I purchased a Gideon Shadow (9mm) from Atlantic and before I even have taken it out to shoot I have run into a few issues. First is that I can't seem to remove the firing pin retaining pin. I assume after depressing the firing pin in, it should just slide out? Not sure if I am doing something wrong and I tried to pull it out with pliers but it would not come out. I cannot get a punch on the other side due to the way the bolt is milled.  

The second issue is when adding the SB brace it is very loose. The hole in the brace to mount it is about 5mm and the screw provided is about 4mm. Even when locked in place the brace is pretty wobbly and does not lock up firmly. I don't think this is typical and I have not seen anything else that this would be okay. I am not sure if the issue would be the brace or receiver. Anyone ever have this issue?

The last issue I have seen so far is that the bolt has some resistance when sliding in the receiver. Not sure if this just needs to be broken in or that it is sliding against polymer a decent amount of lube, but it does not slide like an AR. Is this OK or just needs to be shot to be broken in or a bunch of lube added? If so what lube would be good for this?

The firing pin retaining pin should just pull out, may have to take some pliers and a piece of aluminum to protect the pin and twist/yank it out while holding it down a bit.  Once the pin is out you have to push the firing pin safety over and the firing should pop out, make sure you are holding your thumb over the firing pin so it doesnt go flying.

If you buy a brace alone (or an HK stock) it has a bigger hole, a real UMP uses a large roll pin, the gideon uses an allen screw.  I had a complete S&B MP5 brace and it had a similar screw and fit the shadow retaining screw better but it was still a little loose and if I tried to tighten it up more it was crushing the rear of the receiver.  I ended up using a couple thin stainless washers on each side to pick up the slack and it was OK but not 100% correct IMO.  I was going to fill the hole in the stock with epoxy and redrill but never got around to it.

Bolt is a little rough but should just fall out under its own weight, look for obvious burrs and make sure the front trigger housing pins arent too tight and deforming the reciver.  I just used mobil 1 5w30 for lube.  They are fun guns, but it takes a little fitting.

Regarding the bolt sliding in the receiver, make sure the ejector is flush.  On my upper the ejector was sticking out slightly which ended up causing the bolt to lock up and bending the ejector.  I had to bend it back into shape.

The retaining pis is pretty stuck. I found a post on HK Pro with a similar issue.

The bolt gets hard to slide in the receiver farther back. It seems fine the last few inches near the barrel. I took a flashlight and I can see the bolt is cutting into the plastic. The bolt is also hard to even insert into the receiver. This is without the lower on.

As I have not shot this I put a empty case in the chamber and pushed the bolt in. It got stuck and I put the charging handle against my workbench and smacked the back and broke the charging handle. I ended up using a cleaning rod to get the case out. A factory new round seemed to be a little better. The same casing fell right out of my scorpion but was a little tight in my Stribog but not as tight as the GS.

I don't have much confidence in this.

Anyways I reached out to Omega and it is going back for warranty. I will let them know about the charging handle and I will pay to replace that.

As far as the brace I thought about filling the hole and redrilling as well. I also thought about drilling out the holes in the receiver to the correct size and getting the HK roll pin. I can also see about 3d printing a spacer to sit between the brace and the back of the receiver to take up any remaining slop.

I wouldnt think its hard to break a charging handle, the way mine was molded it looked pretty weak.

I had the .45 version and the bolt was rough but it would slide in and out under its own weight if you held it vertical (without trigger group of course).

I never liked how the stock pin just threads into the receiver but it never came loose or stripped out.  I also had to replace the rear sight assembly with a real HK, the one that was on mike literally self destructed.  I always joked about the Gideon that it was one of the few guns you had to gunsmith with an x-acto knife

Update
Before I sent it back I replaced the charging handle myself with an HK one and it's much better. The old charging handle was all plastic but the HK one is molded plastic over metal. I think I will slowly start changing out parts like the cocking tube rear sight etc.

The bolt now slides freely and I see they test fired it so I assume the chamber should be ok.

The firing pin retaining pin seems to still be stuck. I am not sure if they even attempted to check this. Does anyone know the pin and hole diameter for this? Not sure if the pin is too big or the hole is too small.

I have not come up with a solution for the folding brace yet but I want to get the gun working first.

My 9mm has a .40cal extractor installed in the bolt which led to feeding and ejecting problems. Once I switched that over it ran like a champ.

As for the firing pin retaining pin I just pulled mine out with some vice grips.

I am not sure what the difference between the extractors are but as it was test fired I will assume it should work well. I will find out when I shoot it.

I put some penetration oil on the foreign pin retaining pin, let it soak for an hour then put the bolt in a padded vice.i was able to get the pin out with some good effort. I tried cleaning everything up the best I could and put the pin in. I know I can get it out now at least.

Looking the gun over again I noticed Omega replaced the push pin that it originally came with, with what looks like a sleeved bolt. The barrel locks up much tighter now with no movement like before, which is good.

I am not sure when I will get time to shoot it as I'm pretty busy over the next few weeks. I am looking forward to seeing how this runs.

https://hkparts.net/product/hk-usc-ump-barrel-roll-pin-german-p603.htm

If thats the pin your talking about then thats a good swap. The quick detach pin is an interesting idea but not done the best. If you have no plans to change the caliber often then the solid roll pin is way better.

There is a firing pin safety on the UMP.  When the bolt goes forward, a tab on the ejector pokes into the firing pin channel and releases the firing pin.  That's probably why your firing pin won't move.