Polymer80 AR Build

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  • GuitarmanNick

    Ultimate Member
    Jan 9, 2017
    2,221
    Laurel
    To begin, I was given this Polymer80 #G150 Phoenix v 2.0 lower as a gift and cannot complain about the price. Having done other AR-15s, I was confident this would be a walk in the park.

    I did buy a small X,Y vise which was my first mistake. I used a drill press for milling, which was my second mistake.

    The jig was weaker than I anticipated and allowed too much flex in the small vise so my trigger pocket was tapered with the bottom being too narrow. During the milling process, the chuck came loose from vibration and milled an extra hole through the bottom of the trigger pocket.

    Not being one to admit defeat, I pulled out my Dremel, files and sandpaper and spent more time opening the bottom of the trigger pocket until the dimensions were correct and I could fit the parts.

    Once I had the lower assembled and functioning properly, I grabbed an upper and could not get the take down pin to go in without force, then it would have to be driven out with a punch! Measurements indicated that the take down pin hole was too far to the rear by 1/32".

    Being a little OCD about my firearms, this was unacceptable so I initiated a request for a replacement.

    Polymer80.com's customer service is excellent. They asked me to send some pictures of the problem and confirmed my diagnosis. They then told me to cut the defective lower in two pieces and send a picture. After doing so, they sent me a replacement lower, jig, and bit set.

    Saturday, I milled it by placing it in the 80%Arms jig that I have used on other ARs, grabbed the router and was done in less than an hour. This time my trigger pocket looks great and required no additional work. As with the first Polymer80 lower, a couple of pre-drilled holes needed to be chased before parts would move freely, but it went together like any other.

    I was pleased that when I attached an upper, the pins went in without force and can be removed without tools. After passing function checks, I made sure to thank Polymer80.com for their excellent customer service and decided a post here would be appropriate.

    I went to their website earlier and noticed that they have a new version for the AR-15 and the jig appears to be more robust and less likely to flex.

    If you decide Polymer is the way you wish to go with an AR, Polymer80.com seems to be improving their product with each version and have proven to stand behind what they sell. As always, good customer service is a company's most valuable asset.

    Like most, I am quick to complain. With that in mind, it is also good to tell others when you are treated well.:thumbsup:
     

    Pensfaninmd

    Ultimate Member
    MDS Supporter
    Mar 28, 2010
    1,026
    Harford County
    To begin, I was given this Polymer80 #G150 Phoenix v 2.0 lower as a gift and cannot complain about the price. Having done other AR-15s, I was confident this would be a walk in the park.

    I did buy a small X,Y vise which was my first mistake. I used a drill press for milling, which was my second mistake.

    The jig was weaker than I anticipated and allowed too much flex in the small vise so my trigger pocket was tapered with the bottom being too narrow. During the milling process, the chuck came loose from vibration and milled an extra hole through the bottom of the trigger pocket.

    Not being one to admit defeat, I pulled out my Dremel, files and sandpaper and spent more time opening the bottom of the trigger pocket until the dimensions were correct and I could fit the parts.

    Once I had the lower assembled and functioning properly, I grabbed an upper and could not get the take down pin to go in without force, then it would have to be driven out with a punch! Measurements indicated that the take down pin hole was too far to the rear by 1/32".

    Being a little OCD about my firearms, this was unacceptable so I initiated a request for a replacement.

    Polymer80.com's customer service is excellent. They asked me to send some pictures of the problem and confirmed my diagnosis. They then told me to cut the defective lower in two pieces and send a picture. After doing so, they sent me a replacement lower, jig, and bit set.

    Saturday, I milled it by placing it in the 80%Arms jig that I have used on other ARs, grabbed the router and was done in less than an hour. This time my trigger pocket looks great and required no additional work. As with the first Polymer80 lower, a couple of pre-drilled holes needed to be chased before parts would move freely, but it went together like any other.

    I was pleased that when I attached an upper, the pins went in without force and can be removed without tools. After passing function checks, I made sure to thank Polymer80.com for their excellent customer service and decided a post here would be appropriate.

    I went to their website earlier and noticed that they have a new version for the AR-15 and the jig appears to be more robust and less likely to flex.

    If you decide Polymer is the way you wish to go with an AR, Polymer80.com seems to be improving their product with each version and have proven to stand behind what they sell. As always, good customer service is a company's most valuable asset.

    Like most, I am quick to complain. With that in mind, it is also good to tell others when you are treated well.:thumbsup:


    Great write up. I just bought a polymer 80 AR lower last week from Midway. I have been looking for a drill press to start the process but haven't purchased one yet. Is there anything special I need to know if I buy a router and do it the way you did?
    Thanks again!
     

