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Lightweight AR- Part II

In the first lightweight article I got my build down to 4 lbs, 15 ozs using the Cav Arms/Cav 15 lower. I suggested some options that included a lighter weight bolt from AIM Surplus and a pencil barrel from Palmetto State Armory.

The bolt from Aim is supposed to weigh 8.9 ounces whereas the bolt I was using weighed 10.8 ounces. The AIM bolt went on sale for $89  so I ordered it. I weighed it upon delivery and it weighs 8.89 ozs as advertised. That’s a savings of 2 ounces.

The stainless steel PSA pencil barrel was available and I broke down and ordered it as well. It is thinner than a conventional barrel so you need a .625″ gas block for it instead of a .750″ block on most other barrels. I had a very light aluminum .750″ gas block on the rifle. I could not find an aluminum .625 block so ordered a steel one.

The original barrel weighed 22.96 ozs and the gas block weighed 1.47 ozs for a total of 24.43. The PSA  barrel weighs 22.47 and the gas block weighs 1.48 ozs or only .01 more than the aluminum gas block and a total for both of 23.95.  Not much savings there (.48 oz) but it is about the cheapest and lightest barrel you can find these days. It should be noted that this is a 1:7 twist barrel with a mid length gas port rather than a 1:9 barrel with a carbine length gas port on my original barrel.

Finally, I noticed that PSA had a true slick side upper for sale. Unlike the Anderson Sporter I was using the PSA upper does not have the shell deflector bump on the side. Upon arrival the PSA weighed 5.92 ozs which is .74 oz lighter than the Anderson. It also looks much better. $59.95 and yeah, I just paid $20 to save 3/4ths of an ounce. However, if it had been available first I would have bought the slick side instead of the Anderson.

Total weight savings with these new parts is 3.22 oz. Not quite the 4 oz I was hoping for but within reach.

The next phase of weight savings was to replace the steel receiver pins with aluminum and replace the steel Fire Control Group (FCG) with polymer ones from New Frontier Armory.

The aluminum pins ($14.95 shipped free) save .4 oz off the steel ones.  The polymer FCG parts weigh 2.46 ozs less than the steel ones for a total savings of 2.86  ounces.

Current reduction of 6.08 oz plus take off the weight of the cut down flash hider (1.16 oz) for a total of 7.24

The polymer FCG parts from New Frontier Armory weigh the following.

Steel         Poly

  • Trigger                                               .920             .197
  • Disconnector                                     .278            .053
  • Selector                                              .567             .109
  • Magazine catch w/button              .358            .091
  • Hammer                                            .987            .197

total                                                               3.11              .647

Total reduction  -2.46 oz

Additional Ways to Cut Weight

-Gas Block-The steel gas block weighed 1.48 oz. I had to  grind the top down a bit to fit under the hand guards. In doing do I noticed the very solid sides of the block could be drilled out without compromising the structural integrity.  I was able to remove .37 oz .

-Bolt Release-The solid steel bolt release invited lightening. I drilled holes in the cross piece and button. -.11 oz

-Barrel Nut/Retaining Plate-Drilled four holes in the steel barrel nut and three in the steel retaining plate. -.087 oz

-Re-weighing parts. I went back and reweighed parts in the rifle to make sure I had them right. In the process I weighed a number of buffer springs and was surprised to find a deviation of as much as 2 ozs between 5 different springs. I actually found a spring 1 oz lighter than the one I was using. With the drilled parts the reduction was 1.567 oz.

Total reduction with the lighter spring and drilled parts= 8.807 oz

The original weight of 4 lbs 15 oz minus the reduced weight of 8.807 oz equals total current weight of 4 lbs 6.193 oz or a reduction of over half a pound.

 

To reiterate, here’s the parts and what it would cost to duplicate
Prices rounded up to the nearest dollar (does not include
shipping, or receiver transfer fees)
GWACS Armory Cav15 stripped lower*  $130
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
Delta Team Tactical mid length gas tube $8
GWACS Armory aluminum pins $15 (free shipping)
AIM Surplus light weight bolt/carrier  on sale $90
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 Blem $85   (save $45)
Anderson Sporter Upper $40  (save $20)
*The Cav15 lower is one piece that incorporates the stock, pistol grip and buffer tube into one molded unit which saves considerable weight.
Does it Work?
I took the redone lightweight up to my hunting property and sighted it in. The barrel shot 3 shot groups into one hole at 25 meters.   Once sighted in I took it out to about 125 meters and started to shoot steel with it. 125 meters was chosen because there is a flat spot in my food plot at that range which allows for shooting from prone comfortably. In prone with a loop sling for support I was able consistently banging steel using the polymer back up iron sights. Groups were 4-6″. Those sights aren’t the best for precision shooting but they worked. I had no malfunctions of any kind.  I am happy with the accuracy and believe it could do better off a bench rest and/or with a scope.
Other Things
In my range notes I was noted the sharp recoil when I first put the light weight bolt/carrier in the original rifle compared to the regular weight bolt.  Shooting the rifle with new barrel and the light weight bolt I noted how mild the recoil was comparatively.  All other things being equal I can only surmise that the mid length gas system on the new barrel mitigates recoil better than the carbine length gas system on the old barrel.
I also should note how easy it is to carry this rifle around. I took a walkabout on the property perimeter (over a mile) through rough terrain. It was loaded with a polymer flush fit 10 round magazine and it felt like I was carrying a little .22 rifle.
Bottom Line….
A 4 lb 6 oz  center fire AR15 that is lighter than a Ruger 10/22 .22 rifle. It works, is accurate and won’t break the bank.
Mission Accomplished!

About The Author

Mac created nylonrifles.com. It is the premier website and largest source of information on the internet about Remington nylon rifles. Mac spent 34 years in law enforcement, campus law enforcement and emergency management before he retired. He is a former Federal Firearms License holder and private investigator. He has a BS in Criminal Justice and Master’s Degree in CJ and Security Administration. He has taught criminal justice at a college level and is certified and has taught numerous law enforcement, security and emergency management classes, including classes for the US Dept of Homeland Security. He currently is an emergency management and security consultant as well as being a Revolutionary War Veterans Association Appleseed rifle instructor. He is a Second Amendment Foundation Life Member and NRA Life Member and Range Safety Officer.

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