Defcon4 SD Conversion

The Defcon4 SD Conversion from Ronin Arms is a professional-grade integrally suppressed upgrade for your AR9 upper. Built in Payson, AZ, this conversion includes a 5.75″ ported, cold-hammer-forged barrel, a 12″ Defcon4 SD suppressor, and TIG-welded installation—turning your standard upper into a quiet, subsonic-ready platform using regular 115gr 9mm ammo.

Perfectly tuned for balance, recoil control, and sound reduction, this is the same suppression system used in the RA9 SD Full Build and Ronin Edition RA9SD-K. Built for those who demand performance and precision.

Ryan S

Reviewer

5/5

Being one of the more expensive conversions, I had some high expectations, and Ronin Arms surpassed them. I’ve watched/read several reviews of conversions from other companies and saw things like the a few supersonic cracks from 115s, leaving the standard cocking tube, no refinish, etc. The work and attention put into my gun was well worth the wait and price. They gave attention to the small details like lining the cocking tube up perfectly, clean welds on the SD cage to spec. As far as the actual shooting, this is the quietest, smoothest MP5 I’ve shot. I ran 300 rounds of 115gr with no issues, and thanks to their unique porting, it’s not filthy at all. Highly recommend.

4 weeks ago

AP5-SD Full-Size Conversion

Also, I would like to thank you and your team for the incredible work you guys did! After shooting the MPX last weekend for the first time since the modifications, I can confidently say it’s become my favorite gun—quite a statement considering my collection.

I truly appreciate all your help throughout the process.

Wishing you a great day ahead!

3 months ago

MPX-SD K Conversion Service

Bryan F.

If you don’t absolutely LOVE it, there is something wrong with you.
Quality work resulting in superior performance. I would not hesitate to do this again, as a matter of fact I’m debating a second one.
Sound suppression is phenomenal, especially when compared to end of barrel suppression. Night and day; don’t want, just get it. You know the saying, buy once cry once.

4 months ago

Jeffrey L.

Purchase to range in less than 30 days during the holiday season. Gun runs flawlessly and is "Hollywood" quiet. I am so impressed with this setup I just bought another MPX and will be ordering the full-size setup. A++++ 5 Stars!

Great Job Brother!!!!

David G.

Hands down the quietest gun I own. Build quality is excellent, accuracy and performance are excellent. Another great feature is the fact that you don't need subsonic ammo. Been using nothing but 115 grain 9mm and the gun runs extremely well no hiccups at all. I use suppressors on almost all my guns from 22cal up to 30cal including 300 Blkout, but this one is next level.

11 months ago

MPX-SD Fullsize Conversion Service

Defcon4 SD Conversion

Filters

Price range

RA9-SD DEFCON4-SD K in 8″ configuration (AR9 Platform)

RA9-SD DEFCON4-SD 12″ Standard Config

DEFCON4-SD in 12″ Suppressor Only

DEFCON4-SD K in 8″ Suppressor Only

RA9-SD DEFCON4-SD 6.75″ Ported Barrel

RA9-SD DEFCON4-SD K 5.75″ Ported Barrel

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