ARP 138 - Building a Special Purpose Rifle


Welcome to Episode #138 of the AR15 Podcast. Tonight we are going to talk about building an SPR or Special Purpose Rifle.We want to let you know about a new source of cool products! Please go to to pre-order the Huckleberry patch and buy FRN stickers.

Also, the Firearms Radio Network will be at the 2015 BullPup Shoot in Mount Carroll, IL on September 19th. Go to for more info.

Catch up with the hosts

Main Topic

Building a Special Purpose Rifle, otherwise known as the SPR

What was the SPR designed to do.

-shortened rifle-gassed M16, whereas a RECCE is a lengthened carbine

-provide more punch at longer ranges

-deliver maneuverability

-initially stood for Special Purpose (upper) Receiver

-USN Mark 12 Mod 0/1 (we’ll go into all the details of this platform in a few weeks)

Build ConsiderationsTwist Rate - The origin of the SPR points at a conceptual marriage of height weight match bullets with match grade barrels.

1:12” might be well suited for 55gr, but doesn’t like the heavy stuff.

1:8” is good all-around that’ll stabilize 55gr up to 77gr, whereas

1:7” is more of a dedicated heavy-bullet twist.

Barrel Characteristics- 18”, rifle-length gas, match grade; “SPR-profile”

Stock -  Generally a fixed stock.

Triggers - 2-stage vs 1-stage

Rails - Definitely free-floated

Optics - +6x… 3.5-10x40 or 3-9x36


Accessories - Bipod, night vision

Otis Technology:

August 9: Joe Lautenschleger

August 16: Jones Foxx Jr.

August 23: Don Hall

August 30: David Dickerson

The fine folks at Otis Technology have sent over a mountain of rifle maintenance tools and cleaning kits for the AR-15 and AR-10.  We’ve been tasked with giving them away.  Watch for the special posts on Facebook and Instagram to get a chance to win some of the awesome products made by Otis Technology.  We’ll give away a complete MSR Cleaning kit in either 5.56 or 7.62 in the middle of each month up until Christmas, when we’ll give away a complete Otis Technology Elite Cleaning System to one lucky listener.  During the alternating weeks, we’ll be giving away a host of Otis tools and cleaning supplies.


Stewart P.: Enjoyed your last show, especially the personal experience on parts you used that really seem to work. For future shows, I would love to have you do a comparison being the newer CLPs that have been coming out such as Froglube, Fireclean, EWL 2000, etc. A lot of internet chat has these CLPs as either being the greatest thing ever to the worst snake oil scams in the world.  Would also like to have a future show covering  the DI vs. piston debate.Tom A: Hi guys, I really like the show but I think there may be something wrong with your RSS feed.  I listen to you guys through Downcast and I haven't received your show from the 22nd yet. I thought it may have been my app so I deleted you show a resubscribed but now there are no episodes available to download. Hope you can get this up and running again soon.

Michael A:  Reed, I was listening to the 450 Bushmaster show and heard your call for people to participate. I'd love an opportunity to connect with you and the guys. I'm currently an Army Reserve soldier (don't hold it against me ). I love to shoot and have personally built 2 AR pistols, a DPMS pattern 308, and 9mm chambered AR. Lastly, I speak for a living. My civilian job is training executives at a Fortune 100. I hope you and the guys see fit to connect with me. I think it would be a great experience.


Stephen S: I really liked your money well spent episode. You guys on the network get all of my admiration. The dedication it takes to put out a show every week is amazing. I download almost all of the shows on the FRN and am trying to catch up on all of them in my free and driving time.On the last show, Reed asked for show subjects.I am about to begin my first AR build. I am building a 20" bull barrel for mid range. I don't have the largest budget at my disposal and am interested in the M223 model Nikon scope. Probably 4x-16x. I would like to know how they stack up to vortex and bushnell in the same price point. Maybe the Vortex Viper HS, and Bushnell Elite Tactical for a little more.  Thanks for all your hard work.