What spring will get an ARP9 to 330fps?

[steverebo]

So I've bought an arp9 boneyard as the mofset was dead so I've replaced that and it's working perfectly except some obvious compression issues. 

 

I'm going to reshim it replace the piston, piston head and nozzle and stick with the stock gears as this is going to be my cqc gun and it seems to be snappy enough. 

 

I have no idea what the stock spring is and it's shooting at a max of 304fps on .25's but like I said the variation is huge in fps.

 

Could someone give me some advice what spring this gun uses stock and what I could so to bring it down to my fps target of 330 on .20 bb's?

[strykerles]

probably an m100 or m105 but it depends on various factors like compression, hop and brand of spring

 

i put a ASG ultimate m130 in my DMR expecting to get around the 450 mark but after sorting the compression it came out at 562fps!!!

 

 

[MagpieTactical]

Sort the compression first. A  slightly longer ZCI barrel in my arp556 took me to 355fps on 0.2g. 

 

You may not need a different spring at all to get to your target

Edited March 27, 2022 by MagpieTactical

[Badgerlicious]

I think it's an m120. The incredibly short barrel means the arp runs a heavy spring to get the fps it does. Lowering the spring weight too much may start to cause overspin. Down to a 115 might be enough. 

Edited March 27, 2022 by Badgerlicious

[Cr0-Magnon]

As above these have a strong spring in stock, it's just limited by the barrel. I would be chuck a 200mm zci barrel in it, I would be surprised if that doesn't take you to 340. You would of course need to us a mock suppressor on the end to cover it but I think that looks better than the metallic flower.

[steverebo]

18 hours ago, MagpieTactical said:

Sort the compression first. A  slightly longer ZCI barrel in my arp556 took me to 355fps on 0.2g. 

 

You may not need a different spring at all to get to your target

How long did you go?

 

I'm looking at 141mm 6.01 lambda on3 barrels and 155mm 6.03 prometheus.

 

155mm is the max I could use and still keep my tracer unit on the front 

[MagpieTactical]

3 hours ago, steverebo said:

How long did you go?

 

I'm looking at 141mm 6.01 lambda on3 barrels and 155mm 6.03 prometheus.

 

155mm is the max I could use and still keep my tracer unit on the front 

I think it was a 200mm ZCI. 

[steverebo]

Compression sorted 155mm barrel and 60% cylinder plus I short stroked the stock gears by 2 to prevent any pme and with the stock spring I am now hitting 328fps in .025g bb's

 

So going by the information on here that the stock spring is m120 so would an m110 or m105 get me down to 295 or just under on 0.25g bb's