School me on light weight ARs

[elwarpo]

Looking for a project and was thinking of an ultra lightweight AR. Thinking Faxon 14.5" Pencil barrel, titanium parts, carbon fiber handguard. Where I have questions is with the buffer and gas system. Do you need an adjustable gas system? With a lighter bolt do you need a lighter buffer? going to be a carbine stock and carbine gas system, I am looking for a durable light weight bolt? who do you recommend?

 

[Evintos]

With a lighter BCG, it's recommended you get an adjustable gas block unless you drastically increase the buffer weight (which kinda defeats the purpose of going ultralight). Without one you'll run into issues of bolt overrun, early unlocking, etc. especially since most barrels (especially the Faxon) have a pretty large gas port. You don't need a lighter buffer however going with one allows you to further decrease weight. A combined lightweight buffer + lighter carrier will absolutely necessitate the adjustable gas block. If you want the absolute lightest carrier, it would be an aluminum carrier although longevity is much less, but it'll last enough rounds that you'll end up replacing both barrel and bolt (and in this case the carrier as well). They tend to either wear at the cam pin track or the hammer ramp.

A combo of lightweight and durable BCG (where you can reuse the carrier at higher round counts) would be the titanium offerings by Rubber City Armament, 2A Armament, V Seven, Brownells, etc. No clue who the actual OEM are for some of them but the weights for a lot of the offerings are the exact same. Some are unique in design like the 2A armament.

You can buy the bolt + carrier as the BCG combo or buy them separately and piece together something like 9310 or Carpenter 158 bolt, titanium firing pin, titanium cam pin, aluminum or titanium carrier (or various other combos). Stuff like the titanium cam pin, firing pins aren't usually included in the titanium BCG offerings.

 

[...]

how light do you want to go? and how much do you want to spend.


honestly, unless you have a specific weight goal you are trying to reach for whatever reason.....you can make a pretty light weight AR without much hassle.

• milspec upper and lower
• 16" pencil barrel W/ low profile gas block
• milspec parts kit
• lightweight furniture of choice
• standard bolt/ buffer

that should put you right around 6lbs

the Titanium lower parts kits are going to save you a negligible amount for 10x the cost.

a lightweight BCG is going to save you around 3 ounces......but you are going to need an adjustable gas block or a heavier buffer.

when it comes to light weight, the weight savings is inversely exponential to the cost......you are going to pay more and see less weight savings the more extreme you go.


also realize your choice of optic is going to have the greatest impact on weight than anything else.

 

[iktomi]

What's your intended use?

If it's precision, your stacking the deck against yourself.

If it's just for fun and speed, guys can usually make UL builds work.

Adjustable Gas Block? Yes. Your talking about building your gun around parts your barrel port size was not designed for. Adjustable gas block allows you to reduce the operating gas and run a lower energy system.

There are a couple of challenges you'll be facing:

Lightening your buffer and BCG causes the rearward travel of the system to start sooner.

Carbine gas systems start the system sooner (system is energized sooner from gas port being closer to chamber.)

You may find yourself pulling on brass that hasn't retracted and is still engaged in the chamber, which can lend itself to extraction issues / malfunctions / less-than-ideal tunes.

You can push higher spring rate springs to try and increase bolt lock time (which has its own interesting consequences) to give the brass a little longer to rebound.

It's possible to get UL system to run and be a lot of fun, but it can take a little time and energy.

I usually run pretty consistent ammo / ammo-lots, so I tune to specific ammo. This has resulted in very high levels of consistency and reliability on my builds. I suspect that I would have a more frustrating time if my ammo had a lot of variability or if I was trying to run a wide variety of pressure profiles.

 

[BullGear]

I know someone who built a lightweight AR15 years ago. Started with a non forward assist A1 upper, a Colt pencil 16" barrel and other very light weight parts. Comes in at 5 lb 2 oz. Realize this was long before anything aftermarket was out there. All parts are Colt parts except for the lower.

