.410, 3" - 11/16 oz @ 1135 fps/ 5.5# gun = 10.5 foot/pounds recoil force
28 Gauge, 2.75" - 3/4 oz @ 1200 fps / 6.0# = 12.8
20 Gauge, 2.75" - 7/8 oz @ 1200 fps / 6.5# = 16.1
20 Gauge, 2.75" - 1 oz @ 1220 fps / 6.5# = 21.0
16 Gauge, 2.75" - 1 oz @ 1220 fps / 7.0# = 21.5
12 Gauge, 2.75" - 1 1/8 oz @ 1200 fps / 7.5# = 23.0
12 Gauge, 2.75" - 1 1/4 oz @ 1330 fps/ 7.5# = 32.0
Does anyone see the obvious error in these numbers?
Please explain how the 16 ga. 1oz. load @ 1220 fps in a 7.0 lb gun generates more recoil than the 20 ga. 1 oz. load at the same 1220fps velocity in the 20 ga. gun that is 1/2 lb. lighter at 6.5 lb.???
The total ejecta mass of the 16 ga. 1 oz. load would have to be significantly higher than the 20 ga. 1 oz. load just to make the values equal, let alone greater.
My advice to the OP would be to work on overcoming the flinch and recoil sensitivity rather than spending money on a 28 ga. gun. That is an achievable goal as long as he isn't dealing with some physical medical issue. There are several ways to reduce both actual and perceived recoil too. A 6 lb. 13 oz. 20 gauge is not a featherweight in that bore size, so I personally wouldn't want to add weight. Gun fit means a lot when it comes to felt recoil. I had a very light Ithaca SKB XL 300 20 ga. 3" magnum semi-auto that hit my shoulder as hard as any 12 ga. gun I have. But the L.O.P. on it is at least an inch too short for me, and I never had it pulled snugly into my shoulder pocket when I shot. So it essentially got a running start. However, I shot it very well. I tried installing a 1" recoil pad which helped a lot, but I immediately found myself often shooting under the target, so I removed the pad and decided to just deal with the little jolt. I ended up removing the magazine plug and giving it to my daughter for a house cleaning gun.
Many women and kids are started out on 20 ga. guns due to the lower recoil. All things being equal, switching to a 28 ga. with equal shot weight and velocity isn't going to help matters. My Dad had me start with a 20 ga. because he knew the .410 was better suited to an adult who simply wants more of a challenge. In my own case, I learned early on that my Dad's 16 ga. Model 870 pump was actually easier on my skinny 12 year old shoulder with field loads than my own 20 ga. Savage Model 220A hammerless single shot. My 20 ga. single was much lighter at right around 6 lbs. or a tad less. I agree that the 1400 fps loads he used are pretty brisk, and would certainly make a noticeable difference in both recoil energy and recoil velocity.
