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Getting the most out of your M4S90


Unobtanium

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I have compiled a few tips for those of you who may/may not need them to help you enjoy your M4S90 the most.

 

 

Trigger:

 

Some triggers just feel and sound gritty. The cause of this is the small spring, the trigger return spring, in the trigger group. Remove the pin that controls the trigger (it is a simple push pin, not the rear one, but the one 1/2 fore the rear one.) Push it to the right just enough to get the trigger out. It lifts out and no other pieces will fly out except that spring, and it is not going to fly. Make sure you do NOT push the pin out so far that you release the other items that it holds in place.

 

Now, what has occurred is that when the weapon was assembled, this spring's and trigger's geometry were not accounted for. As the trigger pivots on the pin you just pushed out, the orientation to the spring changes. The spring bends and then grates over the lip of the recess in the trigger. Gritty as ****. Even sounds bad if you listen close.

 

To correct this, re-install the trigger, using some grease to hold the spring into the recess in the trigger. Do not push the pin in yet. Just get the rear niche in the trigger oriented to the bar in the housing (You will understand once you see it). Now, move the trigger (and spring, consequently) forward. Plant the bottom coil of the spring on the housing and now move the trigger back and into place and slide the pin through it. This should orient the spring in such a way that it will not make noise/grate. It is trial and error, and that is what worked for me, yours may require a different placement, but you can fiddle with it until pulling the trigger is silent and smooth.

 

Next up is that "cylinder" the hammer depresses as it's cocked. Grease that thing. It grates.

 

Do not "polish" anything. Go shoot your M4 and let it do that work.

 

O-rings:

 

On one of the four M4's I have purchased, it was torn almost in two upon inspection (regarding the FP retaining pin O-ring). I replaced it with one from my spare parts. You LUBRICATE this BEFORE installing it and you try to twist as you press, don't just press. That will prevent tearing it. I will call Benelli on monday and get another one to replace it. They have them. Brownells does not. They sell JUST the pin (you need the o-ring). Benelli will sent you a new ring/pin.

 

The o-rings on the gas piston setup are no different except they are far more durable. Just use care when cleaning this assembly. I prefer to use Choke-Tube grease on these threads just because I would HATE for it to seize.

 

Choke Tube Care:

 

Use a good grease MEANT for choke tubes. I prefer Birchwood Casey.

Throw away that stupid wrench Benelli sent you and buy a Briley Speed wrench. That way I don't have to read your posts about the choke-tube shooting loose every 25 rounds.

 

Operation:

 

The M4S90 likes to run wet. As long as you use a quality lubricant, that should be fine. Oil it JUST like you would an AR-15. Wet. M4S90's should have a quality grease of medium to lighter weight used on the BCG rails and the cam-pin. I prefer TW25-B. The Fire Control Group also likes grease. A heavy synthetic grease is preferable here. Think the consistency of axle grease. Brian Enos' slide Glide works well.

 

You will also want a "Tornado" bore-brush. It will make clean-up after shooting slugs fast and simple.

 

Anyway, these are just a few helpful hints I have discovered to get the most out of your M4S90.

 

Oh, if Kip makes it, and it is between his product and that of another manufacturer, Kip's product WILL be equal or better. I say equal, only because the follower Benelli sent me appears to be 95% identical to Kips, minus one dimensional change and a US stamped in Kip's.

 

Kip takes time. Don't sweat it.

Edited by Unobtanium
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Good info.

 

I was wondering why you had removed the hammer pin completely from the trigger group.

 

Next time I make an order from Brownells, I'm going to grab some of that SlideGlide to give a try.

 

I was half asleep.

 

Slideglide is good, but TW25B works better on the BCG in my experience. Slide-Glide is mainly for the FCG, because it is so "sticky". It "strings" and stays on parts like the hammer hook better than something like TW25B.

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so the choke grease will help to keep the choke tube from coming loose and what prevent rusty threads?

The choke grease will allow you to properly tighten the choke with a decent wrench without it binding. Rust can occur on/to anything if you abuse it enough, but the grease should help with that, as well.

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Do you have any advice on what oil affects the acoustics of the bolt carrier group the most? I'm looking for the loudest racking sound I can get, so I can scare away criminals with the most ease. I'd have to imagine different lubricants have different sound dampening or amplifying properties, and I feel this is a very important issue that deserves some proper scientific testing.

 

:D

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O-rings:

 

On one of the four M4's I have purchased, it was torn almost in two upon inspection (regarding the FP retaining pin O-ring). I replaced it with one from my spare parts. You LUBRICATE this BEFORE installing it and you try to twist as you press, don't just press. That will prevent tearing it. I will call Benelli on monday and get another one to replace it. They have them. Brownells does not. They sell JUST the pin (you need the o-ring). Benelli will sent you a new ring/pin.

 

The o-rings on the gas piston setup are no different except they are far more durable. Just use care when cleaning this assembly. I prefer to use Choke-Tube grease on these threads just because I would HATE for it to seize.

 

 

Are these the O rings. Brownells has both of these:

 

Firing Pin Retaining Pin O Ring

http://www.brownells.com/.aspx/pid=6388/Product/FIRING_PIN_RETAINING_PIN__O_RING

 

Gas Plug O Ring

http://www.brownells.com/.aspx/pid=23649/Product/GAS_PLUG_O_RING

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