Folding Stock Adapter Comparison Declaring the Winners

1. Doublestar ACE FSA, 2. SB Tactical BTFA, 3. Sylvan Arms FSA 4. MDT Carbine|Carbine FSA,
5. UTG/Leapers FSA, 6. XLR FSA 7. Law Tactical FSA (and clones) 8. Hera Arms

And the winner is… I’ll tell you in a minute. First let me congratulate American and German industry for continuing the tradition of “Made in America” and “Made in Germany” labels as being indicative of excellently engineered and crafted doodads. We’re going to have a few category winners and an overall winner. Categories are Value, Compactness, Toughness, Lockup and Materials Selection.

Winner: Value
What do we mean by value? Getting the most for your money. For that, there’s no possibility of any winner other than UTG. They have the only unit that’s both double locking and under $100. For $15 plus shipping you end up with a workable if unsophisticated solution to a problem. Slickness doesn’t matter here. This is a Soviet type mindset of, “It functions? Yes. Is cheap? Yes.” with no other considerations. If they weren’t something like 5 times cheaper than any other solution I might not have been so generous.

Winner: Compactness
This is measured by displacement and it was a surprise. The DoubleStar ACE won this hands down. It adds only about 1/2″ to the length of pull. Nothing else came really close. The thinness of the adapter is simply not beatable by any other design. The rest were, on average, just over an inch thick which is enough to add to length of pull that fitment adjustments need to be made afterward. With the ACE, just install it and you’ll probably be fine not adjusting your length of pull.

Winner: Toughness
This was almost a tie between two very similar designs done in very different ways, the DoubleStar ACE and the UTG AK-47 folding adapter. Both seem to make strength and double locking priorities. Both manage to keep the cost down, seemingly as a side effect of the design. The DoubeStar ACE in it’s steel and semi-steel configurations is mindbogglingly strong. For its compactness, that’s a major coup. The UTG is also mindbogglingly strong and while it’s nothing like as compact as the ACE, it’s probably just as strong. Either were strong enough that I’d never worry about breaking it even by doing some insane things to them. There is a differentiator though, the lugs on the receiver adapter and pig nose on the DoubleStar unit, those lugs are adding serious toughness to the folder. Where others rely on just the hinge to keep it from getting twisted, the ACE adds fatass lugs. That will keep your butt stock from rotating in a way that a castle nut just doesn’t. So DoubleStar’s ACE wins Toughness cold.

Winner: Lockup
This is about how they lock up out of the box and how that lockup will survive into the future. Most designs had some wiggle. If they didn’t have wiggle they had a lockup adjustment mechanism, simple as that, with 1 glaring exception. The MDT unit had no adjustment feature and still locked up tight as a nun’s cunt. Looking at the interference fit and wear patterns, I have to predict that eventually lockup won’t be as tight and there’s no way to adjust it so MDT cannot win on this point even though I’d like them to. In this case, there was only 1 unit that had adjustable lockup, the XLR Gen2 unit. The SB-Tactical does too but they’re out of stock for MONTHS now and I’ve simply no more patience for them. They’ve got bigger problems now anyway since the ATF has decided to declare basically everything else that SBT makes is basically an NFA item. So the clear and simple winner is XLR Industries Gen 2. The Hera Arms is identical to XLR’s Gen1 unit, neither of which have lockup adjustment. So, great job to XLR industries. This is the category we all care about most when the rubber meets the road and they didn’t forget that.

Winner: Materials Selection
If XLR ever decides to make one of their units out of steel and improve the hold-open feature I’ll revisit this article and declare them the unconditional overall winner. For now though, DoubleStar ACE wins the materials selection hands down. This is limited to the push-button and all steel models though as those are where the manufacture is known to be inclusive of steel in the most important places or of all steel. Steel rules, baby.

Winner: Overall Excellence
This was not easy to decide. It comes down to what works the best now and what will work the best down the road. As much as I really love the DoubleStar ACE the square shape is in the way just a little bit and the non adjustable lock-up is a factor. Knock down 1 corner on that unit and they walk away as the winner adjustable lockup or no. I really hope they’re paying attention to this because they could tweak their design to be round or at least to have less discrete corners (think hexagon or pentagon) and then I’d sell all my other units and buy ACE’s. If they added little delrin inserts in strategic spots with set screws behind them then the lockup would be adjustable and there’d be no reason for anyone else to make a competing product, it’d be perfect for precision rifle usage. Since neither of those two things are currently the case, we have to go to the one that does the precision rifle job best and that means that the XLR Industries Gen 2 side folding adapter wins. I am pretty certain that if I could have gotten an SB-Tactical unit that they would have won simply because the design is so close to the XLR Gen 2 but, critically, the SB-Tactical unit has a lock-open feature which includes a positive lock and adjustable lockup and it’s about as compact as the XLR/Hera units and the price is ok. I just couldn’t get one to save my damned life and that’s a factor to be considered.

