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The lowdown on RIS/RAS/Rail Systems for Colt M4 .22lr


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After trying to find out for months, unequivocally, which rails will and will not fit, I decided to write this post to give people some info not previously available - at least not in my experience.

I have a Colt M4 'Ops' model with the 7" handguard.

I wondered about receiver threading for the barrel nuts. I ended up taking a risk and buying myself one of the 'airsoft' licensed URX4 keymod rails in 14.5" length http://www.ebay.co.uk/itm/CNC-Anodized-URX4-14-5-RAS-Handguard-for-Airsoft-M4-M16-SR16-SR25-AR15-AEG-/321472195982?pt=UK_Sporting_Goods_Paintballing&hash=item4ad93c6d8e. It came with new barrel nut and locking nut for the rail. The rail itself is also threaded.

I had to get a wrench and clamp the upper receiver against the floor as I broke my vice a few weeks before. I used mole grips and stood on them (used a sock to stop any scratching) Lefty Loosey.

Once the barrel nut was off (leave the action in the receiver) you thread the new one on and tighten with a barrel nut wrench (or screwdriver and hammer)

Then its a case of screwing the new rail on until it tightens with A. No gap between it and the receiver B. Is lined up with top rail and C. The rocking ring inside is in the right position to give a tight fit. Then nip this up with a tool or hammer and screwdriver again.

Also, normal ar15/m4 sling mount plates for the buffer tube work fine on this rifle.

Anyway heres some pics.

[img width=800 height=450]http://i96.photobucket.com/albums/l194/shanekiely/20141223_135402_zps9f26aa77.jpg

[img width=800 height=450]http://i96.photobucket.com/albums/l194/shanekiely/20141223_124312_zps81f7a83c.jpg

[img width=800 height=450]http://i96.photobucket.com/albums/l194/shanekiely/20141223_124304_zpsd8d03dfa.jpg






[img width=800 height=450]http://i96.photobucket.com/albums/l194/shanekiely/20141223_124012_zps56c4eb6b.jpg

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