Posted on October 23rd, 2013 by ar15news
As many of you already know, I have been building an SPR (Special Purpose Rifle). There are many forms of an SPR upper but the main components in my mind are an 18″ Rifle Length match grade barrel and a long handguard or rail system. I personally chose a billet receiver set from CMT Tactical, a Black Hole Weaponry 18″ SPR barrel and my friends over at Geissele sent me an SMR MK3 Mod1 15″ rail along with some armorer’s tools to help with the upper assembly process. The main goal of this article is to give you a behind the scenes look at the actual assembly of this upper and to show how these tools are used. The rest of the details will be outlined in a second article coming soon. These pictures are not my usual studio style photos as they were taken at my work bench while I assembled each part.
GEISSELE AUTOMATICS – GAS BLOCK ROLL PIN TOOL
I used to hate installing the gas tube roll pin. It always seemed like you needed four hands to do it. One to keep the gas block and gas tube in the right place, one to hold the punch, one holding the roll pin with needle nose pliers and one to hammer it in. For this upper build I was really excited to have a chance to use the Gas Block Roll Pin Tool from Geissele which is basically a steel punch with a hole drilled in the end that is sized for the roll pin to fit into.
With the roll pin inside of the Roll Pin Tool I could now put it to use. I inserted the gas tube into the Geissele SGB (Super Gas Block) and put a piece of wood under the edge of the gas block to hold it at the right angle. I then tapped the roll pin in as far as it would go with the Roll Pin Tool. The roll pin remains about half way out and you just finish it off with a regular punch.
Using the Roll Pin Tool seriously made the installation a much easier than it used to be. No more having the gas tube roll pin fall over when you touch it with the punch or move to the side as you hit the punch with your hammer leaving nice marks on the gas block. You still have the issue of holding the gas block still while you hammer the roll pin in place but I’ve found its pretty easy to hold the gas block down with the same hand you are holding the Roll Pin Tool in. If you build a lot of uppers like i do this is a great tool to have. The Roll Pin Tool can be purchased at Geissele.com.
GEISSELE AUTOMATICS – REACTION ROD
The Reaction Rod is a tool that I’ve had my eye on ever since they first introduced it one year ago this month but have just never gotten around to picking one up. Its made from a single piece of 4140 Steel and is built to last. On one end the Reaction Rod features flats that allow it to be held securely in most quality vices. The opposite end has grooves machined in that fit firmly into the inside lugs of an AR-15 barrel. With the typical action block that attaches with pins to the upper you are putting all of the stress of installing the barrel nut, etc on the upper receiver itself. By using the Reaction Rod you are taking all of the stress away from the receiver and putting it on the barrel extension which is more than capable of handling it.
The first step is to join the upper and barrel together. You then slide the upper and barrel onto the Reaction Rod and guide the grooves of the Reaction Rod into the lugs of the barrel. There is no specific angle that the upper has to be at with the Reaction Rod as it is engaged with the lugs.
Once you verify that the Reaction Rod is seated completely inside the barrel extension you can now start building the upper. One thing you’ll notice is that there is absolutely no play. The upper doesn’t wobble or twist at all and is very firmly held in place. However, it does not lock in place so you will need to be sure not to do anything that would pull the upper off of the Reaction Rod. It would take a lot to do that though as the Reaction Rod fits snug inside the receiver from front to back not just at the lugs.
The Reaction Rod does not just stop at allowing you to install the barrel nut though. I found it very useful during the installation and assembly of the entire upper. I mounted the gas block and gas tube, rail system and the muzzle brake all while the upper was mounted to the Reaction Rod.
I know how AR owners are. We’re always buying new rails, flash hiders, barrels, etc. not to mention building complete uppers from scratch every now and then. The Reaction Rod is one of those tools that you’ll find yourself using all the time. Plus it would make a great alternate weapon in a pinch. You can purchase the Geissel Reaction Rod at Geissele.com.
For those of us who enjoy playing with our adult Legos (aka building AR’s) the Geissele Automatics armorer’s tools are awesome and well worth the purchase. I plan on using these tools for many years to come and would recommend them to anyone looking for some great armorer’s tools. Don’t forget to also check out all of the amazing Geissele Automatic Triggers as well while you’re over there. Don’t forget to check out the Geissele Automatics Facebook page too.
This is the first of 3 articles regarding the AR15NEWS SPR Build. Next will be an article outlining all of the parts we used and where to get them accompanied by some nicer shots of the complete rifle. After that will be a full range report article. These articles will be happening soon so keep an eye out.