This Rifle won't Shoot! Diagnosing the issue(s).

[boltfluter]

I tend to agree, but my first concern with this barrel, now, is to actually get it fully clean. Then I will have a baseline, for knowing that the fouling is not the main source of the erratic shooting patterns.

I'm in Bend, OR and plan to pick up some Nosler 20 grain Varmageddon FBHP bullets tomorrow. I'll give those a try. I'm hoping the short lighter bullets will make an improvement over the 20 Vmax, and other 25 grain bullets I've tested. Hopefully, those will be a good fit for the slow twist rate.

BTW, what are your "other methods" you might recommend for a cleaning regimen? I've got some I use, but want to hear yours.

Hopefully the 20 grain bullets show some promise. The .17 calibers can really test your patience, to say the least! My .17 Remington really came alive with the 30 grain Berger. It had 9 twist if memory serves. All other brands of bullets looked like a 12 gauge, group wise. A great test for your rifle would be to beg, borrow, or steal some Berger 20 gr FB bullets. Maybe someone has a few they can loan you for testing. Might be a real eye opener. Good luck and I commend you for your patience..17 cal can really test your patience. I finally pulled my .17 Rem. barrel to keep my sanity. Well, what was left of it anyways! Lol. If I had a need for something like this again in would be a .20 VT hands down. Good luck and keep us updated.
Paul

 

[ELR LVR]

I tend to agree, but my first concern with this barrel, now, is to actually get it fully clean. Then I will have a baseline, for knowing that the fouling is not the main source of the erratic shooting patterns.

I'm in Bend, OR and plan to pick up some Nosler 20 grain Varmageddon FBHP bullets tomorrow. I'll give those a try. I'm hoping the short lighter bullets will make an improvement over the 20 Vmax, and other 25 grain bullets I've tested. Hopefully, those will be a good fit for the slow twist rate.

BTW, what are your "other methods" you might recommend for a cleaning regimen? I've got some I use, but want to hear yours.

PM me your address and I'll send you a product I use

 

[AlNyhus]

-The Nosler 20 FBHP @ 3,600 from a true 10.5 twist barrel will net you a Stability factor of 1.303.
-With a 10 twist barrel, it would be 1.437.

-The shortest bullet you've tried is the Hornady 25 gr HP. Even that bullet nets a poor Stability factor of 1.2.


A Stability factor of 1.5 is considered the minimum. In real world testing, we've found that 1.3-ish to be a pretty hard bottom end. It's important to understand that there's no line in the sand where once the bullet crosses over that, it begins to 'tumble'. What actually happens is that as the stability number passes below where the bullet is truly stabilized, the bullets yaw increases...that's why you see bullet holes that aren't perfectly round or sometimes elongated.

It's also important to  understand that accuracy will be lost before you reach that point where you see a sideways hole in the target....the nose of a marginally stable bullet is just wandering around. Think of what happens with a kids top as it slows down...it's analogous to what happens with a maginally stable bullet.

It's not the weight, it's the LENGTH.

Why so many shooters refuse to accept, understand and grasp the proven Physics of this remains a mystery.

Looking forward to your results with the Nosler 20 FBHP. If your frustration gets to the point that you can't live with it, pack that gun up and send it to me in exchange for folding money. Feel free to PM me if you'd like.

Good shootin' -Al

 

[ELR LVR]

It's not the weight, it's the LENGTH.

Exactly, it is the length that we stabilize...
Good writeup man

 

[AlNyhus]

Exactly, it is the length that we stabilize...
Good writeup man

I was educated on the entire Stability, Drag/Twist, etc part of accuracy by Randy Robinett about 25 years ago. There are very few people that can both understand and articulate this subject better than Randy.

Whether people savvy this principle or not, it remains the underlying driver for all accuracy shooting.

Good shootin' -Al

 

[CharlieNC]

I was educated on the entire Stability, Drag/Twist, etc part of accuracy by Randy Robinett about 25 years ago. There are very few people that can both understand and articulate this subject better than Randy.

Whether people savvy this principle or not, it remains the underlying driver for all accuracy shooting.

Good shootin' -Al

Can you direct us to a resource fir this?

 

[J_idaho]

V-maxs like to be very close to lands producing groups like yours if seating isn’t perfect you get group variations. Try a different style of ogive. Berger makes one for a 10 twist.

 

[urbanrifleman]

Might explain why such a nice rifle was a great bargain.

 

[Coyotefurharvester]

If it is only stability issues, than you can rule out any bullet 0.567 and longer. Next common bullet length (.172) is 0.538. I don't have any of the 15.5 gr Hornady on hand to measure. Are those groups still being shot at 75 yards?

