Blowback 300 project.

[MIKEONE]

Hey guys!

Ive been lurking around for a while here, im in the process of building a blowback operated 300 on the AR platform with a 9mm bolt and some other
little goodies.

My question is, have any of you attempted anything like this on any platform?

This will be a dedicated subsonic gun as to keep the pressures in the 25,000 psi range.

I have a feeling this puppy will be pretty cool once the EJECTOR is figured out.

Mike

[Colohunter]

Sounds pretty interesting, I'm not aware of it being done. Maybe it hasn't been done because of the higher pressure loads available for the platform.

[cav_scout_tj]

Use 9mm ejector parts, they should work.

Blow back is louder than DI. This just doesn't pass the "cost / benefit analysis" test.

[MIKEONE]

The main reason for the blowback is that a super short barrel can be run.
Im toying with ideas on how to delay the action a bit for more dwell time in the chamber.

I need a pic of the 9mm barrel extension and or how the barrel is machined where it fits in a 556 extension.

Mike

[cav_scout_tj]

All sorts of 9mm info:
http://thegunwiki.com/Gunwiki/AnalysisAR9mmRRA

A lot of uppers use an ejector on the mag block

or fixed in the lower.


Olympic uses one fixed in the upper:


The parts in the box lower right are what get mounted in the upper. The finger on that spring ride in the left channel on the bottom of the carrier.
http://www.olyarms.com/index.php?opt...d=53&Itemid=37

Note that the oly system and the colt system are very different.
9mm FAQ

[MIKEONE]

Fantastic info thanks!

Id like to know more about this set up fixed on the lower



But the OLY set up looks interesting also.

Its funny how I seem to have completely disregarded the 9mm AR set up until

now, Thanks for the info!

Mike

[cav_scout_tj]

Actually, thats sort of a misnomer, since yes the ejector can be fixed, but its part of a mag block like in the first pic. Those come in several flavors, some pop in from the bottom of the magwell, some from the top, and some of which are fixed in the lower, wedged with screws.

Since whispers use normal magazines not mag blocks, the Oly setup looks much better for your project since its part of the upper only.

I had a 40S&W Oly upper at one point, ran fine. Sold later.

[MIKEONE]

Im still working on it

[tp555]

The 9mm barrel doesn't have an extension.Its all one piece.The oly system has a real weird extension with a taper.

[Fritzcat]

I have the Oly 9mm with a 10 1/2" barrel. The Oly system uses the mag agenced the front of the magwell and the upper can be pinned directly onto a 5.56 lower without any mods.