My Two Builds

[MikeGideon]

I set out to build one, and wound up with two. AR-15's multiply like rabbits around my house. I guess this caliber is no exception. Built on CMT Tactical billet receiver sets from a group buy on the local gun forum.

They're sharing an optic via a LaRue mount right now. That will change when I sort out the best shooter.

[dmsims21]

What are the specs?

[Whelenon]

These ARs are addicting. I started out to build one for hunting(my Grendel) then I built another on for fun(5.56) now I have another one in the works. What fun though.

Looks like you've got a couple of good looking ARs. Had them to range yet?

[MikeGideon]

#1

Shilen 20" HBAR Match Barrel
Magpul PRS
Geissele High Speed Match Trigger
Spike's M16 Bolt Carrier
JP Adjustable Gas Block
Daniel Defense Rifle Length Lite Rail
Spike's LPK
Vortex PPS 6-24x50 FFP, MOA version
LaRue LT745 20 MOA Mount
Upper receiver face lapped. Barrel extension bedded

#2

JP Rifles 22" Supermatch barrel with large compensator and dissipator
JP Adjustable gas block
JP Rifle length handguard
Geissele SSA-E Trigger
Magpul PRS
EGW Bag Rider
Don't know who made the bolt carrier. Parts on hand. Chrome lined semi-auto with properly staked key
Upper receiver face lapped. Barrel extension bedded

The second rifle was an accident. Long story

[MikeGideon]

These ARs are addicting. I started out to build one for hunting(my Grendel) then I built another on for fun(5.56) now I have another one in the works. What fun though.

Looks like you've got a couple of good looking ARs. Had them to range yet?

Yeah. I have seven of them, and wound up parting out a long range .223 to build the second one above.

Just got them finished, so negative on a range trip. I have the first load develpoment phase loaded for ONE rifle. I have a place to do that work on private property, but have to load a few more so I can cover both guns. The first trip will be to set the gas blocks and measure velocities across a pretty wide range of charge weights. Once that's done, I'll use the data to calibrate Quickload, and use the Optimum Barrel Time method to set up a charge range for an accuracy node hunt. In a perfect world, I'll find something that works for both guns.

I'm thinking the Shilen could wind up out shooting the JP, but who knows. They're both great rifles. Anyway, I'll be shooting 123g Scenars until I find a good go-to load. Then, I'll branch out to some other bullets. Right now, I have 300 Scenars and 300 pieces of AA brass.

[customcutter]

Very nice. I also bought a CMT billet upper for my first build. I noticed you bedded the barrel extension on both barrels and lapped them. I didn't lap mine, because I didn't notice any visible gap. Did you notice a high spot when lapping, or just lapped them anyway? My barrel extension also slid in with no tight fit, I was hoping for a tight fit. I measured the barrel extension at .9965-.9975. Did you happen to measure the barrel extension on your barrels?

[MikeGideon]

Very nice. I also bought a CMT billet upper for my first build. I noticed you bedded the barrel extension on both barrels and lapped them. I didn't lap mine, because I didn't notice any visible gap. Did you notice a high spot when lapping, or just lapped them anyway? My barrel extension also slid in with no tight fit, I was hoping for a tight fit. I measured the barrel extension at .9965-.9975. Did you happen to measure the barrel extension on your barrels?

I didn't measure. I have assembled 3 of the CMT uppers with Grendel barrels (one for a friend). The Shilen was fairly tight, and the JP and Stoner barrels were fairly loose. In all 3 cases, the finish on the end of the receiver came off unevenly. So, I'm not feeling bad about lapping them. Who knows if it will make any difference in accuracy. It sure won't hurt it.

[customcutter]

I didn't lap mine. I did check it for gaps looking at while rotating the receiver and the home made tool, and a strong light in the back ground. Waiting for a few more items and a trip to the range to check accuracy. If it's not there, I'll disassemble and lap the receiver and bed the barrel extension. Thanks.

[MikeGideon]

These two steps make lots of sense to me. May not help, but it can't hurt.

[Tedward]

I have been reading up on the lapping and ordered a lopping tool so like your doing, just make sure. Truthfully on a billet upper it is cut by a CNC Machine so lapping shouldn't be needed. On a forged, I guess since its molded there might be more variance and a need to lap them for precision performance. Truthfully for the performance caliber rifles, I prefer billet uppers and don't even use the mil-spec uppers. On the .223 or .556 run of the mil rifles I use mil-spec uppers but even with my .223 Wylde, I like the solid feel and rigidity of a billet upper.

I like your homemade vice block too. Save those $30 items for more better parts....

[Tedward]

Very nice. I also bought a CMT billet upper for my first build. I noticed you bedded the barrel extension on both barrels and lapped them. I didn't lap mine, because I didn't notice any visible gap. Did you notice a high spot when lapping, or just lapped them anyway? My barrel extension also slid in with no tight fit, I was hoping for a tight fit. I measured the barrel extension at .9965-.9975. Did you happen to measure the barrel extension on your barrels?

I like the solid feel of the CMT Uppers. Just got a few and using them on 300BO's. NO movement between the upper and mil-spec Spikes Lower. Good finish too...

[MikeGideon]

I have been reading up on the lapping and ordered a lopping tool so like your doing, just make sure. Truthfully on a billet upper it is cut by a CNC Machine so lapping shouldn't be needed. On a forged, I guess since its molded there might be more variance and a need to lap them for precision performance. Truthfully for the performance caliber rifles, I prefer billet uppers and don't even use the mil-spec uppers. On the .223 or .556 run of the mil rifles I use mil-spec uppers but even with my .223 Wylde, I like the solid feel and rigidity of a billet upper.

I like your homemade vice block too. Save those $30 items for more better parts....

I prefer billet as well. The CMT parts are made from 7075 aluminum. We got them for a helluva price too with the group buy. The billet parts are tighter than the forged. Still, when I started lapping, there was still black finish on one side. I had to go a little deeper to get white all the way around.

The wood block is just for the lapping tool. My DPMS delrin block has reenforcing material inside the receiver. Since the lapping tool pretty much fills the bolt carrier channel, my regular vise block wouldn't work. That's when the wood shop in the garage came in handy.

[MikeGideon]

I like the solid feel of the CMT Uppers. Just got a few and using them on 300BO's. NO movement between the upper and mil-spec Spikes Lower. Good finish too...

It's interesting that with my first pair, I had to knock the takedown pin in with a brass hammer the first few times. No play, obviously. I had to use the set screw in the second pair to take up the slop. The third pair was a little floppy too. So, even though they were cut on a five axis CNC machine, there's still some tolerance stacking. Not complaining. It's why they include the screw.

[customcutter]

I had to tap the rear take down pin in as well the first few times. It is a tight fit to the Spikes lower.

[MikeGideon]

I have 3 Spikes lowers. Never (knock on wood) had a sloppy fit with one.