start the opening at 1/2" and chuck up the endmill inside the buffer when I mount it for plunge milling the hole. I'm going to take my time on this part... then welding on scraps from this before I fill the tail hole. Whatever welding rod I have won't match this blend of bronze. I haven't decided what my filler material will be. Options are yellower bronze welding rod, stainless welding rod, pure copper, or melting chunks of the same material into the void. I'll have to see what sticks well first.

Sounds good; I will drill all the way in. The hole is already close to half inch so I just need to center it up and drill through. I have yet to weld the tail in as deep as I can, so I presume it will weigh a similar amount when finished.

Great, thanks for the link! I left myself some extra room and didn't mill down the long area too much; still quite a bit fatter than stock. In fact I can adjust my measurements further back and work all the way up to the chuck jaws for a bit of extra weight. I can also neglect to hollow out the entire depth for weights if I don't need as many. All told it should still weigh more than a stainless unit that doesn't taper past the spring capture given it's about 10% more dense. I have enough stock left to make more if I really need to; but I suspect I can make this one work with ease. Should be done long before the adjustable gas block shows up here.

I did go to the hardware store but didn't find anything useful as a live or dead center. I ended up turning out a quick aluminum dead center and got to work on the bronze buffer. Here it is nearly finished and looking great. The bronze is easier to machine but makes a hell of a mess which I'm sure I will be cleaning up for months. I expect the bronze buffer it should allow me much tighter control over the buffer weight without using all my tungsten weights. Not sure what this is going to weigh yet as I need to figure out if the part that lives in the spring can be larger than stock. I assume so; but it also might have issues hitting the spring along the way if it's too fat in that area.

JP Enterprises gas ring showed up today and it does indeed measure 0.650", so I probably didn't need to stretch my original gas ring. The tungsten weights showed up as well so I could finish and assemble a roughly 5oz buffer with the aluminum body I have been working on. I tried to chuck up the bronze but can't find an appropriate center point to hold in the tail stock to keep it steady. That tail chuck is quite small and the hole in the bronze is close to half inch inside. I might have to stop at the hardware store tomorrow if I don't come up with anything on my own before that. The adjustable gas block should arrive early next week so I should have a few options by that time. The scope might not arrive until Friday, but that should be everything I need for hunting season. That and another $100 in ammo to waste through it of course.

Yes; that's a Unimat, which I don't use nearly enough. I got hooked when I worked at the local makerspace, and had to have one of my own. The 1" round stock is just too much for the jaws though; they open to a bit less than 0.950". It can be a real pain to get stock this size to spin true. Here is one proof of concept aluminum body, almost finished just for the fun of it; solid it weighs about 1.5oz. Planning to do the finishing work on the drill press/mill and expect it will be well under an ounce hollow. Might try a silicon bronze one next since the density is actually higher than stainless; I've got the time on my hands. I took on this build because I couldn't find documentation of anyone who actually built one, and it seemed like a fun project. I was originally pissed off when I learned they wouldn't release the required measurements for the pocket. I'm pretty sure I would have made some mistakes without having a few measurements to go by; the pocket depth might have screwed me in particular if I weren't paying attention. I should still make up some basic blueprints to post up here as comparison; it certainly is different than anything else I had come across. The Primary Arms 4-14x40mm ACSS HUD DMR 308 scope and adjustable gas block shipped today, so things are looking good here.

I did buy three tungsten weights. That is a decent price for the buffer; I signed up for a notification when it comes back in stock. I'm still working on making my own buffer in the mean time, just for the fun of it. I cut off a piece of aluminum stock; the hardest part is mounting it in the lathe and getting it centered. Once it's spinning true, the cutting should be quite simple. I've already taken all of the require measurements. Almost nothing I ordered actually shipped yet which is a bit strange. Seems like I have some time to kill waiting. I did install a new 5 round metal magazine in this Ceratac 308 build to use for hunting. It seems to add a bit of extra support for the bolt carrier. Much more sturdy than a P-Mag, but also a huge pain to remove the floor plate. Still; I have to stay legal for hunting season and I didn't see an easy way to block out the P-Mag given the way it is constructed. I see now that they sell a limiter, but it is about the same price this metal magazine cost me. I had written to Ceratac again about the gas ring and this time they explained it was a legal concern. Apparently the lawyers told them that providing measurements could expose them to liability issues. I hadn't fully considered that myself, but I'm pretty sure they can tell me who makes each part. I'm going to try again asking a different way to see if I can get some closure on that matter. While I don't believe it has a huge effect on my operational problems, I would like to have a means of determining what it should have been in this particular configuration as sold. It's going to be nice weather today so I was thinking about taking out an AR-15. Am I correct in believing that adding a quarter or two in the buffer tube could add enough spring force to keep it from tripping the disconnector with the hammer? I'm not ready to start cutting off the tips of hammers but that particular problem is much less severe than the 308. I suspect a heavier buffer would be a better solution (since it too has an 18" barrel), but I'm pretty sure it's also a solid mass buffer, so adding weight wouldn't be simple. At this point I'm still well below the extra costs of a jig and conversion kit on this build with all the replacement parts. Not quite the great deal I thought it would be, but I sure did learn a few things along the way.

I had asked about quarters in the 308 earlier, and I wasn't sure if they were appropriate for my current situation. At the moment I have a bunch of stuff coming in the mail, but don't want to annihilate my bolt carrier with the hammer smashing for no reason (it also harms the lower). Sounds like I shouldn't try this short buffer in an AR-15; at least without some compensation in terms of tube length? At this point I'm committed to whatever it takes. At the same time, I want to learn how each of these components interact with each other.