I currently use an MR918 frame with a custom milled G19 slide for my duty weapon and EDC. I’ve enjoyed the Shadow Systems slides as well, and consider them top notch. The frame is outstanding, and is a marked improvement over the OEM Glock frame.
The texture is exactly what I wanted, and I wish it was available from the OEM. It’s a small detail, but one that makes a significant enough difference in wet weather that it’s something that I would demand for any duty weapon since it helps maintain a positive grip when my hands are wet from rain, snow, sleet, sweat, and even blood (non-combat related, thankfully).
The grip angle and size can be adjusted using the backstraps to best suit the individual, and is a better implementation than what Glock has to offer. Another small detail, but one that helps with fitting the firearm to the individual, rather than having to train around a firearm that only mostly fits.
The magwell comes with a minor flare that works well as is, though an additional magwell can be added to ensure a reloads are difficult to miss. An additional benefit to the optional magwell is that it forces my dominant hand into the same position each time, every time. The added consistency is the biggest benefit that I’ve found.
The double trigger undercuts allow for a higher natural grip without the famed “Glock knuckle”. In additional to better ergonomics and control, it adds another index point for my support hand, which again helps with consistency in my grip.
Additional features that I’ve noticed are that the extended magwell is still low profile enough to conceal with a decent holster and belt. It’s on par with the Magpul magwell regarding size, and functions quite well. The beavertail is enhanced enough that I can choke up high on the grip without getting bitten by the slide, and requires me trying to get bitten to do it. The overall layout of the index surfaces and features lends to a repeatable and consistent grip, which allows me to rip and go more naturally.
All of these features are stock, and the added cost to the Shadow Systems offering is still less than the cost of each of these upgrades being added individually to an OEM frame. The same can be said for their slide, so the complete package is on par or costs less than a fully custom Glock, while still providing better overall features.
The Shadow Systems offerings won’t make you master class Tier 1 operators. That only comes with consistent quality training and practice. However, it does reduce limitations stemming from the gun by improving better ergonomics, high reliability, and a better overall fit with the chosen system. If a Shadow Systems is within budget, then I highly recommend one.