Trying to Achieve a Flat Trajectory With Hop at the End. Rather Then Hop and Drop.

[Asomodai]

Hello all. 

I have a CYMA SVU with a Prommy 509mm barrel, Combat Union SVD Hop unit, Modify Flat hop rubber and Maple Leaf Omega Nub. I find that the trajectory starts out high and then falls, not particularly long range or accurate considering its a 420FPS DMR. To lift a .32 to it's maximum current range I have to adjust the hop to the point the FPS is 366FPS on a .2. I have cleaned the barrel and rubber. 

My presumption is that the nub is the problem. What do you think? If so what off the shelf nub shall I replace it with that would give me a flatter trajectory and better range? I can easily get hold of a matching Modify flat hop nub. 

The need for a flat trajectory is high and I cannot adjust my PSO scope enough to follow the current sky high trajectory. 

Cheers!

 

[Adolf Hamster]

tbh the omega nub is really meant to match up to their rubbers, not sure it'd work so well with a flathop as it doesn't have the bulk that your typical flat hop nub has.

i'd try either a 40 degree macaron with the omega or the modify nub (not used modify rubbers in a while but the last time i did they seemed kinda plasticky)

i'd also say going a bit heavier on the ammo would be a good shout too, for a flat trajectory you want the bb to stay in the sweet spot for lift as long as possible and a heavier round travelling slower initially won't slow down so fast.

i know what you mean about the pso, i have a similar issue with mine (real sword pso on a we dragonuv) and if i'm setting the rise for extreme range you do end up having to apply copious amounts of kentucky windage.

 

[Asomodai]

tbh the omega nub is really meant to match up to their rubbers, not sure it'd work so well with a flathop as it doesn't have the bulk that your typical flat hop nub has.

i'd try either a 40 degree macaron with the omega or the modify nub (not used modify rubbers in a while but the last time i did they seemed kinda plasticky)

i'd also say going a bit heavier on the ammo would be a good shout too, for a flat trajectory you want the bb to stay in the sweet spot for lift as long as possible and a heavier round travelling slower initially won't slow down so fast.

i know what you mean about the pso, i have a similar issue with mine (real sword pso on a we dragonuv) and if i'm setting the rise for extreme range you do end up having to apply copious amounts of kentucky windage.

Ta for the reply. a 40 degree Macaron exists? Seems a bit soft for DMR FPS! I may pick up the Modify one as its cheap enough for a test. I have a Prommy barrel which means the barrel window is not that massive so I am slightly limited in choice of rubber and nub. 

I only started using .32 because .30 over hopped and I couldnt lift .4's, though it's likely because of this nub issue! 

Literally the BB is so high it's not even in the window! Bugger if I can see the bb when it drops back into the sight picture as well. 

 

[Adolf Hamster]

Ta for the reply. a 40 degree Macaron exists? Seems a bit soft for DMR FPS!

damn, forgot the whole dmr fps thing, so used to building 1j guns to lift the super heavies

yeah 40 (i think that's what the green is, might be 50, there's another colour even softer might be what i'm thinking of) probably a tad soft, maybe the tan too. tricky as you want soft for good easy spinning but you want hard for air seal (which is the main reason to R-hop so you can have both)

I may pick up the Modify one as its cheap enough for a test. I have a Prommy barrel which means the barrel window is not that massive so I am slightly limited in choice of rubber and nub. 

worth a shot, honestly it's a case of fiddling to find the setup that works nicely.

I only started using .32 because .30 over hopped and I couldnt lift .4's, though it's likely because of this nub issue! 

always the way, overhopping is gods way of telling you to use heavier ammo, underhopping is gods way of telling you to get a better hop

Literally the BB is so high it's not even in the window! Bugger if I can see the bb when it drops back into the sight picture as well. 

not that bad for me, but then i'm using .48's at 1j so got plenty of time to track

 

[Asomodai]

damn, forgot the whole dmr fps thing, so used to building 1j guns to lift the super heavies

yeah 40 (i think that's what the green is, might be 50, there's another colour even softer might be what i'm thinking of) probably a tad soft, maybe the tan too. tricky as you want soft for good easy spinning but you want hard for air seal (which is the main reason to R-hop so you can have both)

worth a shot, honestly it's a case of fiddling to find the setup that works nicely.

always the way, overhopping is gods way of telling you to use heavier ammo, underhopping is gods way of telling you to get a better hop

not that bad for me, but then i'm using .48's at 1j so got plenty of time to track

Maybe we should just use scopes that actually have proper adjustment rather then just moving the reticule. 

 

[Adolf Hamster]

Maybe we should just use scopes that actually have proper adjustment rather then just moving the reticule. 

cmon, what else are you putting on a dragonuv

 

[Asomodai]

cmon, what else are you putting on a dragonuv

Toilet Roll with a couple of bits of glass at both ends. 

