Build Thread My sub 5lb ultralight build

[Jerderv]

What does the adjustable gas key do that the adjustable gas block can't? That's where your setting your dwell timing on the bolt unlock ? Your talking milliseconds ..... interesting.

Nothing, in fact the gas block is a more ideal place to make the adjustments. Whats nice about doing it on the carrier is i can do stuff like drop the full weight carrier and carbine buffer into the gun and close it up, pull the trigger. If i had an adjustable gas block and i wanted to go from a lightweight carrier to a full weight carrier i would need to re tune the gas block to that carrier. This is a moot point if you just run one carrier.

Oh yeah, milliseconds, there are some pretty cool slow motion videos on youtube if you havent seen them already.

 

[KeepnitReel]

I haven't, but I'm going to now.

Nothing, in fact the gas block is a more ideal place to make the adjustments. Whats nice about doing it on the carrier is i can do stuff like drop the full weight carrier and carbine buffer into the gun and close it up, pull the trigger. If i had an adjustable gas block and i wanted to go from a lightweight carrier to a full weight carrier i would need to re tune the gas block to that carrier. This is a moot point if you just run one carrier.

Oh yeah, milliseconds, there are some pretty cool slow motion videos on youtube if you havent seen them already.

 

[jbett98]

Tagging for future reference.

 

[Jerderv]

Got an ERGO Swift grip. 2.5oz


Did this.


Started by cutting the excess plastic off the bottom of the mag. Ground out the inside to thin out the very thick plastic. Thinnest place is still 1/8" thick.


Took off some excess material from the "out of sight" areas. In my opinion, i accomplished this without weakening the structural integrity of the grip.


The above steps resulted in a .5oz weight loss lol. 2oz.


Im very happy with the feel of this grip the angle might allow me to run a BAD LBS. I have one on the way to try out.

 

[2Wheels4Ever]

Have you thought about cutting a couple inches off the barrel and welding on a flash hider?

 

[Jerderv]

Have you thought about cutting a couple inches off the barrel and welding on a flash hider?

Sort of, i wouldn't cut this barrel down, Faxon sells a 14.5" pencil barrel as well. DSA also makes an extended titanium A2 flashider and i have considered doing that. The cost of doing so has me hesitating, however, it is very tempting. I also discovered battle arms development sells a really light weight gasblock, even lighter than the 2A titanium one i have now.

Current setup total: 21.4oz
16" Faxon Pencil 19.4oz
DSA TI A2 flash 1.2oz
2A .625 Gas block .8oz

If i went shorter: 19.6oz
$170 14.5" Faxon Pencil 17.7oz
$40 DSA Extended TI A2 flash 1.4oz
$90 BAD .625 gas block .5oz

So i would loose ~1.8oz off the front of the gun, nothing to sneeze at. The barrel, flash hider, and gasblock come to $300. Is 1.8oz and ~1" shorter OAL worth $300? Not to me.... however i have the option of selling the old stuff at a loss to try and recoup some of the cost. I could probably get $175 for the the 16" setup and that would bring my out of pocket down to $125. Is 1.8oz and ~1" shorter OAL worth $125? Meh, its hard to justify.

 

[Jerderv]

New stock setup. AR10 buffer tube and a bad lbs replica. After modification, the buffer tube weighs 3.4oz and the buttstock weighs 2.6oz with the screw. I still need to make up a spacer for the inside of the tube so that the carrier doesn't over travel. Assuming the internal spacer is ~.3oz i will have dropped ~2.5oz off the back of the rifle which is the last place i want to remove weight from but i cant really think of any more ways to drop weight up front.




The length of pull is doable with the ar10 tube, this butt stock on the normal carbine tube was too short. Im pretty happy with it. Probably going to have it cerakoted.

 

[P7M13]

Very nice and this is cool info, thanks.
I admire how tenacious you have been in trimming weight. That's not for me. When i have trouble hauling 50lbs up and down mountains, I will set out to have a rifle less than 4lbs. Until then, a COTS build that is <6lbs will do me just fine, just as I really like my 7mm-08 Mountain Rifle at 7lbs with glass.

 

[Jerderv]

Very nice and this is cool info, thanks.
I admire how tenacious you have been in trimming weight. That's not for me. When i have trouble hauling 50lbs up and down mountains, I will set out to have a rifle less than 4lbs. Until then, a COTS build that is <6lbs will do me just fine, just as I really like my 7mm-08 Mountain Rifle at 7lbs with glass.

