Tuning Thinking out loud....shorter barrel lower fps

Can you add hammer weight to the Krait Standard to open the valve more to get back some of that heavy pellet speed loss?

dens228 said:

I could but am trying to avoid that. The hammer is slamming hard now. The problem with this particular rifle is that the spring seems to be hyper sensitive and the consistency window with the hammer is excessively narrow. At it's current tune it's accurate and consistent with plenty of speed/power, just not tuned efficiently. I'm stuck with the hammer strike and pellet weight as my only means of finding a happy medium until Huma restocks the reg I need.
If I crank up the hammer more my already low shot count will be too low.

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You could try your hand at porting and polishing the transfer ports to make the shot cycle more efficient at getting the air where it needs to go smoothly. With the poppet style of valve body, and the mass production methods used by most manufacturer's of simply drilling perpendicular holes, this procedure brings a good percentage of gains, even on high-end guns. If your willing to tear into the gun to change the regulator, then you sound like you can also accomplish a little port grinding with some Dremel bits.

Also, there's speed and efficiency to be had by highly polishing the spring, hammer weight, and poppet stem and valve body holes where those parts make contact with another part.

You could add more valve spring (or a spacer if possible) if you're not happy with the balance between the valve at its current pressure and the hammer settings that are available to you...or you could run less hammer travel (increase the length of the hammer striker if possible for example) which will result in less energy stored in the spring in the cocked position. You could also run a lighter hammer spring rating in lb/in if you're able to determine what you currently have.

I cannot comment as to the pellet stability in a shorter vs longer barrel however longer barrels have more 'pellet dwell' and can result in inconsistency due to shooter error / POA drift during the shot cycle.

Reducing hammer travel would improve consistency in hammer strike the most without intense mods, because it forces you to run more spring/pre-load while reducing the travel which minimizes the exposure of hammer to hammer bore friction, and also reduces the lock time (time it takes hammer to travel its distance and strike valve).

(Intense mod) If the valve itself is just overly sensitive, the valve spring / spacer idea will help some, and the most advanced way would to be determine if the valve stem is sub .125", and then if it is boring the stem bore to .125" and running a .125" stem, asvalve closing force is one of the primary factors that control ones 'tuning window'.


Hope this helps some. Feel free to pick my brain if you need more assistance understanding.


-Matt

By and large, longer barrels are generally more accurate and quieter than shorties. Maybe bite the bullet so to speak and grab a huma reg for that bad boy. Never hurts to have a backup reg.

rangur1 said:

By and large, longer barrels are generally more accurate and quieter than shorties. Maybe bite the bullet so to speak and grab a huma reg for that bad boy. Never hurts to have a backup reg.

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This is entirely tune dependent and too generalized of a statement taken to an extreme.

A 50" barrel is not by far and large more accurate than a 20" barrel on a .177 shooting 12 fpe...lol

-Matt

Stubbers said:

This is entirely tune dependent and too generalized of a statement taken to an extreme.

A 50" barrel is not by far and large more accurate than a 20" barrel on a .177 shooting 12 fpe...lol

-Matt

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Well, obviously that set up would be true. But the OP is shooting 22 cal at closer to 30-35 foot pounds. I'm not indicating the generalization for sub 12 foot pound applications. After all, I'm giving general information pertaining to the OP's situation, wasn't directed for what you may have.

rangur1 said:

Well, obviously that set up would be true. But the OP is shooting 22 cal at closer to 30-35 foot pounds. I'm not indicating the generalization for sub 12 foot pound applications. After all, I'm giving general information pertaining to the OP's situation, wasn't directed for what you may have.

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Which is still incorrect, you implied longer barrels are by large, generally more accurate than their counterparts, in a generalized statement that did not impose caliber or fpe restrictions.

A 500mm barrel is not less accurate than a 600mm barrel provided they are both tuned to shoot efficiently, simply due to length alone.

-Matt

Stubbers said:

Which is still incorrect, you implied longer barrels are by large, generally more accurate than their counterparts, in a generalized statement that did not impose caliber or fpe restrictions.

A 500mm barrel is not less accurate than a 600mm barrel provided they are both tuned to shoot efficiently, simply due to length alone.

