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CYMA 420 Round High-Cap Magazine for M1A1 / Thompson Airsoft AEG Rifles

ID: 28555 (MAG-Thomp-420)
C33 / M89
CYMAC33 / M8928555
4.7 stars, based on 9 reviews
CYMA 420 Round High-Cap Magazine for M1A1 / Thompson Airsoft AEG Rifles
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CYMASnow Wolf

$18.00 $15.30

MAP ProtectedExempt From Coupons
The manufacturer of this product enforces a strict minimum advertised price (MAP) policy which excludes this product from any additional discount coupon codes. This item, however, may qualify for free shipping.


  • Durable metal alloy construction
  • Lightweight design won't weigh you down on the field
  • 420 round capacity
  • Works with both M1A1 and 1928 Thompson Airsoft AEGs
Color: Black
Compatibility: Tokyo Marui Thompson/M1A1 Airsoft AEG rifles and other compatible AEGs
Capacity: 420 rounds
Materials: Metal Alloy

Manufacturer: CYMA

Why Mid-Cap Magazines?
Mid-Capacity magazines offer stealth operation by eliminating BB rattle often experienced with Hi-Caps. They feed smoother than Hi-Caps due to their high tension internal spring, similar to a real steel magazine. Since 470 round Hi-Capacity magazines don't exist in real life, a good amount of Mil-Sim players prefer Mid-Cap magazines for an even more realistic type of gaming experience.

Due to the design of all Mid-Cap magazines, they actually function better once you break them in. To do so spray some light silicone oil into the magazine, load and unload it a few times until BB's feed smoothly. This process breaks in the internal spring allowing it to function without problems each and every time.

About CYMA

CYMA is among the oldest, most experienced and the largest Airsoft manufacturing facility in the world. Known for their unmatched quality control and professionalism, CYMA is selected to be the OEM of a vast amount of Airsoft products. Durability and performance meets affordability!

9 Customer Reviews

(Write a review)

by John H. on 09/19/2017
"These are great! I upgraded both my M1A1 Thompsons and they shoot at 25 rps and 35 rps and the mags still feed well. Same goes for the midcaps.
by David B. on 03/04/2012
"I ordered one of these for my cousin. Works as a hi-cap should work. Taking it out is much smoother then with the mid-caps. Does not hold 420rd's holds around 360rds same as my old m4 hi-cap mag, exactly the same! I just filled my mag then transferred them all to this mag and it reached the top perfectly! He got another one of these at SC Viper for only $12 so this price is way to high. But I'm here to review the mag not the price.


Friendly tip, if you wind any hi-cap until you hear clicking it should empty your mag without having to wind it again, takes approximately a minute or so, works with M4, M14, P90, Thompson, etc. Make sure you don't make it click more then twice, I have not tried this, and I don't want to.
by Blake C. on 01/27/2012
"All right boys and girls, I bought 3 of these and they all work good now. What i mean is, when i bought the 3 of them, one did not work. After about a minute or so of winding the mag that did not work, i started to see a piece of what looks like to be a rubber band in the mag being pushed up. So i went and got some nettle nose pliers and pulled out the piece of rubber band, and now it works perfectly! The gun i have is the cybergun Thompson M1A1. Time for pros and cons.

-Hold a lot of ammo (420+ bbs)
-Made to last (More metal than plastic construction)
-The look they give the gun (Sexy)
-Operation is easy (Winding and filling)

-Rattling of the bb's (But its a high cap)
-The price (should be 13-17 dollars)
-Might find strange problem with mags at first (Rubber bands = ?)

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