Shot Pattern 20" vs. 18.5" barrel - any difference?

[luckybaer]

How much difference does an extra 1.5" of barrel length make when it comes to keeping a tight pattern?

I went to the range with my son this weekend to do a little shooting (only 7-yards distance) with our Mossberg 590 (20" barrel), Mossberg 500 (18.5"), and Kel Tec KSG (18.5").

I was surprised to see that the Mossberg 590 had much tighter spreads than either the 500 or the KSG. I mean, the Mossberg 590 was amazing - #4 buckshot 2 3/4" shell with 27 pellets managed to get 21 out of the 27 pellets into a 5.5" x 5.5" target, with point of aim being at the exact center base of the paper target (it was pasted onto a bigger target). The Kel Tec and the 500 performed alike, each getting about 10-14 pellets into the same sized target.

I was using Sellier & Bellot #4 buck.

When I did something similar with S&B #00 buck, the 590 and 500 performed almost identically, getting all 9 pellets into a 6" x 6" area. The Kel Tec had a similarly tight group, but it shot a bit high (it was the first time we shot it, so we were still fiddling with the Troy QR sights we put on it).

Just thought it interesting that #4 buck caused the 500 and the KSG to spray a bit more widely than the 590, so I thought I'd pose the question here.

OH. CYLINDER BORE CHOKE.

Thanks.

 

[MikeD]

Per my experience the choke plays a bigger role in this than the length of the barrel. I doubt difference you are seeing is a result of the slight difference in barrel length.

Have you measured the interior dimensions of the barrel, Cyl bore on one may not be the same as cyl bore on the other.

 

[mingaa]

What Mike said! I'd also pattern them a bit farther - 15 yds. or more. Tapping for chokes is not that expensive (you need enough barrel wall thickness - a gunsmith would know) and with just one choke you could change the HD pattern dramatically - AND make then much more effective in the field at greater distances.

 

[Tony617!]

Shot Pattern 20" vs. 18.5" barrel - any difference?

You can get greater distances using some of the Federal 00 buck with Flitecontrol. But for HD distances I practice at 5, 7, and 10 yards for HD. I have some Federal LE133, which is 8 pellet 00 buckshot and at 10 yards it makes a hole like a slug still.

 

[Water Monkey]

With my 590a1 18.5" barrel I'm getting fist sized groups with federal flight control at 15 feet and palm sized at 25 feet.

Perfect for defense.

 

[Comarade]

Theoretically you should see a tighter pattern with a 20", but in practice you won't notice a difference. A much more appreciable difference will occur with your choice of ammo (such as flightcontrol) and choke.