Sorry I posted this in another section first
Hi

Just brought a Remington 1100 LW 410 and find that sometimes the Primers come fully or part out of the cartridge when fired and jam up inside

The cartidges once fired also get thrown about 12-15 feet from the gun

Using 14 gram No 9's with 2.5 inch

When I first tried the gun it pulled the primer about every third round, have since hanged cartridge and also fitted new barrle o ring and now fired about 75 cartridges with about 5 cartridges with primer pulled out

Not used to semi but cleaned well before the shoot, Any advice would be welcomed

Well, all primers partially unseat at the first moment of ignition. The primer explosion trying to shoot thru the flash hole creates backpressure. This is true of just about all centerfire cartridges, which is why military rifle rounds are crimped in so the primer doesn't come completely out if the headspace is all wrong and rattle inside which jams up an action.

The way a firearm "normally" adjusts to this condition is that the case first expands on ignition of the powder charge to press against the chamber wall but then immediately starts to be forced back toward the breechface in an opposite direction to the payload. This movement of the shell/case back and toward the breechface actually "RE-SEATS" the primer back into its original position.

If your hulls are expanding the metal/plastic base against the chamber wall and it immediately releases and the headspace is within tolerance everything will work to press the primer back in the "SLIGHT" amount it came unseated.

If you have ever seen a 209 shotgun primer, you'll recall that it is one very long object. It's at least double the length of a centerfire metallic primer. That means that your headspace cannot possibly be so far out of tolerance that the firing pin can strike the primer but the entire primer can unseat out the back. It just seems very unlikely.

If chamber erosion or roughness prevents the hull from moving rearward until it slams against the breechface, you'll have partial primer jump on your ejected hulls.

I'd take the gun and your ammo to a qualified gunsmith and have it all examined.