Help with an Orphan Lower

[Skylerbone]

I’ve finally taken the plunge and begun assembling uppers rather than buying complete as I finally have the requisite tools to work properly. The problem seems to be in parts supply which leaves me at a crossroad.

In the safe sits an Anderson lower patiently waiting for an upper to call its own, a new Ballistic Advantage 16” middy pencil profile with low pro, and an Aero upper Brownnells claims is in the mail. The handguard on order is a Luth-AR Palm 15” M-LOK which, while not the lightest option, is one I like based on my other middy with 9” Palm. That appears to be 7-10 days out, possibly more, and that leads me to my question: if you were planning a lighter weight build with RDS only, would you opt for a shorter rail or take the minor weight penalty afforded by a full rail that likely only sees a flashlight? I can buy a number of lightweight KeyMod rails from 12”-17” at the same price, the longest of which would be close to or lighter than the Luth-AR and while all others I own are M-LOK I don’t see a problem due to this being a fairly KISS rifle.

I’ll be running an adjustable key for gas on a ToolCraft BCG , Strike minimalist stock, and Kaw Valley linear comp. No idea on total weight, just wanting to keep it reasonable. So, cover the barrel? Save 3 oz and leave it exposed? Wait for the rail I have ordered?

The lower.


Barrel and gas block assembly.





Luth-AR handguard.


My other mid-length rifle with Luth-AR Palm installed (irons only).

 

[Demi-human]

Modesty states you should cover up.
But, I like long legs and mini skirts.
Run short and light!

Oh, and Keymod is dead. That's why they're cheap. M-Lok!

What's it for? Would having a shrouded barrel be more accurate for your use? Are you going to be leaning on anything when you are shooting? Or is this for carrying?

I like the Luthar handguard and have two of their stocks.

 

[Skylerbone]

This AR is meant for light carry, a sling and red dot, close quarters/SD. The aesthetics of a longer guard appeal to me but my other 16” seems fine with lots of barrel exposed, and I realize KeyMod is dead, but it’s also just about 1/2 price compared to M-LOK. I have no intention of shooting this one from the bench after sighting in.

I figure if the only things attached are a sling (via built-in QD socket) and a flashlight there’s no need to fret over which system I go with. I have 6 other ARs with M-LOK rails, but most don’t reap the benefits of utility offered as they too are fairly basic range blasters.

 

[303 hunter]

You’ve got a nice build going there! I bought a Ballistic Advantage 16” 5.56 barrel for $80, and a Ghost 12” handguard for $30 from Primary Arms Black Friday sale. I’m only short a mid length gas tube to have all my parts. I’ve also bought a few keymod rails lately because they’re a bargain. The only thing I ever attach is a bipod for the range.

 

[<*(((><]

Normally, I would have recommended the Midwest Industries Ultra Light 10.5" rail, but their prices have gone up significantly since I was buying mine a year or two ago. The are very nice rails, but not $235 nice. I think I was paying $160-170 on sale a year or two ago, and I thought that was significant.

 

[Skylerbone]

Odin Works, Phase 5, Seekins; all of these options are hovering around $100 regardless of length, but honestly I am wondering if covering up the barrel is the “correct” answer or do I go with slightly lighter. One of the reasons I’m opting for an adjustable key instead of gas block is for easy access regardless of rail length and because I’m still getting used to the concept of controlling more variables. I have enough rifles now to experiment with, just curious what others would choose in similar circumstance.

 

[Varminterror]

I’m really liking the Aero Atlas S1’s lately for light builds.

I also like 15-16” guards on everything - give me enough room for an open elbow hasty sling hold on the forend with the bipod still out front. If nothing else, I end up using bipods on my rifles all of the time, even if it’s just to keep them out of the grass and mud.

 

[Skylerbone]

I guess that makes sense, and as excited as I am about having a really light barrel out front maybe a bit of forward weight from a longer rail makes sense for balance. I think I’ll wait for the Palm to come in and give it a go, as I’m betting there’s enough back stock on KeyMod rails to survive a good long fire sale if I eventually decide to order one. At under $90 the Luth-AR is hard to beat for an M-LOK, value-wise anyway.

 

[MistWolf]

This AR is meant for light carry, a sling and red dot, close quarters/SD... I have no intention of shooting this one from the bench after sighting in...