 

[colodrew]

I’ve been down this road and back. Built many 3 gun rifles over the last dozen plus years. The aluminum carriers are very hard on firing pins. Titanium carriers are slightly heavier, hold up very well, and don’t eat firing pins.
The must haves for reliable Light weight set up for me are an adjustable gas block, JP bolt, JP silent captured spring with spring kit, and titanium firing pin.
The gas block and silent captured spring so you can tune your reciprocating mass. I found the light components required a heavier spring. If you don‘t want a silent captured spring for some crazy reason I would go with a Tubbs flat wire spring, it has about 25% more spring rate. The JP bolt because they are the toughest and most reliable in my experience. The titanium firing pin so you don’t have a slam fire with the faster cycle time. Light ARs are awesome when tuned correctly. Good luck!

 

[GH41]

6 1/2 pounds with optic, backup sights, light and sling. All duty grade parts. Full ambi lower.

 

[powdahound76]

Looking for a project and was thinking of an ultra lightweight AR. Thinking Faxon 14.5" Pencil barrel, titanium parts, carbon fiber handguard. Where I have questions is with the buffer and gas system. Do you need an adjustable gas system? With a lighter bolt do you need a lighter buffer? going to be a carbine stock and carbine gas system, I am looking for a durable light weight bolt? who do you recommend?

Look at MSTN's posts in the AR15 pic thread and note the components he uses for UL builds.

I cant justify the Ti parts for my budget, and he has a few in there that look a lot like the one above with more top shelf goods, but not the extra $ of the Ti.

 

[kyzim311]

I built a lightweight a few years ago, gun came in under 5 lbs with irons. Best bang for the buck part is a slick side upper and a polymer dust cover. That saves weight for almost no cost. The BFT minimalist is the best stock choice for weight, once again not much money over what you might normally use. If you are going to use a lightweight BCG, get an adjustable gas block for the reasons mentioned above. Any titanium parts you add will cost way more than steel, so unless you are looking to get every 0.1 of an ounce out, use it wisely.

Also, look at what V7 has to offer for a lot of your smaller parts. Aluminum is lighter and cheaper than titanium, so if you don't need the strength use aluminum parts (castle nut, end plate, take down pins, mag catch). 7075 is similar in strength to basic steel, so don't think of these parts as super fragile, but they are soft. I looked at a carbon fiber handguard as well, ended up with the v7 hyperlight. 11" rail with full top rail and m-lok or keymod, 5 ounces with the barrel nut. It is a lot more flexible than most carbon fiber options with minimal added weight. Watch your muzzle device choice as well, plenty of heavier than they need to be options as the end of the gun you will feel the most. Avoid titanium muzzle devices, I had one and it sparked like crazy (fireworks at an indoor range). Good luck with your build.

Edit: I went with the 16" barrel to avoid welding my muzzle device, there is less than an ounce difference between the 16" and 14.5" barrel so something else to consider.

 

[GH41]

How much weight could you save if you used Ti everywhere you could without compromising reliability? My watch weighs 5 ounces... Have you ever left the house forgetting to put on your watch? I have and I never noticed it gone until I looked to see what time it was! I didn't notice the weight missing. The Ti juice isn't worth the squeeze to me.

 

[spife7980]

Do you need an adjustable gas system?

Always get one. It’s like 20 bucks more and you don’t ever have to worry about not being able to get the right gas.

 

[elwarpo]

This is for my GF, She is petite and 4' 10".i have a 5.5 lb factory MAA AR including aN aimpoint PRO, and it is too heavy for her.

 

[powdahound76]

Buy her a gym membership.


Encourage squats and dead lifts. For you.

 

[kyzim311]

too heavy as in heavy to pull up and swing, or too heavy to carry? Do you have a link to the gun she is using now for comparison?

 

[Ledzep]

Balance > weight.

When I graduated high school I was 5'6" 125lb. I did NOT have significant muscle mass lol... I was shooting 10-15lb rifles offhand (with a sling). A 5.5lb rifle is not too heavy. Build on technique and maybe a little bit of physical training. I don't want to this to come off as callous but "getting used to it" may be all that needs to happen.

 

[Ravenworks]

Buy her a gym membership.


Encourage squats and dead lifts. For you.