 

[farmerjohn]

Tag, I'm curious now... John
By the way only thing I might add is to move the target up to 40 or 50yds and try... when working on subsonic loads with a twist that's too slow I've seen one hole groups at 50 and tumbling at a 100... might tell you something..

 

[TheCZKid]

Couple questions:

(1) What bullet(s) existing, that can be purchased currently, has a shorter length and so on, would be the best to use in my 10.5 twist rifle? Since there seems to be knowledgeable folks out there that can look up the Stability Factor of bullet I have been using, and the one I plan on soon using? If you know what bullets are available, that reach or exceed the 1.5 stability factor, please share this information, I'm tired of trial and error, just let me know.

And, (2) how does the velocity of said bullets figure into the stability? Is a faster or slower speed produce better stability?

 

[Coyotefurharvester]

Speed will be your friend, all the 17's slow quickly, so long distances will show more bullet wobble(groups spreading). Interesting that the SD and group size seem to decrease as charge weights increase as 100 yards or less 30-40 fps usually don't show up on in vertical dispersion. Do you have any of the 15.5 Hornady on hand? How long are they?

 

[chop house]

And, (2) how does the velocity of said bullets figure into the stability? Is a faster or slower speed produce better stability?

faster gives marginally higher stability. but the heavy hitter in the equation is bullet length. also playing into it is atmospherics... less dense air giving marginally better stability

you can play around with the input parameters in https://bergerbullets.com/twist-rate-calculator/ and see what has the most effect

 

[TheCZKid]

Speed will be your friend, all the 17's slow quickly, so long distances will show more bullet wobble(groups spreading). Interesting that the SD and group size seem to decrease as charge weights increase as 100 yards or less 30-40 fps usually don't show up on in vertical dispersion. Do you have any of the 15.5 Hornady on hand? How long are they?

15.5 are .598", they have a plastic tip

I know normally speed = stability, but was curious as to an answer from those who are running the calculations on these bullets, and giving us the Stability Factor numbers

 

[chop house]

15.5 are .598", they have a plastic tip

there are some caveats to the miller stability equation when considering plastic tipped bullets. i don't recall the nuances, but of course the goal is still have ~1.5 at the target... which means bc comes into play (wanting to have reasonable retained velocity)

 

[Coyotefurharvester]

At 3600 ft, you should see some help in stability. Where I'm at 970 ft. My 10 twist 17's will not shoot a 25 vmax well (1-1.25" at 100 yards) and open up more at distance. But no issues even at 400 yards with 25 gr hp. Out of my 17 rems (roughly 4000 fps).

 

[TheCZKid]

Of the bullets I have on hand, here are the lengths:
Hornady 25 gr FB tipped Vmax - .669
Hornady 15.5 gr NTX BT Tipped - .598
Hornady 20 gr FB Tipped Vmax - .590
Hammet 25 gr BT HP - .580
Hornady 25 gr FB HP - .564
Berger 25 gr FB Varmint HP - .561

Nosler 20 gr FB HP - .495
Varmint Nightmare 20 gr FB HP - .486

Unfortunately, I started my testing with the Worst of the bunch, Hornady 25 Vmax, no wonder it shot like crap! Plus, I was using unfired newly formed cases, and the barrel was fouled... it's starting to make more sense now.

 

[dfrosch]

And, (2) how does the velocity of said bullets figure into the stability? Is a faster or slower speed produce better stability?

A higher velocity at the same twist rate will result in the bullet spinning at higher rpms. Higher rpms will produce better stability.

You can see this on your earlier targets. The heavier powder charges produced rounder holes.

Please, try pulling the tips from a few of the 20 grain VMax. You could keep the same powder charge.

 

[Coyotefurharvester]

Give the Nosler 20 fbhp a try, keep the load about 90% fill, see if the sd improves. Check the neck dia before and after bullet seating. Keep the bullet off the lands 0.015+.

 

[ELR LVR]

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Of the bullets I have on hand, here are the lengths:
Hornady 25 gr FB tipped Vmax - .669
Hornady 15.5 gr NTX BT Tipped - .598
Hornady 20 gr FB Tipped Vmax - .590
Hammet 25 gr BT HP - .580
Hornady 25 gr FB HP - .564
Berger 25 gr FB Varmint HP - .561

Nosler 20 gr FB HP - .495
Varmint Nightmare 20 gr FB HP - .486

Unfortunately, I started my testing with the Worst of the bunch, Hornady 25 Vmax, no wonder it shot like crap! Plus, I was using unfired newly formed cases, and the barrel was fouled... it's starting to make more sense now.

here is a link to a barrel twist calculator in relation to bullet length
You can input your numbers and play around with what you have to find what should work
If you have Solid Copper take note of changing the Specific Gravity to what is listed

Barrel Twist Calculator

a free calculator, which works in standard browsers, to estimate barrel twist rate

kwk.us