New to building with lots of questions.

[Wonk]

I have been lurking here for about a month now trying to learn all I can. I am very grateful for all the good info on this site. I have decided to build a 6.5 Grendel after pouring over ballistics tables for several nights. This will be my first AR build.

So far I have a Shadow Ops billet lower that I bought from my nephew. He bought it with the plans of building something and when he finally received it other priorities put it several burners back and he offered it to me. I highjacked another thread on here and asked a question about Shadow Ops and decided I should start my own thread.

My plans for this rifle will mostly be shooting targets and occasional deer hunting. My first question is about a CMT UPUR-4 Billet Upper. On CMT's web site they list 2 options and you have to choose one. The options are
WITHOUT M4 FEED RAMPS
458 SOCOM PORT SIZE
I'm confused. I was under the impression I needed M4 feed ramps and why get the Socom port size. Any help would be appreciated.

[PigOPs]

I sounds like those are both options, meaning, you don't have to choose either.

[Wonk]

Thats what I thought but if you don't choose one of them you can't move forward with placing an order. You get a red warning saying to choose one or the other??? Rainier Arms lists it without option boxes, a couple bucks cheaper too. I may just e-mail CMT and ask them. Am I correct in that I DO want M4 feed ramp, correct?

[Younger]

Yes on the M4 feed ramps.

458 SOCOM port size is slightly larger than standard 5.56 port by about .120 inches. .025" on top and .095" on the bottom. This should not be a problem when done by a professional.

[wilecoyote]

Get the M4 feed ramps and don't worry about the SOCOM port size.

[Wonk]

Next question. I've been reading all I can on here about barrels and chambers and bolts. I have looked at about every barrel company talked about on here but don't remember seeing (or finding anything with search) about DEZ Arms.

Here are their specs.

18” 4150 CMV Steel (Not Chrome Lined)

Mid-Length Gas System

1 x 7.5 twist rate

750" diameter gas block seat

5/8” x 24 threaded muzzle

Includes M4 feed ramped extension

Cartridge: 6.5 Grendel cartridge case

H-Bar Contour: Fluted, National Match Barrel, Medium Weight, 18” long, Nitro Carburized finish. Fluting provides weight savings & rigidity.

Weight: 2 lbs 6 oz

Requires: Complete Alexander Arms' 6.5 bolt assembly (not included) replaces 5.56/.223

DEZ Arms' custom machined match barrels are made from 4150 chrome-moly vanadium steel manufactured in the USA. Barrels are head spaced with Alexander Arms' 6.5 bolt, have M4 feed ramped extension installed, pre drilled gas port hole with Nitro Carburized finish. Barrels are particle tested, air gauged, concentrically cut and muzzle threaded 5/8” x 24 twist to accept flash hiders/suppressors, stressed relieved, turned on center to prevent accuracy robbing distortion when the barrel heats up, and hardened, giving the barrel a long life. The 11 degree crown, polished chamber and lapped bore makes the difference! Our pulled-button rifling produces a superbly accurate bore diameter with uniform rate of twist. Fluted models feature DEZ unique fluting designs to improve rigidity and aid in barrel cooling.

*Nitro carburized interior and exterior finish which is also applied to the barrel extension and gas port during heat treating and creates a monolithic black finish that is superior to hard chrome. The process does not add material to the internal dimension of the bore, increasing surface hardness to between 58-65 HRC, lowering bore friction, enhancing surface lubricity, improving running wear performance, enhancing corrosion resistance and heat resistance over industrial hard chrome.

The match barrel is machined to rigid specifications

Any experience/opinions on these? They don't say exactly what chamber spec they use.

[LRRPF52]

That's a heavy barrel profile for sure:

[Wonk]

About 1.5 ounces heavier than a Lilja 319 profile. Other than being fat, do the specs sound good? Just got off the phone with them and they told me they use the Saami spec reamer.

[Wonk]

I pulled the trigger on the DEZ barrel. It arrived 3 days after ordering. Looks very nice. Time will tell on it's accuracy. My next question is, how do I hold my CMT billet upper to tighten the barrel? All the upper receiver vice blocks I've seen say they will NOT fit billet uppers as they are usually thicker/different profile than a mill spec forged upper. What is everyone using? Brownells sells one that attaches to the takedown lugs or top rail but was wondering if that will be enough support for torquing the barrel nut on.

