first .308 AR build came with a surprise.(SR25 version)

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HRnightmare

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Tonight I started building my very first .308 version AR lower receiver build. I have built many "AR-15" versions.

I stumbled when I started to install the rear takedown pin and noticed there was no hole drilled and the spring was NOT held in by the end plate. I first thought my lower receiver was incomplete and was mad. I looked around and COULD not figure out how it possibly was held in place. I removed the pistol grip and low and behold the spring goes underneath and the pistol grip holds it in place.

Is this a common feature among all 308 AR's or is it just the SR25 version? I have never heard of it... but that is not that odd since I have also NEVER owned any .308 much less an AR type.

Quite honestly, I think I prefer this way over the Std. AR-15 way. You won't bend springs when changing buffer tubes out...

Is there a reason it differs from the 5.56/.223 version?



Thanks!
 
S&W M&P10 is the same way and that design has more in common with the AR15 than the SR25.

Mike
 
The ruger I had which is armalite pattern did not have the spring against the grip. Dpms and psa both had the spring at the grip. So I'd assume its a dpms pattern thing.
 
The difference is rifle pattern vs carbine pattern in AR 15's.
 
It was a surprise for me as well (searching through carpet shag for a while) :) I prefer not having to mess with the castle nut.

Mike
 
I know DPMS does it that way... I'm not sure whether Armalite or other mfg's do. It would be interesting to know how the original (1950s) AR-10 did it.
 
thanks for the knowledge. Another question I have is I bought a A2 extension tube because I am going to do the Magpul PRS.

the gun shop told me all I need is the a2 tube. Castle nut and and place is not necessary. given our previous discussion I can see why an end plate is not necessary but why not a castle nut?

there's also no divot cut out on the inside of the tube like a carbine ext tube has. So what holds the extension in place without allowing it to vibrate loose? am I missing something? Like I said I have built plenty of carbine AR15s but never these.

Thanks
 
The bolt into the end of the buffer tube pushes the whole stock against the receiver, essentially doing the same thing as the plate and the castle nut.
 
Let me add a couple of comments, please...

The elimination of the rear take-down pin hole straight-drilled into the lower-right rear of the back of the buffer tube extension is a design change I champion as elegant IF it involves one of two simple replacements:

1. Choosing a receiver with a threaded take-down pin hole passage as above;

2. Drilling of said take-down pin hole passage from the *bottom* of the lower-right side of the receiver which is threaded to accept a 4-40 allen-head screw to secure pin and detent.

Once captured, they are impervious to any pistol-grip changes and effectively sealed from most contamination. Capturing the rear take-down detent and spring is as much a necessity as securing the pistol grip spring/detent for the selector...both are crucial.

Using the newest design makes the entire process much simpler and much more reliable, especially if you are inclined to changing regularly the design of your AR platform.
 
i discovered this several years ago when i did my sr25 project. i also discovered that the magpul miad did not have enough plastic in the top and the spring would fall through. i had to create a plug
 
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