Tightest Lockup Receiver Set

R

rybe390

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Minuteman
Dec 13, 2017
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#1
Looking to spend $300-$500 for a matched receiver set for a precision build. Okay with both forged and billet.

I've run tension screws in the past, they're fine, but I'm looking for a bit more solid lockup.

I've looked at centurion and JP for forged. Rainier for billett. Haven't looked at much beyond this.

What are your recommended matched sets? What has solid lockup? Please specify if it was forged or billett.
 
#4
Zev/mega made sets
Noveske
SOLGW
Zev
Mega

The last SOLGW set I got had a thermal fit barrel and very tight receiver set. Would recommend.
 
#7
SOLGW sells a set that i hear is a nice fit. But man, the premium on a set like that would go a long way toward something that's actually going to matter, like a barrel or trigger.

I quit ordering sets like that. Sometimes their too tight or just a tad bit too loose making the premium paid not worthwhile.
 
#8
Aero Billet lowers are threaded with a nylon grub screw that pushes against the upper pin lug.
You can tighten it up to nearly zero play.

  • Upper Tension Screw - Allows users to fine tune the fit of the upper and lower receiver using a nylon tipped tensioning set screw inserted in the grip tang of the lower receiver. This provides a tight fit with any standard AR15 upper receiver.
 
#9
At the end of the day, you’re dealing with aluminum, one of the hardest aluminums ( 7075 T6), but still aluminum.

You can start off with a really tight receiver set where the rear lug is oversized in width just enough to wedge into the lower, and the TD pin location is puling the upper onto the lower tighter than the TDP call-outs, but with use, the gun will often loosen-up a bit in my experience.

I still like tight receiver sets so the gun feels solid.

Some makers have approached this with a tensioning screw behind the pistol grip screw that applies upward pressure against the bottom of the rear lug and the lower. This pushes the receivers away from each other.

Quality anodizing with a deep-penetrating hard finish helps reduce the wear between interfacing parts, but given the soft substrate, things loosen-up.

The original Cobalt Kinetics had EDM wire-cut receiver seams I think, and were flawless.

JP SCR is great.

My LaRue Stealth 2.0 Grendel has really tight lock-up.
 
#13
bigjake83 said:
Two build kits that I've been impressed with recently is the SOLGW Broadsword and the Cobalt kinetics Pro kits.

Both are rock solid and very clean machining.
Click to expand...
Have you tested either or both for deflection? I'm curious how SOLW's "shouldered" style handguard/upper interface compares to the semi monolithic like Cobalt (and mega, aero, LWRC etc)
Thanks
 
#14
AXMC said:
Have you tested either or both for deflection? I'm curious how SOLW's "shouldered" style handguard/upper interface compares to the semi monolithic like Cobalt (and mega, aero, LWRC etc)
Thanks
Click to expand...

No i didn't run any test like that, I just built them. I would definitely say the Broadsword Upper and Handguard combo with that new locking system are just as good as the Radian MOD 1 Upper and Handguard.

When comparing "traditional"style Uppers/ Handguards, (meaning the handguard secures to the barrel nut) The SOLGW Broadsword is rock solid and has a larger diameter inside the Handguard that will easily accommodate a .875 Adjustable Gas Block and both require a Thermo Fit.

The finish on the SOLGW is nice, I'd say same as a Mega set. The cerakote job on the MOD 1 and Colbalt Kinetics is some of the best I've seen.

The Radian MOD 1 surpasses everyone as a total package thier full ambidextrous lower receivers are outstanding and well worth the money.

If someone has the funds $1200.00 for a complete Build Kit with a traditional style upper and handguard combo Radian is definitely the best you can get.


I've already pulled the barrel on my New ITB 17.5" Radian MOD 1 and packed the 17.5" Radian barrel away for a SPR project I have in mind, just waiting for my Custom Bartlein Barrels to show up. I couldn't decide between a 22" 6ARC or 22ARC so I ordered both 😁
 
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#18
I’ve never been happy with the grub screw under the grip approach. In my experience it is either ineffective or requires tools for disassembly. Neither are acceptable.

Here’s what I have done on a really sloppy upper/lower. Pin set together at pivot pin. Stack something thin (shims, business cards work) in slot between upper/lower-near the pivot pin- to wedge them apart when pinned at TD pin. Check fit. When satisfied, smear the lower face of the upper with a light coat of oil. Apply JB weld to the mating surface of the lower receiver- just the rear portion is fine. It doesn’t take that much. Gently pin set together. You want squeeze out, but you don’t want to squeeze it all out, hence the shims. Wipe off excess JB weld. Hang set such that gravity is pulling the upper from the lower. Allow JB weld to set. Unpin and remove shims.

Hot glue under the pivot pin boss works too.
 
#20
Mega was my go to and still run them, wish I'd kept some as spares. The few Mega/Zev sets I've had seem great but don't match the old Mega finish.

I'd have to create a thread like this to see what the new hotness is..
 
#21
Those Radian sets look great.

Any issues with ambi lowers in real world use? I'm not left handed so the ambi lower isn't a huge deal to me especially if it means I'll accidentally hit the mag release on a plate carrier
 
#22
rlsmith1 said:
Those Radian sets look great.

Any issues with ambi lowers in real world use? I'm not left handed so the ambi lower isn't a huge deal to me especially if it means I'll accidentally hit the mag release on a plate carrier
Click to expand...
Ambi bolt catch/release is to benefit right handers. The basic AR-15 is very friendly to lefties when operating the bolt catch, as all they have to do is push down on the bottom of the bolt catch paddle to lock back, then depress the top to drop. The Charge Handle is the main cumbersome thing for lefties.

I don’t like ambi selectors because the right side interferes with gloves or your hand when doing a lot of CQM drills. I’ve never used them. But I’ve always felt a need for an ambi bolt hold open/release.
 
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#23
Ive handled and shot a couple of radian rigs. They are nice. Very NICE. Nothing I'm willing to pay for though. Ambi controls are nothing new and can be had without paying the premium price tag.

As for a tight receiver fit, i prefer something more flexible. I use rubber flask stoppers to tighten up the rear and if there's any lateral movement up front, i fix that with stainless shim material and JB Weld.
 
#24
When my local gun shop was going to be building guns, they got a couple sets from different manufacturers. Zev/Mega was by far the tightest. That's who they ended up going with. I could fit a stripped upper and lower together and hang them upside down and the upper would never fall off. i have around 9-10k rounds on a set and still tight. The barrel extensions are very tight as well.
 
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#25
I have a few different AR-15's from el cheapo to el oro grande. Each and every one was assembled by this idiot right here.

Anderson lower/upper x 5
Aero lower/upper x 3
DPMS lower/upper x 1
80% Lower with DPMS upper x 1
Wilson Combat lower/upper x 1
CNC 45 ACP lower (https://www.cncguns.com/projects/AR45lower.html) paired with a Ranier PCC upper x 2
WarDog skeletonized lower/upper x 1
Radian Mod 1 builders kit x 1

I have an old Bushmaster in A2 config and a Colt SP1 (my first AR).

I'm going to thin that herd and buy a few more Radian sets.
Radian is where it's at unless you want something real light weight.
 
#27
rybe390 said:
Looking to spend $300-$500 for a matched receiver set for a precision build. Okay with both forged and billet.

I've run tension screws in the past, they're fine, but I'm looking for a bit more solid lockup.

I've looked at centurion and JP for forged. Rainier for billett. Haven't looked at much beyond this.

What are your recommended matched sets? What has solid lockup? Please specify if it was forged or billett.
Click to expand...
The best one I’ve dealt with was SOLGW. No wiggle at all.
 
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