I bought a 20 ga. ush a while back, tried a lot of different ammo and found what shot the best out of it. I shimmed the foreend to float the barrel and re worked the trigger down to a 2 1/2 lb pull ( what a project, worse factory trigger ive every had the pleasure of working on), put a thumb hole stock on it and added the steel bar from the original stock. The gun shot pretty good but I stiil wasn't satisfied. Seemed i'd always get a flier or two. After much spent ammunition I decided the problem had to be differences in shooting form (amount of downward pressure on both ends affecting barrell jump).
A freind and I went to the range one weekend with a bunch of different guns, slug and centerfire. I actualy took a couple of sub moa centerfire guns just to check my shooting form ( I know they are different than slug guns).
After the range session we were cleaning the guns and I grabbed a tape and started measuring barrells,amazingly the ush's were the only slug guns we had with barrels longer than 22 in's.
Ordered a 22 in. youth model the next day and polished the barrel- problem solved, the gun now shoots like a rifle. No need to hold the gun down to control barrel jump. Seems that the slug is out of the shorter barrell before it starts to jump. It now shoots into the same group wether Im holding it down or just layiing it on the bag.
Now I am satisfied. I did shoot the 24 in. barrel well and this may not bother some but this is a hunting slug gun not a bench gun. I tried using the correct shooting form as explained by Tar Hunt and others but just couldn't do it while shooting back over my left shoulder ( real world hunting situation).
I have shot the 22 in. barrell out to 200 yds. with no significant difference in point of impact as compared to the 24 in.. Leads me to beleive all the powder is being burnt in the first 22 in's