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Budget Lightweight Build Parts

6K views 42 replies 15 participants last post by  mac66 
#1 · (Edited)
Okay, one more post about building a cheap lightweight AR.

I know some people like the best of the best. I just want a toy to play with and don't want to spend a lot of money to do it. Good enough is sometimes good enough.

For an upper here's a good way to get started

AIM Surplus has a light weight bolt/carrier for $90. 8.9 ozs That is about 2-3 ozs lighter that a standard one. Most bolts weigh 11-12 ozs.
https://www.aimsurplus.com/product....ail&utm_term=0_6870497a6a-16ff4df39a-17883481

AIM also has a Anderson Lightweight Sporter stripped upper. $40. 6.6 ozs. It does not have the forward assist or dust cover but does have the shell deflector. They are frequently out of stock but get them in regularly. (get on their notification list) I have couple of these and the are about 2.5 oz lighter than an A3 upper.

https://www.aimsurplus.com/product....htweight+Sport+AR+Upper+Receiver&groupid=4329

If you want a pure slick sided upper PSA has one in stock for $59. It may be fractionally lighter than the Anderson but It doesn't have the shell deflector bump. I can't find a weight for them. I'll let you know when mine gets delivered.
http://palmettostatearmory.com/psa-ar15-slick-sided-upper-receiver.html?utm_source=Back in Stock&utm_medium=email

Pencil Barrel, mid length stainless 1:7 $90. An M4 barrel weighs 28 ozs. An A1 govt profile carbine barrel weighs 22.96. The Faxon pencil bbl supposedly weighs 19 ozs. This bbl is supposed to weigh 20-21 ozs.
http://palmettostatearmory.com/psa-...7-ss-pencil-barrel-5-56-nato-1-7-freedom.html

You'll need a low pro gas block in .625" $19
http://palmettostatearmory.com/palmetto-state-armory-low-profile-gas-block-0-625-516444612.html

And a Mid length gas tube $13
http://palmettostatearmory.com/ar-15-gas-tube-midlength.html

You will of course need hand guards. Hand guards themselves tend to be light but the delta ring and barrel nut adds weight. Most free float hand guards are deceptively heavy comparatively. The cheapest light weight free float hand guards I've found are carbon fiber jobs from Delta Team Tactical for $47. I have one on my light weight build and they work fine. About 7 ozs with the barrel nut but without the metal rails and endcap (which come off).

https://www.deltateamtactical.com/Carbon-Fiber-Free-Float-Hand-Guard-7-Carbine-Length_p_4180.html

The lower is up to you but I weighed a bunch of combinations including some polymer ones. The lightest without going to titanium or plastic parts is the one piece Cav Arms, now known as the Cav 15 from GWACS Armory. I have three of the original Cav Arms lowers, built one sub 5lb AR with one and am building another lightweight with the above mentioned parts. Most metal lowers with standard parts weighs 28-30 ozs. The Cav weighs 23.7 ozs. Stripped they cost $130 but look for the blemished ones for $85.

http://www.gwacsarmory.com/lower-receivers-ar-15/
 
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#4 · (Edited)
I hear ya, but one has to consider what one is using the rifle for. I have full size ARs for service rifle matches. I have tactical ones for running and gunning. I have some basic ones for home defense. I wanted something light weight to carry around in the woods at my property and to play with. I ran 100 rounds through my original light weight (the sub 5 lb one I am going to use these parts in) and it didn't hiccup.

Would it last through 1000 round two day class? I don't know but that's not why I built it. It's not a race gun.

As for "cheap" that's kind of a relative term. A $500 pistol isn't considered cheap. A $500 shotgun isn't considered cheap, nor is a $500 bolt action rifle. But a $500 AR is "cheap" even if it fundamentally no different than any other AR and it works?

"Gimmicky"? Most of the parts are pretty standard off the shelf stuff. The one piece CAV lower has been around for 10+ years and mine have proven to be reliable.

One could argue that Slick sided uppers are less gimmicky than ones with spring loaded doors and jam buttons (aka forward assists).

Govt' profile (aka pencil) A1 carbine barrels seemed to work fine on the first generation of ARs. Lo pro gas blocks seem to be pretty conventional as are free floated hand guards. Flip up polymer BUIS are also pretty standard stuff these days.

I will admit the skeletonized bolt is kind of gimmicky but other than that everything else is pretty mainstream stuff. None of it is expensive titanium or specialized, expensive high tech stuff. Everything can be used in or returned to conventional AR use.



Ultimately this project is about building a light weight AR with off the shelf parts that are affordable. Granted, this build is outside the comfort zone of most people but I've been building ARs for 20 years. I hope it holds up and will let you know it.
 
