What bearing should I use

Hey guys just wondering, What size bearings should I use in a m4a1 gen8?

Thanks in advance


whilst bearing do offer a little extra in terms of free run performance bushes will serve you better, longer and with less maintenance.

you can also lap a bush down if you need to customise your shimming…you can’t lap a bearing

Bearing size is what he wants ?

1 Like

yea i get that but if he’s not yet committed i’m always happy to give them something to consider before forging ahead with maybe a lesser of multiple evils

bearings for my M4A1 gen8 were 8mm.

Some are 7mm and some are 8mm and some can only fit bearings and not bushes

1 Like

damn…learn something new every day :slight_smile:

I built a Lucky gen8 a few weeks ago and it was 8mm but the shs bushes would not fit because the flange was to big to let them sit down in the recess so I had to fit bearings

1 Like

So if possible bushes would be the best way to go? Cause I am upgrading everything inside, I have the motor, I have the gears, I’ve done the barrel already.

I still want to get a one piece cylinder, metal tappet plate, heavy return springs, nylon piston with metal ladder, piston head.

If there are any other suggestions I’m open to all. Thanks

Your going to have to do some measuring or take it with you to you local store.
Nothing wrong with good quality bearings in a mild spring setup.

What’s considered a mild spring? Or where’s the rough spring or fps point where you’d be better off forgetting about bearings and going to bushes instead?

18:1 gear ratio and say a 1.3mm spring.
Tbh the gen8 switch and wiring can’t handle much more than that anyway

1 Like

ok thanks, sounds like I’m in the danger zone then. Bearings seem to be so much more easy to find then bushes.

1 Like

Shows the randomisation in manufacturing, I have a Lucky Singularity box I am building and the flanges on the SHS bearings were too big, so tried SHS bushes and they fitted perfectly.

1 Like

Exactly there are a few different SHS bushes as well and a lot of variation in gen8 style boxes, hence my suggestion to get measuring.
I rebuilt this Lucky for a mate and I noticed the bearings in the box were very worn so he bought new SHS bushes from m4a1 and when they didn’t fit I just took the bearings out of my APS box and used those which were identical in size to the bearings that were in the Lucky then I used the bushes in the APS :grin:

1 Like