A Thread About Skara Questioning His Arp-9

[Skara]

i'm assuming you're running a macaron or equivalent so the answer is i'd be surprised if it didnt.

Yep, I'm running a MR 50° but I didn't phrase it right. What I meant is: will it hop 0.32s at 24 rps without acting funny?

I also need some high caps (because reloading every once in a while is fun), but from what I've seen mp5 high caps are a bit shit.

 

[Adolf Hamster]

Yep, I'm running a MR 50° but I didn't phrase it right. What I meant is: will it hop 0.32s at 24 rps without acting funny?

assuming it feeds, can't think why it wouldn't if it's running ok on lighter.

 

[Skara]

This gun is cursed

This aged like fine wine.

Receivers (yes, both) are badly bent, I knew there was something off but didn't pay too much attention until yesterday night.

Upper is not compatible with other brands as it's 3/4mm longer.

Buying a replacement from King Arms is ludicrously expensive because of postage and import fees (€70+, not even counting the price of the receiver set itself) which makes it cheaper to just buy a new gun.

At this point there is a whole new gun I'm looking at....

Stay tuned for more OCD autism

 

[Skara]

So, this new gun.

magazine wise it doesn't like stock high caps, there is a bit of wobble and I have to move them around to "feed" 5/6 BBs before needing to wind them again.

Absolutely flawless on the G&G ARP-9 drum, it sits very tight (actually needs a tap to lock in place) but feeds every BB, specna midcaps are okay although the one I have seems to have a too weak retention tooth, first time I loaded it some bbs went flying, feeds fine.

I have tried the bevel to pinion shimming method on this one, unfortunately the amp meter I have doesn't want to register semi auto, spamming the trigger showed 20 amps, while full auto showed 20 at startup, then 12 still going down.

This on a 11.1v 1450mAh 60c.

Energy and rof are 1.25J and 27 rps. Cycling in semi is quick.

Setup is:

RA gearbox

Perun Hybrid

Wanker Maxx adjustable trigger

Zci 22tpa

Rocket 13:1 gears SS'd by two at the front

SHS m110 (m120 really)

Type B cylinder (for 200-250mm barrels)

Knackered shs nozzle, to be replaced with an FPS one

Maxx TE hop unit

ML 70° Super Macaron

Prommy 6.05x208 barrel

Range/consistency wise I've only briefly tested it yesterday night on 0.25s, range seems okay but there is a weird horizontal spread that I will have to address somehow.

 

[Skara]

'nother update.

I'm turning this into a DSG, for maximum wanker factor and because I'm bored.

I have the following parts coming:

Shs dsg sector + tappet plate

Modify spring spacer

Retro arms dsg piston body.

I'm keeping everything else intact, hopefully I can make it work.

 

[Skara]

Alright.

First test shows 37.3 RPS, 85 m/s on semi but 60 in full auto @11.1v, which shows that:

a) it feeds on the g&g drum;

b) I have to adjust the tappet timing because the results indicate that the piston is being released when the nozzle is still moving forward, I will cut the fin half a millimetre shorter, shorten the tappet spring and, just for testing purposes, slightly modify the tappet pickup point to have it delayed by a tiiiiiiiny bit, just to rule out tappet PME.

 

[Skara]

Test no.2

Shortening 4 coils (two on each side) of the tappet spring alleviated some of the power loss issue, along with a slightly stiffer spring (shs m110 + a spring guide spacer) and a smidge more air volume by running a different cylinder the gun now does 94-96 m/s on semi and full auto on a 7.4v (20 RPS), but still drops to 92/93 on a 11.1v at 37 RPS.

The following animation shows what I believe to be happening inside the gearbox, nozzle starts to retract while the piston is still moving....

So I'm thinking, what if I knock off a tooth off the release side(s)? This way the piston releases a tiny bit earlier which in turn gives it more time to hit the cylinder head before the nozzle is pulled back.

Thoughts?

 

[Skara]

My thinking was correct.

Knocked off one tooth off the release side(s), BB velocity is now consistent between semi and full @39 RPS.

Also found a random spring in my box o' bits that upped the energy to 1.05J before short stroking, now it's sitting at a very comfy 0.96J (98 m/s on 0.2s).