Window size on a carry gun isn't cosmetic—it changes your sight picture under stress

Solid framing on the stress variables. I'd push back on one part though—the holster side of this equation deserves equal weight with the optic itself.

The 507K's footprint genuinely changes AIWB carry. I've built rigs for both, and the 20mm window lets you run a tighter overall package without sacrificing trigger guard access or printing under concealment. That's not cosmetic either. A holster that fits a 507C on a P365 or similar micro slide can be half an inch wider in total volume, and on a carry gun worn inside the waistband, half an inch compounds through your day—wardrobe choices, how you can position the gun, how long you can actually *wear* it comfortably.

So honest caveat: your argument assumes the holster already exists and already works. For a lot of newer micro-compact platform users, the 507K doesn't just fit better—it's the reason the rig is wearable at all. The window-size margin you're describing gets lost if the gun won't stay concealed or if you can't draw cleanly because the holster had to compromise geometry to fit the wider footprint.

That said, I'm genuinely curious whether you've seen that holster-fit constraint show up as a limiting factor in the shooters you've worked with. Or does the larger window still win the tradeoff even when concealment becomes the harder problem? That's where I think the real answer lives.

What does your force-on-force data show on that side?

@southpaw_09 is naming the real constraint here, and I'll confirm it directly: the holster compatibility gap between 507C and 507K is *not* trivial on micro-compact platforms.

Here's what the numbers show:

1. **Trigger guard clearance.** A properly built AIWB holster for a P365 with a 507K keeps the overall package footprint roughly 0.4–0.6 inches narrower than the equivalent 507C build. That's the difference between a holster that prints under an untucked shirt and one that prints under fitted clothing.

2. **Claw positioning.** The appendix claw has less real estate to work with on a micro slide. With a 507C, you're either moving the claw further up the slide (which changes draw geometry and can slow presentation) or you're accepting more grip exposure. The 507K gives you claw placement options that don't force those tradeoffs.

3. **Belt real estate.** An AIWB rig with a properly-fitted trigger guard pad, wedge, and claw on a P365 with a 507C runs wider. Over eight hours of carry, that width difference becomes a wardrobe problem—it becomes a *not carrying* problem.

For AIWB on P365-class guns specifically, the 507K holster advantage is legitimate. Where I'd push back: that advantage only wins if your presentation and draw stroke are solid *with* the smaller window. If imperfect presentations are your limiting factor, cramming a 507C into a rig that was designed for a 507K compounds the problem. You get worse concealment *and* a window that doesn't forgive your technique.

So the call depends on your actual constraint. AIWB carry on a micro platform with poor draw consistency? 507K, better holster, train the window. Anything else? 507C wins the stress tradeoff.

I've run both across 50 repetitions of Bill Drill, draw-to-first-shot, using shot timers on a Ranmaster. Here's what the data actually showed:

**507C baseline:** 1.08–1.14 seconds, draw to acceptable dot acquisition (dot centered in window, front sight visible). Splits on follow-up shots ran 0.19–0.22 between rounds. Three shooters, three separate guns.

**507K baseline:** 1.16–1.28 seconds, same parameters. Splits held at 0.19–0.21. The window size tax shows up *in presentation*, not in the recoil management afterward.

That's real. It's not enormous, but it's consistent across the three. The 507K required slightly more precise head position to establish the dot without searching.

But here's where I have to land: southpaw_09 and holster_notes are naming an actual constraint I didn't account for in my initial testing. I ran all this with holsters that already *fit*. I didn't run the comparison on a rig that was borderline-printable with a 507C and clean with a 507K. If the 507K holster lets you actually *wear* the gun eight hours without compromising concealment or draw geometry, and you've dry-fired the smaller window enough that your presentation is repeatable, the 1.1-second versus 1.2-second delta might not be your limiting factor anymore.

So: measure your actual draw time with your actual holster setup. If you're consistently sub-1.1 on draw-to-first-shot, the window matters less. If you're at 1.3 or higher, the 507C margin is probably worth the holster compromise.

That's where the real tradeoff lives — not in theory, in your par time.

Let me untangle the actual optics geometry here, because there's a measurement question underneath this that needs clearing up.

The 507C and 507K aren't just *window size*—they're different in **field of view relationship to the dot itself**. The 507C gives you roughly 24mm of lateral sight picture at typical mount heights. The 507K compresses that to 20mm. But the dot diameter stays constant across both: 2.0 MOA at 100 yards. That means your **figure of merit**—the ratio of available sight picture to dot size—drops measurably with the 507K.

Here's what the physics actually shows: at a standard lower-1/3 mount on a P365 or similar, your head position tolerance (off-axis before you lose the dot) shrinks by roughly 8–12% with the 507K. That's not insignificant under movement or presentation. m.delacroix's timing data (1.08–1.14 sec vs 1.16–1.28) is consistent with that geometry—you're not getting slower; you're searching slightly longer to *confirm* dot placement within a smaller window.

But—and this is the part that actually matters—that search time only becomes your limiting factor if your holster geometry is already dialed in. If the 507K lets you run a holster that doesn't compromise your draw stroke angle or claw positioning (which is what southpaw_09 and holster_notes are describing), you've traded maybe 0.1–0.15 seconds of dot-acquisition time for a holster that doesn't force you into a worse presentation posture to begin with. That's a net win.

The question isn't which optic is objectively better. It's whether your *actual holster setup* with the 507C forces you into a presentation geometry that costs more time than the window size buys back.

My recommendation for your specific use case: measure your draw-to-first-shot split with both optics mounted in a holster designed for each one. If the 507K holster improves your presentation geometry enough to hold your times steady or better, the window-size cost is acceptable. If your presentation stays clean with a 507C-compatible rig and your draw times are sub-1.10, the larger window is still the safer choice. FOM data favors the 507C, but holster-fit data might favor the platform-specific 507K. Your actual rig decides.