Apr 9th 2019



The Gen-12 upper was designed around the DPMS GEN1 308 lower. This allowed the end user to convert their 308 to a 12ga. Our upper is 100% proprietary. The hand guard, bolt carrier group and upper are all unique to GENESIS ARMS and no 308 parts are compatible within the upper.

However, the lower is 100% compatible with all 308 parts in the market and that accessory list is based on the lower used. Our upper will work with most aftermarket triggers, and buffer tube opts. We recommend using a buffer weight around 4oz for bird shot and you can run up to the H3 (5.3oz) for magnums or hotter shells.

Pull the detent pins and switch the uppers.

The only thing you have to do before shooting the GEN-12 upper is to install the BEEF-UP KIT. Best part is installing the BEEF-UP kit will not affect reverse compatiblity. So when you want to remount your 308 upper, no need to uninstall the BEEF-UP kit.


The GEN-12 will mount to most other lowers which share a similar spec as the DPMS GEN1 308.

Some common fitment issues:

- Mag-well tightness. On the Aeroprecision M5 for example, the front of the magazine needs to be sanded down ever so slightly to insert.

- Upper to lower alignment. Check the mag-well to upper alignment. Lock the bolt back and run your finger on the mag-well wall nearest the front take down pin. Where the upper meets there should not be a lip, if there is, the magazine may not seat all the way in. We don't recommend modifying the magazine if this is the case, and we recommend removing upper receiver material.

- Magazine bar catch location. For example on the STAG 308 lower this is located too high and disqualifies it as compatible. Also, note if this is in the correct location then the supplied spring and mag catch bar in the BEEF-UP kit must be installed.

If you have any questions about these or any other questions please reach out to us.

The following is a list of lowers we have tested or that been known to work:

Manufacture Name, model/ compatibility rating:

-2A Armament, XANTHOS/ Bad (will not work, different pattern)

-Aero Precision, M5 lower/ Fair (magwell tolerance, may require modification to magazine to drop free)

-Anderson Mfg, 308 lower/ Good (customer supplied photo, and no issues mentioned)

-Barrett, REC10/ Good

-Black Rain Ordnance, 308 lower/ Good

-CMMG, MK3/ Fair (magwell tight but can be modified to work)

-Double Star, STAR-10/ Good

-Franklin Armory, Militia Series 308/ Good ** and their Binary trigger is compatible

-Grey Ghost, MK2 308/ Good

-Palmetto State Armory, PA10 lower/ (magwell is too tight/ requires modifications to the magazine, not recommended)

-Juggernaut Tactical, 308 lower/ Good

-POF-USA, P308/ BAD (takedown pins dia. too small)

-SLR Rifleworks, B30/ Bad (will not work/ different pattern)

-S&W, MP10 308/ Bad (will not work)

-Diamond Back 308 (will not work/ different pattern)

-Springfield Saint 308 (magwell is tight/ requires modifications to the magazines, not recommended)

*updated 4/12/21

Please do not hesitate to contact us via social media or via email. Best email is support@genesisarms.com