What causes the blank spot?

[agent eight seven O]

  What causes the blank spot in the middle of my patterns when I shoot at paper? Usually 2 inches in diameter and generally on the bulls eye. Rest of the pattern looks good and even. Shooting at a range of 30 yards.
   Thanks in advance for any help.

[Gutsdozer]

Over-constriction I thought. Causes a donut pattern.

[allaboutshooting]

  What causes the blank spot in the middle of my patterns when I shoot at paper? Usually 2 inches in diameter and generally on the bulls eye. Rest of the pattern looks good and even. Shooting at a range of 30 yards.
   Thanks in advance for any help.

It sounds like you have a 2" gap that is right in the middle of your pattern(s)? What brand of gun, barrel length, choke tube (brand & exit diameter) and shell (brand, length and shot size) are you using? Just so I'm clear, you have the same gap in all of your patterns and it's in the center? Lastly, how many shots have you fired when you see this?

I understand that's a lot of questions but maybe I can be of help with a bit more information.

Thanks,
Clark

[agent eight seven O]

   Clark, thanks for the willingness to help. I am shooting Remington 870's and a 11-87 with 21" and 26" barrels. These are 12 guage. Choke tubes are Jellyhead, Kicks, Rem. super full, and Carlson's in .665 exit diameter. Ammo is 3" #5 and #6 from Winchester, Federal, and Remington. All lead.
   Yes, the gap is close to center. This gap is not always there and I see it a lot more with the 11-87 26"barrel. I know that is a lot of variables.    Thanks again.

[allaboutshooting]

   Clark, thanks for the willingness to help. I am shooting Remington 870's and a 11-87 with 21" and 26" barrels. These are 12 guage. Choke tubes are Jellyhead, Kicks, Rem. super full, and Carlson's in .665 exit diameter. Ammo is 3" #5 and #6 from Winchester, Federal, and Remington. All lead.
   Yes, the gap is close to center. This gap is not always there and I see it a lot more with the 11-87 26"barrel. I know that is a lot of variables.    Thanks again.

It's always more common to see gaps in patterns with #5 shot or larger than with #6 shot or smaller. It's a bit unusual to have  a gap right in the center of a pattern, especially to have it show up consistently. I would expect to see the possibility of more gaps in the shorter, 21" barrel than I would in the 26" barrel.

The way I read it, all your chokes have a .665 exit diameter, at least some are ported, correct? Yes, you do have quite a number of variables and it can be very hard to see the kinds of patterns you're looking for when shooting so many different combinations.

You question was about the cause of the gap in the center of your pattern, so I don't want to range too far afield from that question. Gaps can be caused by a number of factors and from what you've told me, I don't think it would be a choke that is too tight for any of those loads or barrel lengths.

There are at least a couple of ways to look at the situation. The first is that if the pattern is dense overall, with just one 2" gap in the center, it may not be bad coverage. You'd really want to look at your patterns closely but some adjustment in POA might cure any deficiencies.

As always, I'd recommend that you really clean, deep clean, the bores of your guns and your chokes. Plastic, lead residue and unburned powder can form a thin layer of gun in the bore, chamber to muzzle, that reduces the performance your gun and degrades the patterns. http://allaboutshooting.com/article_info.php?articles_id=282

You might also want to consider shooting some of the WLB shells, if you've not tried them. It would be interesting to try the new Triple Beard lead shells from Hevi-Shot as well.

There are some other alternatives but that's where I'd start. If I may be of any help whatsoever, please let me know and I'll do my best to be of assistance.

Thanks,
Clark

[agent eight seven O]

   Thanks for  the insight Clark. I think you hit the nail on the head with trying so many different combinations. I need to stick with one load and choke. I have not deep cleaned the 26" 11-87 barrel, so I will give that a try.