I recently purchased two new butt stocks for my AR-15's, one that I bought was a BCM Mil-spec M4 stock kit from brovocompanyusa, and the other was a New Improved Six Position Collapsible Buttstock Assembly from PK Firearms. So anyway what I was wanting to know was if whether or not the one I got from PK is Mil-spec or not? I tried swapping the buttstocks out on both weapons and the one I got from PK fits both buffer tubes, yet the BCM will not fit the buffer I got from PK. So Im assuming the PK is a commercial buffer tube, however this was not specified on the PK website. I thought I was getting a Mil-spec tube. Im not mad or anything but I was just curious if maybe I was sent the wrong tube or if the PK stock they sell on their website is a commercial stock.

Look at both tubes side by side. The commercial will have a thicker cross section.

Also if it's commercial it will have a slanted back.  Not all stocks are exactly the same size so there might be a tollerance issue.

Not all commercial receiver extensions are slanted.

1.  Ask PK.

2.  Commercial tubes are larger in diameter to allow the threads that go into the lower receiver to be cut into the tube.  A milspec tube has threads that are larger in outer diameter than the rest of the tube.

FWIW; AFAIK; IMHO; YMMV; yadda, yadda, yadda.

Regards, Ed Mann    
[email protected]

Bobby Bowden is doing a fine job - just leave him alone.

Well, like I said I'm not really angry at all. I was simply asking if the stock they are selling is commercial or mil-spec. Because as far as I could tell, nowhere on their site does it state whether or not the stock is mil-spec or not. So I just assumed it was and we all no what happens when you assume. I did find out that it wasn't mil-spec because the back of the tube is slanted. However, I don't hold a grudge against PK I think they do a fine job. I've ordered stuff from them before and the products I've received have always arrived in timely fashion, and I'm sure I'll will purchase more products from them in the future. But like I said as far as I could tell it isn't stated in the product description as to the specs of the product, and someone else could make the same mistake is all.

I would like to thank everyone for your responses.