Chrono Results from the first 70 shots

[Shaggy]

First of all i shot 20 in their 10my range
So our Gert went to bed so i got the Living Room Pellet Catcher Ver 1.1 set up

First up Jsb Heavy's 10.34gr first 2 hot then settled in


2nd up Baracuda FT 9.57gr


3rd up were 13.43 gr jsb monsters and they were a surprise as i thought they would be very hot
4th up were qys domed 9.56gr

fifth up were jsb exact 8.44gr


6th were jsb match middle weight 8.02 gr


and the last were baracuda 8's 8.44 gr


So thats the first 90 shots through it folks

 

[mitch21]

That's some very nice results Shaggy, don't look like you have to worry about grain weight, Keep up the good work, Good luck mitch21

 

[Shaggy]

I am confused how it is that the U2 i sent back would run hot with the heavier pellets but this one does not?
Is it a different internal set up?

 

[Ed 86]

Nice results. The factory have obviously done a decent job of keeping it legal before it left for the RFD

 

[sagalout]

don't look like you have to worry about grain weight

No, but it does need setting up better, not sub 12 with heavys.

done a decent job of keeping it legal

I'm confused, how is it legal?

I know I'm old and thick, but I'm sure on the days I went to skool 12.18 was bigger than the 12.00. Dunno when that changed?

I would hazard a guess the reg has some reg creep and the reg is not set to the ideal operating pressure, so the first couple of shots are higher than those following. More Loutsplaining

how it is that the U2 i sent back would run hot with the heavier pellets

It is hot with 10.34gr JSB. It is making more power with 10.34 and 13.43gr than with 8.44. It's all to do with the tune of the gun, a lot of high powered guns are re-tuned for sub12 by fitting using a small transfer port, this means the air pulse (AP) for the shot is delivered as a relatively long slow pulse as opposed to a short sharp blast.

Think of the same amount of air arriving behind the stationary pellet in a football or a 50mm tube.

When the AP arrives behind the pellet, the AP wants to get from 90 bar to 1 bar as quickly as it can. It does this by expanding. To expand in the barrel, the AP has to get the pellet out of the way. A heavy pellet has more inertia than a lighter pellet, so the lighter pellet will accelerate faster than the heavier pellet.

A long slow air pulse gives the slower accelerating heavy more pellet more time to reach a higher muzzle energy before leaving the barrel and the AP quickly expands to 1 bar in the atmosphere. The lighter pellet accelerates faster and leaves the barrel quicker, therefore not reaching a high enough speed to match the heavier pellet for ME.

The pellet that is most efficient is not just dependent on weight, there are other things at play here, friction for example. For any tune, assuming all other factors are equal, there will be one pellet weight (10.34gr looking at your results) that matches the gun's characteristics the best, this is the most efficient for that gun, ie any pellet that is heavier or lighter will not be as efficient.

More Loutsplaining

 

[Shaggy]

OK so i had just filled it to 250 bar from 150 bar when i got the first 2 shots hot.
I then shot them in quick succession so does that mean i didnt give the reg time to creep ?
Will the reg bed in or does it have to go back to RR?

 

[sagalout]

OK so i had just filled it to 250 bar from 150 bar when i got the first 2 shots hot.

That will push the plenum pressure up in a lot of guns. Because you are running so close to 12fpe when reg is cycling between shots, you are going over with a slight change.

I then shot them in quick succession so does that mean i didnt give the reg time to creep ?

Yes.

Will the reg bed in or does it have to go back to RR?

I'm not a great believer in the reg bedding in having never seen any evidence of it personally. When I build a reg it either works as I want it to or it doesn't. If it doesn't, I strip it and improve the sealing faces. I have no idea who or what RR is, apart from Rolls Royce but my spidy senses tell me that ain't what you mean.

I have no idea what gun it is so I have no idea what adjusters are available to you. If it was my gun, I would turn it down on the hammer initially and do more testing**. If it was running at 700-705 fast shooting with heavys and the reg don't creep a lot, I wouldn't worry about it.

**Having turned the hammer down, using the 10.34gr pellets I would test:

• immediately after filling
• after it has not been fired for at least 12 hours
• as the bottle approaches reg set pressure and continues to clearly off reg

I would also test coming of reg with the 13.43gr pellets as they are close to the 10.34gr in power and the heavier pellets tend to favour a lower pressure.

