G&G Mp5 sd5 firing issues

[Abcd1234]

Hi, This is my first post here on Airsoft Canada and I am having an issue with my first gun. My G&g Mp5 sd5 which i bought just to shoot at targets with in my basement(I have a LONG hallway) worked fine with the starter pack of BB's it came with and i used all of those. I then went out and purchased some .20 bb's that I recently found out were crappy low quality bb's. They worked fine for a bit but then the gun would start to double-feed or fire a shot only 25 feet or just not fire at all. I shot it like this for a day or two and then the mag the gun came with stopped twisting. I opened it up and found an out of place spacer and adjusted that and the mag went back to normal, but the gun still had the issue. I was wondering what the issue was? I read it could be the hop-up bucking or is it the bb's or could it be the magazine?

Thanks

[Styrak]

You might have damaged your hopup rubber with those crappy BB's.

[Abcd1234]

Do you know where I can get one? Also is there any specific type I should get?

[Styrak]

Almost any airsoft parts store. AEG rubbers are all the same type/fit.

[nrados]

Also having firing issues with my MP5. It's also a G&G, and I have verified that the spring is not broken as some of the suggestions at my local field suggested.

I had a VERY sudden and dramatic decrease in FPS from one game to the next - as in from around the 360FPS mark to 100FPS. I didn't touch the gun between games, and the battery also seems to refuse to hold a charge [- different issue], yet, even with a different battery, it just refused to co-operate. I haven't tried since opening the gun to verify my spring isn't broken, but only because I've since lost the stupid front clips for the SD front end [which is kinda important, since that's where my battery sits].

Yes, I plan on getting a new battery and a different charger as the current one is the stock G&G smart charger, but ignoring the battery issue [especially since the gun worked great up till that exact moment] any suggestions?

[Rusty Lugnuts]

The symptons seem to suggest several different scenarios and the first part of finding an answer is trying to narrow the possibilities with some questions. First could you clarify this line "I haven't tried since opening the gun to verify my spring isn't broken" Second Has the rate of fire been affected?Third Have you tried a different mag, battery?

[Styrak]

I would tend to think it's a damaged/broken piston head since a lot of stock G&G piston heads are a horrible design that cracks/breaks easily. Have someone with experience open it up and take a look.

[Rusty Lugnuts]

That occurred to me as well, thats why i asked about the RoF