i posted my writeup on it yesterday with some info/pics:
http://militarymorons.com/weapons/ar.furniture2.html#a5
"The Vltor Weapons Systems A5 Buffer & Recoil System was developed for the specific needs of U.S. Military users of the M16A4 rifle (or AR-15's with rifle-length gas systems). The A5 system provides the functionality of a collapsible stock while maintaining rifle-length buffer system reliability. It includes a newly designed buffer and receiver extension.
Description - One of the issues encountered by current users of the M16A4 rifle (the USMC and U.S. Army) is its overall length and maneuverability. The 20" barrel (while providing additional velocity) and fixed A2 stock configuration has proven less than optimal for some of the close-quarter/house-to-house fighting encountered in recent engagements, especially when combined with the body armour being worn. The added thickness of body armour, sometimes consisting of soft inserts plus a plate can cause the A2 stock to be too long, especially when a less bladed stance is used.
Another issue is that of reliability. As the M16 series of rifles evolved into specialized configurations like the SPR, Mk18 etc, each of them using different combinations of barrel and gas-systems, attempts to universally use the standard collapsible stock on all platforms have encountered issues. The solution is not as simple as sticking the A4 rifle uppers on lower receivers with carbine collapsible stocks. Some of the issues that arise are increased rate of fire on full auto and inconsistent carrier velocities. Putting a heavier weight buffer in a carbine system (like the Army's H6 buffer) is one solution, but also comes with its share of associated issues.
The Vltor A5 package is a replacement stock system for users of the the M16A4 rifle (as found on the M16A4) who want to maintain the same reliability, carrier velocity and rate of fire as the rifle-length A2 stock, while adding the functionality of an adjustable stock. This is achieved by a new buffer and receiver extension (buffer tube), and the use of the standard rifle length buffer spring.
The A5 system can be used on all direct impingement systems of any gas system length, and also reduces cyclic rate on short-barreled rifles and maintains a much more consistent bolt velocity and rate of fire on all current issue weapons based on the M16. With different A5 buffer weights available, the A5 system can also be used with piston systems, or over-pressured rifles.
The Vltor A5 Kit consists of an A5 Standard Buffer, rifle-length spring, A5 receiver extension, EMOD stock, receiver end plate and castle nut. Other A5 buffer weight configurations will be available individually/separately.
Buffer - With an AR or M16 rifle stock system, part of the rifle buffer is just 'spacer'. It's there to allow the longer rifle-length buffer tube to be used without affecting the length of travel of the bolt carrier (which is the same whether a rifle or carbine buffer system is used). Vltor saw that this extra spacer length could be eliminated while still using a standard rifle length spring, and came up with the A5 buffer. The A5 buffer is approximately the same length as a rifle buffer with the 'spacer' portion at the front removed. It is 4", versus the 3.25" of a carbine buffer. The A5 can be had in different weights, but the standard A5 weight (shown here) is about 5.3 oz (2 steel, 2 tungsten weights), and matches the same carrier velocity as the A4 configuration. Instead of a carbine spring, the standard rifle-length buffer spring is used. The A5 H1 buffer has 3 tungsten, 1 steel and the A5 H2 buffer has 4 tungsten weights.
The use of a rifle spring provides consistency that the carbine-length spring does not. It was found that the more coils that a spring has, the more consistent the spring rate upon each compression.
Receiver Extension - Just as the A5 buffer is 3/4" longer than the carbine buffer, the Vltor A5 receiver extension is 3/4" longer, making it 8" long, vs. 7.25" for a carbine tube. The A5 receiver extension has 7 positions and was designed to be used with Vltor's EMOD stock. Any mil-spec carbine stock can be used with the A5 receiver, but the additional length means that standard carbine stocks won't close all the way, as illustrated in the photo with the IMOD below on the right. For me, it's a non-issue as I usually shoot with the stock in that position or another notch out.
Shooting with the A5 system is almost identical to shooting a standard rifle-length stock/recoil system, except that you have a collapsible stock. I tried out the A5 with a few different uppers, and felt recoil is a bit softer than with a carbine system. I have a few hundred rounds using the A5 so far (with no issues), and one carbine system upper I had which was a bit finicky with a regular buffer worked 100% with the A5 kit. I'm just a very limited statistical sample of one, but A5 kit-configured weapons have gone through extensive testing (over 70,000 rounds) so far with very promising results. It has also been tested on the HK 416 with 10.5" and 14.5" barrels and shown that the cyclic rate is decreased for both barrel lengths substantially in unsuppressed and suppresed configurations. "
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