A big congratulations to XLR industries. You earned it. Just don’t go resting on your laurels. You know where you’re at risk of losing to innovation in the future, so go fix those things. Make a 100% steel unit. I’ll buy one. Fix your hold-open so it’s not a drag based system. I’ll buy two. Gate the pushbutton release. I’ll buy three.

What I’d like to see is for XLR and DoubleStar to both take my suggestions and then to run this comparison again but this time include test to destruction so we can see if it’ll be the folding adapter or the stock that gives up first and we’ll pit just the XLR and the ACE against each other. See who’ll rule the roost. What I’d especially like to see is SB-Tactical get their inventory shit together so I can buy their stuff and then compare it against XLR and DoubleStar.

Why did MDT not show up in any winner’s circle? The cost is high for the features, the features are very well implemented for out of the box performance but long term durability remains in question and the installation was made more difficult than it needed to be. Basically, MDT made a great swing but it was pretty far short of the fences.

Where do Sylvan Arms and Law Tactical sit? Law Tactical’s unit on a precision bolt action rifle is nearly ass but it’s one of two all steel offerings and it’s the only one that works on both AR-15s and bolt-guns. It’s near indestructible and very well thought out. Sylvan’s offering is ass on a bolt action rifle since it doesn’t offer the strength upside of a Law but offers all of the downsides. On a gas gun, I would not hesitate to use a Sylvan if I just wanted folding for transport. If I wanted folding for rapid employment, then I’m going to Dead Foot Arms.

Final Thoughts: It’s 99% sure that each of the various companies whose product I reviewed is aware of my review. To date only 1 of them has come forward to acknowledge in any way the review that they were given. That company is: DoubleStarUSA. They took the opportunity to thank me for doing a fair, open and critical review. They didn’t dispute any of my points or try to reinforce any other points. They simply said, “Thank you” for me being fair. It takes a lot of guts to look a critic in the face and say, “Thank you for being a critic.” It says a lot about who they are inside. I know today that when I go looking for my next side folding unit, I’ll check DS first and see if they’ve rounded off any corners yet and if they did then I will look no further. If not, I may or may not look further and hit up XLR Industries. I do know that it’s unlikely I’ll look much further afield than those two though. See below for the wrap-up of scores, points and value assessment. In the end, the Value column identified the winner very clearly. You can also see that the idea of functional points divided by dollars is a decent but not 100% viable way of deciding on things like this. XLR/Hera/MDT/DoubleStar placed in a tight cluster using the Value system. The problem is that UTG blew the curve so far away it became invisible for a long while. When looking at scores like this it’s important to take the highest and lowest scores and to discard them if they’re more than 3 standard deviations away from the mean of any cluster of samples. We ended up here with 2 clusters of samples and then 1 unit that was not even on the same planet as the other samples. The UTG is scoring way too differently meaning it’s of a different kind or someone is cheating. (Hint, it’s both.)

Looking at the stats, if we remove the UTG part then the SD of Value scores is .04. Adding the UTG back in changes the SD of Value points to .23. That increase of the SD by 5x tells me that that sample should be discarded as it’s of a different kind to the rest. Similarly, look at the the distribution of low Value scores and you see another cluster with an internally low SD. If we remove both the UTG and the Chinese garbage pail kid from the stats then everything tightens up. The SD of points goes from >5 to 1. What this is showing is that Chinese made stuff cannot be directly compared to American made stuff. They’re on different economic planets. This should also expose just how thorough China is when playing unfair economic games. They’ll steal intellectual property, violate patents and trademarks, use slave labor and low wage workers, use substandard materials and terrible designs or whatever else they have to do to make sure you get a pile of shit for your money and that they get your money. The table below should tell you all you need to know about geopolitics between the far east and the west.

Brand	Model	Ordered	Received	Price	Vendor	Points	Value	Stars
DoubleStar	Push Button Lugged	Loaner	Loaner	$130	DoubleStar	16	.12	*****
SB Tactical	Buffer Tube Folding Adapter	N/A	N/A	N/A	N/A	N/A	N/A	N/A
Sylvan Arms	Folding Stock Adapter	12/6	12/12	$180	Primary Arms	9	.05	**
MDT	Folding Stock Adapter c/c interface	11/10	11/13	$149	MDT	16.75	.11	***
UTG	AK-47 Side Folding Stock Adapter	10/31	11/9	$15	Leapers	10.5	.7	**
XLR Industries	Folding Stock Adapter	10/31	11/5	$115	XLR Industries	18.5	.16	****
Law Tactical	Folding Stock Adapter	On Hand	On Hand	$239	Law Tactical	19	.07	*****
Hera Arms	Side Folding Unit	11/15	11/23	$119	Ballistic deals.com	14.75	.13	***
Facebook/ China	Folding Stock Adapter	9/5	10/24	$58	China	2.4	.04	*

part 1.
part 2.
part 3.
part 4.
Mid-Series Check-in.
part 5.
part 6.
Declaring the Winners