I want to build a Remington 870 for shooting clays, but not the traditional route (over/under).  I want to build something that will double for home defense/SHTF/pumpkin assault.

I'm thinking along the lines of:
18-20" vent rib barrel
Replaceable chokes
Pistol grip buttstock
Full length mag tube
and maybe a mount for my EOTech for when I feel like "cheating"

What I'm wondering is, will I have any major disadvantages with a shorter barrel compared to the typically much longer barrels used on most trap/skeet guns?  Will velocities be much lower with a 18" or 20" barrel, versus say... a 28" barrel, or do shotguns work more like pistols, getting most of their velocity over a shorter distance than a rifle?

I suspect you will have a difficult time with trap.  Skeet might work with the appropriate choke.  I used my M1Super 90 once for hand thrown birds.  I worked okay.

Gary

Does anyone know where I could find information on shotgun velocities from different barrel lengths?

You should be fine with a short barrel for sporting clays. I use a Benelli M1 Super 90 with a 21" barrel, vent rib and either Modified or Improved Modifed for choke.

Also use a Benelli Super Black Eagle 24" and have shot sporting clays and trap with a Benelli M1 18.5" with ghost ring sights and a pistol grip stock.

You will get some dirty looks from the high end Over Under crowd for using a short barrel black shotgun.....but who cares what they think.

I know someone who used a Red dot sight when he was having trouble getting back to his usual shotting. (Were talking 99 100's all day) and I guess it worked for him I just want to hear a range report of your first time shooting with that thing

Forget about velocity. The problem with short barreled shotguns for clays is the guns are short and 'whippy'. And not very well balanced either. Its difficult to keep a good smooth swing going with such a short barrel. A steady smooth swing is of the utmost importance in clays shooting. And field shooting for that matter.

I'd recommend at least 26", preferrably a 28. I have some 30" barreled guns but thats getting long.

Quoted: Forget about velocity. The problem with short barreled shotguns for clays is the guns are short and 'whippy'. And not very well balanced either. Its difficult to keep a good smooth swing going with such a short barrel. A steady smooth swing is of the utmost importance in clays shooting. And field shooting for that matter. I'd recommend at least 26", preferrably a 28. I have some 30" barreled guns but thats getting long.

+1     Slug-O-Matic.....................NSCA Master Class 536121

Quoted: Forget about velocity. The problem with short barreled shotguns for clays is the guns are short and 'whippy'. And not very well balanced either. Its difficult to keep a good smooth swing going with such a short barrel. A steady smooth swing is of the utmost importance in clays shooting. And field shooting for that matter. I'd recommend at least 26", preferrably a 28. I have some 30" barreled guns but thats getting long.

Wouldn't weight at the end of the barrel help with balance?

That would depend on the shooter. I like others like tha balance about in the middle. Remeber that your frount hand guides the shotgun to the target.  See the bird, move to the bird , and kill the bird...

Slug-O-Matic

Quoted: Quoted: Forget about velocity. The problem with short barreled shotguns for clays is the guns are short and 'whippy'. And not very well balanced either. Its difficult to keep a good smooth swing going with such a short barrel. A steady smooth swing is of the utmost importance in clays shooting. And field shooting for that matter. I'd recommend at least 26", preferrably a 28. I have some 30" barreled guns but thats getting long. Wouldn't weight at the end of the barrel help with balance?

It might help some but its not the same as having the weight evenly distributed all along the barrel.

If you took a stick and tied a brick on the end, and it weighed exactly the same as your favorite Louisville Slugger, it still would not swing the same.