Blowback 300 project.

[MIKEONE]

Can you post a pic of the inside ejector side of the receiver so I can see how the thing sits in there?

Thanks Mike

[Garrett]

Just thinking in a different direction - could you use a .223 bolt & carrier and modify the bolt so it does not rotate and lock into the barrel extension? You would then have the ejector issue taken care of.

You could use the guide / key from a 9mm bolt.

Of course, it may end up being more work than using a modified 9mm bolt.

[redtazdog]

I'm waiting to hear someone say that it wont work well because the bottle neck brass wont get enough support in a blowback system without the brass getting blown straight wall looking like a 30 carbine or worse.
To keep the brass looking like 300 whisper the delay of the bolt moving will
need to be long i would think.

[Hoser]

It *could* work. Both the 9x19 and Whisper run around the same pressures.

[cav_scout_tj]

Thats silly, the 357 sig and 400 Corbon are bottle neck pistol rounds. They run fine blow back.

The AR57 uppers are blowback, and the 5.7 round is a higher pressure bottleneck round.

[redtazdog]

The lugs on the bolt hold the bolt closed longer with the delay of the gas
then the hi preasure is reduced to safer low levels before the bolt comes back.
on a blowback the bolt comes back with very little delay, in fact its
almost instant.
Yes a pistol is blowback but they are made to have delay before
the slide comes back on some calibers like a 357 sig.
If you think a blowback 300 whisper has not been tried,
call Olympic Arms or JD Jones and ask how there AR blowback
prototypes in 300 whisper and 357 sig worked.
They will tell you they did work but the brass was destroyed after
the first round.
Oly tried a AR 357 sig prototype using a 40 sw bolt and a 9mm barrel rechambered for 357 sig
and it blew up the brass.
There is a artical about a blowback AR 357 sig that Kurts Custom firearms built and it destroyed the brass but was fun.

[redtazdog]

Originally Posted by Hoser

It *could* work. Both the 9x19 and Whisper run around the same pressures.

9x19 is not a bottle neck like 300 whisper.

[redtazdog]

Originally Posted by cav_scout_tj

Thats silly, the 357 sig and 400 Corbon are bottle neck pistol rounds. They run fine blow back.

The AR57 uppers are blowback, and the 5.7 round is a higher pressure bottleneck round.

357 sig and 400 corbon pistols have barrels that cam back and cause a delay
to reduce the pressure before the slide comes back.
If the barrel came straight back without delay the hi pressures would
make a straight wall case out of a 357 sig or a 400 corbon.
.
Figure out how to delay the bolt from coming back until the hi pressure is dropped and a bottle neck
will work in a AR.

[MIKEONE]

LOL, Well we will just have to see.

[Hoser]

Originally Posted by redtazdog

9x19 is not a bottle neck like 300 whisper.

And your point is?

I was just saying it could work. Not that it should/would work.

I dont have enough experience with blowback rifles, other than a SBR 9x19 and a SBR PS-90, to know if the case design would be too much of a player.