Alternatively, since it not sub 12 return for a full refund.

 

[Shaggy]

Thanks for the help @sagalout i appreciate it
I will fire another 10 shots through the chrono with 10.34 gr and since it will be 12 hours we should replicate the results and if it doesn't then i will top back up to 250 and see if that happens again.
I just want to be on the right side of the law and enjoy the gun
RR is Range Right the importers of the guns.

 

[sagalout]

RR is Range Right the importers of the guns.

Just remember your contract is with the retailer you bought it from.

 

[Shaggy]

Forgot to ask @sagalout does the size of the pellet make a difference ie- 4.49 4.50 etc?
I know the powers that be will have certain pellets they use but i just wonders what difference that makes

 

[sagalout]

does the size of the pellet make a difference ie- 4.49 4.50 etc?

Don't know, not played with that characteristic of the pellet.

 

[Mark Newbie]

That will push the plenum pressure up in a lot of guns. Because you are running so close to 12fpe when reg is cycling between shots, you are going over with a slight change.


Yes.


I'm not a great believer in the reg bedding in having never seen any evidence of it personally. When I build a reg it either works as I want it to or it doesn't. If it doesn't, I strip it and improve the sealing faces. I have no idea who or what RR is, apart from Rolls Royce but my spidy senses tell me that ain't what you mean.

I have no idea what gun it is so I have no idea what adjusters are available to you. If it was my gun, I would turn it down on the hammer initially and do more testing**. If it was running at 700-705 fast shooting with heavys and the reg don't creep a lot, I wouldn't worry about it.

**Having turned the hammer down, using the 10.34gr pellets I would test:

• immediately after filling
• after it has not been fired for at least 12 hours
• as the bottle approaches reg set pressure and continues to clearly off reg

I would also test coming of reg with the 13.43gr pellets as they are close to the 10.34gr in power and the heavier pellets tend to favour a lower pressure.

Alternatively, since it not sub 12 return for a full refund.

RR probably Range Right??

 

[sagalout]

RR probably Range Right??

You was beaten to the punch , but thanks anyway.

RR is Range Right the importers of the guns.

 

[keithy]

Turn the hammer spring down so it runs about 11.4 ftlb.

 

[jesim1]

I hate it when a gun like this is almost perfect, but not quite, too close to 12fpe with heavies for my liking, I wish they just made it simpler for the rfd to turn it down a fraction, just a 1/2 fpe type of adjustment built in would solve so many over power issues, or just test them with 10.34gn in the factory, which of course, we all know would then be different with the next tin you tried

Why oh why can't they just say it's under 12fpe on average over 10 shots when tested with 10.34gr pellets so we all know where the goal posts are?

 

[Shaggy]

I am about to test it now so we will see in 5 mins and i will know what to tell them exactly whats happening tomorrow

 

[Shaggy]

OK so first 1 hot again NOT BARACUDA 8s But JSB 10.34 Heavies

 

[BallisticBill]

Two observations:
1. The reg is set below ideal operating pressure - the pressure which gives maximum ME. When you fill the gun the plenum is running above set point. If it was set at IOP, the gun would be running consistently over 12fpe with the 10.34gr.
2. If the 8.44gr are JSB manufactured, the transfer port is smaller than ideal. The difference in ME between 10.34gr and 8.44gr is quite large - more than it could be - but not something that necessarily needs rectifying if you are happy running 8.44gr at mid-10s fpe, which you would need to do to keep the gun safely legal.

The characteristics are symptomatic of the bodged sub-12 tune seen on many Eastern European and Turkish guns. If you return the gun to be fixed you might want to know exactly what adjustments have been made. I would be concerned that the fix could be another bodge rather than a proper tune. If you are competent to disassemble and reassemble the gun, and you don't mind voiding the warranty, you could fix it yourself with a little help via PM. If you exchange it for another of same model, the chances are the next gun will also be a bodge.

 

[Shaggy]

So waited till 8 pm and shot another 4 then the last shot was at 8.30

 

[Shaggy]

The gun is getting swapped and RR will be checking the new one over the chrono before getting it to Luke at Wighill Park Guns for me in the morning.
I will take my @NateChrony with me and double check everything is right.
I wanted to swap instead of getting the money back as i want the gun.
It helps that RR is only a few miles away from the shop so all is quick