F4 Defense SF-10, Small Frame AR10 – Review with Field Experience

F4 Defense SF-10
F4 Defense SF-10

U.S.A.-(Ammoland.com)- F4 Defense was great to work with. I got a complete Small Frame AR10 build into my hands early in last year (2019) when things were at their craziest (SHOT Show and the trade show season). I planned a hunting and hard-working review.

The rifle I received is NOT a production rifle – it was built from available parts as a one-off model and in the 7mm-08 caliber. I like it like that, sometimes it can really show you if the receiver sets are going to function under mixed tolerances.

Looking at it closely, the F4 Receiver Set is quality work, solid machining. I like the lines, their own interpretation and mark leave no doubt this is their product. Anodizing is a quality finish, this receiver is set up as an ambi receiver, the magwell has a no wobble, not too tight, and a clean smooth fit for Magpul magazines that I use.

F4 Receiver Set
F4 Receiver Set

Setting the F4 Defense Small Frame Receivers side by side to the older SI-Defense (now Falkor Defense) standard AR10 receiver you can see where the design shortened up. You see it immediately out of the box but when you put them side by side it makes very obvious… why didn’t they (the industry) do this decades earlier is a question that might run through your head.

The Small Frame AR10 Receiver stands out for weight reduction, as a shorter more compact platform overall, and for using AR15 parts from the magwell back to the fire control area. What you can not see or touch immediately but is the real key to what makes this special, is the internal engineering that results in reliability. If you know anything about AR10s; it is that they can be frustratingly finicky or temperamental to tune in different calibers & configurations, not to mention how they might function with different parts and shorter barrel lengths.

There have always been a few mechanical changes needed to “clean up” the standard AR10 format. No previous manufacturer ever undertook the task because the focus and popularity have been on the M16/AR15 all this time.

Small Frame AR10s have officially changed the game. I can honestly say this F4 Defense build has not malfunctioned once right out of the box. It has been treated to all the harsh elements of dry dusty hot windy climbs through desert canyons to the sub-freezing weather of a January Elk hunt and has not been lubed, cleaned, or treated special in any way. I can not say that for the SI-Defense receiver set that I had built into a .308 upper and a 6.5 Creedmoor upper. It was a long frustrating row of troubleshooting and fine-tuning to get them to run consistently. The standard AR10 format has a long history of this finickiness from a manufacturer’s stand point.
Here is the magic in F4 Defense’s own words:

So what makes the Small Frame AR10 more reliable in feeding and function across every caliber you throw at it?  Simple; the geometry is improved in subtle but significant ways, particularly the bore axis, which is lower on the Small Frame AR10, and that makes a substantial difference in feeding reliably.  Why is that important?  It has to do with the travel as the bolt returns and strips off a new round.  In layman terms, the cartridge has an easier path into the chamber.  The higher bore axis on the standard AR10 means the round has to travel at a steeper angle before entering the chamber.  The lower bore axis on the Small Frame AR10 lends itself to creating a more linear path for the bullet to travel as it’s stripped off the magazine.  It does not need to travel as high, before it redirects into the chamber.  Furthermore, damage to the projectile tip is less likely because the travel is smoother.  When discussing true precision shooting and getting everything you can out of a rifle and cartridge, minimizing the damage done to the tip of your projectile certainly warrants a discussion.  Hollow point and ballistic/polymer tipped projectiles are very common with high-end quality match grade ammunition.  Unfortunately, these projectiles are susceptible to damage during feeding.  The more linear and streamlined travel of that projectile in the Small Frame AR10, because of the lower bore axis, results in less damage and more uniformity between shots.F4 Defense – Dave Fairfax Jan 13, 2019

I believe the AR10 standard format just never completed it’s engineering cycle. No one cared enough to revisit it and address the inherent issues that where being presented over and over. The M16 was battle born and pushed into service in mass numbers, the civilian market followed, and the most mass produced American Rifle was the reality. I’m happy with all that. The 21st Century is here and we have good folks like F4 Defense stepping in and they have done so with a splash. The era of the Small Frame AR10 has just begun…. You will see some very cool things coming from Small Frame AR10s from this point forward. I’m excited to see it too. The package is Lighter, more Consistent, Accurate, and hungry for all the fitting calibers… I have some predictions about what might follow in the phase II evolution of this receiver too but lets wait and see who does it first.

