My Ar10 Build

[dave2176]

I promised to post my barrel. I videoed it but haven't been happy with the cut down version from 4 hours of tape. Anyway I'll try to detail it in photos. I did the barrel 14 months ago, before any of the other parts. Here goes:
I've watched the video from Grizzly on chambering a barrel and follow his guidance. In the first picture the barrel is passed through the 4 jaw leaving just enough protruding for the full chamber. Notice the go gauge position and picture the neck of the cartridge just under the front of the jaws. The bits of aluminum allows the barrel to pivot a little and can protect a barrel that won't be turned later. Aluminum also has good stick to it so you don't have to overtighten the jaws to hold the barrel securely. Some people use a ring here.


The next picture shows the setup to dial in the barrel. The range rod is held in the drill chuck to keep it from turning. With the bushing of the range rod at the end of the barrel as shown (I left the bushing showing in the end of the barrel) you adjust the spider on other end of the spindle. Adjust each of the 4 spider bolts until there is no movement in the DTI needle when the chuck is rotated by hand. Run the range rod in until the bushing us under the aluminum bits where the neck of the cartridge would be. I place a yellow paint mark on the rod so I know when it's there. With the range rod bushing under the aluminum adjust the 4 jaw as you rotate the chuck until there is no movement in the DTI. Repeat the step for each position until you eliminate all movement in the DTI's needle. Your barrel is now ready to chamber.


Here's a picture of the spider for reference. Make sure you tighten the lock nuts to secure the bolts for turning.


More to come soon.
Dave

 

[Karl_T]

Great original thinking. I've always turned between centers to get the bore true to the OD. Never even thought of just indicating to the bore.

 

[rwm]

Very interesting.
What did you do for optics on this weapon?
Robert

 

[dave2176]

Great original thinking. I've always turned between centers to get the bore true to the OD. Never even thought of just indicating to the bore.

Thanks, but I learned it from Gordy Gritters. He did the chambering video Grizzly sells. Here's the dial in part.

Very interesting.
What did you do for optics on this weapon?
Robert

I have a 6-25x56 scope right now I grabbed off EBay.

 

[dave2176]

Here's more on the chambering. The next step was to turn the end to diameter.


Cut the section for the threads.


Cutting the threads. I'm using a left-hand insert threading tool upside down, lathe running in reverse to cut the right hand thread.



The bore is pre-drilled to remove some mass and save the reamer. Don't go deeper than the reamer's bushing can reach. Otherwise the reamer could run free and damage the reamer and/or the bore.


After drilling run a boring tool in the bore to make sure the drilled section is true. Don't want the reamer being pushed to one side because the drill ran off center.


Start reaming. I cut about .050" before removing the reamer to clean the bore and reamer. Lots of cutting oil. I use Viper's Venom.


Blow the bore clean after removing the reamer.


Continuing 0.050" at a time. The marker gives be a point I can cut to before I need to start checking head space.


Making the first test fit. You can see in the second image with the bolt in it that there is a gap in between the barrel extension and barrel. Measure the gap with a feeler gauge. That is how much is left to reach zero head space.



The self made go gauge says we are a go. With the extension hand tight the bolt can be rotated.


Make the go gauge into a no go gauge by adding a piece of scotch tape to the end. This adds .002" to the gauge. Cut the excess tape off with your pocket knife.


My goal here is to have 1 piece of tape fit giving me at least .002" head space. This is important to the semi-automatic action. They require a bit more clearance than a bolt action will. A second piece of tape will not fit with the extension hand tight. This gives me at least .002" head space but less than .004". Once the extension is torqued down you will lose another .001" of head space.


At this point clean up and emery cloth the bit of the barrel sticking out of the jaws. This area will be gripped to turn the outside profile.

Dave

 

[dave2176]

Forgot the picture of cutting the feed ramp and the finished chamber.



Hope these pics are useful.
Dave

 

[rwm]

Really beautiful. I cannot believe how nice your threads came out. What RPM were you running at for those?
Robert

 

[dave2176]

Really beautiful. I cannot believe how nice your threads came out. What RPM were you running at for those?
Robert

Running left to right like that with no need to stop at the shoulder you can run much faster. The 16 tpi I can do at 360 rpm because I don't have to start on a particular number on the thread dial. Just clamp the half nuts anywhere.

Dave

 

[dave2176]

More pics of the barrel work. The steady rest was used to support the 23" barrel. I I used the 4 jaw on the breech end and dialed it in using a DTI on the finished section from the chambering setup. To put the taper in the barrel I stepped down a little each pass.


A few minutes with the file and some emery cloth puts a nice finish on the barrel.


I put a threaded section near the muzzle for a future suppressor if I choose. A thread protector will be placed on it for now.


Here it is setup for fluting. I used a 3/16" ball nose end mill. 60 degree spacing using a spin indexer. 3 different sections of flutes.




Thanks for viewing,
Dave

 

[dave2176]

Finally, here's a pic of the completed rifle.


She shoots nice. Got a big roar but little recoil probably both due to the brake. With 168 gr. HPBT match ammo you are shooting the same hole at 100 yards. Can't wait to get her to a longer range.

Dave