Sig Sauer SB15 Arm Brace On The Kriss Vector SDP Pistol *Updated 9/24/14-Mod Completed*

Today I received my Kriss Vector M4 Stock Adapter from Kriss USA.  My buffer tube and Sig SB15 Arm Brace should arrive next week.  Removing the old sling attachment end piece and installing the adapter is a bit involved on the pistol.  The adapter installation instructions included with the adapter only apply to the carbine with the folding stock.  

I will post a tutorial on installing the adapter along with pictures if anyone is interested.

I would be incredibly interested in such a write up when you have the time! I've had all the parts already, but hadn't gotten much further than realizing the instructions were clearly for the carbine, and that something was incredibly different about the break down of the pistol. I've googled it a bit then just scrubbed this forum until I found your post.

I would love to see a tutorial if you were planning on putting one together!

Thanks in advance!

Edit:  Perhaps I should preface this with the obligatory safety warning.  

Before performing the following procedure double check and make sure your Kriss Vector SDP Pistol is unloaded. 

Here's what you get for your $75.




Package contents:


Installation instructions.  As you can see, they are intended for the carbine.  It appears that Kriss is keeping their distance from any involvement with the Sig Sauer SB15 Stabalizing Brace being used on their SDP Pistol.


As I've noted in another thread, Kriss states that removing the "butted end piece" will void your warranty. Still they're willing to sell you this piece of plastic for $75. I haven't yet figured a way to install the M4 Stock Adapter without removing the butted end piece.

Unlike the carbine, the Kriss Pistol has a fixed pin ....... I'll call it a rivet for lack of a better term. First step is to drill the head off the rivet.


Once this is done, push the rivet out through the bottom. With the rivet romoved push sling attachment end piece toward the right to remove it.


Remove the now exposed plug with the appropriate allen wrench.


Now we come to the interesting part. How to remove the enclosed threaded plate. This plate prevents installation of the Kriss M4 Stock Adapter.


I spent some time thinking about this. Had some really bad ideas like using a Dremel to cut the plate into small pieces so it could be removed through the rear hole. Then I noticed what appears to be a cover directly above the plate.


Here's a better view with the rear sight removed.


Obviously the picatinny rail is blocking access. Remove the screw at the front of the rail.


Next remove the rail retaining pin. You need a really small drift. I didn't have the proper drift so I used a hammer and a small drill bit. Broke the bit but I got the pin out and small drill bits are cheap


Next, use a hammer and a wooden dowel to tap the rail forward enough to clear the cover. Use a flat screw driver under the dovetail of the cover to pry it up and remove it.




Remove the threaded plate. Replace the cover. Tap the rail back into position and install the rail retaining pin then the screw at the front of the rail.


My pistol buffer tube arrived today so I'll proceed with the installation.  Slip M4 Stock Adapter into the rear opening and push it against the SDP.


Push the adapter to the left until the holes in the "hinge" are aligned.  I used my original pin inserting it from the top.  I would like to have a Kriss takedown pin but this original pin on my particular firearm is a really snug fit.  It would probably stay in forever.


Here's my new pistol buffer tube with an end plate and castle nut installed.  I have a sling attachment end plate on order.


WARNING:  When screwing your buffer tube into the M4 Stock Adapter be very careful to ensure you're not cross-threading.  The metal threads of the buffer tube will chew up the plastic threads of the adapter.  I messed  up the  first couple of threads on my adapter.  I stopped when I felt a little resistance.  Anyway ........... the buffer tube is installed.  My SB15 brace and sling attachment plate should be here later this week.


I immediately discovered that the end plate when installed AR style would interfere with the right hand.  Since orientation of the tube can be varied it could be installed like this.  It's not high enough to interfere with the sights.


I probably could have just drilled a hole in this end plate for a sling attachment point.  I may still do that.  That would allow a choice of sling attachment locations.  I'll decide when the rest of my parts arrive.



Well ........... It's Wednesday September 24th and my Sig Sauer SB15 Stabalizing Brace just arrived.  I purchased mine on eBay for around $132 with free 2-day FedEx shipping.  Here's what comes in the box ........... The brace, simple instruction sheet and a reduced size copy of the ATF compliance Letter.  Oh yeah .......... there's an extra Velcro strap that I didn't get in the picture.


Here's the brace installed on my SDP.  I decided to go with my original end plate for a sling attachment point.  I drilled a hole in the indent then used a round file to remove the rest of the indent.


With this buffer tube (also purchased on eBay) the brace extends ~10 in. beyond the point where the M4 Stock Adapter attaches to the SDP.  Total length of the firearm (5 in. barrel) is ~ 24 3/4 in.  I must say ............ with the brace against your shoulder and your cheek pressed against the brace, it really feels good.  