Why 7mm-08?

First response – why not? Second, this caliber has a rich history of hunting and field performance that can’t be denied. I like that it has a lot of factory availability, wide range of weight choices, is reasonably priced and runs in an AR10 platform without any mag or other accessory modifications… and I had that head turn reaction when I first heard they had an AR10 barrel for this caliber on hand.

F4 Defense SF-10
F4 Defense SF-10

Magpul’s AR10 mags have had zero problems feeding the 7mm-08 and there were zero modifications made or needed to run this caliber in the standard mags I already own.

I ran factory 139gr Hornady Deer Hunter ammo through it on the first break-in. When I spoke to F4 Defense about recommendations for a quality round they referred me to Sparks Munitions (their preferred ammo partner) and recommended we build an AR load specifically for Big Game.

After an exchange with Anthony at Sparks Munitions – I sent the Upper to him (he already had an F4 Defense SF-10 Lower). The Upper still had a zeroed scope on it and he went to work finding the best load for the setup. I soon got the Upper back and took it to the range. Sparks Munitions nailed it, a 165gr Sierra GameChanger, with solid consistent data, powerful payload, and accurate to boot. More about that in a minute.

The Barrel

In making arrangements for this review – F4 Defense said they had a barrel they needed to be tested from a manufacturer they are using for production rifles…. I don’t know if they suggested it or I suggested it but the result was “hey, put that barrel on the Small Frame Receiver Set you send me and lets test, review, and play with both the barrel AND the receiver set at the same time.”

The Barrel is made by Craddock Precision. It is a heavy fluted 20” stainless steel barrel. The flutes are uniform and even (important for longer range accuracy in warm+ barrels). The finish is quality work, and F4 Defense topped this barrel with a Seekins Muzzle Device. It has an adjustable gas block but no adjustments where needed right from the first round… it shot well straight out of the box and has never malfunctioned between the two loads of ammo I have ran thru it.

F4 Defense SF-10
F4 Defense SF-10

I did a slow fire break-in. Then for paperwork on a 100yd range, the first round was low 4” and right 2”. I made adjustments and the next round was low 1.5” and right 1”. Adjustments and the third round was touching the 1” ring. The next couple strings all started touching each other and from that point on, any adjustments I made I confirmed with 3-5 round groups and everything stayed touching out of this barrel using common factory, over-the-counter hunting ammunition at 100yds.

My next trip to the range I made no adjustments and the barrel shot solid from first-round cold bore to end of the magazine. Groups stayed tight and I had solid first-round hits to 500yds.

After everything I had seen the Craddock Precision barrel is doing a bang-up job. I am both pleased and have no complaints or even suggestions. This was my first time shooting their barrel so it was fun, interesting, and I like the results. I hope they keep doing what they are doing, American quality craftsmanship that is everything I want in an accurate AR Hunting Rifles.

Did you know, F4 Defense has a Sub-1/2 MOA Accuracy Guarantee! To my knowledge, they are the only AR manufacturer in the industry with that kind of promise. It is another reason why these Small Frame AR10s they put out are so great right out of the box.

As of the printing of this Article they also claim to have the lightest production AR10 rifle in the world at 5.8 pounds. It is worth checking out.

Real Experiences in the Field

F4 Defense SF-10
F4 Defense SF-10

This F4 Defense Small Frame AR10 rifle has been in my hands for over a year. The Receiver Set, the Craddock Precision barrel, and the Sparks Munitions ammunition recipe for this caliber have worked perfectly together and I am happy to say this really is a solid Hunting Rifle. As a parts build that I can appreciate – their production models excel in quality, finish, and attention to detail as much and even more so than this demo rifle.

