vastly inconsistant velocity!

[badger906]

i bought a gun from here and it was shooting hot and inconsistently. is to me that meant new spring, new o rings in the gear box and a new hopup rubber.. so i:
Put in a new spring,
Put a new oring on piston head
Put a new oring on cylinder head
Put in new Hop up rubber.
Now the gun shoots at between 283fps and 345... still widely inconsistent.

Ive done everything that my knowledge of airsoft tells me is the issue.. and yes the bbs are round and the same weight.. sooo wtf is going on!?!?!?!?

[Panoptes]

Re: vastly inconsistant velocity!

Airseal problem between hop and barrel.

[badger906]

Re: vastly inconsistant velocity!

yeah good though, could pop an oring over the end of the barrel to hop up.
But then again thompsons have a plastic shroud that goes over the end of the hopup, so i cant see it fitting. so i guess ptfe tape is the next port of call.

[badger906]

Re: vastly inconsistant velocity!

airseal from barrel to hopup is air tight, so not that.

[Bleedout]

Re: vastly inconsistant velocity!

Airseal between hop and gearbox. Streatch the spring pushing the hop back.

[badger906]

Re: vastly inconsistant velocity!

thompsons dont have a spring, theyre hopup is seated in place with screws.
think ill replace the air nozzle as well, need to crack open the gb again as it is to put metal bushings in, so guess ill have to keep it inconsistant for this weekends game, and replace the parts i pick up on site.

[No1_sonuk]

Re: vastly inconsistant velocity!

I suppose you've tried cleaning the barrel?

The only time my Thompson has been inconsistent is when it had a broken spring, but you've already done that.

Something else to look at: -
Is the receiver seated all the way back on the frame and screwed down? Sometimes the lock plunger doesn't hold it far enough back.
Is the gearbox seated properly?

Trouble with inserting a mag might indicate the receiver isn't in quite the right place WRT the frame.

For those that don't know:
The Thompson mags are rigidly mounted in a rail/groove system on the frame, and the hop is rigidly fixed with screws to the receiver. There's virtually no flexibility in that setup, so misalignment can be a problem.

[badger906]

Re: vastly inconsistant velocity!

i would like to put my hands up for the biggest retard of they year award...
It wasnt anything wrong with the gun.. and i only discovered this after i spent £41 on new parts at my local shop...

It was that the bag of BB's i had stolen off my brother (as i use .25s) to chrono the gun, was in fact a mixed bag of bbs, containing .25 and .2 as well as different brands, which he uses in his pistol...

So yeah... im retarded!! gun was still hot, so ive cut a considerable amount off the spring to make it less than 345fps. bit it only has to last one day as ive got a m90 spring to collect at urban assault at the weeken

[No1_sonuk]

Re: vastly inconsistant velocity!

I have a mixer-bag of BBs - I use them in 40mm grenades.