Well ............ It looks like this case is closed.  I hope it's been informative to other Kriss SDP owners who might be considering the modification or any SDP owners who are going through a real SBR conversion and don't want to send their firearm to Kriss to have them put a stock on it.

Trace Kimber , excellent post.

Thanks, AZ

Thanks AZ .............. appreciate the comment.

Nice post. I wish I had read this one before I did my mod. I went into my mod blind, and almost never found out how to get that threaded block out of the back of it.

I put one of these on my SDP about two weeks ago. Total work time was about 20 minutes. For me, the hardest part was removing the "rivet" from the butt cap, but once that was done, the rest was easy. One tip - use a wooden dowel to tap your picatinny rail forward to access the "trap door" to avoid marring the finish. Overall, I am extremely happy with the addition of the SB15 and strongly question the need to SBR at this point. My only gripe is the inability to fold the brace, but removal and reattachment is so easy it doesn't impact me that much.

if anyone is not aware once you put on them M4 adapter you void the warranty

HEY If you use just the m4 adaptor and just use a buffer tube without the brace it self would it be legal?
.

Really great post - just what I needed!

Do you see any way to extend the total length by the addition 1 1/4" needed to get to 26" so you can have a VFG?

^THIS
i have a bad wrist from breaking my arm/wrist 3 times as a kid (ooor insert early onset carpal tunnel joke here) so the shallow angle of the AFG doesnt work for me, and i dont like the idea of modifying it anyway...i know i know the atf wouldnt repel from the ceiling and arrest me but im an overly safe kinda guy. if there was a way to get this SDP to 26" i'd be in heaven

diamondhead rail could work for this
it would obviously be past the muzzle, but gives you an excuse to buy a suppressor.
only other way i can come up with is making your own buffer tube to meet the req length...

Anyone thought of throwing one of these on? 1.3" Extra length should get you to 26"? and fold to charging handle side with enough gap to clear Left hand safety.....spendy but cheaper than tax stamp.


http://www.lawtactical.com/ar_folding_stock_adapter_gen_3_p/2014003.htm

dont know if the price went up but $220 is more than a tax stamp
i guess after you factor in the cost of a real kriss stock

i've been looking into this for a while and shouldnt have been so hard headed and listened to the post (i think it was maddog) somewhere on here the sigbrace is crap on the kriss and to just sbr it. if i did i would have already got the paperwork back. and SAVED money...
IMO it functions better, is more realiable, and looks 10x more kickass
frankenstiening all this crap to get what you really want...an sbr...isn't worth it

SBR is not a legal option in some places. Sometimes "Frankensteining" is the only option.

true...i welcome you to move to the republic of texas friend

Alas, one day I can move back home to San Antonio. Till then...

Thanks for the post. It was extremely helpful. I had just acquired a KRISS pistol and got a M4 adopter with it. I found this post just in time.

Alabama Arsenal has posted an excellent video showing the installation of the Kriss M4 Stock Adapter on the SDP Pistol.

https://www.youtube.com/watch?v=knO5Zy1-kZ4

As you may know by now, ATF has ruled that shouldering a pistol with one of the Sig Sauer braces is now illegal.  Here's a direct link to the ATF open letter.

http://www.atf.gov/sites/default/files/assets/Firearms/FirearmsIndustry/open_letter_on_the_redesign_of_stabilizing_braces.pdf

You can also find it going directly to the ATF website and clicking Firearms ............ Firearms Industry ........... and selecting News.

I don't believe they'll ever say that you can't hold a pistol with two hands.  The SDP even with the arm brace is an awfully lot of weight to hold out with one hand.  If you have the Sig brace on your SDP and you have a long enough buffer tube try this ............assuming a right handed shooter.........

Insert your arm into the brace as far as you can.    Tilt the firearm ~45 degrees counter-clockwise. Grasp the bottom of the firearm with your left hand just in back of the magazine.   Brace your left elbow against your body.  This provides a fairly stable platform.  At least it does for me.  I'm not tall with long arms so the brace butts up against my bicep.

After drilling the head off the original pin, what do you use to replace it with when the m4 adapter goes on the SDP? I have the adapter coming, but the instructions that come with the adapter are for the carbine, which allows you to remove the pin without destroying it. I looked at Kriss website and cannot find anywhere to purchase replacement parts. Any help would be greatly appreciated.

I've seen the pins sold as pairs on eBay although not at this time.  As noted earlier in my installation instructions, I used the original pin and found it to be a really snug fit.  One could probably make it a little more secure with a little blue Locktite.

You might also try these parts from the KWA airsoft version.

http://store.kwausa.com/KrissVectorstocksetpin.aspx
http://store.kwausa.com/KrissVectorStockPinScrew.aspx

You can use a take down pin

Thanks guys, if the original pin doesn't work I'll order some extra takedown pins. I odered the sig brace with the KAK buffer tube, which has already arrived. The adapter will be here tomorrow, then let the Frankensteining begin.