#7 · (Edited)
Definitely looking forward to the final weight and report on reliability. Looks like a fun project.

Sent from my SM-G935T using Tapatalk
The rifle shown in the photo weighs 4lbs 15 ozs. With the light weight bolt it weighs 4lbs. 13 oz.

I hope to trim another 2 or 3 ozs off of that with the new barrel and upper reciever. A savings of 4 ozs is 1/4 lb which is pretty good when you get below 5 lbs.

From there you either stop or start shaving grams. Possible reductions include lighter BUISs, replacing the flash hider with a thread protector or simply machining the threads off. Don't really need a FH on this type of rifle.
 
#10 · (Edited)
More parts just were delivered. Here are the weights.

PSA Stainless Steel "Pencil" barrel, mid length, 1/7 22.47 oz. That's only .5 oz lighter than what I have.

PSA FSB .625" 1.48 ozs, it's 1/100th oz heavier than the aluminum .750" block I currently have. Edited to add that I skeletonized the new gas block and it now weighs 3/10s of an ounce less that the aluminum one.

PSA Slick Sided stripped upper 5.92 oz. It's .74 oz lighter than the Anderson and looks a lot better.

Total weight saving by part
Bolt -2.0
Barrel -0.5
Upper -0.74
FSB +0.01
Total reduction 3.25 ozs.

I am a little disappointed that I didn't get to 4 oz. I expected the barrel to be lighter.



However, I should be able to find 3/4 oz somewhere. The cut down flash hider weighs 1.2 oz and I don't need it. The rubber butt plate on the CAV lower weighs 1.73 oz. I'm guessing I could find a lighter/thinner butt plate for it with smaller screws. I just found out that GWACS Armory who now sells the CAV 15 lower offers aluminum receiver pins that are .4 oz lighter than the original steel pins.
 
#11 ·
Another thought regarding both weight reduction and matching components:
If you go with a lightweight bolt carrier, you SHOULD (I believe) be able to lighten the buffer, thereby losing another ounce or so, plus matching it to the weight of the boltcarrier.
 
#15 · (Edited)
After much research I figured out that the polymer fcg weighs about 3.5 oz less than standard steel parts. That's by switching out the hammer, trigger, disconnecter, selector, and mag release.

So the second round i.e, barrel, bolt and slick sided upper saved me 3.25 oz. Replacing the steel FCG parts with polymer should save me another 3.5 oz. Eliminating the flash hider is another 1.16 and replacing the receiver pins with aluminum saves another .4 oz for a total loss of 8.31 oz or over half a pound.

The quest continues.
 
#17 · (Edited)
Got the new barrel, gas block, bolt and slick side receiver together. It is now 4.37 oz lighter w/o flash hider. Total is now 4 lbs 9.63 oz. I do think it looks better without the shell deflector bump.



Next step is a poly FCG which will save 3.5 oz and lightweight receiver pins with is another .4 oz off.
 
#18 ·
Got my lightweight up to my hunting property to test fire it with the new barrel, receiver and bolt. Recoil even with just a 3.25 oz reduction in weight is noticeable. Didn't notice it before but it really slaps my cheek now. On the other hand, the barrel was accurate. I sighted it in at 25 meters with the polymer iron sights and was shooting cloverleaf groups with it. I ended up carrying it around the property for a day, checking my trail cameras, food plots and such. It is really a nice rifle to carry around. I had a 10 round polymer mag flush mounted mag in it. This thing is the weight of a 10/22, you hardly notice it.
 
#40 ·
Got my lightweight up to my hunting property to test fire it with the new barrel, receiver and bolt. Recoil even with just a 3.25 oz reduction in weight is noticeable. Didn't notice it before but it really slaps my cheek now. On the other hand, the barrel was accurate. I sighted it in at 25 meters with the polymer iron sights and was shooting cloverleaf groups with it. I ended up carrying it around the property for a day, checking my trail cameras, food plots and such. It is really a nice rifle to carry around. I had a 10 round polymer mag flush mounted mag in it. This thing is the weight of a 10/22, you hardly notice it.
Looks like it's overgassed with the lighter bcg and buffer. Using an adjusable gas block would help you tune it. You probably don't notice the bolt bounce? No issues with BHO?
 
#21 ·
Been looking at light weight builds for some time and many guys use them. This is kinda of an experimental thing. If it works, fine, if not back to the original parts. Remember this isn't a primary or SD rifle. It's more of a range toy/project to see how cheap and light I can get.
 