Thanks man! Hahaha im more or less just having fun with it now. I enjoy the challenge of finding the next few grams to shave off. 7lbs with a scope isnt bad at all! I do love a nice bolt gun.

Made the action spacer today. .2oz! nylon. Not sure how it will hold up. I might end up having an aluminum one made or just hack up another carbine buffer.

 

[KeepnitReel]

So have you had any bolt bounce miss fires yet ?

 

[jsparks747]

What are the grips and hand guards made of? You could see about purchasing one made of carbon fiber and that would shave off a good amount of weight. Just an idea though.

 

[Jerderv]

So have you had any bolt bounce miss fires yet ?

No, because it would be impossible for me to shoot the gun fast enough for that to be an issue. Original full auto O1 models running imr propellant cycled at 600-700rpm and did not use a buffer system. At 600-700 rpm a simple spring guide worked fine, it was only when they made the switch to ball powder that the cycle rate increased to nearly 1000rpm. That is when they started experiencing light primer strikes. Colt started selling a solid polymer spring guide in their semi auto rifles because they knew it would work fine at that rate of fire. People freaked out of coarse because it wasn't mil-spec, we all know how everyone has to have everything mil-spec.

The video below is very informative and the man speaking is an ex colt engineer. Start at 2:20 to get to the point.

What are the grips and hand guards made of? You could see about purchasing one made of carbon fiber and that would shave off a good amount of weight. Just an idea though.

Hand guard is 6061 T6 aluminum, the grip is just some sort of plastic composite. You are absolutely right there are several ounces i could drop by going with a carbon fiber hand guard, unfortunately the price prevents me from making that commitment.

 

[jsparks747]

No, because it would be impossible for me to shoot the gun fast enough for that to be an issue. Original full auto O1 models running imr propellant cycled at 600-700rpm and did not use a buffer system. At 600-700 rpm a simple spring guide worked fine, it was only when they made the switch to ball powder that the cycle rate increased to nearly 1000rpm. That is when they started experiencing light primer strikes. Colt started selling a solid polymer spring guide in their semi auto rifles because they knew it would work fine at that rate of fire. People freaked out of coarse because it wasn't mil-spec, we all know how everyone has to have everything mil-spec.

The video below is very informative and the man speaking is an ex colt engineer. Start at 2:20 to get to the point.

Hand guard is 6061 T6 aluminum, the grip is just some sort of plastic composite. You are absolutely right there are several ounces i could drop by going with a carbon fiber hand guard, unfortunately the price prevents me from making that commitment.

That was what I was thinking because not many people are willing to pay $300 for a hand guard.

 

[Jerderv]

Just another picture.

 

[Jerderv]

Put some round through it today, shot great!

 

[Jerderv]

Weight update, im happy, its exactly 6lbs with light, sling, and a full 20rnd pmag. I think im pretty much done with it...

 

[Diamondback]

Nice!

For the rest of us in the Peanut Gallery, here's a thread from M4C (not mine) with some more inspiration...
My 4lb AR range build
Right now I'm considering a pistol build as radically lightened up-front and as heavy to the rear behind the grip as possible for better balance. Hmmm... could you mount rails and a couple mag-carriers on a pistol buffer tube?

 

[Jerderv]

Thanks! Got the buffer tube back from cerakote. Added some talon grip material to the tube to keep it from being so cold/hot on my cheek. New DD sights are all sighted in, put a few hundred rounds through it. I think im done... Final weight is 4lbs 9.9oz. Thanks for looking. Ill post updates as i put more ammo through it.





Exactly 6lbs with 20 rounds in the mag

 

[Procyon]

For those tracking this thread, Faxon is in the works to release a 10.3 or 10.5 inch pencil barrel within the next 4-8 weeks.

Also, thanks for starting this thread. I had been following the ar15.com ULW under 6 thread as well.

I'm also a backpacker and have a desire to build a sub-6lb (w/o magazine) for backpacking once in awhile. It would be helpful if costs were posted. I don't plan to sink $2k into a new rifle, but $1k might be do-able.

 

[Diamondback]

For those tracking this thread, Faxon is in the works to release a 10.3 or 10.5 inch pencil barrel within the next 4-8 weeks.

Also, thanks for starting this thread. I had been following the ar15.com ULW under 6 thread as well.

I'm also a backpacker and have a desire to build a sub-6lb (w/o magazine) for backpacking once in awhile. It would be helpful if costs were posted. I don't plan to sink $2k into a new rifle, but $1k might be do-able.

Hopefully both... I have a Mk 18-inspired p[istol build I'm penciling out, and 10.3 barrels are A Farking NUISANCE to find at tolerable prices.