-Matt

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Mr Stubbers, I have no intention of hijacking the OP's thread going back and forth with you on this. If you wish, you can PM me and we can clarify our differences there. As for this thread, I've shot Several brands of high end guns. FX, Taipan, Edgun, AGT , Epic. If barrel length makes no difference. Why are their "sniper barrels" lenghts for FX at 700mm? My taipan long always outshot my Taipan shorty. My friend and I shoot the vulcan 3 both 500 and 700mm barrel versions and almost unilaterally the longer barrels were generally quieter and more accurate - FOR ME!
Now, can a better shooter with a shorter barrel gun out shoot me when I'm using a longer barrel version? OF COURSE!
Now, If you put the same shooter, with proper tuned guns of different barrel lengths, and they gave honest effort, I seriously doubt more accuracy will be attained towards the shorter 350-500mm barrels.

Short barrels require less follow through, so in that case, more accurate for most.

Shot cycle can affect a shooters accuracy. Lighter projectiles at low velocity give a more sedate shot cycle. So generally, easier to shoot more accurately.

External ballistics can play a role in accuracy. Heavier projectiles at higher velocity can hold together better over longer distances.

Though it is sometimes possible to get good heavy projectile performance in a short barreled airgun, the shot cycle becomes harsh, which can degrade accuracy.

Accuracy at close range usually favors the shorter barrel, lower FPE airgun.

Accuracy at long range usually favors the longer barrel, higher FPE airgun.

A particular pellet can stabilize well over a wide velocity even with a slow twist rate. Not the case with slugs.

I tend to prefer longer barrels, but my 12fpe airgun with a 14.9” barrel is probably my most accurate airgun, but only out to about 35yds.

At what distance do you want the best accuracy? That will affect your barrel length decision.

rangur1 said:

Mr Stubbers, I have no intention of hijacking the OP's thread going back and forth with you on this. If you wish, you can PM me and we can clarify our differences there. As for this thread, I've shot Several brands of high end guns. FX, Taipan, Edgun, AGT , Epic. If barrel length makes no difference. Why are their "sniper barrels" lenghts for FX at 700mm? My taipan long always outshot my Taipan shorty. My friend and I shoot the vulcan 3 both 500 and 700mm barrel versions and almost unilaterally the longer barrels were generally quieter and more accurate - FOR ME!
Now, can a better shooter with a shorter barrel gun out shoot me when I'm using a longer barrel version? OF COURSE!
Now, If you put the same shooter, with proper tuned guns of different barrel lengths, and they gave honest effort, I seriously doubt more accuracy will be attained towards the shorter 350-500mm barrels.

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Too many variables apply to simply generalize, mislead, and misinform with the statement "longer barrels are more accurate than shorter..."

@Scotchmo gave a great, reasonable explanation, however still left out a lot because its too generalized and open ended. The fact is, no, longer barrels are not by any rule of thumb more accurate than shorter barrels, however they can be, just as shorter barrels can a be more accurate than longer barrels, entirely contextual.

-Matt

dens228 said:

I've been playing around with my Krait Standard just for fun. I've generally shot pellets at around 900 fps give or take.
My Krait reg is jammed and came that way so it's pretty much un-adjustable while I await a replacement reg.
Trying to get optimum tuning is difficult to match my expectations since I'm limited to just adjusting the hammer spring and pellet weights.
With 15 gr pellets it's way too fast until I get the hammer so low it's inconsistent.
18 are a bit closer but still flying.
So today I remembered I had some 26 grain JSB's and gave them a go. At 35 yards they are nice and tight and FPS is very consistent. They are also shooting at around 805 fps.

I know that shorter barrels need more pressure to get to speed, but I'm now wondering if shorter barrels may perform better in general at a slower speed to allow the pellet to be more stabilized? IE a longer barrel at more pressure allows more spin/stabilizing of the pellet before it leaves the barrel? Therefore a lower speed keeps the pellet in the barrel a bit longer without needing to stabilize as much forward velocity?

I could be way off or over complicating this as I'm no expert on ballistics.

I was just surprised at how well these performed at over 100 fps slower speed while actually increasing fpe.........

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I have re read your post and got off on a tangent. Upon re reading the thread I'd take stubbers up on their offer. Based on what the krait is doing, his idea may be the key.