#22 ·
Got the new barrel, gas block, bolt and slick side receiver together. It is now 4.37 oz lighter w/o flash hider. Total is now 4 lbs 9.63 oz. I do think it looks better without the shell deflector bump.
Next step is a poly FCG which will save 3.5 oz and lightweight receiver pins with is another .4 oz off.
I did not know you could get that light. The 8" Python I shoot Bullseye with weighs exactly 4 pounds with a red dot scope/mount, unloaded.
 
#23 ·
Some guys shoot for sub 4 lbs. There is one blog I read that shoots for a 60 oz rifle. That's 3.75 lbs. However it costs him thousands of dollars to do.

I think 4.5 lbs and $500 is about as low as I can get it without having to start drilling holes in stuff or spending big money on titanium parts to make them lighter.
 
#26 · (Edited)
Had my light weight up at the hunting property/food plot shooting this weekend. Basically shooting from prone with a loop sling. Was banging a steel sillouette consistently at 125 meters. It is actually much nicer to shoot prone than off a bench. Didn't notice the recoil this time but did notice how light it is to carry around.

BTW, the Magpul MBUS sights are actually pretty good. First time I've shot at that distance with them. The front post is a bit too wide for precision shooting at distance but it is easy to see even with my old eyes. I suppose I should slap a scope on this just to see what kind of accuracy I can get but frankly the point is light weight not small groups. I was actually pretty pleased with it's performance. Been about a year since I've shot anything with iron sights at that distance. Once I got it zeroed in all the rounds were in a 5 or 6 inch group. No support or bipod, just a sling. I may just swap out the front sight post with something a bit thinner for my next go round. And of course it didn't blow up in my face so I got that going for me. :)
 
#27 · (Edited)
It occurred to me that if one didn't want a polymer lower they could always build that upper for a regular carbine lower. Weight is about half a pound heavier but still only about 5 lbs.

I weighed a number of stocks and the A1 carbine stock was the lightest at 4.2 ozs compared to an M4 stock which weighs 6.4. I should also mention that a basic A2 pistol grip is about the lightest grip I found. It weighed 2.4 ozs. Some people drill holes or cut slots in it to make it lighter. If you wanted something more stylish I suppose a MOE grip or something like that could be used, I don't have one so don't know the weight.

Buffer tubes, castle nuts etc pretty much weigh about the same unless you get into the really expensive stuff.




Though the Cav15 lower is more comfortable to shoot the carbine lower makes it more compact and still pretty lightweight.
 
#28 ·
Cool science project you got going on here!

I kinda laugh at some of the responses the thread has generated...

But I'm interested to see how it turns out...did you look into a side charging handle?

If you drilled some holes in your gas tube it might same some weight...:clown:
 
#29 · (Edited)
Cool science project you got going on here!

I kinda laugh at some of the responses the thread has generated...

But I'm interested to see how it turns out...did you look into a side charging handle?

If you drilled some holes in your gas tube it might same some weight...🤡
I get the skepticism of some people but it really is just a science project...that so far works, and is fun to shoot and light to carry.

And no, I didn't lighten the gas tube...yet :supergrin:

I don't think a side charger would be any lighter considering you need a bolt handle. Can't see that being lighter than a regular charging handle, but then again...I forget to mention that I shaved 1/2 oz off the charging handle before I took it shooting. Hand cycled 30 rounds through the action before shooting it. No issues with it while shooting. In fact I forgot I did it until I swapped the upper around in the above photo. Someone once said, "it's only weird if is doesn't work and you still do it".

 
#31 · (Edited)
Final Update....

The New Frontier FCG parts were installed and I did some final tweaking on a few parts. I drilled the bolt release both in the cross piece and the button.



I drilled a hole through the side of the steel gas block to lighten it and ground down the front corner to clear the handguard



I also drilled some holes in the steel barrel nut and retaining plate. Those three saved about 3/4 ounce.

Finally, I went back and weighed a bunch of different parts and was surprised to find that there was a difference of 2 ounces between all my buffer springs. The one in the rifle was an ounce heavier than my lightest. I swapped out that for the lightest one.

I took the rifle to my hunting property and shot it. Everything worked and once again I was surprised that the recoil was less than it was with the other barrel. It occurred to me that even though the rifle is lighter, everything else being equal the difference in recoil must be that the mid length gas system bleeds off the gas differently. I was surprised before at the sharpness of the recoil using the lightweight bolt with the old carbine length barrel.

Bottom Line....

The first LW project using the Cav15 lower, thin barrel and carbon fiber handguards got me down to 4 lbs 15 ounces. That was using parts I already had except for the carbon fiber handguards and aluminum gas block. I replaced the upper, bolt, barrel, gas block/tube, receiver pins, buffer spring and FCG parts. I drilled a few holes and took off the flash hider for a total loss of 8.807 ounces or more than half a pound.

