Tuning Dual TP install on Crown MK2 380mm barrel

[gendoc]

it seems, that the barrel is so short and the pellets im

using are jsb rd's...its doing all it can do at 850fps.

the oem tp produced 844fps, both tp's tested with all combinations

of external adjustments.

these were the velocities that were best consistant and accurate.

i bet i get much more that 6fps increase with my 700mm barrel

with nsa 24.8gr slugs.

with oem tp im getting 963fps 

 

[Vetmx]

Yeah, I jumped on the dual TP bandwagon last year with my DL Compact with a 380mm. Zero gains even after port matching the probe. Just not enough barrel length. That TP is in a box somewhere right now. My stock oval TP matched it so the Huma doesn’t deserve to be in my gun.

 

[gendoc]

does your DL have the "fat shroud" ?

i converted a lite to tac model with the 320-??mm barrel with the 

dual TP and it did about 16fps increase with 18.1's

i was hoping for around 870 or so from the crown mk2.....nada!!

 

[Vetmx]

Yes mine is a fat shroud. But here is something interesting. I had a Dreamline 500mm barrel lying around. It has a round port. I assumed my little Compact had a round port. When I took the barrel off my Compact, it had a nice oval port right from the factory. 

 

[gendoc]

that is interesting !!

 

[Vetmx]

It became clear that when swapping in the Huma dual port on a gun that came with a round port, those guys saw a nice gain. If your gun came with an oval, not so much. Unfortunately with a 380mm barrel, we just don’t have enough runway. We just start wasting air. I have an extra plenum on my Compact and I’m shooting 18.1’s 840-850fps. With the 500mm barrel and not touching the tune, the 18.1’s are screaming.

 

[gendoc]

my Dream-tac with the skinny shroud, pp, dual TP and cf bottle

shoots the 18.1gr at 888fps very stable and accurate out to 35yrds.

i was shooting the hades at 940 but had erratic poi (too fast i guess)

but, whats wild is.....it does the CPD's 1009fps 5 shot group

in one big hole @ 25 yrds

but i prefer FPE over FPS any day 

 

[Long_Gun_Dallas]

My Crown 380 peaks at 950fps with JSB 18.13s @130 bar (It is turned down to 125 bar, and sees 915-920fps) It is tuned to shoot hades at 960fps, and will dome squirrels no problem out to 78 yards at the furthest I've actually taken that shot. I have also switched to using light weight slugs. But the same tune remains on the gun. Just add a hammer weight for slugs

With the same modified port on 700mm barrel, the gun shoots 30gr slugs @ 988fps. With a 7gm hammer weight, and 145 bar reg pressure

 

[gendoc]

thats great !

my crown mk2 with 380mm barrel, dual TP achieves 962fps

with the 18.1gr jsb....too fast for what i need at that setpoint.

 

[Long_Gun_Dallas]

I was wondering.... It seemed like the monster speeds you were seeing would put your gun about on par with mine. But I only shoot the 18gr due to the pellet liner in mine being designed around THAT pellet. The choke was adjusted and dialed in while shooting THAT pellet. The 16gr hades do surprisingly well, too, I am suspecting due to almost identical dimensions as far as skirt/head spacing, and head size. I'm still shocked just how well that short pellet liner shoots.

I expected the mk2 would make more power (like yours) although it seems a lot of people's dont. I would be curious to see what a port design like mine would do in your gun. But it seems once you get past 920fps with those 18gr pellets... the tune starts becoming quite inefficient, and consequently, loud/inaccurate 

 

[gendoc]

the hades do fairly well in the mk2 if you turn it down a click or 2....

the rd's are most accurate out of the short barrel, so thats

what i like to hunt with.

 

[Long_Gun_Dallas]

Makes sense to me! Happy shooting