Or a pair if shoes with a red stripe on the bottom

 

[...]

This is for my GF, She is petite and 4' 10".i have a 5.5 lb factory MAA AR including aN aimpoint PRO, and it is too heavy for her.

I mean, children regularly shoot ARs....so I find it hard to believe a full grown woman cannot handle a 5.5lb rifle.

Also realize even the lightest weight AR is not going to be significantly lighter than 5.5lbs

You can try ditching the Aimpoint pro for something lighter, like irons or a pistol red dot.

But frankly it sounds like an ergonomics or training issue more than a weight issue.

Hell, when I was shooting 3P, there were 5' 100lbs girls shooting 12-15 lb match rifles with ease.

 

[BullGear]

You might want to consider recoil as well. The lighter you go, the more recoil may be felt. Even if you find a 4 lb AR, the likelihood is that she may not be able to handle the recoil If she can't handle a 5.5 lb rifle, maybe she should stick with a lightweight 10-22 or some other 22lr.

 

[Jefe's Dope]

The barrel is the biggest weight factor. After that, you're working w/ an ounce here and an ounce there and paying out the nose to save fractions of ounces of parts. How light does it need to be and why?

 

[Jefe's Dope]

My opinion is she doesn't like shooting but doesn't want to tell you that so she's making excuses as to why she doesn't want to do it.

 

[Hesperidins]

This is for my GF, She is petite and 4' 10".i have a 5.5 lb factory MAA AR including aN aimpoint PRO, and it is too heavy for her.

Shoot from a bench or prone.

 

[elwarpo]

She actually loves shooting and we go often. Yes, it is an issue of muscle mass, but at over 50, having her bulk up is not really an option. Recoil does not bother her, she shoots my 3 1/2 lb 12ga. She shoots my MPK and loves it. I think it is more of a leverage issue, as you get shorter, so do your arms, so the weight is further out and feels heavier. I was planning on a light weight AR or AR pistol.

Anyone make super lightweight barrels for an Ar pistol. Since the weight is all upfront, that is where I am most trying to save it. Just do not like the fireball from a 8.5" AR pistol barrel. That is why I was thinking of the 14.5" Faxon pencil barrel on a pistol. Her size is perfect as a pistol brace fits her nicely (too short for me).

 

[Evintos]

AR pistol will be a better choice for someone of a smaller stature. https://faxonfirearms.com/10-5-pencil-5-56-nato-carbine-length-4150-qpq/

Lighter weight than a 14.5" pencil and will shift more weight rearwards. You can even do a lightweight AR pistol if you want to spend the money. Use a low mass set up combined with a lightweight rail, lightweight receiver set, etc. will make it a very light but the rearward push into the shoulder will be harder which can even push a person off balance with poor stance. The muzzle deviation if you have an adjustable gas block will be less due to the lowered reciprocating mass. If you combine it with a muzzle brake, it'll be flat shooting with negligible rearward push but higher concussion. It all depends on how much you want to spend and how you want it set up. To give you an idea of the cost, my lightweight 16" cost around $2300 and that was buying stuff with 20% off and no sales tax. If you want to just take away the leverage, go with a lighter 10.5" barrel and handguard and leave everything rearward standard mass. That'll shift the balance point to where she'll naturally be stronger (closer to her body).

Are you building this for her or for you or both of you? You don't like the fireball of an 8.5" AR pistol but does she care? You gotta be honest about this otherwise you're gonna end up with something that neither of you like.

 

[evil erik]

gym lift weights smile for the camera my 45/ 70 weighs 12.5lb and im petite at 210 lbs

 

[loveha]

I was willing to add a little weight here and there for comfort and what I wanted in looks.
F1 Receiver set, 12.5" Proof barrel, Smoke Composites handguard and buttstock, enlightened Cryptic Coatings BCG. Under 6# without mag and muzzle device. If I went with a lighter optic, didn't opt for the cheek riser and butt pad. Also changed the weights to something other than an H2 in my JP SCS, just been lazy about it. It would of course be lighter. Smoke Composites makes lots of options, from buffer tubes made of carbon, to pistol braces.

300BLK just for subs.