Inertia semi auto question.

Should have no effect. Adding weight to an inertia gun can hinder the action.

Gas guns are tuned to work with a certain barrel length and pressure range of the ammo. None of that matters with inertia guns.

Working from the free body diagram. . . anything you do to lower the exit velocity of the shot will lower the impulse provided to the action.

That said, I expect most of the impulse is provided early in the barrel dwell (during peak acceleration) so shortening the barrel by x% should cause less than x% reduction in impulse. I wouldn't cut a barrel based on this guess, but further research is reasonable.

That said, semi-auto shotguns are notoriously finicky already. . . do you think you can re-tune the kinetics better than the designers did the first time? Maybe. . .

Virginian said:

Should have no effect. Adding weight to an inertia gun can hinder the action.

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This.

My Benelli's all have short barrels and extended magazines. I don't recall ever having a misfire and I have shot a lot of skeet with my Super 90. I shot them with magazines fully loaded (lots of weight) to lightly loaded (e.g. two shots for skeet). I also do not shoot light loads as that can definitely affect performance. I have seen kits to allow shooting light loads but have no experience with them.

My 20" Beretta 1201FP functions just fine. Now that is the original barrel length.

My M1 super 90 has never had a failure of any kind. 26" barrel box stock.

I carried the 20" Benelli 12 ga w/ the extended mag tube on patrol in the 1990s'-2000's...and other than being finicky with light target loads they worked 100% with standard duty slugs/buck...but they came that way from the factory so I don't know if the springs were optimized for that specific barrel length.

Maybe a call to the manufacturer would give a solid answer?

Stay safe.

jmr40 said - "Gas guns are tuned to work with a certain barrel length and pressure range of the ammo. None of that matters with inertia guns."
That is about as close to exactly backwards as you could get. Gas guns use many different methods to meter the gas. Inertia guns have whatever springs were put in at the factory and that's it.

To the OP's question, cutting the barrel won't have a measurable impact on cycling. Barrels weigh a little less than an ounce per inch of length (I've weighed some cut barrel, but don't recall the exact ratio). My Auto 5 (inertia operated) requires approximately 55 POUNDS of force to cycle the action rearwards against the spring tension. Reducing 5 or 6 ounces of barrel weight from the equation is inconsequential.

I6turbo said:

To the OP's question, cutting the barrel won't have a measurable impact on cycling. Barrels weigh a little less than an ounce per inch of length (I've weighed some cut barrel, but don't recall the exact ratio). My Auto 5 (inertia operated) requires approximately 55 POUNDS of force to cycle the action rearwards against the spring tension. Reducing 5 or 6 ounces of barrel weight from the equation is inconsequential.

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Is your Auto 5 an original or the new model that came out a couple of years ago?

cdb1 said:

Is your Auto 5 an original or the new model that came out a couple of years ago?

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It's a 1954 model.

Then it is not inertia operated, it is a long recoil action.

cdb1 said:

Then it is not inertia operated, it is a long recoil action.

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Ahhh... You're right of course, and I stand corrected. I carelessly thought recoil when I read the OP's question.

But on the subject, a LOT of internet wisdom says don't cut a barrel on a Auto 5, Model 11 or 11-48 shorter than 20 (or whatever) inches because it won't cycle correctly due to the slight difference in weight, which isn't correct. My A5 has never malfunctioned with the 18" barrel, and as I wrote above, it makes sense given that a few ounces of missing barrel weight is nothing compared to the spring tension in 12 gauge recoil guns.

I agree and believe the friction ring settings determine cycling ability and barrel length has zero affect.