Benelli barrel, too thin for choke

[linofelarca, md]

I was thinking of sending my smooth bore open cylinder Benelli barrel of my M1 Super 90 to a local gunsmith to have it choked.

I read from a previous thread that it was thin and there might be a problem to have it threaded for chokes. Is this true? thanks.

Lino

[AH6IP]

Lino-

Briley makes a thin wall choke system that is in my opinion the best there is. It is what I use when I cut and choke Browning barrels-they are backbored and are similar to a Benelli with a thin barrel wall.

Look here-

Briley

and go to gun services, mid page.

[davidwiz]

When my shotgun was at Beven Grams (Grams Engineering) for work, he had to cut down my bbl (b/c I couldn't find a 21"), and he was able to thread the bbl for thin-wall screw-in chokes.

[richardschennberg]

1. Don't assume that your original barrel is smooth bore. My old 18.5" barrel looked like a smooth bore, but when I used calipers to measure the exit diameter, I got 0.715". The interior diameter before the fixed choke was 0.725", so this represents .010" constriction, corresponding to Improved Cylinder (IC).

2. I found a 24" barrel on e-Bay and purchased it for $175. For me, the extra 3" did not warrent cutting and threading the barrel, but YMMV.

Richard

Schennberg.com

[linofelarca, md]

Richard,

I measured the exit diameter of the barrel and found out it was 0.709". Is that more or less an open cylinder bore? thanks.

Lino

[AH6IP]

The SAAMI recommended standard dimension bore for a non back bored barrel in 12 gauge is .729 +/-.

Bore Specs

[richardschennberg]

---------- Lino wrote: -------------

> I measured the exit diameter of the barrel and found out it was 0.709".

> Is that more or less an open cylinder bore? thanks

---------- AH6IP wrote: -----------

> The SAAMI recommended standard dimension bore for a non back bored barrel in 12 gauge is .729 +/-.

--------------------------------------

My barrel's interior diameter was 0.725". If your Benelli barrel also has interior diameter 0.725" before the choke, and if your barrel has exit diameter 0.709", then the constriction is 0.016". That should be a light modified (sometimes called skeet 2) choke, but another way to tell is to shoot a pattern at 40 yards with your usual load and count the holes within a 30" diameter circle. Divide by the number of pellets that should have been in your shotshell, and consult a table such as the one about a fourth of the way down the article http://www.trulockchokes.com/chokeinfo.asp

If your fixed choke is in fact light modified, 55% of the pellets should have hit within the 30" diameter circle. Improved cylinder would be 50%.

Another factor in knocking down steel is impact velocity. The loading of your shells and the barrel lenth determine muzzle velocity, and the shot size affects how much speed it loses on the way to the target. Less than average power shotshells, too short a barrel, and too small a shot size can result in not enough power to knock down all of the steel target.

I personally found that my 18.5" barrel with fixed Improved Cylinder (IC) choke did not do the job. I looked for a 21" barrel with changeable choke but had to settle for a 24" that I found on e-Bay at a good price. A 21" barrel will give you more muzzle velocity, and #6 shot (or larger, if allowed) will allow it to retain more velocity until it hits the target. The combination of a longer barrel and larger shot should actually allow you to use less choke and still knock down all of the targets. Less choke (IC to M versus M to F) gives you a wider pattern, requires less precise shots, and allows you to target transition faster, or even swing the shotgun while slapping the trigger as you pass each target. DVC!

Richard

Schennberg.com

[linofelarca, md]

thanks richard and the rest of the gang for your responses. it was very informative.

I guess i have to do some mesuring and go back to the range for some patterning.

lino