Thanks to a friend who clued me into the Lingle Industries SCAR AR 17 caliber conversion. If you have a SCAR 17S, well, Lingle Industries makes a caliber conversion so you can use mini action calibers like 5.56, .300 BLK, 6.5 Grendel and even 7.62×39! Lingle Industries was kind enough to let me borrow one of the conversion kits for this review so let’s take a closer look.

More SCAR 17S Content @TFB

• Lingle Industries SCAR 17S Caliber Conversion (5.56)
• TFB Review: How To Build A Pistol SCAR17Shorty With Imperial Arms Co’s CYPHER X
• Imperial Arms Co. Buffered Bolt Carrier For SCAR 17/20

Caliber Converting FN SCAR 17S/MK17

I remember reading about the MK17 caliber conversion kit in an FNH USA catalog back when I staffed the FHN USA 3-Gun Championship matches. Apparently, FN made a conversion kit for the MK17 to allow it to shoot 5.56. However, FNH USA does not sell this conversion kit to the civilian market.

In the photo above, the lower fits the MK17 or in this case a SCAR 17S receiver. Due to the position of a SCAR 16S magazine, there are some changes made to make this work. Look at the mag catch, it is much longer so it brings the mag release button where it normally is for a SCAR 17S lower receiver. Now look at the image below. The SCAR 17S lower is on top and the 5.56 MK17 lower is below. Look at the bolt catch. It is much longer to reach forward where the SCAR 16S magazine will be.

 Lingle Industries SCAR AR 17 Caliber Conversion

While you cannot buy the FN USA MK17 5.56 conversion kit, Lingle Industries makes one that you can use for your SCAR 17S. Below is what Lingle Industries lent for this review.

SCAR AR 17 Conversion Parts:

• SCAR 16S barrel assembly*
• SCAR 16S Bolt*
• Lingle SCAR AR 17 lower
• Lingle SCAR AR 17 firing pin
• Lingle SCAR Buffer*

The FN SCAR 16S barrel assembly and bolt are not necessary. You can go with Deadshot Barrels and their bolts. The Lingle SCAR Buffer is also not necessary for the SCAR AR 17 but it is necessary for his SCAR AR 16 lower. That lower allows you to use AR triggers and hammers. You need Lingle Industries’ buffer to prevent the SCAR 16S carrier from over traveling. Similar to Lee Sporting’s MP5 lower. If the carrier moves too far back, it will get behind the hammer and get caught on the back of the hammer as it tries to move forward.

The Lingle Industries SCAR buffer is a lot thicker. He included it to see what would happen with the IAC BBC.

Here is the SCAR AR 17 lower next to my IAC MTM. You can see the differences when they are side by side.

Due to the shorter length of the 5.56 PMAG, the mag catch and bolt catch are a lot more forward than the SCAR 17S/MTM. Look at how long the trigger guard is in comparison.

This increased length poses a slight issue. I have average-sized hands and I cannot press the mag release without shifting my hand.

I grabbed an extended mag release from one of my AR15 lowers and now I can access the mag release without shifting my hand from fire control.

The SCAR AR 17 lower is rather straightforward except for this slot on the left side. This is for a sled that can trip an FRT trigger or possibly an M16 sear for post-sample guns.

Below is the SCAR 16S barrel assembly Lingle Industries lent me and my chopped 17S barrel assembly below that. The gas block is the same except for the jets. If you look closely. the barrel trunnions are the same. So the SCAR 16S barrel assembly will mount inside a SCAR 17S receiver.

Lingle’s SCAR AR 17 conversion has you re-use your SCAR 17S carrier. You need to remove the bolt and firing pin. You will use the cam pin and retaining pin. Below is my SCAR 17S bolt and the 16S bolt below it. The diameter of the bolt body is the same.

You will need to use Lingle Industries’ firing pin. The 17S firing pin tip is too thick and will not protrude out of the 16S bolt.

You can see the 17S firing pin next to the Lingle Industries firing pin.

Another friend of mine has a SCAR 16S so I compared the factory FN 16S carrier to the Imperial Arms Co. BBC. You can see there is about half an inch of less carrier and the firing pin is shorter. That is why you need Lingle’s firing pin.

Here is the 16S recoil spring above the 17S recoil spring. I installed the Lingle SCAR buffer on my 17S recoil spring.

SCAR AR 17 Completed

No issues with mag compatibility. I tried the following magazines:

• USGI magazine
• Gen 3 PMAG
• Steel HK416 magazine
• Polymer HK416 magazine
• Lancer magazine

Firing The SCAR AR 17

My friend Regi told me the MK17 5.56 conversion is the smoothest shooting 5.56 gun he has shot. I can confirm. There is no rearward recoil. But now I am more aware of the forward recoil when the bolt closes. Watch the slow-motion video above closely. I tested the SCAR AR 17 with my factory FN 17S carrier and the IAC BBC. The buffered bolt carrier had a discernible different recoil impulse. It seemed reduced. I think the hydraulic buffer in the BBC is helping to slow down the carrier so the forward recoil feels lower.

Final Thoughts On The Lingle Industries Caliber Conversion

I love this conversion. I want to get a SCAR 16S bolt and barrel assembly. The cost is not great but not terrible. A 16S barrel assembly retails for around $1,200 but if you switch to Deadshot Barrels you can get a completed barrel assembly for under $900. They offer barrels in 5.56×45, .300 BLK, 6.5 Grendel, and 7.62×39. The only minor issue is the 7.62×39 as you could need AR mags that feed that round. Then you need the bolt which retails for $400. The last thing you need is the Lingle Industries SCAR AR 17 lower receiver which retails for $450 which includes the firing pin. You will need your own trigger, hammer, mag catch, and pistol grip. All said and done you can convert a SCAR 17S for $1700.

The ambidextrous bolt release is a good idea but due to the extended trigger guard, it is a bit difficult to manipulate the bolt catch elevator. I suggested to Lingle that they should make a shoe that can be pinned to that elevator. That way it will be wider and reach further back toward the index finger and hopefully be easier to manipulate. Worst case you just use the normal bolt catch and release.

I really liked the lack of recoil on the SCAR AR 17 so I think I will go convert my spare Cypher X receiver into 5.56. For more information or to order the Lingle Industries SCAR AR 17 caliber conversion go to their website.