Precihole VX100: An Alternative State of Tune!

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prashantjha19
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Re: Precihole VX100: An Alternative State of Tune!

Post by prashantjha19 » Wed Jun 27, 2018 3:23 pm

baggafx wrote:percihole accepted that there SX 100 did not produce 12 ftlb power in .177...sx 100 produce 800fps with 7.3 grain pellet 10.38fpe.... again when i ask is SX-VX 100 is same then they reply VX 100 is almost same but produce 760 fps with 7.3 grain pellet mean 9.4 ft-lb power...see email pics
Dear Baggafx,
Not many are so dearly caught up with muzzle energy output as you ...so much evident in how you have persisted on this forum through the case of PH guns giving lower ME than 12fpe. That, however, is a fine attribute in itself...unless there are things or agendas beyond just the ME output of a particular gun make (as in this case)!

If you really are after power and a decent quality and workmanship, then (as many have suggested here, too) you could opt for the Artemis. Or, why not your neighbourly Hurricane from Aarmr, for that matter?? I trust its macho-look stock would complement your appetite for power!!

Having said that, if we try to see through the PH case, then here's what I think: If you insist on being on the right side of the law, you must stick to it in letter and spirit. As I understand, making (lawfully that is) a sub-12fpe gun means (in purely legal terms) at least two things: One, no pellet exiting from its muzzle should exceed the limit; and two, it should be non-viable and most difficult to alter the standard build of the gun to shoot in excess of the limit.

Now, if the VX, as I have shown in the first post of this thread, can be made to shoot accurately and sweetly at 10.5fpe with just some basic pre-load alterations in .177, then there sure is ample room to ramp it up further to in the vicinity of 12. (Pls remember, the replacement spring's rate was as good as the standard one in this case....which means no great alterations done!). Also, in .22, the gun would surely be more efficient.

Further, have you ever encountered anyone claiming to make these PH guns shoot CONSISTENTLY above 12fpe?? I haven't. You could possibly do this....but it will more likely wreck either you or the gun for sure. That makes it non viable.

Most people I believe value these attributes. No wonder, the gun remains being sought after.

From my tuning experiences, I can further vouch that the VX does not diesel (a point worth noticing in the official response, too). We sure know of people who have claimed great power in videos posted online.......only that all of it was in thick dieseling smoke. How dependable ME output claim would you rate those??
In fact, my peak pressure and temp calculations across all my guns worked out to be the lowest for the VX100 in its factory state of tune (@942 PSI; under 20:1 comp ratio and a peak temp of 980.2*C). For your ref, by the same calculations, a sub-12fpe Walther LGV in its standard tune would get rated at 1374; 25.8:1 and 1088*C, respectively on all these three counts!
As a tell-tale evidence of this attribute, when I opened my VX up after 2000+ shot cycles, there was barely any scorch on the seal or on the cylinder walls.

From Precihole's perspective, and esp now that the .22 era is over for us, it may be expedient to start marking the velocity and ME attributes of their guns more precisely. Alternatively, they could either state the max velocity, or the max FPE.....because when you state both side by side, you do get people in a bind.

In this regard, I like the rather straightforward way the SDB does this, for instance....The catalogues on their new guns clearly state: So and so velocity achieved with so and so grain pellet. You can do your calculations..and make up your mind.

Disclaimer: I have no associations, commercial or otherwise, of any sort with any of the makers, makes or models mentioned in my post, which is solely my individual opinion.
Best regards,
Prashant

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prashantjha19
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Re: Precihole VX100: An Alternative State of Tune!

Post by prashantjha19 » Thu Jul 05, 2018 5:32 pm

Hello all,
Finally I had someone confront me with a query I had expected to come first off-the-block, and soon as I made this thread public; and this was: Why do I call the VX100 a "high surge" gun when, owing to its heavy piston, it should be a high recoil gun? Well, for the record, a heavy piston, nominally, does imply high recoil (and not surge), all things equal. Then why did I say surge?

Here’s what I answered and how I put my arguments:

First, since I do not have the facility of precise recoil measuring instruments, I go mostly with shot cycle feel, accuracy behaviour with varying start pressure pellets, energy outputs, and my energy calculations for spring, preload and piston, ....in all the analysis I do with my air rifles. The proof of the pudding, too, is in eating it....and so the results must speak for themselves! So, let's look at the results.

If my VX in its original state of tune (very soft spring and heavy piston+tophat assembly) was indeed a high recoil gun, it would not record a near-130% increase in ME with just a slight increase in the available piston energy, which albeit came at the cost of a significantly high preload force.
It simply means that the instance of piston bounce happened too early in the compression stroke, and that the softer spring (with the 58mm preload) could not keep even this heavy piston assembly nearer the transfer port long enough to maintain enough pellet driving pressure and impart energy to the pellet. As a result, the ME was significantly low (roughly in the region of 8 or so fpe).

Going by how the gun shot after increasing the preload force – on all three critical counts, i.e., increase in ME, better accuracy, and smoothened shot cycle – tells us clearly that the piston got driven father in the actual compression stroke and/or it resisted far longer the force of the compressed air before it bounced at the end of the primary recoil cycle.

What this essentially implies are two things: One, RECOIL INCREASED! Yes, if the piston’s travel in the stroke became longer, then recoil certainly increased. No doubts there! Two, and more important, more of the piston energy got used in driving the pellet, and less in driving the piston bounce in this case.
Now, couple these with the fact that there was no compromise in accuracy, and you have evidence enough that in its previous state of tune the gun was a high surge one.....meaning, the piston bounced early (which means less recoil, and more surge force and acceleration)
That is how I called it a high surge gun.

Also, we will look at understanding and qualifying these further when I try the next tune where I will lower the piston weight assembly. Needless to say, to maintain ME, I will need to increase preload and/or deploy a higher rate spring. I will do both of these in moderation, record the results (and accuracy), and update here. Till then,
Best regards,
Prashant

shahzanms
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Re: Precihole VX100: An Alternative State of Tune!

Post by shahzanms » Sat Nov 16, 2019 8:01 pm

i just bought one, is there any way of making the rifle a little silent,i use it indoors mostly and dont want to disturb the folks around.


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