I have put this Small Frame AR10 Hunting Rifle through its paces. It’s now scratched, was never cleaned or lubed after break-in, has been packed into the woods, the desert, in the rain, the snow, -12 degrees, and been at various elevations and operated flawlessly.

The Stage is Set

I seasonally Guide Elk Hunters for an Outfitter who operates on Private Land Leases in CO & NM. A returning hunter agreed to use this rifle for his Elk Hunt. 
As soon as he arrived we made the drive to the nearby and well known NRA Whittington Center in Raton, NM. I like the long-range with the White Steel Buffalo at 1,123yds. The Shooter (Chris) is a USMC Vietnam Veteran. He hunts with Bolt Action rifles and I had to convince him this was a great gun to kill an Elk with… it only took one shot to win him over!

F4 Defense SF-10
F4 Defense SF-10

The rifle is zeroed at 100yds and I had Sparks Munitions Data on hand as we discussed the various ranges. I hoped he would start at the obvious and easy 100yd target just for a warm-up. Chris said, “Nope, I’m going out to the 357yd steel target first shot using the ammo data just like I would do if I was looking at the Elk I wanted…”

It took him a few extra seconds to get his cheek weld right. then the Small Frame 7mm-08 barked and the beautiful sound of hard slapped steel banged instantly after.

He looked up, grinned real big, and said, “I think I am gonna want one of these…”

He preceded to center punch and bang steel targets at every range they had and a few got follow up shots just to hear the steel slap again. While I was loading another magazine for him, he was eyeballing the range thru a pair of Binos, I heard him say, “I wonder if I can hit that White Buffalo…. whats the hold over on that?”

The data I had on hand only went to 800yds. I told him I didn’t have the data to 1123yds where the Buffalo was cause we would probably be shooting Elk within 600yds. I could sit down and penciled it out though. We came up with a pretty steep holdover and I handed him the magazine and told him it had better be a first-round hit.

When the shot rang out, the Grin on his face said it all…. the first-round hit. You could hardly hear the slap but you could see the bullet splatter looking through the Binos at the White Buffalo. That is a 1,123yds hit folks! In all, three shooters (including myself) had rounds on the White Buffalo and we shot about 180rds total at every distance the steel range had targets on.

Chris didn’t get his chance at a Bull Elk this year but we hiked, climbed, and put in some miles. He was ready, he carried that rifle like it was his new favorite rifle (I think it might be). He has asked me several telling questions – questions that tell me; I bet after the tax returns of 2020…. Chris is gonna have a new Small Frame F4 Defense Hunting Rifle to sight in.

Colorado Bound and Down

I had picked up earlier in the year 2x leftover Antelope Doe tags for Southern Colorado. I got to the property and started scouting right at first light still sipping a McDonald’s coffee. There were no animals waiting for me right on the other side of the gate, I expected weather and maybe some predators had moved the Antelope around. I had been seeing Antelope daily for several months Guiding Elk Hunters passed this location. I really expected a pretty easy hunt. I scouted west; soon I was convinced the Westside had no Antelope – the Mule Deer paid me nearly no mind at all and casually went about their business as if knowing I didn’t have a tag for them in my pocket.

I headed to the Eastside. I came to a fork in the road and decided I’d glass up the fork I wasn’t going to take just real quick… Just as I was about to pull my binos down I noticed right at the crest of the nearest hill was an Antelope head staring right at me at about 275yds! I did a double-take, relocated, and there was a Doe Antelope staring me down. I grabbed the camera, eased out of my seat, grabbed the F4 Defense Small Frame 7mm-08 and poked it through the window of the open door. I was just a hair too low of elevation so I rested the handguard on top of the mirror. I was still too low but the Doe was on the move. She was angling right in front of me at a steady walk! 200yds…. 175yds…. broadside. It could not have been any better. Except, I was fumbling with the camera (self-filmed hunts are not easy). No sooner than I had her in the frame, she would keep walking right across it before I could re-mount my rifle…. then she had cattle in the background and I couldn’t shoot, then I had to readjust the camera and get her in the frame – she was still steadily walking and would not stop. She walked over the crest of another wrinkle in the terrain and was gone.

