9mm Sig mpx suppressed

[ds1]

Our 9mm Sig mpx started life off as a 16” barrelled PCC ‘ IPSC gamer gun’ ( 16” barrel and 14” hand guard are at the top of the picture). One of the great features of the Sig system is its modularity. It took less than a minute to replace the barrel and hand guard with a 6.5” barrel and 8” hand guard.

 

 

It may seem odd that the barrel is shorter than the hand guard but the explanation is in the picture in the form of a 9mm GIS suppressor. We are also keen to try an A-Tec 9mm SMG suppressor if we can sort the 13.5x1 LH thread of the Sig barrel out with an adapter.

 

We will report back after more testing, so far preliminary results indicate that standard NATO 9mm ammunition is shootable without ear protection and heavy bullet (147 gran) subsonic is of magnitudes better. There is no excessive gassing (gas travelling back behind the BCG to the shooters face). 

 

 

Point of impact shifts  have been experienced due to the suppressor unscrewing itself when firing however using a rubber O ring behind the threads may have solved the issue- further testing required……..we are also aware that some people do not recommend using an O ring due to the potential of thread alignment/ baffle strike issues. We have checked this and there is no issue with our system.

[Scotch_egg]

I thought Sig used tapers on their barrel threads? 

[ds1]

There is a taper behind the thread but the issue seems to be that the threads are a small diameter and also short.

 I tried it again today and if you put an O ring on the taper the suppressor will “find” it and push it up the taper as far as it wants. Return to zero was fine taking it off both hot and cold.

It still got on my nerves that I had to use an O ring though so plan for tomorrow- I’ve loctited the 13.5 mm barrel thread to the adapter / thread reducer so I am now left screwing the suppressor onto a much more beefy 18x1mm thread. The friction may be enough to stop it unscrewing itself. Also I can get the A-ATec suppressor that I want in 18x1 mm. More testing required.

[ds1]

21 hours ago, Scotch_egg said:

I thought Sig used tapers on their barrel threads? 

Barrel, adapter ( reducer), suppressor.

Testing today- the 18mm thread has enough friction to stop it unscrewing itself. The 13.5x1 LH thread unscrews itself from the barrel with 242 (blue) Loctite on. Having both RH and LH threads together is not a bright idea.

I will bond the adapter to the barrel threads with a heat resistant epoxy.

[Scotch_egg]

I can only think it’s because of the shoulder on the barrel taper interfering with the mechanical lock that should be forming on the adapter. I have Q barrel’s in 6.5 Creedmoor and .308 with taper and an Oceania defence flash hider/mod adapter. Not a semi auto, but plenty of rounds and it’s solid. 

[Desmond]

On 9/28/2021 at 6:15 PM, Scotch_egg said:

I can only think it’s because of the shoulder on the barrel taper interfering with the mechanical lock that should be forming on the adapter. I have Q barrel’s in 6.5 Creedmoor and .308 with taper and an Oceania defence flash hider/mod adapter. Not a semi auto, but plenty of rounds and it’s solid. 

Completely off topic (sorry). But is your Fix black?

[Scotch_egg]

1 hour ago, Desmond said:

Completely off topic (sorry). But is your Fix black?

No, it’s standard raw anodised. 
 

 

[Richiew]

Try the green loctite types . This stuff will bond threads very well and will need a lot of heat to release the threads . We use it as a bearing fit mostly . The fitters love it but sometimes needs a blowtorch to release the bearings . Lots of different numbers so check loctite web page for different duty’s . Cheers 

[ds1]

1 hour ago, Richiew said:

Try the green loctite types . This stuff will bond threads very well and will need a lot of heat to release the threads . We use it as a bearing fit mostly . The fitters love it but sometimes needs a blowtorch to release the bearings . Lots of different numbers so check loctite web page for different duty’s . Cheers 

Thanks for the tip. I did try Loctite 242 originally but it does not take that much heat to release it. At the moment Novadurit T230, is working very well- it needs an activator for it to work though.