I wish I could stick my Simmons Whitetail internals in the the PSO

 

[Adolf Hamster]

Toilet Roll with a couple of bits of glass at both ends. 

thought the PU only had mosin style mounts?

I wish I could stick my Simmons Whitetail internals in the the PSO

i dunno, i kinda like the pso, it's not good by modern standards but it's very simple and afaik the doctrine was mostly a case of "if he ain't really far away just hold-over is good enough" as opposed to the more western dial in for a perfect shot

 

[concretesnail]

The first think I'd look to change is that rubber.

The omega nub is one of the harder nubs available, and its very good as as it can apply pressure over a wide area.

As you need to crank the hop to get backspin to lift the heavier bbs I'd guess that rubber is too slick and doesn't have the 'grip to hold the bb and the high pressure is being used to compensate.

If you swap the rubber for something softer which will grab better, but wear slightly quicker.

I use a maple leaf rubber in my dmr and its great.

 

[Cr0-Magnon]

I never really got along with a flat hop when I used one in my Scorpion Evo. The trajectory thing sounds the same, it kinda "lobbed" the BB's, with a high arch pattern and sharp drop (kinda like a subtle mortar!)

I would say go 60 degree maple leaf 2021 silicone and omega nub.

 

[Asomodai]

Quick update. Found a Prommy Tensioner for a Nub. Cut it down to size. Installed. Checked bucking and it's not modify soft. It's a plain black straight bucking, could even be a Prommy Extra Soft.  Anyway, pretty much the same performance. A few less flyers, but same FPS loss. I tried some .4's and the power went down by a few tenths of a Joule. 

I am starting to think the bucking is an issue and suspected air leak with all the joules I lose when going heavier bb. 

 

[Adolf Hamster]

Quick update. Found a Prommy Tensioner for a Nub. Cut it down to size. Installed. Checked bucking and it's not modify soft. It's a plain black straight bucking, could even be a Prommy Extra Soft.  Anyway, pretty much the same performance. A few less flyers, but same FPS loss. I tried some .4's and the power went down by a few tenths of a Joule. 

I am starting to think the bucking is an issue and suspected air leak with all the joules I lose when going heavier bb. 

what's the consistency like?

might be that's just what you're losing in spin?

 

[Asomodai]

what's the consistency like?

might be that's just what you're losing in spin?

FPS Consistency? Reasonable. I'd say 4 fps+/- 

I know I need to whack up the hop to lift more, but a loss of 50-70fps is a little extreme. 

 

[Adolf Hamster]

FPS Consistency? Reasonable. I'd say 4 fps+/- 

I know I need to whack up the hop to lift more, but a loss of 50-70fps is a little extreme. 

yeah, this is where the different compounds/patch shapes come into play with a larger contact patch/softer compound needing less pressure to get the desired spin.

of course you're always gonna lose something.

it's a tricky one because the question then becomes how/when fps is measured ie off versus hopping game weight

personally i lean on the latter, as turning the hop completely off as some sites ask can lead to erroneously low fps readings because the bb has half rolled out of the barrel before firing.

 

[Asomodai]

yeah, this is where the different compounds/patch shapes come into play with a larger contact patch/softer compound needing less pressure to get the desired spin.

of course you're always gonna lose something.

it's a tricky one because the question then becomes how/when fps is measured ie off versus hopping game weight

personally i lean on the latter, as turning the hop completely off as some sites ask can lead to erroneously low fps readings because the bb has half rolled out of the barrel before firing.

Well I currently have a prommy barrel which has an infamously narrow hop window. Maybe I should go for its ZCI equivilant to help with that as well as a different bucking? 

 

[Adolf Hamster]

Well I currently have a prommy barrel which has an infamously narrow hop window. Maybe I should go for its ZCI equivilant to help with that as well as a different bucking? 

could do, those zci 6.02's are cracking for the price and happy enough with the ml stuff.

tbh i suspect window length is probably more important than width, but we're getting into very theoretical territory

 

[Skara]

maple leaf 2021 silicone

Don't.

I've had only issues with those.

Regular MRs are great though.

 

[Asomodai]

Don't.

I've had only issues with those.

Regular MRs are great though.

What sort of issues? I have been using Guarder Clears for some time and love them! 

 

[Skara]

What sort of issues? I have been using Guarder Clears for some time and love them! 

Tested my new compression parts, silicone MR was installed and the chrono readings were the following (hop all the way off):

325, 300, 240, 170, 90, jam. Didn't test full auto for obvious reasons.

Good ol' rubber 50° MR in, constant 315 without hop, constant 325 with hop applied.

No power drops in full auto.

It has something to do with the lips, also the fact that bbs are super hard to manually push past the contact patch without any pressure from the arm tells me there's something wrong with these new rubbers.

 

[concretesnail]

Zci make cracking barrels and theybwork really well with both the macron and Mr hop mapleleaf rubbers.

I've used both macaronnand Mr in mine, currently there's a Mr silicon rubber in my dmr and the seal it has is great.