I was sitting there cussing myself for the lunacy of trying to set up a camera, of having the easiest hunt ever, with a shot right from the driver’s door and not getting a round off.

I was pretty sure I had an idea where she was bee lining to. So I backed out, drove east (away from the direction she had went). I was in hustle mode. I grabbed my pack, checked to make sure I had knives, a bag, gloves. I slung the pack, put 3x extra bullets in my pocket and speed walked to this deep ravine that would give me cover for about three-quarters of a mile. I crept up slowly and scanned the view to see if I had guessed right. I was just emerging when I spotted her – already watching me. I slowly ranged it – 480yds. I could easily do this shot, she was broadside, relaxed and not even giving me concerned body language….. but I didn’t have the zoom lens on the camera! I needed to be closer. Looking at the terrain I hatched a new plan. I’d walk casually parallel to her directly west to the drainage about 500yds away then double back south, walk under a little ridgeline to a clump of trees that would be directly on the other side of her from where I currently stood. It should be perfect.

It was – it was perfect. I got where I wanted under the concealment of the ridge and now behind two cedars that I could squeeze between and set up for a shot. I sat down, scooted on my butt inch by inch outwards with the camera on a tripod, with the pack, with the rifle. When I eased around the branch – she was staring directly at me again! This time in obvious alert mode (you will see). I slowly raised my range finder…. 207yds. I eased the camera out a bit more. Hit power, found her, focused it and she was still staring head on at me and just over the crest of the hill in my seated position. If I went prone I lost her over the edge. If I stay seated I could barely see her upper chest and head. She would not move – it was a 15 min stare down. The camera battery was low! It would not take more than 45 secs of footage before shutting down. So I got set up hoping she would turn to move away and give me the shot.

I scrolled through my mind the possibilities of what was going to happen. She might take several steps forward to get a better look (Antelope do that) and then turn to leave and I would hammer her, she might just wheel and run any second if she turned directly 90 degrees either way and walked a way she might be lost in the terrain again. If she wheeled 180degrees and ran straight away I would be S.O.L Could I make this shot? Could I hit her mid-chest and just favor the left side for a throat/heart combo? Could I put one up her nose?

I set up for the shot. Seated, Leaning backward slightly against my mostly empty pack, legs bent and crossed at the ankles, knees together with the rifle tucked into the notch of my knees. One-handed I reached over and pressed Power on and Camera, Pressed Rec, mounted the scope, found my crosshairs, second breath, third breath, and a light press to the trigger….. one of the most solid fleshy bullet slaps I’ve heard following the rifle report in a long time! She was staring me down in the crosshairs and then she wasn’t. I had to power up the camera again, hit replay and make sure it happened the way I thought it did.

When I walked up on her, still pointed straight in the direction I just came from. It was here I realized – headshots are not media-friendly and the 165gr Sierra Gamechanger round Sparks Munitions built had solidly wrecked complete havoc of the best kind. She had died instantaneously, the perfect lights out death and I would honor that and enjoy the meat she was going to provide. I bled her out, processed her right there and realized I wasn’t but like 350yds from the vehicle in a complete circle from where I had dismounted.

Click here for the short video… #1

Use the CODE: ARHUNTERS for a 15% Discount on thier website!
Use the CODE: ARHUNTERS for a 15% Discount on thier website!

