Thread: internal lock
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Old 10-17-2020, 07:33 PM
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Fastbolt Fastbolt is offline
Join Date: Jul 2002
Location: CA Central Coast
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Yeah, call S&W and ask for a set of the little keys.

The ILS (lock) was an option in the early years. Most guns came without the ILS and with a plastic cap plug to fill the hole in the left side of the frame.

Here's a couple quick pics I just took (so excuse the lack of good focus, as I didn't take multiple pics to get the best ones ).

These are a couple of M&P 40 sear housing blocks.

The SHB on the left is from '07, and the one of the right is from a few years later, after they'd integrated the manual safety option into the regular line.

The '07 vintage ILS SHB also has a magazine safety lever, but don't be distracted by that difference. I took the pics to show how the ILS takes up critical real estate later needed for the manual safety, and it also affects ejector design. (The rail sections molded into the MIM SHB's, and in the plastic frames, later changed and the production vintages aren't interchangeable, but that's another topic. Serial numbers can tell the company which SHB will fit in what frame.)

You can see the large cylindrical space needed for the ILS. It's smack dab in the middle of where the manual safety plunger and spring needed to go in later guns. It also requires the tail of the ejector to be different, to clear the ILS space (I don't have an older ejector where I could find it to put it in the SHB with the ILS, for this pic).

FWIW, the ejectors in the older 9/.40's fit sitting against the L/side of the SHB, while the .45 and newer 9/.40 guns had a raised rail at the front of the ejector space to hold the ejector in place, as well as larger ejector pin that helped hold the tail. It made it easier on armorers to have the ejectors held in the SHB, so they didn't fall away from the side of the SHB while you were trying to install it in the frame.

Once the manual safety became such a high demand option by customers, S&W changed the "standard" SHB from the earlier design that would accommodate the ILS, to the SHB that could be used for the manual safety option. In guns ordered without the manual safety, the same SHB could be used, and plastic plugs of the appropriate color filled the diagonal frame cuts (black or tan).

I'd be surprised if customer service wouldn't just comp you the "keys" if you called them.
Ret LE Firearms inst & armorer

Last edited by Fastbolt; 10-17-2020 at 07:37 PM.
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