So....in heavily upgrading many items on my 15-22, I *somehow* slightly stripped the plastic grip screw threads in my receiver.....

I fixed it quite nicely with an M7 (1 inch) 22/tpi hex bolt from Lowes Home Improvement. Note: if you use the 1 inch long bolt, you will need a couple of washers so the bolt doesn't bore through the receiver. The original AR15 grip screw is probably 3/4" long.

The M7 size is 'just' slightly thicker than the original 1/4 inch AR15 grip screw, but the 22-threads-per-inch on this M7 bolt matched 1/4" screw's original threads (which were now stripped a bit), so with slow turns of a socket wrench (properly aligned, of course), the new M7 bores new threads very securely. Essentially, it did what a tap and die usually does.

All in, I'm very satisfied this will be a good permanent fix without needing to send the whole rifle back to S&W customer service.

1/4-28 will never match metric threads. What you have done is further displace the remaining material.

I pity the next owner if you sell it.

I beg to differ. I believe you've underestimated (or overestimated) the density of the polymer lower on this 15-22.

The threads this M7-1.0-22 pitch bolt created are solid and from what I can see, permanent. After creating them with the original grip, and tightening, I then replaced the grip with an Ergo. Everything went fine, no issues. After your post, I got worried. I removed the Ergo, inspected it, and put it back on. Again, everything appeared great and the bolt went in and tightened as it should.

From all appearances and evidence, I have to take exception to your assertion. I'm not an expert, so I could be wrong. But this 15-22 seems to have new M7-22 threads that are healthy....the lower itself doesn't appear to be suffering from displaced material (e.g., cracks, bunches, warps, dimpling, etc.).

The thread title is misleading as this fix is hardly definitive.

The complaint that merely screwing in a larger bolt being a questionable fix is quite valid.

Now if there was a fix featuring a standard thread repair technique, such as threaded inserts, you might reasonably call that definitive, but this is not.

Let's clear up a few things.

A "M7-1.0-22 pitch bolt" is 7 mm diameter, 1.0 mm pitch and 22 mm long.

So in more American terms it's ~.275" diameter, 25.4 threads per inch and 7/8" long.

Really not a bad choice to screw into a stripped 1/4" hole in a polymer lower.

Downside is that if you pull out the 7mm threads you have a mess too big to fix with a heli-coil so it's install an insert or send it back to S&W.

Why the metric bolt? Too lazy to get the proper 1/4x28 in the first place?

LOL, because the 1/4 x 28 threads in the hole were stripped out - as he stated in the first post.

The 7mm metric screw is .276" diameter. Being 26 thousandths larger in diameter than the original .25" screw it is close, but just enough larger than the original to cut new threads in the hole.

Maybe not the "definitive" repair, but certainly a reasonable option.

Yep, pretty clear. First sentence in the first post, but you do have to read it...

It remains solid. After this approach, I've removed the original grip and replaced it with an Ergo. Then, I removed the Ergo, just to check on the threads. Fastened the Ergo back on. Solid. Ten minutes ago, I repeated the removal/re-apply procedure, and I am pleased with the threads and this M7 bolt.

By all appearances, putting the M7 on created new, sound, and lasting threads that work like a charm. I can't find any imperfections in the lower this has caused - I think it didn't cause any harm and only helped. I could be wrong - but I don't see how.

Well guys, I had to play this card today. And while it might not be definitive it appears to be very acceptable.

I went to Lowes today too after somehow stripping mine last night reinstalling my Magpul MOE grip.

I searched the internet and came across the above solution.

I used an M7-1.00 x 30 hex cap screw.

This bolt is of course too long so I bought a pack of 7mm flat washers too.

I put six washers on the bolt so that the bolt would wind up being the same length as the Magpul grip bolt. I verified this by holding that bolt and my new M7 bolt with the half dozen washers on it end against head. With the washers on the M7 bolt, I ended up with the same length bolt as needed. I didn't want this bolt to bottom out in the receiver and strip, hence the washers.

Here's where my technique differed somewhat from the original post.

Just into the receiver only, I hand tightened my new bolt about 4-5 threads to make sure it had the best chance of starting off straight when I put the grip on.

Because this bolt is wider than the stock bolt, I ran it through the grip only in order to widen the hole in the grip. I didn't want the grip to be pulled into the receiver when I went to tighten things down.

I wanted my new bolt to apply a clamping force only. So the hole in my grip was made larger then by running my new bolt through the grip only, and then removing the bolt from the grip. This widened the hole in the grip some.

I then fully seated the grip to the receiver with the detent springs lined up.

I took a 11mm socket on an extension, making sure beforehand of course that it would fit the head of my bolt and inserted my bolt with the washers on it, making sure that the grip stayed seated and started torquing it all down going straight and following the old hole.

After a few turns, I'd shake the receiver listening for the rattle of the washers.

I tightened to just the point where I could no longer hear the washers rattle if I shook the receiver.

And then went a tad more making damn sure I didn't strip it again.

I was using a hand or palm ratchet Knowing that I'd really ***** things if I over torqued it.

The result is a resounding success. It's as tight as it was when new.

Unlike the original poster, I'll never take this grip off as I feel I got lucky.

Well done, and thanks for the tip. I didn't realize there wasn't anything more solid in there. I'll have to be careful when I change the grip on mine soon.
It's hard to believe that the manufacturer would cheap out on a nickel worth of steel insert.

I find it more hard to believe that people ignore the warnings about over tightening the screw.....

Tough crowd tonight!

In my case I don't believe that I over tightened it.

I believe that I may have done something worse. Cross threaded it.

I say that because I don't remember over tightening it at all.

It's either that or I changed grips one time too many and wore out the threads.

I replaced the grip with the MOE. Then later removed the MOE grip to try it on one of my AR 15s. The trouble started when I went to put the MOE grip back on the M&P 15-22.

I don't recall the bolt ever feeling snug the whole time I was tightening it down the other night. That's when I knew it was stripped.

Exactly

I love this rifle and believe it to be the Best Buy in a .22 out there for what you get.

But they should have molded a threaded metal insert into the receiver for the grip screw. Or a threaded metal cap over either side of that portion of the receiver.

If they were to do that, this rifle would be close to perfect.

Better than a pop rivet, I guess . . .

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Wisdom comes thru fear . . .

I had to remove my grip and I believe the original screw was mucked up to begin with..I removed the grip and upon reinstalling the threaded hole was trashed..
Now I have a stripped hole..not sure but I may epoxy a thread insert into the grip screw hole..
And be done with it

Hey, I fully sympathize with what you're going through. I've always felt that the thread insert was the way to go. But luckily mine's still intact. Be sure to keep us informed on the results. Good luck!

Ever work on a modern automobile or truck?

Their goal is to assemble it. They don't care about taking it apart and repairing them. Same with most things.

As tried in another thread on here, ref the same subject, a helicoil for the size of OEM bolt and boom. Done!!!!

Contact 1coolcat if needed, he has a box of spares, which I'm sure he would pass on at a buck apiece mailed.

Rob

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Utrinque Paratus