I just pre-paid for this.  May only be there for first half of day.  It all depends on if opening night for my daughter's play is Friday or Saturday, if it's Friday all is well and I am free to airsoft, if it is Saturday I will have to leave in time enough to get back and clean up to attend her show.

I would suggest pressing on it from different angles while firing to see if you can figure out what isn't lining up correctly.  For my gun I found I had to hold the magazines forward and push up for them to feed correctly.  To fix I put some material (loop side adhesive velcro) in the back of the magwell so that my mags sat far enough forward and up to connect properly with the hop up.

1. Full Seal eye protection -- DO NOT skimp on this.  It is easily the most important piece of equipment you will purchase ahead of your primary weapon
2. Best quality (out of box) gun you can purchase within your budget (remember: most characteristics can be affordably upgraded after the fact if you stay away from proprietary guns)
3. One set of m-81 woodland bdu's, one set of 3-color desert bdu's (these are almost universally accepted as the base green and tan uniforms for most events -- others are sometimes allowed but these are almost universally allowed at all events -- there are some exceptions but probably not for a starting player)

Having these 3 you should be ready for any rec game. The rest of the list is optional and personal preference (You will probably want more mags for your gun, but the one that came with it should be good enough to get started)

4. Mid-Cap mags for your chosen gun platform -- don't forget to get a speedloader to push the bb's into the mid cap (assuming gun came with one hi-cap mag, -- and your chosen platform is not a belt fed gun -- if it didn't then these will be higher priority - These will be required for most real sim/mil sim events)

5. Chest Rig/Vest/Plate carrier and pouches -- Do research first and see what others use, and if possible try out different setups to see what you like before you dump a lot of money into it then find out you don't like it. This is highly personal preference and is NOT necessary, but done right can be useful. I can't stress enough to go to a few games and see what others are using and talk to them about it and why they went the way they did before dropping alot of money on something that looks cool, but just isn't what you thought it would be.

6. Upgrades, Bling (external gun attachments, helmet systems, grenades, secondary weapons, alternate primary platforms, other camo pattern clothing, etc.  AKA things that are nice to have but not necessary for you to enjoy a day of airsofting)

I don't know the answer to your question, but with a 500mm barrel you will most likely be under volumed in air when using a ported cylinder.  Most that I see are recommended for 400mm or less barrel length. In addition it will matter where the ports are in relation to the end of the cylinder.  More towards the center the shorter your barrel will need to be, closer to the back the closer to 400mm you can be.

As with anything though experiment with your setup and see what you get.  Actual results don't always match "theory"

Overall had a decent time out here.  There were a couple glaring safety issues that I am greatly concerned about:
1. Chrono -- Refs running chrono did not have any .20 BB's to chrono with.  I only had .30's and when I told them this they said their chrono would only go up to .25 and had me shoot at that setting with my .30's.  Now i know my gun shoots ~385 with .20's consistently so I knew I had a 20ft engagement distance by MiA standards.  They just told me I was OK and let me go.  They did nothing to mark the guns to signify the MED's for the weapon.  In the future I would suggest the hosting team provide the chrono refs with a few speedloaders of .20 bb's and some color coded zip ties so that we can have a safe game for all. I didn't get hit with anything that felt too hard or out of spec, though I did see some people bleeding.  I don't know if this was from mosquitos, injury on the field or hot fire.

2. Safety netting was down or only waist high in several places.  At one point toward the end of the event there were a large group of us OUTSIDE the netting in the safe zone with goggles off and walking back to the staging area and some jackass inside the play area was shooting OUT at us on the outside.  We had no goggles, what the hell were you thinking???  If you don't know where your shot is going to go or don't know where you are and what you are shooting toward then DON'T shoot. This could have very easily turned into something serious.  Always be aware of your surroundings and be aware of your backdrop, if there is ANY danger at all do not take the shot.  If you thought it was funny to shoot your friend in the leg while he walked back to staging, you are wrong, it wasn't funny and you should have had your ass kicked. It wasn't your fault that the field was unsafe, but it was your fault for taking a shot/shots at people clearly not in the game and not wearing eye protection.

Other than that:
We were told during the briefing to stay out of the woods or to make our excursions in there short because of the mosquitos, however the green team was in the woods most of the day.  Genuinely felt bad for them.  I was only in the woods for a short time towards the end in the hostage rescue mission and it was brutal.  Kudos to those on Green that stuck it out in spite of it.

On hit calling, I personally did not have any problem.  However there were several people shooting towards the village who's shots were dropping 10 to 15 feet before they reached the group of us.  We of course turned and fired back and as it turns out had longer range and were actually able to hit the people shooting at us without ever being in danger ourselves. Just because someone is not calling a hit doesn't necessarily mean they are cheating.  It might well be you or your gun aren't as good as you think you are.

I think the joking and razzing of Abbott during the briefing got a little out of hand and took away from people being able to hear what he was saying or telling us about. There is plenty of time to do that, the briefing should be serious and conducted so that everyone can clearly hear without distraction or interruption.  Also I think Safety should be talked about more, there were a few people there that just didn't get it and maybe another reminder could have helped.

Overall, while I wouldn't classify this game as a mil-sim on any level it was a decent scenario/rec game and with some work and management could in the future turn into a real mil-sim or scenario type event.  Though I think the size of the field and limited variety of what you can do will likely restrict it to scenario or rec only.

Thanks to Abbott and crew for hosting.

What do you mean by a "large capacity magazine" do you mean a Hi-Cap?
If so then you don't need anything special.  Just open the door at the top and dump BB's in.

If you are talking about a Mid-Cap that holds more than standard then you just need a speedloader to push the BB's in through the feed hole at the top. They come in various shapes and sizes and hold various amounts of BB's, (I prefer the KWA M-4 mag speedloader,) but all work basically the same.  There is a plunger that you depress to force ~5 BB's at a time into the feed hole.

Hey I just registered for this. I have an extra gun so I was hoping of bringing my buddy with me. Midcaps only? Plus we only have ACU and woodland marpat.

From the first post:
Teams
Green Team
     Dice:
      Woodland, Woodland MARPAT

Tan Team
     CAG:
      Multicam, DCU, Desert MARPAT
     Grodna Underground:
      Civilian Attire, Solid colors NO CAMO.

Weaponry Rules:
Mid-Caps only. Hi-Caps are not allowed AT ALL unless used by a designated LMG replica(e.g. M249, RPK, PKM, M60, Mk46, Mk43, etc.)

So yes, mid-caps only, unless you have a LMG replica.  Woodland MARPAT is an approved camo pattern, ACU is not (would most likely be classified as Tan if Abbot did allow it.)  If you both don't have the same approved camo you could always join the Grodna underground in civilian attire.