Improve the stripped lower design?

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Given a crucial component that has been essentially unchanged for decades, what do you think can be improved in the basic, stripped AR-15 lower?

I'll go first:

I have a passion for the total elimination of the larger roll pins in a lower assembly. The single most dangerous aspect of a lower build...hammering in the trigger guard roll pin...has a simple solution:

Utilize a 5/32" drill to convert the trigger guard's inside bore to a diameter which will accept threaded brass inserts to be secured by allen-head screws.

Absolutely no assembly stress involved other than being aware that some will want to retain the option of using the detent to lever the trigger guard downward in certain situations.

If that's the case, just torque the screws a bit lighter than solid to retain the pivot function.

What are your ideas on improving the basic lower design?
 
Rainier Arms' billet lowers have pretty sweet built in ambidextrous controls for everything.
 
I have a passion for the total elimination of the larger roll pins in a lower assembly. The single most dangerous aspect of a lower build...hammering in the trigger guard roll pin...has a simple solution:

Utilize a 5/32" drill to convert the trigger guard's inside bore to a diameter which will accept threaded brass inserts to be secured by allen-head screws.

Absolutely no assembly stress involved other than being aware that some will want to retain the option of using the detent to lever the trigger guard downward in certain situations.
Click to expand...
Roll pins were chosen not because they made assembly easier but because they eliminated threaded bits that could work loose during actual use. They're simply a better choice for use in a service arm.

Quite frankly, the only aspect of the lower design that's always bugged me in the semi-auto form is the sear/hammer interface. It lacks for mechanical advantage, and competing designs in the aftermarket have done a better job of managing that.
 
The roll pin is very secure and prevents the soldier messing with it. For the Barbie builder it is an issue, spring loaded detents that snap into the holes eliminate the issue. One maker offers ejection port covers that do that - snap in.

One area that might be improved is to move the mounting lug for the grip back about half an inch. It would lengthen the pull for the index finger and get it out of the trigger guard as much, exactly as the grips with fillers do. It would reinforce the buffer tube lug by putting a lot more support under it so that it's not leveraged as much.

The mag well length is another - does it actually have to be so deep? It forces a user to insert the mag with a lot more precision, adds weight, forcing more machining cost into the lower, etc. One reason may be that the M16 magazine was too flimsy to begin with - but polymer mags seem to have compensated for it.

Another is simply not forging it at all - extrude it. Instead of machining a mag well and introducing a host of variables into the sizing, get it right from the first pass pushing it thru the dies. Forging requires machining the magwell, but extrusion cuts down that requirement because it can create two dimensions of the shape continuously. The machining would need to be done on the third axis - which is how the plethora of freefloats are made. The tubular shape is run out of dies and the Hole of the Month added in the shop, cutting to length.

With the lower extruded and a mag well only as deep as the trigger works, the issue of trigger ears is eliminated by having an actual trigger guard extending down from the lower surface and then back to the grip. Opens a lot more possibilities. And the front lugs holding the upper pin can be much more substantial in length to reinforce the front of the shorter mag well opening.

At that point two of the major issues of polymer lowers are also addressed. From there a drop in trigger works could use snap in spring loaded pins instead of driving them thru the lower and having them exposed. They couldn't walk out. Paper clip pin holes would allow disassembly.

The result would be better ergonomics, a lower that would resemble the AR180, lower manufacturing costs, and it would still take all the remaining parts that were GI.

I'd buy that.
 
Do something like FN did with the SCAR*, polymer with steel inserts as needed for strength.

The problem is that the rifle was designed with a forged 7075 aluminum receiver in mind. The forces that are exerted by the buffer tube attachment and forward pivot pin ears can exceed the strength of other materials that are substituted. It's really easy to find pictures of broken plastic receivers that have snapped at those locations.

BSW

*When FN designed the SCAR lower, they did away with the forward pivot point and the butt doesn't impart and stress onto the lower that it wasn't designed for. There are advantages of starting a design with a clean sheet of paper.
 
"Roll pins were chosen not because they made assembly easier but because they eliminated threaded bits that could work loose during actual use."

I've installed hundreds of those roll pins and never broken a tab, but I have also seen many a lower ruined. Two cents worth of Loctite will anchor those threaded bits which are highly unlikely to work loose anyway.

"The roll pin is very secure and prevents the soldier messing with it."

So is a guard anchored by small machine screws. And I'm no longer a soldier; sucks being too old to serve again.

I like your idea of extrusion but would extruded alloy be strong enough without reinforcement a critical points?
 
"One maker offers ejection port covers that do that - snap in."

Do you mean the Strike Industries UDC? Anything that does away with installing that flea is fine with me even if it is more expensive. :cool:

Two more good designs:

1. Anyone here build AR-10s? Using an allen wrench to install the bolt-catch screw eliminates another roll pin.

2. Several mfrs. are threading the takedown pin detent channel to allow capturing the detent and spring with a 4-40 set screw. If you're inclined to experiment with different end plate, tube and buttstock designs like I am, it's a handy mod.
 
components-tm-tfb.jpg
Easy, low-cost improvement. Adding the A-DAC pin allows the magazine release to activate the bolt catch when doing remedial actions. (Other than that, it has no negative effect on wpns handling).

A second thing would be a redesign to allow ambidextrous bolt and magazine releases.
 
I think it's perfect:) It's the only system I know of that has anything you want.
The upper is where design changes can be made.
 
Is there a reason that the lower wasn't made with an integrated trigger guard from the beginning? I hate the little flat mil spec version and replaced mine with a Magpul that feels a lot better to my middle finger.

The next AR I buy/build will have an integrated trigger guard like this:

1269922_01_smith_and_wesson_m_p_stripped__640.jpg
 
The trigger guard was designed with capability to rotate downward so personnel could operate the rifle in winter environments. Think gloves and providing more space inside the trigger guard area.

I use either type of Magpul guard [polymer or alloy] depending on projected use of the AR. Weight difference is not an issue but strength might possibly be.

Monolithic lowers tend to be a bit more expensive but are worth the extra money if you're building a higher-tier rifle.
 
That S&W lower looks a LOT like a Noveske "Chainsaw" lower. The flared magwell and beefy trigger guard are definite bonuses.

see here: http://www.thehighroad.org/attachment.php?attachmentid=186419&d=1374051947

The skull lower.. looks neat but thats a lot of open space around the trigger guard, esp. on a poly lower--and that hole up front can let dirt and crud in.
 
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A bufferless lower would make for a heck of a lot more adaptable unit, as far as form factor. It'd basically be an HK lower with a magwell (why not put the magwell on the caliber-defined upper, for that matter?)

TCB
 
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