...I figure if the only things attached are a sling (via built-in QD socket) and a flashlight...

In your shoes, I would build a 16" version of this (without suppressor)-View attachment 878909
I use this AR in exactly the role you're talking about. The Slimline handguard will give you a lot of performance for the money. After putting a lot of rounds down range over the years, I've never felt the desire or need for a free float tube on this AR. There is a QD socket on the other side of the handguard for installing a sling.

 

[Skylerbone]

It’s not that I’m ultimately concerned with accuracy with freefloating, some of the rails I’ve considered were even money once you add the delta ring, etc. In fact I was planning to go Magpul SL with the irons only rifle but couldn’t find a single source for everything I needed (delta, handguard, cap) in stock. After shipping would have been more than the $57 I paid for the mid-length Luth-AR which has a sort of retro look with the triangular shape and allowed me to skip on an angled light mount thanks to that geometry.

As affordable as MBUS sights are they ought to be on every one of my range rifles JIC but I intentionally opted for low pro to keep it clean looking and relatively snag free. Like the other middy I’m opting for an MFT quick release 1913 mount and small PIC rail up front, Strike angled QD attachment near the barrel nut for sling. I do like that setup though @MistWolf with its fsb light mount.

 

[MistWolf]

The rail the light is mounted to is attached to the handguard. Instead of attaching the rail to the top, I attached it underneath to keep it low.

Are you committed to the Luth FF tube? I got the impression you were having second thoughts and was looking for alternatives.

 

[Skylerbone]

Looking for alternatives due to a potential wait, and again, because it’s a barebones upper I’m not opposed to KeyMod if it saves money. I’ll probably keep the Luth on order and repurpose if I find an alternative, mainly asking in terms of length if I should go ~11” and just cover the GB or go big and hide the whole barrel. The extra bit of forward weight, potential for sight radius if I do add BUIS later, favors long rail. The keep it a little lighter idea favors a 12” KeyMod rail.

 

[mshootnit]

I recently looked at an Aero Quantum m-lok tube and it was very nice. Priced right at $100.
If you just cover the block it saves weight, but if you go longer it helps with a more forward grip or resting in improvised situations. So it just really depends upon what you see as being the higher priority.

 

[Skylerbone]

My 7.5” AR wears an Aero Quantum, nice rail and dehorned well. I suspect that ultimately it matters little which specific model I chose so long as it holds up, as most general purpose ARs tend to acquit themselves to roles less common than more narrowly specific rifles. I’d rather not have it collecting dust and as I know what the Palm offers in terms of offhand shooting comfort I think I’m settled on trying it in 15” form. If that means a wait, I suppose I’ll wait, and if the balance is off, I’ll order something shorter.

My suspicions are that I’m justifying my original plan, I’ve been guilty before, but I do appreciate the insight and it does factor in, though at times only to leave room for doubt. A good bit of this build is based on another thread that brought up a point about ARs becoming, to paraphrase, heavy, bloated, over accessorized carbines.

As I don’t participate in 3gun or precision matches I’ve been looking to make more sensible choices while not fully understanding the why’s of each component. I want one of everything but for now I’d like to continue learning the platform, practicing assembly, shoot for enjoyment, and of course minimize regrettable choices.

 

[greyling22]

you're talking about what, 2-3oz? that's nothing. Love the one you're with. Just use the parts you have on hand. If you don't, they'll turn into a another upper. Keymod may be dead, but there are plenty of accessories for it, it's cheap, and functionally it's fine. I've got a couple keymod handguards, and I have no intention of swapping them out for (my uses) no functional gain.

I keep trying not to buy this handguard https://algdefense.com/ergonomic-modular-rail-v0-e.html but I already have a 7" & 15" handguards in a drawer doing nothing. I certainly don't need more.

 

[mshootnit]

https://www.stngrusa.com/

 

[MistWolf]

you're talking about what, 2-3oz?...

