Blowing the pattern?

[Dylan Rhodes]

Okay, I need some help here. Apologies if this is the wrong forum. I have a parked reproduction 28 gauge that is quickly becoming my favorite gun. Except, with whatever I’m using the pattern is absolutely terrible and I can’t hit jack. After firing 4 shots at a wounded bird in a tree 20 yards away and watching it ultimately fly away I became very curious. I was so perplexed after the first two I actually checked to see if I fired a double squib. Nope.

So after the hunt I hit my pattern board. At 20 yards I had 15 BB’s in a 30” circle with the IC choke and 21 with the modified. . 15!!! And 21!! So I’m left to assume my patterns just are going all around what I’m shooting at. I have 7/8 oz of 5 shot at 1300FPS. I’m curious if it’s to fast for a 26” barrel and it’s just “blowing” apart once it leaves the muzzle. The pellets were generally centered so at this point I have no reason to suspect POI or regulation issues. And yes, I have measured the bore constriction with a proper bore gauge, the chokes are correctly marked.

Obviously I need to try a new load but I’m at a loss for direction. Slower? Solve the problem with more bb’s and smaller shot?

Thanks in advance.