Sukhoi_fan

Your options: Go back to your FFL and show them the problem Take it to a range with a rangemaster (who should be able to provide assistance), drop a shell into the ejection port, let the BCG slam the shell into battery then see it if goes bang when you pull the trigger and auto loads the next shell (this is what I would do to fully diagnose the issue), use only full power rounds like buckshot for function testing a new shotgun Contact Benelli after troubleshooting with someone with more experienced with the Benelli M4

Bevel/concave side goes up, note how it matches angle of underside of fastener.

Attach a Hoppe's 12 gauge tornado brush to a shotgun cleaning rod and chuck that up into a drill, have no further suggestion on what solvent to use. It's how I remove lead fouling. https://www.ebay.com/itm/225020120626?_skw=12+ga+tornado+brush&itmmeta=01JC9NWAJCR1ZQSJ00RM357VB4&hash=item34643e8e32:g:t-8AAOSwbqFinmDx&itmprp=enc%3AAQAJAAAA8HoV3kP08IDx%2BKZ9MfhVJKn3YSuChYYBLMhYSlVwae2CDMoAy%2BhY%2BeTy2WLum7oPECVsVy7zFvFIZU1ZwkaK0gP6aAPmXyDYzhbVR59iGulasI5qamDuLhsuYTS5rqIMGj9gzqZ2NqWwV2AWPYJlKiQRVd9hBz1NKCD4i3EqSNc%2BzkAeYC1vYgGovy29IFeHg9dYPYk%2FuN3fYu4uQwHN6UmDpkZzHLZ45Hz896WPWR0rF0yABr%2BvrYF5M3cZ%2BDvRJvfHDMJCrZa72329nhwNpOhFx4ZJNdWDhduojrgTsAClRZeo9Z8kAx8xzA7AUJSiTw%3D%3D|tkp%3ABk9SR6qp8bXiZA

Mag capacity.

I love my Tubb's flatwire AR buffer springs. I can see the advantage using a flatwire spring in a M4 magazine.

On the lower end there’s also the Vortex SPARC https://vortexoptics.com/vortex-2019-sparc-ar-red-dot.html I’ve no experience with the Vortex red dots but they do offer a lifetime warranty. I suggest going to the source and contacting Holosun and vortex and inquiring as to what are the recommended maximum recoil impulse limits, e.g. can I mount this particular optic to my .50 BMG rifle? The optic manufacturers know the limits of their RDS.

Smaller shot size such as #4 buck is preferred for safety when one is concerned about barrier penetration. IMO that’s the only reason for using #4 buck, it just doesn’t retain energy like 000 or 00 buck.

Personally I’m a huge fan of 000 buck however at five yards just about any 2 3/4” rounds of 00 buck won’t disappoint. 3” shot shells are a waste of money and magazine space IMO. Typically a shot pattern opens up about 1” for every yard traveled so at five yards the shot pattern will be about five inches in diameter.

https://ammoseek.com/ammo/12-gauge?ekw=steel&ikw=1500 fps

On the low end of the spectrum there's the Foster pattern lead slug and the Brenneke pattern lead slug, many prefer the Brenneke slug. Suggest you research Foster and Benneke slugs. (Brenneke still regarded as a genius a century later) There are other alternatives for instances where a slug may be called for, this youtuber posts about all sorts of 12 ga. slugs https://www.youtube.com/@taofledermaus/videos So you have options. Personally I'm not a big fan of the 1 oz. lead slugs in either the Foster or Brenneke pattern. For one thing I don't like having to clean a leaded up barrel from shooting lead slugs, and the other is I can get better and more versatile results from a variety of DDupleks steel slugs. DDupleks rounds are much more expensive than lead slugs. The DDupleks Monolit rounds are apparently unavailable in the USA at this time. I stocked up on DDupleks slugs years ago when DDupleks slugs were much cheaper. https://www.ddupleks.com/products DDupleks introduced a frangible slug they call the Kaviar since I loaded up on DDupleks slugs years ago. Kinda like a Glazer safety slug, it has much lower muzzle velocity and energy, making it safer overall when innocent bystanders are in the immediate environment. And just like a Glaser slug there are limited instances where you'd use it, just another tool in your toolbox. YMMV

I'm guessing your trainers meant high brass and not high base, probably because they want to train you using shot shells that aren't wimpy so you get to feel the full effect of a higher powered round. You want to avoid 'low recoil' rounds for this reason when taking a shotgun training course. An easy way to judge how much recoil one can expect is to check out the feet per second (FPS) of a particular round you're considering. 1,500 FPS in the Federal Prairie Storm ammo is on the higher end and definitely not low recoil. IMO 'low recoil' shotgun rounds are anything below 1,300 FPS. The Federal Prairie Rounds you're considering would be perfectly suitable for your training course purposes as you're definitely going to get the full effect. If a manufacturer doesn't state the FPS spec then they should indicate 'dram equivalent', and here's an article with a chart for that - https://www.ammoforsale.com/ammo-club/what-is-dram-12-gauge-equivalent-chart/ Buy in bulk and $ave - https://ammoseek.com/

One can always get a Benelli M2 with a 26" barrel to be used as a drone killer...then one could install a much longer mag tube for much more capacity.

Is heat a factor? Are you storing your loaded shotgun in a vehicle subject to getting high interior temperatures in the summer? Or is this happening in a climate controlled environment?

Blain, I know that the folks at Benelli are very interested in helping you resolve your issue with your C-stock collapsing while doing rapid fire. And I know that you sent your M4 into Benelli with that issue and the Benelli gunsmiths were unable to replicate that problem even when rapid firing. They would like to see a video of you or anyone else rapid firing your M4 and having the C-stock collapse. So I suggest you record of a video of this happening and send it to the folks at Benelli so they can help you get a resolution.