Home Forums Hunting & Shooting AR and Tactical Rifles Tac 20 build (pic heavy)

I found myself in possession of most of the parts to slap together another AR upper, and happened across a set of 20 Tactical dies by Hornady so I thought I'd try one. I'll be machining the barrel from a Black Hole Weaponry blank, so I thought I'd post some pictures of the process here for anyone who might be interested. (And I figure it's fair to call this a "build", since I'm actually making the barrel myself.)

Here's the parts I'm starting with, still need a handguard. AAC receiver, some sort of nitride BCG, generic adjustable gas block, and a Fail Zero barrel extension. The truck axle is a 24" .20 cal 1:10 blank; basically a solid bar with a rifled bore. Pardon the low light cell phone pic.


This'll be a work in progress; I've just started and will be working on it as time allows so I'll update the thread as I go. I'll add a few more pics below though.

Looking forward to seeing how it turns out. Are you going with a BHW blank primarily based on getting a good deal, or do you think they’re on par with other quality SS button blanks? Say Shilen, Criterion, X caliber level...

I’m asking because I’ve had a couple of AR barrels from them that shot well, but I don’t see BHW mentioned nearly as often on rifle forums as I did a few years ago

A little about the cartridge itself - for those who don't know, the 20 Tactical is just a 223/5.56 case necked down to 20 cal, and the shoulder is pushed back to 30 degrees. The body/shoulder junction doesn't really move, so it doesn't take much to bump the shoulder back, and it gives a longer neck. Velocity numbers often quoted online for 24" barrels are 32gr @ 4200 fps and 39/40gr @ 3900 fps, essentially duplicating the 204 Ruger but with plentiful 5.56 brass and plenty of room in an AR magazine. Those numbers might be a little optimistic, but we'll see.

One thing I've discovered in my online research of the 20 Tactical, and then actually sizing my own brass, is that most of the "internet wisdom" about this cartridge vs the 20 Practical is wrong. Most discussions about it claim the Practical is so much easier because you can use 223 bushing dies and swap bushings. However, that assumes you're already using bushing dies, and also requires several steps to neck down with bushings. The same sources claim the 20 Tactical is difficult to bump the shoulder back, and many list fireforming as another downside. I'm pretty certain most of those are just repeating what they've read without any experience with the 20 Tactical.

With these Hornady 20 Tactical dies, forming cases is done by just one pass in the sizer die. That's it. It doesn't even take appreciably more effort than just normal 223 case sizing. The case length shrinks by about .004" on all the different headstamps I've tried so far. None had any trouble with the shoulders, including Winchester brass, and no fireforming is required. For my uses this is ideal, because I intend to just start loading with processed 223 brass, and don't want to turn case necks, fireform, or mess with necking down in stages with a bushing die.

20 Tactical on left vs 223 on the right.


20 Tactical vs 223 brass


a small handful of different headstamps sized to 20 Tactical, with one 223 case on the left

Walter - good question, and the answer is a little of both. BHW's retail outlet has a number of blanks in stock and ready to ship for reasonable prices, but I've used several of their barrels now and have been very impressed with them; they're accurate, fast, and foul as little as any other barrels I've ever used. I think you don't hear of them partly because the 3-groove "polygonal" Caudle rifling is just different and scares people off, but I've had really good luck with it in 6.5 Creedmoor and 243 LBC.

Also, I've been doing machine work since the mid-90's, but this BHW blank is one of the nicest barrels to machine that I've ever worked with. Partly that translates to good bore and chamber finish, but it's also just a pleasure to work with.

Thanks for the answer and for the informative post

Before I started on the barrel, I figured I'd check bolt lug contact in the barrel extension, and lap the face of the upper receiver.

Wrong bolt in this pic (that's a Grendel bolt), but you can see how the bolt and barrel extension lugs interface in an assembled upper:


Bolt lug engagement was adequate but not ideal. You can see less contact on some of the lugs; this was a result of the receiver face being slightly out of square.


My lapping fixture in the receiver. The fixture is a Brownells receiver extension, I bored out and pressed on a large nut, then turned the face square for lapping.


Where the lapping action happens:


Results of the first pass are pretty good. Could stop there but might as well take it a little further. We're looking for bright white lapped area all the way around, or close to it:


I'm calling this done. Looks like a low spot at 3:00 on the face of this receiver, but we have enough contact everywhere else that it won't matter:

Neat project & should be a great round; really great that one pass through the sizing die get's the job done.

I'm sure it will turn out well; good luck with it & keep us posted on the results.

MM

This looks like a great thread! Thanks for posting and keep it going.

Got started on the barrel, and will be reaming the chamber tonight or tomorrow.

Truing up the barrel with a fitted bore rod. This required turning a tool steel rod to .1993" to fit the bore in this barrel. The barrel is held only by the first tooth of the chuck jaws (blank is oversized so I turned a locating ring that is centered to the bore), and located at the rear with a spider. This allows me to adjust the angle of the barrel in the chuck to align the bore. Usually this is done with a 4-jaw chuck, but I got lucky with this very well zeroed 3-jaw. I adjusted the spider until neither indicator needle moves when rotating the chuck.


