I love, love, love my Sig MPX and it has been just completely reliable to the point I own several models. The trigger though on the pre-2020 models was possibly the crappiest factory trigger in existence with a gritty feel you would swear someone dumped sand into. Since the 9mm round and resulting impulse is a bit hard on triggers, Sig designed the original with a unique trigger bridge that protects the disconnector. Though the MPX factory trigger was technically AR compatible it had the feel of a $4 Chinese knockoff mil-spec trigger.
The Sig MPX is not quite as abusive as most PCC on triggers, however it has special needs and does not do well with typical AR mil-spec and aftermarket triggers. The 9mm round requires a good hard smack to set off reliably, but the MPX still tends to beat up the disconnector on standard triggers; not as bad as PCC, but enough that it will eventually push the disconnector to a point of failure. I had been having very good luck with most drop in cartridge style triggers if they had heavier hammer fall energy and featured flat bobbed hammers, but it was a little hit or miss and some would fail and started to double on me as they failed.
These are the reasons that Sig publicly noted on the first generations of MPX that you should not use an aftermarket trigger, that is until Timney developed the purpose built MPX trigger. Of course now current buyers get the incredible trigger included on the new models. Frankly the Timney trigger is a transformational upgrade for legacy MPX owners with a nice crisp 4.5lb trigger.
As with all Timney triggers the feel is that of a fine match trigger, but Timney has upped the break to a 4.5lb which is about perfect for this application and the platform. Installation was simple and easy with a cartridge style drop in unit. Push out the hammer and trigger pins, remove the old trigger, slip in the Timney MPX, install the two existing hammer and trigger pins and tighten down the two pin screws. The Timneny MPX is available with a traditional curved or my preferred straight trigger shoe. If you have an existing MPX and think that you do not need this… you do. The Timney MPX is the trigger to reach for.
- No gunsmith needed, easy to install
- Ready for the range, no adjustments needed
- No additional parts needed to install trigger
- Trigger shoe options to fit your feel/style
- Trigger allows you to become more accurate with your rifle
https://timneytriggers.com/ar-pcc-trigger/