The weight of the rifle right now is 4 lbs 6.19 ozs

That's pretty much as far as I can go with it without swapping out more parts with expensive titanium or chopping the Cav15 stock which voids the warranty.

Total cost to duplicate from scratch with the parts I used is $546 not counting shipping or FFL transfer fee for the lower. That could be $45 cheaper if you used the blemished Cav15 lower from GWACS Armory and an additional $20 cheaper if you use the Anderson Sporter Upper instead of the PSA slick side upper though you will gain 3/4 ounce.

The rifle works and while very light it feels solid not flimsy. For comparison this rifle is half a pound lighter than a Ruger 10/22. With a 10 round polymer mag it weighs what a 10/22 weighs empty.

Overall, I am happy with the project. I learned a lot about AR parts. Many are overbuilt and there is a wide variance in weights between spec'd parts. You need to weigh everything to find the right part. Finally, you don't have to spend a fortune to have a solid light weight AR.
 
#32 ·
Final Update....

The New Frontier FCG parts were installed and I did some final tweaking on a few parts. I drilled the bolt release both in the cross piece and the button.



I drilled a hole through the side of the steel gas block to lighten it and ground down the front corner to clear the handguard



I also drilled some holes in the steel barrel nut and retaining plate. Those three saved about 3/4 ounce.

Finally, I went back and weighed a bunch of different parts and was surprised to find that there was a difference of 2 ounces between all my buffer springs. The one in the rifle was an ounce heavier than my lightest. I swapped out that for the lightest one.

I took the rifle to my hunting property and shot it. Everything worked and once again I was surprised that the recoil was less than it was with the other barrel. It occurred to me that even though the rifle is lighter, everything else being equal the difference in recoil must be that the mid length gas system bleeds off the gas differently. I was surprised before at the sharpness of the recoil using the lightweight bolt with the old carbine length barrel.

Bottom Line....

The first LW project using the Cav15 lower, thin barrel and carbon fiber handguards got me down to 4 lbs 15 ounces. That was using parts I already had except for the carbon fiber handguards and aluminum gas block. I replaced the upper, bolt, barrel, gas block/tube, receiver pins, buffer spring and FCG parts. I drilled a few holes and took off the flash hider for a total loss of 8.807 ounces or more than half a pound.

The weight of the rifle right now is 4 lbs 6.19 ozs

That's pretty much as far as I can go with it without swapping out more parts with expensive titanium or chopping the Cav15 stock which voids the warranty.

Total cost to duplicate from scratch with the parts I used is $546 not counting shipping or FFL transfer fee for the lower. That could be $45 cheaper if you used the blemished Cav15 lower from GWACS Armory and an additional $20 cheaper if you use the Anderson Sporter Upper instead of the PSA slick side upper though you will gain 3/4 ounce.

The rifle works and while very light it feels solid not flimsy. For comparison this rifle is half a pound lighter than a Ruger 10/22. With a 10 round polymer mag it weighs what a 10/22 weighs empty.

Overall, I am happy with the project. I learned a lot about AR parts. Many are overbuilt and there is a wide variance in weights between spec'd parts. You need to weigh everything to find the right part. Finally, you don't have to spend a fortune to have a solid light weight AR.
Impressive, you can grind a little more off the bottom of the GB and
turn some off the barrel in front of the GB.
 
#37 · (Edited)
Here is the list of parts if you wanted to duplicate this rifle...

Prices are rounded up to the nearest dollar. They do not include shipping or FFL transfer fee for the lower.

GWACS Armory Cav15 stripped lower* $130
GWACS Armory aluminum LW receiver pins** $15
New Frontier Poly LPK $40
PSA Slick Side Upper $60
PSA Stainless 1/7 mid length pencil bbl $90
PSA lo pro .625" gas block $19
AIM Surplus light weight bolt/carrier on sale $90
Delta Team Tactical mid length gas tube $8
Delta Team Tactical Carbon Fiber free float hand guards $47
Delta Team Tactical Carbine buffer & spring $17
Delta Team Tactical Omega Polymer BUIS $14
Delta Team Tactical charging handle $12

TOTAL $542 + shipping and receiver transfer fee

Alternative Parts

GWACS Cav15 Blemish lower $85 (save $45)
Anderson Sporter Upper $40 (saves $20 but adds 3/4 oz)

Notes:
*
The Cav15 is a once piece molded polymer receiver which includes the pistol grip, stock, and integrated carbine length buffer tube.
**The Cav15 receiver comes with steel pins, the aluminum ones are .4oz lighter

Links to specific parts are found in first post and elsewhere in this thread

Delta Team Tactical has the cheapest prices on the parts listed and free shipping over $100.
 
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