Interesting problem with a thread adapter and rubber gasket

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Odd Job

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I bought a new rifle, a Rimfire Magic .22LR here in the UK. It is essentially a Ruger 10/22 pattern, but very few Ruger parts on it. It has a 16" Volquartsen barrel threaded 1/2"x20 tpi, Rimfire Magic receiver (they mill it here in the UK), enhanced Ruger BX trigger unit, upgraded firing pin and charging handle and a Magpul X22 stock:

2q8f5Kg.jpg


Its current configuration is different from what you see above, because I intend to use it mainly for off-hand shooting at 25 yards. So it now has a Yankee Hill Machine Riser and a Burris Fast Fire 3 red dot on it.

As an aside, this rifle is really sweet! Beautiful trigger, comfortable stock and the FF3 does what I want at this distance. Here is a target shot at 25 metres without a suppressor using RWS target Rifle ammo:

4kzc1GK.jpg


The suppressor in the photo is a Hogan Decimeater but I am not using that yet. To get everything sighted and for plinking, I have started with an ASE Utra Dual Rimfire suppressor (which I clean regularly) and which has different threads (1/2" x 28 tpi).

On to the interesting finding...

I bought a cheap thread adapter from Ebay, which converts 1/2" x 20 tpi to 1/2" x 28 tpi.

I will call this "adapter 1"

I posted in another thread previously that I had issues keeping a flash hider secure on a SIG522 and I found that a rubber o-ring sorted that problem out and still enabled me to take that flash hider off and attach a suppressor at will.
So, with this in mind, I got a flat rubber gasket and attached that to the adapter so that it would sit between the adapter and suppressor. The sequence of devices is therefore:

Barrel--> adapter-->gasket-->suppressor

Having already sighted the rifle in at 25 metres with no suppressor, I attached the adapter with gasket and ASE Utra suppressor and fired 5 rounds. Imagine my displeasure when this was the result:

ssb1D6b.jpg


I immediately thought the adapter was to blame (since I have used this suppressor on two R55 benchmark rifles with no issues at all).

So I got a second adapter which is better quality all round and tried the same thing, also with the gasket attached. Here is the result:

kjYAYIz.jpg


Don't pay too much attention to the group sizes, as these were shot under less than ideal conditions on an indoor range. The main point is that the rounds went where I thought they should go. I will call that adapter "adapter 2"

Continued....
 
As soon as I saw the difference between the two adapters with the gasket in place, I decided to do two more tests without the gasket, firing 18 rounds. Surprisingly the problem with the first adapter went away:

7ETcf85.jpg


This was the target using adapter 2 with no gasket:

ys310Kn.jpg


Lastly, I carried out one more test where I put the gasket in front of the adapter, so the sequence of devices was as follows:

Barrel-->gasket-->adapter--> suppressor

Imagine my surprise when I checked the target and found absolutely no rounds had hit. They went down range just fine because I heard them hitting the bullet trap at the back, but they went off paper.

This happened with adapter 1 and adapter 2, which I cannot understand!

One of the guys at the club says it might be a case that the gasket is too soft and is allowing an angle to form between the barrel and the suppressor. He says I might be better off with a fibre washer.

I'll try that and post back.

But I am wondering how much play there would have to be with these threads if that was the case, and why it did not happen with the gasket up front on adapter 2...
 
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