I know little about shotguns.  I can tell you how to disassemble a Roth Steyr 1907, but would seem like a newbie to guns if asked a shotgun question without an obvious answer.

I've got a cylinder bore defensive shotgun with 18.5 inch barrel that consistently prints a 7-8 inch pattern at 15 yards.  The ammo was standard Remington 00 Buck 2 3/4 (I forget the number of pellets).  

I was under the impression that the pattern would be a bit larger.  Does this seem normal?

For 45 feet yes, that sounds average. 9 pellets in 00 buck 2 3/4 -----------12 pellets in 00 buck 3 inch
mags.

All in a pie plate or dinner sized paper plate, of course a pie plate measures 12 inches, yours is shooting  tight at 8 inches.

Thanks!  I thought it was a bit tight.  Are any defense loads available that have a rep of producing wide patterns.  I know that the mantra is that one should try out loads in their particular gun, but I'd think all 18.5 inch cylinder barrels perform similarly.

Quoted: Thanks!  I thought it was a bit tight.  Are any defense loads available that have a rep of producing wide patterns.  I know that the mantra is that one should try out loads in their particular gun, but I'd think all 18.5 inch cylinder barrels perform similarly.

You're probably right if you're talking recent guns made by Rem/Win/Brown/etc.  

There's a lot of variation in barrel diameters in older guns, though.  Some defensive guns are also sold with an improved cylinder, instead of straight cylinder.

Still best to double check with your gun & ammo.

-hanko

That is tight for a standard, cylinder choked barrel. Shotguns are perhaps the most individualistic of firearms, and this could change with a different brand of the same size Buck, or even a different lot# from the same manufacturer.

Me? I would LOVE to have one of my cylinder barrels print #00 this tight! The general...VERY "general"...rule of thumb for such barrels is "about" 1in. of pellet spresd for each yard of distance, so a more typical pattern for a cylinder barrel at 15yd. would be 12-15 inches in diameter. Larger shot usually patterns more tightly than smaller, etc. This "rule" is not quite as consistant now that we have shot cups, plated shot, and the reduced "Tactical" (HA!) loads available, as these may shoot a little tighter patterns than older loads did, but it is a good starting point for what to expect from an "unknown" gun / ammo combination.

12-15 is what I expected.  The gun is a Mossberg 500A Marine, and the barrel is clearly marked as being a cylinder only.  

I've read several shotgun reviews and Mossberg 500's always seem to group considerably better than Remington 870's and Winchester 1300's.  I wish that I would have read these reviews before I purchased my 1300.  It doesn't group too bad but the groups you are talking about is what I wish mine could do.  I the 500's I've shot are consistent with what you and the reviews say.  In my opinion Mossberg makes the best defensive shotguns for the money.  If I ever decide to add another shotgun to my collection it will be a Mossberg 590.

Try 0Buck or #4Buck -it will probably widen the pattern a bit.

I personally like #4Buck for home defense.


Tony

Quoted: 12-15 is what I expected.  The gun is a Mossberg 500A Marine, and the barrel is clearly marked as being a cylinder only.

Use a choke gauge......available at any Galyan's, Bass Pro, etc.....

Many manufacturer's use a different tolerance for "cylinder" -- though they should be very close from maker to maker.

Yes, your group should be bigger....mine was huge at the Va BRD 3-gun.....I was using 2 3/4" 12 pellet 000....

I am shooting a Mossie 590 Mariner cylinder bore...

Ammo in every scattergun will pattern differently, even though you can hypothesize the results they will vary to differing degrees.

My Beretta 687 with 27.5" barrels patterned differently than my best friend's 686 with 27.5" barrels using the same factory load sporting clays load.....my group was about 2" bigger in diameter.  Go figure.  Same Briley mod chokes....