I was ready to fill the second tag. I had watched a band of Antelope feed up to dark and then found them early the next morning as I had hoped. I made my stalk, got closer than I actually expected and then was busted by a few animals much closer than the main group. A few Does and a young Buck I couldn’t see earlier saw me through a tree I was using as cover. So I turned my attention to them. I tried to keep a tree between us but they got curious and angled out to come around the tree while I was trying to get the camera set up. I was ready, then they changed direction and I knew they walked out of frame. I edged out further around the tree, set up the camera again, and just before she exited the frame; I pressed the trigger. She was at a lower elevation than I was, angling away and so my shot was slightly higher than I had wanted at a close enough distance I had not even ranged it. Dead again, right there. Instantly dropped her in her tracks. The 165gr Sierra Gamechanger solidly did its job. Completely disrupted the spine and exited the far side shoulder with a medium to large exit (I believe a lot more bone exited than normally would have and created a larger exit).

Final review on Antelope: I’d say the F4 Defense Small Frame build did very well. The caliber, 7mm-08 and how I hunt was a good combination. I have shot Antelope before through the heart with my AR10 chambered in 6.5Creedmoor and had them run 75 to 125yds. In an AR15 platform, I have shot them with a 243WSSM and a 6.5Grendel each and had them make some tracks too. The added bullet weight of the 7mm-08 caliber is obviously a benefit. It isn’t too overpowered of a caliber for the small body mass of the Antelope and anchored both animals in their tracks (both these shots interrupted the central nervous system – singularly the only shot placement that will shut the lights out instantaneously but not necessarily the preferred shot in hunting ethos for some. I am a big believer in using all the available tools of the tradecraft (appropriate distances, proper shot placement, and confidence/skill to make the shot that makes whatever the chosen caliber be the tool it’s expected to be). Antelope can be one of those animals you need to take from extended ranges, and that might mean different caliber choices. For this area, this hunt, the 7mm-08 was the right choice and I had recent extended range confidence shooting this rifle on my side.

Click here for the short video #2

Elk Steak for Dinner

Fast forward another 6x weeks. My brother is late season bow hunting a Barbary Sheep in NM. He gets snowed out as I am returning from a Mule Deer Hunt (filming for a client) in Sonora, Mexico. I had a late-season private land Cow Elk tag I had paid for to be used by a former Girl Friend (you guessed it). I told him since he wasn’t going to finish the Archery hunt he should activate this Cow tag and lets run out and get a Cow Elk with this F4 Defense rifle!

It was negative12 degrees the first day and about 5 miles hiking in 10” of snow. The second day, all before 7:15 am, in 12 degrees, it came together way too fast to film. He killed a young cow from 260 yards. A bullet placed right behind the shoulder clipping bone going in and exiting the other side was a solid through and through with lethal results. Be as it may, he was a shooter who had never even shot this rifle until the crosshairs settled on his target. The F4 Defense 7mm-08 Small Framed AR10 is not done yet. I have a feeling it will be well employed for a while to come and more stories are to be told with it included. I am enjoying it.

F4 Defense SF-10
F4 Defense SF-10

The Nit Picks

There is not a lot I don’t like about what I have seen in this Small Frame AR10 design. In fact, I like everything I have seen in the design aspect of the F4 Defense Small Frame AR10. I am impressed, relieved, and onboard 100% with the Small Frame AR10 design concept. My wants are superficial. 
F4 Defense is building Premium Rifles. These are not really entry-level rifles, they are not budget buys, nor should they ever be. They are standing firmly on their reputation, they are tightly supervising quality control, and craftsmanship is obviously something they take great pride in. They have the only AR I know of with an accuracy Sub 1/2 MOA guarantee! Rifles of that heritage come with a price…. and they clearly do. I know what goes into it more than most having manufactured ARs myself and they are not wrong in their price structure. It is not overly padded and it is not unreasonable but it does exclude a category of AR buyers. It isn’t intentional, it is the result of a strict standard and a high demand they have put upon themselves. You will clearly benefit from this if you step into one of their Small Frame AR10s.

