SPR Barrel length: 18inch or 20inch?

[CQB]

I am building an upper on the Vltor VIS platform with an Acog TA-55. Wanted to know some opinions between the accuarcey differences between an 18 inch to a 20 inch barrel with a mid-length gas black. The barrels would be a standard 1&8 410 stainless flutted with match +-1.
Comments?

[KevinB]

I prefer the 20" to the 18 but thats just me.

I dont know why you want to go with a midlength gas system for either though? K.L.Davis has "some" experience with a SPR gas system for the 18" barrels which is longer than the middy and shoter than rifle (IIRC) -- you may want to PM him.

For a 20" - I would stick with a rifle gas sytem.

I only have used the middy on 12.5" and 16" barrels.

[edwin907]

I say go 18".
Here's my 18" Douglas with DD 13.5 and TA55.

[militarymoron]

K.L.Davis has "some" experience with a SPR gas system for the 18" barrels which is longer than the middy and shoter than rifle (IIRC) -- you may want to PM him.

K.L. was probably referring to Vltor's intermediate system. more info about it here under the daniel defense rail writeup on my site:
http://www.militarymorons.com/weapons/ar.uppers.html#dd

it's an 18" barrel with intermediate gas system:


i have another upper with a 20" barrel with rifle gas system. it doesn't have a flash hider so it's actually the same overall length as the 18" upper.

[DocGKR]

I am in full concordance with KevinB's comments and recommendations above.

[JaxCatm]

To be honest I work with government weapons everyday and I can't tell a big accuracy change between our weapons that use a mid length gas system and the full length system. The are not match rifles but never the less the location of the gas system does not appear to effect accuracy for us.

[bones]

I agree with KevinB

I prefer the 20" to the 18 " barrel length.

[SethB]

To be honest I work with government weapons everyday and I can't tell a big accuracy change between our weapons that use a mid length gas system and the full length system. The are not match rifles but never the less the location of the gas system does not appear to effect accuracy for us.

It is about reliability.

[DacoRoman]

sorry for the necropost, but this has left me hanging

So what is more reliable in an 18", a mid-length or a rifle length?

I was reading that while an 18" with an rifle length gas system is smoother shooting, a mid length gas system is more reliable for the 18" bbl, especially in cold weather.

Actually, I just found this post and got this answered! This forum is good!

I actually recommend the mid-length for use with a suppressor.
Mid-length runs a smaller port size so the addition of a suppressor has LESS effect than on a rifle setup where the port is opened up more to account for the shorter dwell time.

For pure competetion, I recommend the rifle length setup for it's smooth operation ans short dwell which helps you stay on target.

Cold weather reduces the operating pressure of the ammo and can also make the lubrication heavier (more sluggish movement).
Cold weather combined with a short dwell time has a potential for short stroking problems.
In reality it usually just causes a failure to lock back on an empty mag.
Function from shot-shot is usually fine.
__________________
Randall Rausch
ar15barrels.com
Specializing in custom barrels and barrel work.
If you want something that's not available off-the-shelf, I can probably do it for you.

[eaglecp]

I prefer the 18inch with rifle length gas system. Reliable as hell and there is VERY little velocity loss between the two.
Mine is based on a MK12Mod0 However it is built on a VLTOR MUR1A Upper and LMT 2000 lower.
Douglas 1x7 SS SPR contour, (Real deal) I have been EXTREMELY happy with this set up.
Heres a Pic without the Scope and Irons deployed


I have ran all kinds of ammo through it and it like BH75GR best Blue or red box doesnt matter.

I am currently running a TA11 or TA11E on it for Mid Range work and a Leupy 2.5x8 MR/T ILLUM TMR ret.
ALWAYS in A LaRUE Mount.......... Always!
chuck