16 vs 18 for 3gun

[MarkCO]

Why not do both 16" with rifle gas

Not enough dwell time, so you need more gas and that defeats the benefits. 17" will work okay, but 18" is the sweet spot.

[moose76]

Not enough dwell time, so you need more gas and that defeats the benefits. 17" will work okay, but 18" is the sweet spot.

As Mark said, there isn't enough time after the bullet passes the gas port, but before it leaves the barrel to get enough gas into the system to work the action (dwell time).

Here is a link that does a pretty good job of explaining what happens, the good charts are at the bottom of the page: http://www.ar15barrels.com/prod/operation.shtml

[cofi]

Not enough dwell time, so you need more gas and that defeats the benefits. 17" will work okay, but 18" is the sweet spot.

As Mark said, there isn't enough time after the bullet passes the gas port, but before it leaves the barrel to get enough gas into the system to work the action (dwell time).

Here is a link that does a pretty good job of explaining what happens, the good charts are at the bottom of the page: http://www.ar15barrels.com/prod/operation.shtml

The couple I have built have thousands of rounds of cheap Russian steel case through them I'd have to disagree....... softest shooting rifles I have ever shot like shooting a .22

[MarkCO]

The couple I have built have thousands of rounds of cheap Russian steel case through them I'd have to disagree....... softest shooting rifles I have ever shot like shooting a .22

Lets not get silly basing this on crappy Russian ammo that uses fast powder. Sure a Dissapator set up is soft shooting, but not like a .22LR by any stretch. Shooting 69s and 77s are almost impossible to get tuned correct in them. Erroneous/niche feedback does not help the OP at all.