was successfully added to your cart.

The Process: Bringing the F4 Defense Small-Frame AR-10/.308 to Market

By October 13, 2017Uncategorized


The F4X: Small-Frame .308

We have had several folks contact us with questions about the F4X (Small-Frame .308) and when it will be ready.  Being completely up front, the best I can do is give an estimate, but that is entirely based on Test & Evaluation.  This led to quite a few questions on the process of bringing a new product to market.  And of course, there are many ways to approach this, we will just document what we are doing and changes we make along the way to field a top-notch weapon system.

Design Goals

Obviously, size and weight were very important, right behind performance and reliability.  Being a small-frame system we wanted the weight to be in line with that type of design.  Weight seems to be a major factor in today’s market and there are quite a few differing opinions.  We determined during design that we wanted a sub 8 pound .308/7.62 (Dry).  This drove several design decisions.  The Adaptive Rail System – Lite (ARS-L) was originally developed for the Small Frame .308.  After the feedback we got from industry and shooters, it was decided to develop one for the F4-15 as well, at least in the 12 and 15-inch configurations.

Before I talk specific decisions on how and where to cut weight, I think it is crucial to talk about weight distribution and the importance of making weight reductions in the right places/components to keep the rifle well balanced.  The last thing we wanted to do is develop a rifle and then load it up with a bunch of lightweight aftermarket parts.  So naturally we started with the center; the receivers.  The great thing about strategic machining is that you can cut weight and make it great looking at the same time, they usually go hand in hand.  So, we got started on machining certain areas of the receivers to give it a lightweight balanced feel.  So far that has been very successful, especially removing material from behind and under the brass deflector which is just a massive section of Aluminum.  Additionally, all the recessed cuts throughout takes a little bit of weight off at a time.

The 15.5 “ARS-Lite comes in under 11.5 ounces with the barrel nut so that was a good fit.  The barrel, which is crucially important was another decision we went back and forth over for months.  Because our barrels for the F4-15 are manufactured for us by Black Hole Weaponry, it made sense to start there.  We chose a profile that is light/standard but with enough mass to balance and handle recoil from a .30 caliber weapon.  The barrel is 18 inches with a 1×9.73 twist rate and of course features their kick-ass polygonal rifling.

We are now testing and evaluating different buffer systems, to dial it in even further.  The F4X uses a mid-length gas system with an adjustable gas block for fine-tuning.  What we ended up with was a 7.53lb Small-Frame .308 that is still heavy and balanced enough to shoot comfortably.  With the introduction out of the way, let’s jump right into day 1 of testing.

Testing Day 1

The F4X felt good and shot accurately, but we had a short day because the magazine was dropping after each shot or when the Bolt Carrier was driven closed.  Oh, the joy of new weapons system.  We immediately looked at 2 potential problems.

First, the magazine catch position, depth, and movement.  The other area that may have potentially caused this issue is the broaching of the magwell.  The broaching process is straight forward and chances are, that was not the reason.  You can see a short video of magwell broaching here:  Broach Video-1  As it turns out, it was the magazine catch slot depth.  We were too shallow by .058 +/- .005.  We updated the models and prints and fortunately we are removing material, rather than adding.

Mag Catch Slot Depth

These types of hurdles are the exact reason we only fabricate a few receivers, before we run 10-15 T&E guns for full-scale operational testing.  Fortunately, this is an easy fix and we’ll be back in business almost immediately.  The areas we were able to evaluate did great.  Ejection and timing was solid, recoil impulse was manageable and comfortable, and accuracy was good.  No surprise there considering the barrels we use.  Of course, these were very limited sample sizes due to it being the first run and the issue with the magazine catch.  All-in-all it was a great start.  We will continue to update the blog as T&E continues.  If any of you guys have questions/comments please don’t hesitate to reach out, we would love to hear from you, as this blog is designed for you guys, not us.  The point of our blog posts is to inform the 2A community and to share the experiences we have.  When building F4 from the ground up there was very little inside information into the industry.  We are going to lift the curtain and give everyone a glimpse at what we are doing behind the scenes.  It also needs to be stated that there are several ways to accomplish what we are writing about, but we’re just going to share our process.

Thanks for reading, stay tuned for more updates.

Dave Fairfax, COO


Leave a Reply