My wants are for more pieces and parts in the Small Frame AR10 market. AR enthusiasts like to tinker, change, re-dress, and build their own rifles. Right now there are very limited options for that in the Small Frame AR10 space. I know my mind is already racing forward to what other uppers I now want. What I would build on a receiver myself if I had just a receiver set to start from. It will not be long, the tide won’t be stopped – someone will be in that space very soon. F4 Defense may or may not but they clearly are busy building Premium Hunting Rifles right now and doing it with impact.

Take this Rifle Hunting….

I like this Small Frame AR10 design a lot and I think F4 Defense is leading the way as they tailor more and more of their rifles specifically with Hunters in mind…. the Hunt is being updated, traditions are modernizing, changing for the better and I am glad it’s happening while I am still participating. The AR is a rifle to take hunting now and has been for a while. If only PA will catch up so I may come to hunt a Black Bear – I want to Hunt in PA but not until they modernize their Hunting Codes to the 21st Century.

This review was about functionality, the consistency of the Small Frame in a working environment, and my experiences with it. In the last year, I have truly put this Rifle through its paces, it has been treated as a working rifle and not a safe queen. It has been dirty since it came back from Sparks Munitions and it continues to function. It has been through two different weights and brands of ammunition and performed flawlessly. It has not been cleaned, lubed, or coddled in any way. It is scratched, it is used as a tool, and it has held up as it was intended. It is shaping up to be a workhorse and I will continue to work it as my tool in the field – I will clean it now that this review has been done.

I have already carried this F4 Defence Small Frame AR10 Hunting Rifle and camera gear repeatedly into the field on solo Barbary Sheep hunts that include horrible terrain conditions and many many long miles. I can tell you the F4 Defense Small Frame AR10 is already lighter and more maneuverable than my previous Gen I, full-sized, heavy barreled AR10 I used to carry. I have read, been told, and seen the spec sheets on their Production Rifles to know they are refined and have trimmed out even more weight for their customers.

This IS what a Gen II AR10 should be. The engineering and mechanical solutions of tired, temperamental Gen I AR10s have clearly been addressed head-on. AR10 rifles will never be the same again, its a good thing. The reliability, durability, accuracy, and consistency has made me a confident, loyal believer in this Small Frame AR10 that F4 Defense has produced. Semi-Auto Hunting Rifles just took a leap forward, as far as I am concerned and F4 Defense is one step ahead of the leap. They have plenty of calibers, plenty of barrel lengths and reliable configurations in production.

This IS a rifle I can recommend. In fact, to date, this is easily the most finely tuned, consistent, smooth operating AR10 I’ve had in my hands (remember I used to Mfr ARs too!). The AR10 has evolved and it has become a Small Framed Receiver format. It’s ready to go to work.

Use the CODE: ARHUNTERS for a 15% Discount on the F4 Defense website!

About JJ Sutton, C.P.S., C.M.A.S. :JJ Sutton

A Native Colorado resident & lifetime Hunter. JJ served 7yrs in the US Army during the 90s and logged 12 months downrange during hostilities in the Balkins. Mostly work / some play he has traveled/visited 20+ countries. He owned a highly regarded Private Security Firm for more than 15yrs., as a Certified Protection Specialist & Certified Master Anti-Terrorism Specialist, he worked Int’l Celebrities and personalities related to his business throughout Colorado & Caribbean. He has consulted & worked for private security interests during the 2002 Winter Olympics, later as a Presidential Security Detail Member with the President & First Family of Haiti. His skills and interests also include Firearms Training, Manufacturing & Consulting for custom design & builds of AR15s & AR10s. He now is an Industry Contributor, Consultant, Certified Range Master, Seasonal Hunting Guide and His current pet project includes promoting the Modern Sporting Rifle like it truly is intended to be with ARHunters: YouTube / Facebook (please “Like” AND Follow!).

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Stag (@eriggle83)
1 year ago

Gotta have it.

Robert (@robert)
1 year ago

And like that FN became afraid ….