[p35bhp55]

First, I don't use the splatter method of forum posting but I will be posting this anywhere there might be an answer.

Does anyone have any information on how long a 20 gauge sabot barrel has to be to burn the powder and stabilize the sabot? I'm old enough to remember when slug barrels were shorter but back then the slugs were Fosters not sabots. The Mossberg brand I use is now standard at 24" and my friends and I have had nothing but trouble with group size. For whatever reason the 12 gauge seems to work fine. To be clear we have been through about 6 of the 20s. I have the last one now and will probably buy it if there is a chance I can mod it to work. The reason to fixate on barrel length is a history of using H.D. barrels or "riot guns" for deer hunting pre sabot. It seems that the closer the barrel ends to the mount for the magazine tube the more rigid the barrel stays and the better the group. My thoughts so far are either 20" or all the way down to 18 1/2" Any information about velocity or groups from someone who has a shorter barrel would help.

[hiwall]

Most or all shotgun ammo uses fast burning powder. I doubt you would get much or any velocity loss if you shortened your barrel to 18 inches.

[Old_Crow]

You might want to try another type of sabot. The sabots that are really a rifle bullet do very well in my 500 12 ga. You are not the first to complain about the 500 20ga sabot barrel. I have seen a 20 ga cantilever come out of the box unusable. Mossberg cuts every corner on the 20 ga 500. I own one I shoot sporting clay with. It does well for that purpose.

[hiwall]

If you decide to cut the barrel a wise move would be to cut a couple inches and test for accuracy then cut and re-test. Maybe there is a "sweet spot" at 22" or 21" or 19" or whatever.

[Virginian]

Just remember if you go hacking on a rifled barrel you better get the crown right or you will get lousy accuracy. Think rifle.

[p35bhp55]

Originally Posted by Virginian

Just remember if you go hacking on a rifled barrel you better get the crown right or you will get lousy accuracy. Think rifle.

I have access to a lathe, but if I can decide on a length it will probably just get sent to a shop.

[locutus]

The powder will burn completely in 16-18 inches.

[Virginian]

Tests have shown you still get velocity increases out past 32". The rate of increase certainly slows down, but it is still happening. Down in the lower 20" ranges the velocity changes may equal 25 to 50 feet per second per inch. What makes you think Mossberg didn't do a little homework before settling on 24".

[hiwall]

" Barrel length

Shotguns generally have longer barrels than modern rifles. Unlike rifles, however, the long shotgun barrel is not for ballistic purposes; shotgun shells use small powder charges in large diameter bores, and this leads to very low muzzle pressures and very little velocity change with increasing barrel length. According to Remington, modern powder in a shotgun burns completely in 25 to 36 cm (10" to 14") barrels.

[Virginian]

The powder may have burned, but the gasses still have sufficient pressure that the velocity will continue to increase out past 30". I have chronographed enough heavy loads to confirm this. With mouse fart loads I can't say, but it's interesting that the mouse fart shooters seem to be the longest barrel proponents. I can state with absolute conviction that a 10 gauge will definitely kill a skyscreen with one shot. Long barrels were demanded by black powder to burn all the charge.