[spectra]

I use the DPMS CLAW on billet uppers. I have one for both AR15 and 308 designs. They seem to work well as you stated the normal bench vise will not hold a billet upper. There are a few designs out there that will work. Good luck in your search.

[Wonk]

And my next question, I just read on AR15.com that standard AR mags WILL work with the 6.5 Grendel ammo. I was under the impression I needed specific mags for the caliber. ???

[NugginFutz]

Wonk - your instincts are good. By no means should you use the takedown pins for barrel work. Plenty of pictures of the wounded and dead from that battle. In your case, I'd consider using either the Geissle Reaction rod or the Magpul Bev Block.

Both will do the job, if you can find one.

[Bwild97]

And my next question, I just read on AR15.com that standard AR mags WILL work with the 6.5 Grendel ammo. I was under the impression I needed specific mags for the caliber. ???

Save yourself a few headaches, and get some specific mags for 6.5 Grendel.

[Wonk]

Just found this. Sounds like what I need.

BROWNELLS AR15 BARREL EXT. TORQUE TOOL
080-000-637WB
AR-15/M16 Barrel Extension Torque Tool


Thanks for the quick replies guys. Really anxious to get this thing done. My biggest holdup now is budget.

[spectra]

I like the looks of the reaction rod but it seems as there are none to be found in stock.

Wonk I would just buy Grendel mags as they are cheap and they work. Yes some people get the AR mag to work but look at how many also have problems. I am also doing my first Grendel build and this all a learning curve for me also. IT is just another AR build but there are a few different parts here and there.

[spectra]

Just found this. Sounds like what I need.

BROWNELLS AR15 BARREL EXT. TORQUE TOOL
080-000-637WB
AR-15/M16 Barrel Extension Torque Tool


Thanks for the quick replies guys. Really anxious to get this thing done. My biggest holdup now is budget.

I saw that to only thing I do not like is the normal wrench is in the vice and nothing really holds the upper and barrel. You are using gravity and hoping it all stays in place.

[Wonk]

Save yourself a few headaches, and get some specific mags for 6.5 Grendel.

I already have a C-products mag in my Brownells shopping cart. Again, this site is great with lots of knowledge, and friendly assistance.

[Wonk]

I saw that to only thing I do not like is the normal wrench is in the vice and nothing really holds the upper and barrel. You are using gravity and hoping it all stays in place.

One of the reviews from a smith on Brownells site suggested using twine or a bungee to stabilize the barrel while torquing.

[Klem]

G'day Wonk,

I use the Brownells torque rod and it works for me.

How you put it all together in the vise to torque-up depends on the design of the barrel nut. Handguard manufacturers have different designs of barrel nut so I am wondering what handguard you have chosen.

For example, Centurion's CMR handguard has small holes designed for a pin spanner like those found on AR15 spanners for the old design castle nuts. For this the torque wrench handle is clamped in the vise and the spanner is in the hands for tightening. The torque rod sits on the torque wrench pointing up. You lower the receiver onto it vertically then do it up with the spanner until you feel/hear the torque wrench click at your chosen setting.


Another example is SLR's Solo series of handguards. These have flats on the nut. You sit the flats in the vise with the barrel pointing down. Again, this is a vertical setup but this time the torque rod and torque wrench is pointing down and you are holding the wrench in your hands.


In all cases you insert the barrel into receiver and do the barrel nut up by hand to hand-tight before clamping in the vise for torqueing.

Also, keeping the barrel/receiver vertical while torqueing keeps gravity even reducing the chance of run-out between barrel and receiver.

[Wonk]

Thanks for the info Klem. I think I am going with a Midwest Industries GenII SS series. It is a clamp type handguard that comes with a barrel wrench that will probably involve locking the torque bar in the vise in a vertical position with the barrel pointing up, torque wrench on the supplied barrel wrench. At least thats the way I'm envisioning it. If that does not work I'm thinking I could machine a block to go in the vise to stabilize the supplied wrench, barrel pointing down, and torque with the torque bar from above.