What we're discussing is Skyler configuring an AR the way he wants it. It may be only 2-3 oz, but it's 2-3 oz with moment. It's 2-3 oz that can change how the rifle feels. There is almost no practical difference between a pinned 14.5" barrel and a 16" barrel. But when handling the two, I prefer how the 14.5" barrel feels. I bought a Colt 6920 with 16" government profile barrel. I swapped out the 16" barrel for a pinned 14.5" SOCOM profile barrel. The difference in weight is less than 2 oz, but with the 14.5" barrel, the AR handles better- and it's the heavier of the two barrels. The difference is the mass of the SOCOM barrel is closer to the center of gravity than the mass of the 16" barrel. This reduces the polar axis of movement.

A handguard that's 2-3 oz heavier puts that extra mass forward. A subtle difference indeed, but noticeable nonetheless.

 

[Skylerbone]

Well...I set it in motion last night and solidified things today. Once again I chickened out on gas adjustment but this being my first upper build and it going so smoothly has me thinking I’m going to hunt down a JP clamp on AGB and order another gas tube.

With the consistency of my range ammo there shouldn’t be any fiddling after initial gas tuning and I’ll know it’s reliable. I measured .078” for the port which looks to be on the large side so a bit of insurance couldn’t hurt, but my debit card needs to cool off a bit this week.

 

[MistWolf]

Skyler, before dropping money on an adjustable gas block, check out these options from Black River Tactical-
http://www.blackrivertactical.com/c...able-Gas-Drive/c/6464009/offset=0&sort=normal


If you have any questions, hit me up.

If you decide to go with the Slimline handguards, let me know and I'll dig around for a spare hand guard cap. If I can find it, it's yours.

 

[Skylerbone]

I appreciate the offer and I’ll definitely look into things further.

What concerned me most as I considered the adjustable gas key was the idea that the same volume of gas is entering the gas tube through the block leaving me to realize it therefore must be vented into the upper and, depending on how much restriction is used, can potentially increase pressure within the tube.

The gas tube being the sacrificial piece is noted but no sense in blowing it out if an AGB simply reduces that volume before it enters the tube and leaves it a single-shot rifle or worse peppers the support hand with shrapnel and hot gas.

I recalled from older posts several people measuring various barrels and Faxon coming under fire for port size but wrongly assumed BA would not be over gassed. For what I shoot, which isn’t at 5.56 pressure it probably makes no difference but I like the idea of knowing I can correct for it if needed. Range toy or not, I insist it be reliable and this one in particular I’m hoping to use as my truck gun once I’ve installed a suitable box in the new vehicle. Beyond that is a fair bit of homework on suppressors and perhaps an SBR or two.

 

[MistWolf]

What concerned me most as I considered the adjustable gas key was the idea that the same volume of gas is entering the gas tube through the block leaving me to realize it therefore must be vented into the upper and, depending on how much restriction is used, can potentially increase pressure within the tube.

None of the parts I posted the link for is an adjustable gas key. What I posted the link for is the EZ tune gas tube. It has a smaller gas port and works very well.

The other is the Micro Port which reduces the gas port diameter in the gas block. I use one on a Colt 6933 upper that's shot suppressed. It also works really well.

The gas tube being the sacrificial piece is noted but no sense in blowing it out if an AGB simply reduces that volume before it enters the tube and leaves it a single-shot rifle or worse peppers the support hand with shrapnel and hot gas.

The pressure isn't going to blow the gas tube out of the gas block. The flow enters the tube from the bottom and pushes the tube up against the gas block. When the gas exits the back of the tube, it pushes the tube forward. It's not going anywhere.

 

[Skylerbone]

None of the parts I posted the link for is an adjustable gas key

Of course, and very interesting and cost effective means of dealing with incorrect port size, and, in my novice thinking, from the correct end of the problem (before gas enters the tube).

The gas key I was referencing was the RCA available from Right To Bear that I chose not to order as an add-on to the ToolCraft BCG. https://www.righttobear.com/RCA-Adjustable-Gas-Key-p/1ad-gky.htm

 

[MistWolf]

Gotcha.

I found the hand guard cap. It's the round style and the correct one for the Slimline. PM your address and I'll drop it in the mail for you.

 

[Skylerbone]

16.1 oz for the handguard and barrel nut combination, + 2.9 oz for the linear compensator should make for ~6 lbs 5 oz before optic. That’s 5.2 oz. if I snag my SPARC back from my son and swap in a scope for him. 6.7 lbs imo gets me where I want to be, and I think the balance should be good.

Weighed with another TC BCG and KVP H2 installed on my $10 Amazon scale.