Ceratac AR-308 Build

[98Z5V]

20 hours ago, Lane said:

 Looks like simply buying weights might have been a bit premature.

 

 

Nope, you're okay.  You buy some tungsten weights?

Buy this buffer, when it comes back in stock:

https://dsgarms.com/dsg-4201-0021

It's a stainless steel body, filled with steel weights.  Replace those two steel weights with two tungsten weights, and you'll have a buffer that weighs 5.15oz. 

Sign up for the email notification on it, when it's back in stock, and snatch it as soon as you see that email...

[Lane]

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.

Edited October 12, 2018 by Lane
learning

[Matt.Cross]

Holy mother! That's a Unimat! That's a rare little gem!

[98Z5V]

6 minutes ago, Lane said:

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.

What you're doing here will benefit so many people in the future - so this is an investment, of sorts.  You are the one that laid the groundwork, and did the hard work. 

In a 2.5" buffer, only two weights will fit.  Hang onto that extra tungsten weight, because it can turn another buffer in the future into something else.  Standard to H1,H1 to H2, H3 to H3... that's insurance, when you need it.

2 of those weights need to go into the buffer I suggested, to get the weight I specified. Done it already.

Now, you have options - with the skills you have.  Don't machine an aluminum body.Machine a Stainless body.  If you "match" the profile of a regular 2.5" buffer, made of stainless, include 2 tungsten weights, you'll be 5.15oz total. If you don't taper that stainless body, after the spring-capture point, and you bring that body down FAT, you'll be at a 5.7oz buffer, overall...  

[Lane]

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. 

[Lane]

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. 

[Lane]

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.

[98Z5V]

Hit this thread, man - I go all the way through it.  Notice that RRA buffer at the end of the thread...  that body doesn't taper down after the spring capture point.  That's where you gain the extra-extra weight. 

 

[Lane]

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. 

[98Z5V]

1 hour ago, Lane said:

I can also neglect to hollow out the entire depth for weights if I don't need as many. 

 

You need every bit of the depth, in order to get two weights and two pads in there.  All of it.  That shorter RRA buffer (short by 0.250") would only accept weights, and not one single pad...

[jtallen83]

5 minutes ago, 98Z5V said:

You need every bit of the depth, in order to get two weights and two pads in there.  All of it.  That shorter RRA buffer (short by 0.250") would only accept weights, and not one single pad...

How much room to move do the weights need, if any? I have read it is there to prevent bolt bounce but that shouldn't be an issue on semi, never hear that issue come up here.

[98Z5V]

Bolt bounce is only an issue in a semi  - you'll never get bolt bounce on anything else but a semi-auto.

87GN did a bunch of videos on it, for his blog. 

 

 

[Lane]

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. 

Edited October 14, 2018 by Lane
not sure

[jtallen83]

22 minutes ago, 98Z5V said:

Bolt bounce is only an issue in a semi  - you'll never get bolt bounce on anything else but a semi-auto.

I should have expanded some, thought bounce only caused issues in full auto?

The space for the weights is there to spread out the impact time and prevent bounce, heavier weight sees less bounce, got that. Would not a heavier buffer with no space for the weights or solid still bounce some?

Ever hear of any documentation on what space is needed for the weights to have the correct delay or movement inside the buffer?

Sorry Lane, didn't mean to hijack your thread just trying to get every bit of info I can on the topic from 98, he's busted more than a few urban myths for me!

[Lane]

2 hours ago, jtallen83 said:

Sorry Lane, didn't mean to hijack your thread

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. 

[98Z5V]

These things are JUST like a deadblow hammer.  JUST like it.  That's how they work.  As designed, anyway.   Solid buffers - don't work.  Solid buffers WILL bounce on forceful closing. That reciprocating mass in a standard buffer design - all slams into each other by design.  Tungsten-powder buffers (Spike's Tactical, predominantly) work in the same manner.  Solid buffers don't do this. They bounce - when not induced by "bolt bounce" - which is real.  Just like Dolphin Rape. It's real... FOr Real...

Lane, you can't drill that thing all the way through, man - that buffer face has to be solid.  I see that buffer face that you've got drilled all the way through - that won't work.   You drill in from the backend, to the depth you need, but that face needs to "be-one-with-the-body..."  Buffer body is one piece.  One piece...  

I don't have numbers on buffer pad thickness, or buffer internal depth, but I'm gonna bust one apart right now and find out those numbers. I'll be back in a ew, with pics. 

[98Z5V]

DSG Hybrid buffer - let's break this thing down.

 

[98Z5V]

Buffer body depth 1.965".  Gotta capture that now...  post will be edited

Buffer body, stripped, OAL is 2.127". Call it 2.125".

That's enough to calculate buffer face thickness, after milling.  Buffer depth (center) at 1.965, with an OAL of 2.125" leaves you with a buffer face thickness of 0.160" - on a STAINLESS buffer body.  I'm sure it's identical on an aluminum buffer body, because NO OTHER dimensions change.  That's your buffer face thickness.  160-thou.

Edited October 15, 2018 by 98Z5V

[98Z5V]

Buffer pad thickness, I got 0.093" and 0.094", even pressure on both.  I'm certain that these are not "precision determined" items, but "general thickness items". I measured both several times, and came up with the 93 and 94 on each, repeatedly.  One is 93-thou, the other is 94-thou. 

 

I listed the lengths of the weights int he other thread.  They're 0.607" long. 

So, internal depth of the body is 1.965".  Buffer weights that at 0.607" each (1.214" per 2) and buffer pads or 0.093" and 0.094" (0.187" combined). 

We have to account for the depth of the tail on the buffer bumper.

This pic doesn't really do it justice, but I pulled a 0.496" tail depth.

 

Mash all that together, and you can determine how much "bounce" is going on in there.  Take that depth of the tail OFF the internal depth of the buffer body, because it goes down into it...

So, 1.965" - 0.496" is the available depth inside the buffer body.  = 1.469" available space inside the buffer body, capped and pinned.  The pads take up 0.187" and the weights take up 1.214".  You have 68-thou running around in there to bounce around.  About the thickness of a quarter, as space, inside this type of buffer...

I don't know if it's more on a 3.250" carbine buffer, I don't know if it's more on a 5.200" 308AR Rifle buffer, and I don't know if it's more on a 5.900" AR15 Rifle buffer.  You have 68-thou running around inside a 2.500" DPMS-based LR-308 Carbine buffer, though.  That's how much "deadblow" you have. 

Edited October 15, 2018 by 98Z5V

[txdo_msk]

I just noticed this thread as I was wanting to build a .308 and started looking for info on...  Ceratac jigs (I bought one of their carbine)!

Does anyone know if ceratac is even worth it?  Whats the likelihood of dropping in a different lower to work?  Or is this where all these measurement are coming into play.

Stellar job, BTW.  Ive learned a lot just lurking here...

[Lane]

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.

[Lane]

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.

[Lane]

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. 

[Lane]

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.

[Armed Eye Doc]

Excellent job on the build and thanks for writing it up so others can learn from your process.