Located at the rear by a spider:


Facing the blank:


Chamber end of the barrel is ready to thread. The section to be threaded is .810" OD x .620" deep, and will be threaded 16 TPI to match the barrel extension.
That second step sticking out of the chuck is the 1" OD the barrel will be at the chamber end before tapering or stepping down the profile. Lots of material to remove from this 1.25" blank!


This pic shows the raised ring in the blank where the first tooth of the chuck jaws grip:


This is a different barrel, a pre-chambered BHW blank in 243 LBC, but it shows what the 20 Tac chamber end will look like after machining, before the barrel extension is attached.

One more update before the holiday weekend; got the barrel threaded and chambered, pics below.

I like to stop after the first light pass with the threading tool (only a few thousandths deep) to double check the thread pitch; easy to correct it now if it's wrong, but a lot harder later.


Threads are complete so the barrel extension threads on with a close fit. This is also the time to adjust the barrel shoulder to "time" the barrel so that it points either up or down, rather than off to one side; just a little accuracy trick that usually gets skipped in production barrels.



Now time to ream the chamber. This reamer has a floating pilot, so I chose a pilot that is a close fit to the bore. The Caudle rifling in this barrel has a larger bore (not groove!) diameter than standard, at .1993", so I used the largest pilot available at .1986"; not quite as close fitting as I'd like but close enough to work well.
With a small reamer like this, there isn't a lot of room for chips, so I only cut about .060" at a time and then retract the reamer to clean the chips out. It does get tedious, but gives better results than just ramming the reamer into the bore till it's done. I use lots of cutting oil on the reamer.


Part of chamber reaming is setting headspace, this is the equipment needed to do that. Go/no-go gauges, a good caliper (and also feeler gauges, not shown), and the bolt and barrel extension.


Setting headspace in AR barrels is actually pretty easy when done this way - by screwing the barrel extension on over the bolt and Go gauge, the gap between shoulders of the barrel and extension can be measured. This measurement shows that I need to advance the reamer another .3585" deeper to close on the Go gauge.


Headspace is now correct, with the bolt able to close on the Go gauge (as shown) but not quite on the No-go gauge. In this cartridge, the difference between the Go and No-go gauges is .003", so I chambered .002" deeper than the Go gauge. The sizing die will be adjusted to match that setting of course.

Yodering,

Where do you buy your barrel extensions, and bolts at ?
I’ve been thinking of making my own 204 ruger barrel for my AR’s, I have the lathe, but only do bolt work right now.

I’m looking forward to seeing pictures of drilling the gas hole in the barrel.

After chambering is complete, I cut the feed ramp. A lot of commercial barrels cut the feed ramp deeper, but I prefer a shallower angle for more case web support. I cut a 30° angle to .100" larger diameter than the chamber (.050" per side).


The final step is to lightly polish the feed ramp and break the sharp edges with emery cloth, and burnish the chamber. I use 0000 steel wool wrapped on a bristle brush for burnishing; we want a tight fit that will apply lots of pressure.


Final result - a clean smooth chamber and feed ramp with no detectable roughness or rings in the chamber.


That concludes the chambering part of this job. What remains is to profile the barrel, size & drill the gas port, and thread the muzzle; I'll share progress of those as they happen but it may be a few weeks from now.

I get my barrel extensions from Brownells. This one is a Fail Zero extension (about $25) but I have had really good results with the uncoated steel extension Brownells sells for ~$18.

I don't have a favorite source for bolts, usually just shopping around for whatever fits my needs.

That 204 Ruger barrel would go pretty much identically to this 20 Tac. I highly recommend the blanks from True Sporting Arms (that is BHW's retail outlet); they had this 1.25"x24" 20 cal 1:10 blank on sale for well under a Benjamin even after shipping, although if you pay full price they are fairly expensive. This is one of the nicest machining barrel blanks I've worked with though, it makes the machine work a real pleasure.

All my parts for builds have come from White Oak Armament or White Oak precision, I used to buy barrels chambered with bolts from them... not that I have my own lathe I could do it myself, however I’ve never seen anyone drill the gas port yet... so I have reading too do. I have built multiple HP competition AR’s so I have all the other piece parts, and as you showed headspacing the barrel extension isnt’ much different that you do with a bolt gun.

Thanks great information. In the posts.

OP great post thanks

I'll definitely post some pics of that when I do it. It's fairly simple with the right tools. I do it in the mill so controlling the depth is easy, and stepping up the size in small increments with sharp drill bits minimizes the burr on the inside. Sharp drill bits are the key though; I only use them a couple times for gas ports and then replace them.

Outstanding!

Love the pics!

This is a great thread !
You remind me of my now passed on retired NASA machinist friend.
He was very anal about whatever he did.
Made me some awesome shooting rifles.
This is very informative about ar's.

Ever get you stock back ?

No........