Twenty Gauge: Do Magnum shells equal denser patterns?

[charles p]

The extra 1/4 oz of shot in the magnum load who provide a denser pattern at the same range, through the same barrel and choke.

[George Foster]

All shotguns pattern differently so a 3" 1-1/4oz 20ga load might or might not have a denser pattern at a given range.  You might also find that a 1oz 2-3/4" load would give a denser pattern as the 3" 1-1/4oz might be blowing the pattern.

[foxchase]

I think you suggested your best answer. If you want to continue using the same gun for 35 yd. shots on squirrels then
have choke tubes installed in your gun.
A modified choke and HV # 5 or 6 (2-3/4") should provide what you are looking for.
Always check on the pattern board.

[Couger]

All shotguns pattern differently so a 3" 1-1/4oz 20ga load might or might not have a denser pattern at a given range.  You might also find that a 1oz 2-3/4" load would give a denser pattern as the 3" 1-1/4oz might be blowing the pattern.

Yepper!
 
Some folks seem to get the point George.     ...... others, NOT! (oh well,    )

[mannyrock]

 
   Well, thanks to all of the fine advice here, I've gotten this cylinder bore double all figured out.
 
    Using the Federal, #6, premium 3 inch turkey loads, with the flight control wad, I get a very dense killing pattern out to 35 yards on a paper plate sized target.   More than dense enough for squirrels.
 
   And for fun, I bought a box of ordinary Remington 20 gauge, 2 3/4 inch slug shells at Walmart.  They were only $12.50 for 15 slugs.    Shooting from the bench at 35 yards, and just using the front bead, both barrels consistently hit a 2 inch by 2 inch square of duct tape at the center of the target, often touching.  So, I have a great 35 yard double rifle, which I can use in my deep woods stands for deer.     But when I moved the target out to 50 yards, wow what a difference.  Each barrel was shooting almost a foot to the right or left of the bull.  I guess the projectile paths from the double barrel cross at 35 yards and then continue outward at a sharp angle.  The rounds also went about 6 inches high at 50 yards.   
 
   Since the effective slug range is only 35 yards, I think that for fun I might try to take some regular #8 dove shells, and cut the casing 90% around, to make fake slugs.   Since there is no choke in the bores, I don't think it would hurt the gun at all for the ends of the plastic casing to pass out of the barrel, with all of the shot still firmly inside.     If you go on youtube, you will see a guy using cut 12 gauge rounds out of a single shot, consistently hitting milk jugs out to about 40 yards.
 
   Last year, I also patterned it using the standard 3# buckshot shells, at 15 yards (self defense range) on a torso target.  Each and every pellet hit within the black chest area of the target in a perfect pattern.   Not one pellet missed.
 
    Just alot of fun to see exactly what can be done with what amounts to a 20 gauge coach gun, sporting 20 inch barrels.  With the right shells, you have a squirrel and rabbit gun to 35 yards, a dove or quail gun to 40 yards, a deer gun from 35 to maybe 40 yards, and a self defense buckshot gun from 15 to 20 yards.  Pretty impressive for a shotgun with no chokes. 
 
    Thanks, Mannyrock
 

[LONGTOM]

Only the patterning board will tell the story. I have two 16 gauges. One patterns better with 1 oz loads and the other patterns better with 1 1/4 oz loads so no, more shot does not always equal denser patterns. It depends on the gun.

That right there is the best advice given on this subject for sure!
If you don't pattern your gun & loads then you are just guessing as to what they are doing at any distance.
I will add to this that choke selection is also very critical.
I know the op is stuck with a cylinder bore and as such will not have much range with his shots.
Do consider having your gun threaded for tubes.
You will be surprised the difference a different choke will make.
 
To fall back on a comment made earlier, I have come to believe that a good patterned 12 GA magnum with the right choke will do everything a 10 GA will and do it just as far.
At least that has been my experience.
 
 
LONGTOM

[Couger]

..... Last year, I also patterned it using the standard 3# buckshot shells, at 15 yards (self defense range) on a torso target.  Each and every pellet hit within the black chest area of the target in a perfect pattern. 
 
Not one pellet missed.

Excellent!  Hard to improve on PERFECT-shun. 
 
I have a M870 20ga youth synthetic COMBO purchased for a multitude of chores,
including HOME DEFENSE (long with another plain barrel off eBay, to cut off to CYLINDER become the 'home' barrel!).
 
Tried some 3Buck rounds in the 20inch rifled barrel, and got a [bonafide] donut pattern at 11-12 yards with absolutely no pellets in the middle; only the wads.
 
Real glad to have that third barrel! 
 
 

[Graybeard]

Let's bring this one back up and see if folks might want to talk more about it.