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Writer's pictureGraham Baates

Maskas Precision XXL Slide & Barrel for the Sig P365

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Maskas Precision XXL slide on a Sig P365XL frame
Maskas Precision XXL slide on a Sig P365XL frame

In a follow up to the earlier post about Sig P365 options here is a dedicated piece on the Maskas Precision XXL slide and barrel which gives the little P365 a 4.1" barrel for real 9mm performance.

Maskas Precision XXL slide on an Icarus Precision Macro polymer frame.
Maskas Precision XXL slide on an Icarus Precision Macro polymer frame.

What Is It? Maskas Precision is a brand I was not familiar with before, but they produce a number of slides, barrels, and other parts for the Sig P365XL and now their new "XXL" size. The designs are tasteful in my opinion with functional texture and options for windowed or non-windowed slides.

The example we have is an XXL non-windowed version with a 4.1" barrel. The barrel is fluted to help reduce weight. This new length of P365 slide uses the P365XL recoil assembly. At the time this was written the slides are shipped bare and will need a slide completion kit ($99.99 from Sig). Our sample came equipped with sights from Angry Bear Arms ($48.25 from Angry Bear Arms)


Why? is a natural question to ask. If the Sig P365 is so popular because it's small, why would we want to give it a longer barrel and slide? Aside from aesthetics, I can think of thee major practical reasons.

  1. Longer slides tend to make for a more comfortabel shooting experience. Longer slids tend to cycle a little slower and make for a more comfortable and controlable recoil impulse.

  2. Longer slides make for a longer sight radius. This makes aiming precisely easier and allows for finer control. I realize many prefer to shoot with an optic, but for a serious carry option I've yet to be convinced that a red dot is reliable enough to not also take into consideration using the irons in the event of a failure.

  3. The most important aspect for me: ballistic improtance. SAAMI specifications for 9mm ammunition made in the US is based upon the use of a 4" barrel. As a result most common defense ammunition you find is loaded to perform optimally from a 4" barrel. Sig, and others have created specialty loads which can perform with less velocity and energy, but why compromise?

Aim easier, shoot more comfortable, and hit the target harder. More barrel simply makes sense.


Do we know if it's any good? To find that out of course required range time. I adapted some of our nromal range protocol to get a feel for the Maskas Precision slide and barrel by effectively reviewing it as a complete gun.

  • A warmup comparison with a P365XL grip frame and slide followed by initial thoughts with the Maskas Precision XXL slide.

WFD for the Maskas Precision XXL Slide & Barrel
WFD for the Maskas Precision XXL Slide & Barrel

The process was lengthy, but can be seen in the video below.

On the range, especially when paired with the Icarus Precision Macro grip module, the Maskas Precision slide and barrel ran great. There were some slight hangups with Federal Premium 124gr Law Enforcement HST, but not with any other loads which tells me those rounds may have been slightly out of spec, or perhaps running the setup dry as I did (worst case scenario) was robbing it of just enough energy to not feed that load.

I really wanted to install the DPM Systems spring kit because I know what a difference that makes with a regular P365 XL, but didn't want to take the test too far out of what just the Maskas Precision parts were doing.

Maskas Precision XXL slide on an Icarus Precision Macro polymer grip module.
Maskas Precision XXL slide on an Icarus Precision Macro polymer grip module.

The XXL video was so long because of the science I wanted to explore. We know that up until 10-12" 9mm continues to gain velocity and as a result muzzle energy. I wanted to see how the XXL barrel contributed to that, but knowing each load of ammunition has a different burn rate, and combined with other factors it's not fair to measure those speeds with just a single type of ammunition. In attempt to show both that there can be differences and find out what we're gaining with a 4.1" Maskas Precision barrel I chronographed five rounds from two different loads through all four Sig P365 barrel variants that I had on hand. While the video shows every shot fired and some basic computations, here are some visuals that help explain the gain.

Sig P365 Barrel comparison with two different ammunition loads.  P365 SAS, P365, P365 XL, Maskas Precision XXL
Sig P365 Barrel comparison with two different ammunition loads. P365 SAS, P365, P365 XL, Maskas Precision XXL

This first chart shows us the calculated muzzle energy of both loads through each barrel length. We can see that the Sig P365 ammunition is less powerful than the Browning ammunition and that explains why it's also more pleasant to shoot from the smaller platform. However, with the Maskas Precision XXL barrel we get more energy from Sig's 365 ammunition than the hotter Browning ammunition generated from any of the shorter barrels.

Percentage of muzzle energy gained over next-shorter option. P365 of P365 SAS, P365XL over P365, Maskas Precision XXL over P365 XL
Percentage of muzzle energy gained over next-shorter option. P365 of P365 SAS, P365XL over P365, Maskas Precision XXL over P365 XL

These result ssurprised me. It appears the gain of going from an P365 to a P365XL is not as great as going from a P365XL to a Maskas Precision XXL. The ported P365 SAS was the lowest level and so not included in this chart as it wasn't a "gain". We also see that although the Sig P365 ammunition was intended for a shorter barrel, it really seems to take off with a 4.1" barrel.

Percentage of muzzle energy gained over next-lower option averaged between the two loads. P365 of P365 SAS, P365XL over P365, Maskas Precision XXL over P365 XL
Percentage of muzzle energy gained over next-lower option averaged between the two loads. P365 of P365 SAS, P365XL over P365, Maskas Precision XXL over P365 XL

Lastly we have an average between the two loads of the muzzle energy percentage gained over the next step down. The P365 ported SAS was the baseline and sow was excluded, but we can tell that the gain by not porting a 3.1" barrel is almost as much as moving from a 3.7" to a 4.1" barrel.


The conclusion we can make from this data is a reconfirmation that more barrel is better, and that the jump from 3.1" to 3.7"did not produce as much gain with these two loads as 3.7" to 4.1". Pressure build isn't linear and it could also be that Maskas Precision, as a smaller afterarket company can afford the time to produce higher-quality barrels than a massive manufacturer trying to turn out magnitudes more quantity.

If you move to a Maskas Precision XXL slide you will experience smoother recoil while delivering more energy on target and ensuring proper performance of a broader range of ammunition.

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Interesting upgrade. What was the weight difference between the stock XL "upper" and the Maskas upper? Also wondering if holsters for the XL will still work? I'm thinking an open-ended holster should be ok.

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Unfortunately I no longer hav ea complete basic XL slide to compare with, otherwise I'd have weighed them. I have an Icarus slide and a Spectre slide that are complete. An open-ended holster would work and I imagine custom holster makers could get the job done.

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