Well I have my PR built now. The spring had to be quite considerably clipped to get to 350fps.
Has anyone upgraded/downfpgraded their spring? Ive got an ASG vented piston head to get a good seal and tightbore, but it looks like a reguar v2 M100 spring would be too long.

I put in an M100 spring and a tight-bore barrel in my TM M1A1. I didn't notice anything unusual about the spring length when I upgraded that gun about 8 year ago?

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BANNED USER

its standard spring lenght
but spring lenght differs from brand to brand (i mean aftermarket springs)

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NO BRAIN NO PAIN

Thanks guys. The kings arms piston head has awful compression so I put in an ASG one and the fps went up considerably. I chopped on an additional 1.5 coils. i think I'll give a standard m90 spring a go as i think an m100 may be too much.

Go with the M90 spring first, and if that's not enough, try a tightbore barrel. It will give you a small boost in FPS (say 10~20 for a short barrel like an M1A1) and also accuracy. I always recommend a tightbore barrel upgrade. It's one of the easiest things to do, and it does make a noticable difference.

If the barrel's internal diameter is 6.03mm, and you're using a high end ammo that's consistantly 5.95mm or better, your BB will be making a snugger fit in that barrel, and more of the energy from the action will transfer into the BB.

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BANNED USER

yep ive got a mad bull v2 tightbore at the moment. Im planning to put a tk twist in there later as ive found them to be phenominal range and accuracy ( i play in doors so near zero cross winds)

Indoors with 350fps? brutal.

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Sgt. Jake Tucker - 13th Regt. 1st Batt. Freebooters.

yep, but auto is not allowed. Normally Most of my AEGs put out around 330 to 340 as that gives a nice range outdoors. I've just ordered an m90 so I'm hoping for around 330 with tightbore and decent piston head.
Idid a full auto game indoors, yep it was brutal and I looked like a purple Mr Blobby the next day.

As an update, I put in an ASG ultimate head and nearing spring guide, madbull 6.03 barrel and m90 spring. Gives a nice 330 ish which is a balanced power. Very good on semi, blowback mod works well. The only funny is that on semi it sometimes stops with the cut off engaged, so needs a quick auto. An AB mosfet should sort that out.