    GuitarmanNick

    Ultimate Member
    Jan 9, 2017
    2,221
    Laurel
    You will still need a drill press for the trigger pocket pilot hole even if you use a router for milling. I would not try to drill that with a hand drill. The drill press should have a chuck that is bolted to the drive shaft if you intend to mill using the drill press. Most are just pressed onto a tapered shaft and are not retained. Lateral movement while milling will cause vibration and likely loosen the chuck. In my research, an acceptable drill press for this milling operation is more than most are willing to spend unless they have other uses for a drill press of such quality. The tolerances are much tighter, the bearings are intended to hold up when lateral force is applied and keep the drill bit stable during such operations.

    Drill press method: I suggest using a basic drill press to remove as much material as possible if you use the provided jig. If it is the v2.0, make sure that the jig is fully supported in your vise reinforcing the sides if needed. Flex here is a killer. A 4"- X,Y vise would be my recommendation but a standard vise can be made to work. Harbor Freight has them pretty cheap. Plunge cut using the mill bit and only move the work after you have raised the bit. Repeat until only a small amount of material remains on the side that can be removed with a file

    Best method IMO: Using a router. You need to drill one main pilot hole from top to bottom centered in the bottom trigger opening using a basic drill press. Proceed with router cutting from the pilot hole in clockwise direction as you make each cut. This will give you the best result for the finished trigger pocket. The one I just finished looks as good as any aluminum lower that I have done.

    Using drills or router, go slowly on lower speeds to avoid melting you work area.

    If you have a metal jig for building ARs, put this lower into it and follow the jig instructions as if doing an aluminum lower. Just remember to lower the speed on your router and drill press.

    Tools I would suggest for the most cost efficiency without sacrificing the quality of the result:
    drill press - basic, nothing fancy, but straight, square, and tight! Use for pilot hole and side holes only.
    Router - medium grade or better, variable speed(savings from above can pay for a nice one)
    4" or taller vise to attach to your drill press and move to a table for routing

    As with any build, measure twice, cut once and have fun!
     

    Pensfaninmd

    Ultimate Member
    MDS Supporter
    Mar 28, 2010
    1,026
    Harford County
    Great information... I will be starting my lower soon. I am going to use the router after I use a drill press as you directed.
    Thanks!
     

    GuitarmanNick

    Ultimate Member
    Jan 9, 2017
    2,221
    Laurel
    PSA: Adding an update to this old thread after experiencing a catastrophic failure last weekend with my P80 G150. I was firing my 9mm pistol build and decided to increase my rate of fire on the last magazine. About 5 rounds in there was an OOB discharge that blew the magazine well and magazine body apart, leaving a case partially in the chamber and the magazine lying on the bench surrounded by some 9mm rounds. Surprised the crap outta me, too!

    Upon investigating the cause, I have determined that the buffer is too light and there was too much rearward bolt travel which combined to cause the bolt to bounce when closing. Since there is no positive lock up and the bolt was actually extracting the round from the chamber slightly when I squeezed the trigger, it detonated out of battery. Now, if this had been an aluminum lower, it is likely that no damage would have been done to the lower although the magazine body may still have been destroyed.

    These lowers are best used for builds in rifle caliber rounds that have locking lugs on the bolt or for .22LR.

    If you decide to build a pistol caliber using a blow back bolt that does not lock up, an out of battery discharge is possible which will likely result in significant damage to the polymer lower. Special attention will need to be given to selecting the correct buffer and spring for your build.

    My remedy after this failure will be to build a new aluminum lower and get a longer and heavier buffer for this toy.

    I have been very pleased with my other Polymer80 products, not so much with the G150. This particular one was a replacement for the first one that had the take down and pivot pin holes too far apart and could not attach to an upper. Their customer service is great and I have contacted them to advise them of my concerns. If they offer another replacement, I will pass but may seek a discount on another product. No more polymer ARs for me!
     

    tony7815

    Member
    Feb 11, 2016
    30
    I have completed 3 80% polymer lowers. To start I drill though the holes for holding the two halves of the jig together and use 4-40 screws and nuts to ensure the jig holds the lower tightly. I clamp the jig and lower in a heavy vise and rather than use the drill bit provided to hog out the material in the FCG I use a 5/8" Forstner bit. A Forstner bit drills a flat bottom hole and the holes can be overlapped without the bit wandering off. I drill to a depth a few thousandths shy of the final depth. Because there is a tendency of a drill press to deflect slightly I make multiple passes with the end mill bit to achieve a straight wall.
     

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