fps changing

[DanBow]

Couldn't word the title properly but here goes,

I took out my Cyma MP5 last weekend, passed chrono and enjoyed my time out in the field. Went to the same site yesterday with the same MP5, shooting the same .25s and it was just over the limit. I'd cleaned the barrel and rubbers before the first game and not touched it since. I've no idea what it was reading on the first visit as a pass is a pass. As a test, I put a handful of .28s through it and it was even more spicy.

So, is some variation in AEGs normal? The site owner said that as it's essentially a new rif, it could help if I put a couple of hundred shots through it to run it in sort of thing.

What say the Collective?

Oh, it was like shooting a laser beam on .28s. ?

 

[JimFromHorsham]

Warmer weather ? 
 

Different chrono ?

Typical airsoft weirdness?

??‍

 

[DanBow]

Warmer weather ? 
 

Different chrono ?

Typical airsoft weirdness?

??‍

Wearher was pretty much the same, same chrono so I'm stuck at airsoft weirdness until a better explanation is presented! Lol

 

[JimFromHorsham]

As you don’t know what it was running at first time round then it’s a bit difficult to guess, how much was it over at the most recent game ?

 

[DanBow]

Not sure on the exact numbers, he said its just over. I'm sure I saw 320 fps on the screen but couldn't be sure.

 

[gavinkempsell]

Same battery?

clean the barrel again?

 

[The_Lord_Poncho]

It's entirely plausible that the variable here was the marshal/ the marshals mood when you chrono'd rather than the gun shooting at different power levels between the visits. If you were only just over this time, they may have let you have the benefit of the doubt on your previous visit? Other possibility is that the hop had loosened off (MP5 hops are susceptible to this - I had to sort my Cyma with a small rubber o-ring between the tightening screw and the hop body) without you necessarily touching it during your last game. A reduction in hop can lead to a higher FPS.

Might be worth investing in a Chrono at some point if you are sticking with the hobby and will start tinkering with your guns - mine was very cheap (from memory, less than £40), yet has been reliable for years and always matches the readings that I get from the more expensive chronos on game days.

 

[DanBow]

Same battery?

clean the barrel again?

Same battery, hadn't touched the barrel. Literally put it back in the box after playing the week before, then took it out yesterday morning.

It's entirely plausible that the variable here was the marshal/ the marshals mood when you chrono'd rather than the gun shooting at different power levels between the visits

Actually, the site owner didn't chrono it last week, it was one of the marshals. So yes, maybe let off as it was only just over, whereas the site owner is more strict. Completely understandable.

Other possibility is that the hop had loosened off (MP5 hops are susceptible to this - I had to sort my Cyma with a small rubber o-ring between the tightening screw and the hop body) without you necessarily touching it during your last game. A reduction in hop can lead to a higher FPS

That's a good call. Now that you've said it, I do recall reading about the hop on MP5s. 

 

[Rogerborg]

Sorry to hear this, it can be quite the surprise - and a good excuse reason have a backup to hand.

Springs tend to be stiffer when colder, so just putting some rounds through it on the morning can help.

While it's cheating-the-chrono in spirit, you might find that you'll see lower energy from 0.2g.

MP5 hops are indeed prone to winding off, and always worth re-adjusting.

 

[Sewdhull]

I've added an o ring to the other hop adjuster screw and took out the plastic pin at the front and replaced it with a bolt to clamp things down a bit.

It's only friction holding the slidey part in place so I added some.

Put some markings on the gearbox cylinder maybe.

sourcing map 10 Pcs Adhesive Backed Tape Measure 10cm Left to Right Read Measuring Tapes Stick on Workbench Ruler (Black) https://amzn.eu/d/ccTv0Nn