378 fps with .2's using an m85 spring? any advice?

[wardivich]

hi, early this year i made an m16 from parts - upgrade parts rather than second hand parts (cost a fortune, anyway).

i put an m100 in it first and didn't crono it (assuming it would be fine, then forgetting i hadn't checked) , on a game it was getting about 389fps with .2 bb's (with the hop up set).
ive just had an aip m85 spring arrive in the post, i installed it and the rifle now crono's @ 372fps (-/+ 6fps) (.2bb's with the hop up slightly too high).

any ideas for geting it down to the 345 mark

it's got the following.
high torque motor.
mad bull 6.01 inner barrel. 42cm long
mad bull 3 in 1 hop up.
aps gearbox and gears.

or should i put a larger spring in, turn it into a dmr and sell it on?

[Boo-Sabum Ben]

Re: 378 fps with .2's using an m85 spring? any advice?

Is the inner barrel longer than the original barrel?

[wardivich]

Re: 378 fps with .2's using an m85 spring? any advice?

there was not an original barrel, as all the parts were bought separately. i am guessing that the barrel would be longer than a normal m16a4

[Boo-Sabum Ben]

Re: 378 fps with .2's using an m85 spring? any advice?

Perhaps the fact that it's 6.01 combined with a mismatched cylinder

[wardivich]

Re: 378 fps with .2's using an m85 spring? any advice?

im going to swap out the piston head for a silenced one and see if that makes a difference, i suppose i could swap the cylinder as well while i have the gearbox open.

thanks for the advice

[jonny lovegrove]

Re: 378 fps with .2's using an m85 spring? any advice?

are they M100's or SP100's? a fair few manufacturers rate their 100 springs with 100m/s @ 0.25g (so theyre actually M120!)

[Figjam]

Re: 378 fps with .2's using an m85 spring? any advice?

Have you anything compressing the spring more than it should be?

[1Hunter1]

Re: 378 fps with .2's using an m85 spring? any advice?

Check your spring guide, see if it as the swivel washers on it. If so try changing it for one that don't then see what you get

[wardivich]

Re: 378 fps with .2's using an m85 spring? any advice?

right, i've done it. basically the cylinder / piston was far too efficient. as i took out the cylinder head (the bit that the piston hits) it was so tight, i thought it might be glued into place, it wasn't, just a real snug fit. i replaced it with the head that goes with the silent piston and that easily slides in and out (much more air leaking out instead of going down the barrel). now i'm getting 347fps (-/+6fps) with the m100 and .2bb's.

thanks for all the advice given, it is much appreciated

[dexadrine]

Re: 378 fps with .2's using an m85 spring? any advice?

Get shot of the 6.01.

[wardivich]

Re: 378 fps with .2's using an m85 spring? any advice?

what would you recommend it gets replaced with?

[RitchieTheBrit]

Re: 378 fps with .2's using an m85 spring? any advice?

6.03mm is the preferred choice. Wide enough to cushion the bb with air as it travels down the barrel, resulting in less barrel contact, in theory making the hop more effective.

It's worth noting that the quality of the barrel is probably more important than the ID. A more expensive barrel will tend to be truer and consistent along its length. Prometheus or PDI or usually the goto-choice, with madbull being the best for a lower budget. However, I found my Lonex very effective when combined with an SCS nub, but a b##ger to tweak. Shots still hook left slightly due to the SCS being slightly less than true.

[wardivich]

Re: 378 fps with .2's using an m85 spring? any advice?

thanks for that - now the rifle is week enough to be used at my local sight, i'll keep an eye out for performance issues when i next go.

[dave38x]

Re: 378 fps with .2's using an m85 spring? any advice?

I second the lonex barrels - they need some serious cleaning when you first buy them (cellulose or petrol is necessary) but they rule.

I'm not surprise that a full length m16 is giving you that sort of velocity. IMO you want that efficiency, I'd have bought a selection of SHS springs (they are only £3 each) and played about till I got the right muzzle velocity. Why?

Because your current system (a leaking cylinder) can go one of two ways: Way one, the seal deteriorates and your gun rapidly drops muzzle velocity, or way 2: As the gun settles in bits of debri/oil/grease glock the leaks, and bingo, your blasting people way over the limit, someone gets one stuck in their face from 5m away, you get chrono'd on the spot and I'm pretty sure the rest is self explanatory.

[dexadrine]

Re: 378 fps with .2's using an m85 spring? any advice?

As above - you want a good an air seal as possible, if nothing other than to get a consistent range and hop, I dont know anyone who would want an intentional leak. The issue you have is that you have a very tight bore, long inner barrel matched to a (I presume) non-ported cylinder. You need to reduce the volume of air by using a wider bore and/or shorter barrel.