12 gauge Improved Modified vs. 20 gauge Full Choke

[Armchair Bronco]

What's the rule of thumb for comparing a 12 gauge choke to a 20 gauge choke to get about the same pattern?

Let's assume a 12 gauge Improved Modified choke with 1 or 1-1/8 oz loads stacked up against a 20 gauge shotgun using 7/8 oz loads.

I haven't been able to find any IM winchokes for my 20ga gun, so I'm assuming that for a similar pattern shooting trap w/ the 20ga I'd need to go with a Full choke.

 

[Virginian]

The choke results are measured in % of shot in a 30" circle at 40 yards. Doesn't matter the gauge. Now, if you take the weight of shot of both loads times the percentage of the choke, it should give you the theoretical weight of shot in the 30" circle at 40 yards. But, until you actually shoot some patterns you will never know for sure.

 

[waidmann]

The Virginian is spot on!

My obsevation in patterning is comparing the 20" or so sweet spot. While the chokes tend to fill the 30" circle at similar ranges (I shoot for range as well as 40 yds.), the pellet density and uniformity are different.

If you take #7 1/2 at 350 to the ounce, 1 1/8 = 394 vs. 7/8 =306; thats a whopping 22% handicap, leaving holes in that 30" circle.

But digressing back to my predecessor, you have to shoot the guns and if I may, with a variety of loads, and more than twice each sampling. Then you will know.

 

[Milkmaster]

I agree with what has been said above. Just remember that 7/8 oz of shot is still 7/8 oz of shot whether it comes out of a 12 or 20 gauge.

 

[Armchair Bronco]

Here's the background. This week I took my 12 year old son trap shooting with me. We brought along my '67 Winchester 101 and a used Winchester 1300 20 gauge I bought for him. The 101 is choked Full & IM with 32" barrels; the 20 gauge has a Modified Winchoke with a 22" barrel. I typically use the lower IM barrel on the 101.

Now, I know the 20 gauge isn't the ideal trap gun, but it's all my boy can handle right now. He's a small kid and the gun fits him well. But even I had a tough time breaking clays with it, and when I did I never managed to smoke one of them. I'd usually break off 2 or 3 big pieces.

I'm thinking that the only way to get a decent pattern for trap shooting is to swap out the Modified choke on the 1300 for a Full choke; I've looked around for IM Winchokes, but have never seen one for sale.

 

[rcmodel]

Carlson's makes them.
Here ya go:

http://www.choketube.com/wbmw.html

But don't throw away the Full choke tube just yet, unless you find some 1 1/8 oz 20 ga loads..

rc

 

[Armchair Bronco]

Carlson's makes them.
Here ya go:

http://www.choketube.com/wbmw.html

But don't throw away the Full choke tube just yet, unless you find some 1 1/8 oz 20 ga loads..

rc

Thanks for the link.

It's actually the 20ga Modified Winchok I'm thinking of retiring. My hope is that with either an IM or a Full choke, my son and I can dust the occasional clay pigeon w/ the 20ga 1300.

 

[waidmann]

Winchoke, Mossberg and Browning Invector(not plus) are the same thing and Hastings makes them.

 

[oneounceload]

It's actually the 20ga Modified Winchok I'm thinking of retiring. My hope is that with either an IM or a Full choke, my son and I can dust the occasional clay pigeon w/ the 20ga 1300.

I SERIOUSLY doubt it is the choke tube - sounds more like an issue with form, stance and fit. A Modified choke will break 16 yarders all day long. Too many overthink chokes and worry about whether .005 either way is going to make a lot of difference.

It ain't the arrow, it's the Indian - head on the stock, eye on the rock. Both of those old sayings say a lot more about shooting shotguns than just about anything else.

Get your son fitted to whatever gun you want to use. Personally, a 22" barrel doesn't allow for smooth swing dynamics - that short and light of a barrel is real easy to swing fast and just as easy to stop fast - resulting in a miss behind. Using a tighter choke with an even smaller pattern just means he has to be even MORE right on the bird and leaves him little room for error in lead judgement

 

[Armchair Bronco]

I agree that a 22" barrel isn't ideal, but he did manage to break a few birds his first time out.

Once he has the basic mechanics down, I'm planning to spring for a 28" barrel for the 1300 20ga. I'm seeing them for around $150. I might also add some lead to the butt stock to make the gun heavier. Yesterday, I ordered a youth-sized stock with a 12" LOP. The 14" LOP on the stock was WAY too big for him. The change to a smaller LOP will probably have a much bigger effect on accuracy than anything else.

In the meantime, I'll take your word and not get too pre-occupied about tighter chokes. We'll stick with the Modified Winchoke for now.

 

[Dave McCracken]

Adding lead to the stock will make it heavier, but it will also it even harder to hit with.

Adding weight to the mag tube or muzzle,however, will smooth the swing dynamics and add inertia.

One 870 here, yclept Frankenstein, has two barrels usually on it and no other. One's a cut down 21" Express barrel and the other is a 26" Light Contour one. Both are a bit light to keep the swing going unless I push it a little.

So, I took an extra mag cap and drilled a hole in it, then installed a 3" 1/4-28TPI bolt loaded full length with washers and secured with a lock washer and nut. A wrap of black tape finished it. 3 oz and works to make the muzzle a bit harder to stop.

Redneck Engineering at its best.

As for chokes, Mod works for a lot of things...

 

[Armchair Bronco]

That's a good idea. We have room for this in the magazine tube on the 1300. There's currently a wood plug in there that could be replaced by a bolt and some washers as you suggested.

I had a pound of weight added to my Winchester 101, but that was to tame the kick, not to help with the swing dynamics. I forgot that weight in the stock is not the same as weight near the muzzle.

 

[Dave McCracken]

If you reload or know a reloader, you can fill a pair of trash hulls with lead shot, crimp them down hard, and install them in place of the mag plug.

Keep us posted on this and good luck!

 

[Armchair Bronco]

If you reload or know a reloader, you can fill a pair of trash hulls with lead shot, crimp them down hard, and install them in place of the mag plug.

Keep us posted on this and good luck!

Wouldn't I also have to modify the spring in the mag tube? Currently, it fits over the wooden plug and extends almost to the end of the tube.

 

[Virginian]

Shoot some paper. Make sure you know where the pattern is going first of all. Gun may shoot high, low, or whatever. Once you have confidence in where and what it prints you have a big leg up.

 

[Dave McCracken]

See if it works w/o cutting. Mine did.