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Last year, I reviewed the now discontinued Heckler & Koch SL8-6 after making an impulse buy at my LGS. My reaction to the rifle was a mix of hot and cold, but much of the “cold” was related to its horrible ergonomics. The ill-conceived thumbhole stock, of course, was a consequence of government-mandated restrictions. But even then, HK seemed to have gone out of their way to make it extra crappy. Well, for the last year I’ve been debating whether to go all in and convert my SL8-6 to a G-36 configuration, or simply stick with the designated marksman rifle concept. Either way, I knew TommyBuilt Tactical LLC had my six . . .

Ok, so I went with the significantly less expensive fix, which was to simply dump the thumbhole stock in favor of a custom stock made by TBT.  Truth be told, I really couldn’t stand to see that beautiful, accurate barrel get chopped on. And, of course, cost factored into the equation as well (a total rebuild would have cost another $2500 +/-).  A quick call to Tom Bostic and $475 (+ shipping) later, I was the proud owner of a new TBT drop-in stock!  The good news is that the TBT stock counts as two 922r compliance parts. Unfortunately, the three extra needed 922r compliance parts costs another $200. Ugh.

So what exactly is a TBT custom buttstock?  Well, he makes about six different combinations, consisting of off-the-shelf buttstocks, handgrips, and a part which I will call a “SL8 trigger group housing.” This housing is similar to an AR’s “lower receiver,” but unlike on an AR, it is not the serialized part that constitutes the firearm.  Prices for Tom’s creations range from $300-$475, which isn’t bad when you factor in the fact that this price includes the retail cost of the parts.

Courtesy Joe Grine

For my build, Tom started out with a Magpul PRS-2™  buttstock, a DPMS Panther™ Tactical Grip and then he mated these two items up with a “SL8 trigger group housing.” Tom uses a plastic welding process to join the three items together. Then he applies a surface treatment to the parts to hide the welds. When he is done you can’t even see where the welds occur.

When the stock shows up at your door, it’s basically a drop-in unit. The only thing you have to is take out the trigger pack out of your thumbhole stock and add it to the new stock. It takes about the same level of skill as adding an AR trigger into a lower receiver. Every once in a while Tom will send the kit out with an extra trigger pack already installed, and I guess I got lucky and received a loaded one. I ended up taking the trigger out to put in the compliance part, however.

Courtesy Joe Grine

And once I got everything up and running, I couldn’t be happier. The ergonomics are so much better than before. All of a sudden I could actually reach the safety with the thumb of my trigger hand.  The better ergonomics seem to have also translated into better accuracy (although since the trigger pack is new, that may factor into the equation as well). My first three 3-shot groups were all under ½ MOA at 100 yards using Hornady 75-grain BTHP Match ammunition, and the gun continues to function at a sub-MOA level with most loads I feed it, with the sole exception being the light 40-grain Winchester varmint rounds, which print at just over an inch.

Courtesy Joe Grine

Well, what started as an impulse buy has turned into a fairly expensive little project gun. Overall, the difference between the original configuration and what I have now is night and day. And because it’s an HK, I have no doubt I could flip it for every penny I have into it if I ever decided to move on.  But I also know that if I want to get another SL8-6 and do the G-36 conversion, Tom Bostic and TBT can handle the task.  And he even answers the phone when you call!

Ratings (out of five stars):

Ergonomics:  * * * * *

The difference between this and the OEM buttstock cannot be overstated.

Durability: ?

Only time will tell how well those welds hold up. Tom Bostic reports to me that he is confident in the quality of his welds, and the lack of customer returns over the years backs up his confidence. If something does break, he will make it right. Besides that, the rest is good to go: both the Magpul PRS 2 and the DPMS Panther grip are high quality parts and will give you a lifetime of service.

Value: * * *

Given the labor-intensive nature of the manufacturing process, I would say that TBT’s prices are more than fair. In fact, they may just be a little low. But even so, when you add in those pesky 922r compliance parts, though, the overall cost isn’t cheap. Then again, HK isn’t exactly a value-oriented brand to start with, so most purchasers who own HK SL8-6 aren’t the penny-pincher types.

Overall: * * * *

If you own an HK SL8-1 or SL8-6, the thumbhole stock is a mandatory replacement, and you can’t go wrong with the TBT upgrades.


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    • Yes, 10 round single stacks. TBT can convert to double stack, and Magpul makes G-36 mags, so that might be a kool way to go. But honestly, The way I shoot it (more like a sniper rifle), you don’t really need or necessarily even want the high caps.

      Scope is a (now-discontinued) IOR Valdada Super M2, which is a fixed 6x with a BCD turret calibrated to work with M855 62 gr. 5.56 x 45.

    • He can convert to double stack magpul mags, but you’ll need a Magwell adapter, there are a few varieties out there, plus you will also need a G36 bolt (for double stack mags), as the SL8 bolt only pulls from a single stack mag.

      Tommy did this build for me as well, couldn’t be happier – awesome shooting gun now.
      I upgraded and use 20 round Magpul Mags, really fits the looks and getting rid of the HK’s terrible single stack mags, and is far better for cross platform uniform mag loadouts.

  1. I’m just going to say h&k rifles are almost never worth the price if I could get a true semi auto g36 that would be one thing but as it stands I will never buy an hk rifle

  2. Tom Bostic is also working on an XM8 conversion for the sl8. For an hk guy it is seriously spectacular.

    • Thank you, Sir. My wife actually told me that I need to post less often, and get back to focusing on my day job. Something about “paying the bills” or something like that.

      • Nonsense! The bill fairy rectifies all those issues! So says the .gov!
        But seriously, your articles are top notch.

    • Its a Grizzly Muzzle Brake – clamp on, not threaded. Review is on the way (Should be up up next week).

  3. Tom did my SL8-6 also, outstanding work. Spuhr makes a drop in AR mag conversion. Please be sitting down when you see the price, then again HK is very proud of their G36 mags. Spuhr moves the bolt release also. There is/was a company in Canada making the conversion but seems to have dimension issues and claimed they were going to start production again. I had the trigger pack sent off to have it worked and it’s much better. A search should turn up who can do it as I don’t want to come off as shrill for any business.

  4. “Unfortunately, the three extra needed 922r compliance parts costs another $200. ”

    What three parts did you get for compliance? Where to get?


    • is a good source for HK parts. If you convert it to use AR mags the mags will count for 3 parts. If you contact Tom he might have some info where to get parts at also.


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