View Full Version : recoil action vs inertia action?

April 9, 2009, 06:45 PM
What is the difference between a weapon being "recoil operated"
and "inertia operated"?

Why is a benelli not "recoil operated" but it is "inertia operated"?

I fail to understand the difference because public schooling roted my mind.

April 9, 2009, 07:40 PM
Believe it or not... Wikipedia has a pretty good explanation of the various forms of recoil operation (http://en.wikipedia.org/wiki/Recoil_operation)... including the Benelli M2 inertia system. Complete with diagrams!

The video found on the Benelli (http://www.benelliusa.com/innovations/inertia_driven_system.php) (and other) site is also a useful educator.


A/C Guy
April 9, 2009, 10:19 PM
Inertia is quicker and runs cleaner than a gas system.

April 9, 2009, 10:38 PM
A gas operated SX2 holds the world record for speed, but the inertia operated gun might just be cleaner. But who needs to shoot so fast and we always clean our guns after heavy use.

To me both inertia and recoil operated are about thr same.

April 10, 2009, 07:55 AM
Both recoil and inertia systems share similarities and are based largely on the same principle - using the force of recoil to engage the autoloading action.
The Browning A5 and Remington 11-48 are the best known examples of the recoil systems in shotguns [pistols use the short recoil mechanism] In these, the force of recoil causes the bolt and barrel to move rearward, ejecting the spent shell and reloading a live round before a spring mechanism returns them to the pre-firing position.

Benelli's inertia system [which it licenses to other manufacturers] differs in that the entire firearm is used to absorb the force of recoil and a rotating bolt system [similar to that used on autoloading rifles] performs the function of ejection and reload.

In gas operated systems, some of the expanding gas used from firing is bled off to feed the ejection and reloading of a new shell, generally using some sort of piston mechanism.

In theory, inertia systems are supposedly more immune from jamming or failure to eject because of the way it actually works, supposedly combining a mechanical with a recoil action. Thus it supposedly is more "reliable" and "cleaner"

Gas systems by contrast are generally felt to be smoother and softer.

In actual fact however, these alleged differences and advantages are not so clear cut. Modern firearm design and ammunition are sufficiently developed and reliable to ensire that the choice of one or the other system is really largely a matter of personal preference with quite likely, very little if any perceptible differences on the field or when otherwise handling the firearm.

April 10, 2009, 08:00 AM
I always thought recoil and inertia were the same thing? I know gas operated is different..... Will have to look this one up :confused:

April 10, 2009, 09:08 AM
My admittedly oversimplified way of viewing the differences between recoil operated and inertia operated is that...

Recoil operation can theoretically be "limp-wristed shouldered". It requires that the firearm not be allowed to recoil freely.

Inertia operation REQUIRES a certain amount of "limp-wristed shouldering" - if one were to be backed up against a tree and fired it would not cycle. Hence the reason Benelli pitched their trademark inertia system overboard for gas (ARGO) operation on their tac-tickle model: hang enough fru-fru, NV gear, scopes and other weights off the thing and it doesn't recoil enough for reliability.

In the real world, it's a bear to limpy-malf a recoil operated shotgun - it's not exactly trivial with a short recoil metal handgun either but that's another fight. Neither is forcing a malf from rigidity out of an inertia system real easy in normal use.

April 10, 2009, 11:20 AM
A gas operated SX2 holds the world record for speed, but the inertia operated gun might just be cleaner. But who needs to shoot so fast and we always clean our guns after heavy use.
To answer your question, when in a self defense situation facing the legendary and much feared 6'5" 300lb hopped up on drugs gang banger charging down the hallway of your home it might be nice to be able to double or triple tap the monster with 2-3rds of 00 buck to the chest in about a 1/10 of a second. That's doable with a Benelli M1 S90 (inertia system) and I suspect would take the fight out of just about any attacker no matter how large or drugged out.

I went through 200rds on Sunday. When I got it home disassembly for cleaning took less than a minute working at a leisurely pace. The receiver was so clean that I just wiped it out with a cloth, and the polished interior of the barrel took about a minute to clean. Swapping between my 28" sporting barrel and my 20" home defense barrel takes less than a minute.