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Several years ago, I bought a Smith & Wesson M&P 15-22 semi-auto rifle. I have detailed some of my experiences in this M&P 15-22 write-up. It has been a reliable .22LR caliber rifle and never failed to perform. I've used it to introduce a couple of young teenagers to rifle shooting and it was the hit of the day.
In the write-up reference above, I commented on the 15-22's barrel not have a
flash hider on it. S&W now makes a model that has a threaded flash
suppressor. While reading a few threads on the S&W forum, I found that a
Tacticool22.com, that manufactures and sells quite a few
accessories for the M&P 15-22 and several other rifles. Tacitool22
manufactures an adapter that fits on the end of the 15-22 that allows a AR-15
style flash suppressor to be attached to the rifle. Not long after
browsing their website, I had a threaded barrel end adapter on the way.
A close-up view of the adapter as delivered. The threaded portion of the adapter is threaded 1/2-28. This supports a variety of muzzle brakes, flash suppressors, or even fake silencers. The set screw secures the adapter to the 15-22's barrel.
When the threaded barrel end arrived in the mail, I located the flash suppressor in the parts drawer and screwed it onto the adapter. The threads matched up perfectly. After unscrewing the suppressor from the adapter, I grabbed a spare crush washer and reassembled the two pieces.
As I slipped the adapter onto the end of the 15-22's barrel, I was surprised to see how much clearance existed between the barrel's outside diameter and the adapter's inside diameter. Using my vernier caliper, a quick check of the two showed a difference of .007". Hmmm.....that was more than I wanted. A closer fit would certainly be preferred.
I sent an e-mail to the address included in the paperwork that came with the adapter to inquire about the expected tolerance. I received a prompt response indicating that very close fit is the norm and that my clearance was greater than normal. While I was asked what I wanted to do about the situation, it was suggested I might consider shimming the adapter to improve the fit.
When Saturday arrived, I headed off to the local auto parts store. It went like this.....
Counter person: Can I help you?
Me: Yes, I need some brass shim stock.
Counter person: <deer in the headlights stare>
Me: What size do you have it in? I was looking for some .002" thick stock.
Counter person: What year is the vehicle?
Me: Do you know what shim stock is?
Counter person: No
Me: <I explain what it is>
Counter person: Never heard of it. You might want to look in the repair section over there. <points to where the body putty, electrical tape, etc. is displayed>
OK....so much for the auto parts store. Next stop, ACE
ACE Hardware had a nice variety (thickness) pack of brass shim
stock for under $5. I cut a piece of the .002" shim material to a 1/2"
width and then proceeded to trim its length until it would wrap the inside of
the adapter while leaving the set screw exposed. This removed .004" of the
measured .007" clearance that I started with.
With the brass shim stock trimmed to fit inside the adapter, I
carefully slipped it over the end of the barrel. The finial fit and
clearance was just right, in my opinion. The install instructions
recommend between 80 and 120 inch pounds on the set screw between. I wish
the initial fit had been as good without resorting to the brash shim but I
believe the end result will be the same. There is more than ample
clearance for the .22LR bullet to clear the hole in the adapter and flash
suppressor even if I am off a couple thousandths of an inch.
I am now satisfied with the overall look of the M&P 15-22. The barrel no longer looks like it is missing something, as it did before. It is a low cost alternative to purchasing and shooting a 5.56mm AR-15. The manual of arms is the same and except for the lack of recoil, practicing with it will be the closest you ever get to the real thing. If you are looking for a fun .22LR rifle, give the Smith & Wesson M&P 15-22 some serious thought. If you don't want it for the AR style practice, get one just because it's a fun plinking gun. And if you get the model without flash suppressor, consider the Tacticool22 route to attach one.