Gas port location vs. barrel length question

[Trekbike]

Given the location of a gas port on a semi-auto shotgun, does the length of the barrel beyond the port have any real influence on the gun's ability to cycle?

[Chucktshoes]

I know that the dwell time absolutely affects a semi auto rifle, but I honesty don’t know much how it affects a shotgun. 

[Trekbike]

2 hours ago, Chucktshoes said:

I know that the dwell time absolutely affects a semi auto rifle, but I honesty don’t know much how it affects a shotgun. 

I'm guessing it has the same effect, but not sure since I'm thinking the wad likely doesn't seal against the barrel ID as tightly as a bullet does in a rifle barrel.     

[xtriggerman]

On ‎1‎/‎2‎/‎2020 at 1:14 PM, Trekbike said:

I'm guessing it has the same effect, but not sure since I'm thinking the wad likely doesn't seal against the barrel ID as tightly as a bullet does in a rifle barrel.     

 Actually, a modern shotgun shot cup wad seals exceptionally well.  Being a hollow skirted bottom, the relatively low shotgun bore pressure & heat makes for a perfect seal. On the other hand, Rifled bores seep pressure past the rifling impressions on the projectile. HK firearms use polygonal rifling to eliminate most all of that seepage.  As for bore length vs gas port size, yes, it has a similar math to rifles. Obviously, the actual port sizes are considerably larger due to the much lower shotgun bore pressures. 

[TomInMN]

@xtriggerman, do shotgun's tend to be any more forgiving than rifles (or vice versa) of sub-optimal gas port sizing or location?

[xtriggerman]

5 hours ago, TomInMN said:

@xtriggerman, do shotgun's tend to be any more forgiving than rifles (or vice versa) of sub-optimal gas port sizing or location?

 I'm not sure what you mean by the term forgiving. The semi auto gun designs have been trying to build "forgiving" autoloaders for decades and to this day, there is no simple solution in porting. I'm not a big auto shotgun guy so I'm not up on the latest but making a forgiving gas system can work to a degree but its a trial & error with all the various loads. Personally, I think they have been over thinking auto gas regulation for decades. Back in the 70's High Standard had an auto loader that had an adjustable mag tube cap. You just turned it one click and you were good for magnums, click it back for low brass. Simple & effective. The only real forgiving way to shoot everything is just over gas it like what the industry has done with aftermarket AR barrels. Most people will never shoot their guns enough to see ware on the parts. Location and porting are very much linked together effecting action function.

[TomInMN]

Thanks @xtriggerman. By "forgiving" I meant more likely to still be reliable even if undersized or located too close to the muzzle. Not likely to happen, I know, but I was curious.

I guess, thinking about shortening a shotgun's barrel, it would be smart to not go any shorter than the shortest length offered by the factory until you do some math...