Rail length/outer barrel length

[Lozart]

Right then - leading on from my DD rail fitting thread debacle, I have two questions:

 

Firstly - where do you measure the length of a floating rail? The one I have measures 7.5 inches along the top rail which makes sense as it was sold as a 7.5" DD style rail. Now the thing is - I know that if you have a standard M4 with original sight post and Delta Ring arrangement that a KAC style RIS handguard 7" long will fit. Which leads me on to the next question.

 

Secondly - from exactly where to where on an M4 outer barrel is the length taken? Is it from the very end of the the prongs that go into the receiver to the tip of the 14mm thread or is it to the shoulder of the barrel (so excluding the threaded part). If I have a 7.5" floating RIS it makes sense to me that an outer barrel measuring 7.5" from base to shoulder should just have the threaded portion sticking out the front of the rail. With me so far? Good. I have seen a Madbull kit which purports to be a 4" rail that comes with a 9" barrel but the barrel only seems to stcik out by about an inch www.popularairsoft.com/news/daniel-defense-licensed-4-lite-rail-kit

 

So does the picture in the article NOT show the barrel they say comes with the kit or am I measuring the whole thing wrong?

 

The main reason I ask is that I want to get a new outer barrel to achieve the "Strike Back" look as below:

 

and I don't want to end up buying yet another part that is slightly the wrong size. The barrel appears to have about 0.5" between the end of the rail and the back of the flash hider/suppressor in this pic.

 

 

HAAAAAALLLPPPP!!!!

[straffham]

Afaik that is correct about rail length being just the top (or longest) surface length, and without the adapter fitted to it.

 

I always thought barrel length was the full length from barrel tip (so including thread) to the prongs that hold the hop in place, but I'm open to correction. I have a 10" M4 barrel but it only measures about 9" from tip to receiver, on a gun with KAC style rail and standard M4 front sight.

 

On that Madbull 4" rail link the outer barrel is 7" not 9", which would sound about right I guess allowing both for an inch or so hidden in the receiver and for the rail adapter fitment, plus half an inch of thread, so only about half an inch of barrel showing proud of the rail. As the Strike Back gun looks to me like a 7.5" ish rail (apologies again if anyone knows more definitively) then if so going with Madbulls idea of a barrel 3" longer than the rail gives a barrel around 10 to 10.5" so should be spot on (Madbull's website is worth a look as their range of barrels and rails is massive).

 

Sorry its not especially definitive but hope its helpful.

That is an awesome looking gun in fairness!

[Lozart]

I currently have a 10" barrel and it's too long. By about 2"! :-)

 

The madbull site has measurements as you say, but if you look the m4 barrels (m4a1 14.5" for example) show the length as not including the flash hinder threads. The 7.5" diplomat barrel is 202mm tip to tip which is nearer to 8" which would suggest again that the barrel length doesn't include the threaded tip.

 

Either way, I had the tape measure out tonight. There's now an 8" urx barrel and a short kac ad suppressor en route from ehobby asia ;-)

[Lozart]

A standard knights armaments ris handguard for an m4 with delta ring and cap is actually 6.25" by the way. That's from knight's own website.

[straffham]

yeah not always easy to judge sizes from photos. Glad you got it sorted.

 

I notice Madbull do a 16.5" M4 barrel as well as the 14.5", didn't realise there was a version that long!

[Lozart]

yeah not always easy to judge sizes from photos. Glad you got it sorted.

 

I notice Madbull do a 16.5" M4 barrel as well as the 14.5", didn't realise there was a version that long!

Sooooo many lengths! #confused