Custom contour from 1.250 cylinder blank

[Ilya S.]

Hello.
May be it is a common gunsmithing question about building f-class rifle, but I need some help to clear this. I have read gunsmithing books from Gordy Gritters & Fred Zeglin, John L. Hinnant, Lilja and Bartlein articles and have no answer.
I have a 31" 1,250 cylinder blank and want make a barrel that weights 6,5-6,6 lb. That numbers are a barrel clearance given by weighing other parts of my FTR rig and I wont change them.
The typical 30" heavy varmint contour, chambered and ready to screw in, will be around 7,37-7,4 lb - too heavy.
30" heavy palma with its 6,1-6,2 lb is too light in my opinion. I think matching 18.18 lb. maximum will help to reduce recoil of 200+ gr bullets in .308. So, my idea is making a "custom" heavy palma contour, increasing some diameters and lengths:

mod. 1:
A = 1,250
B = 1,000
C = 1,000
D = 5,000
E = 7,500
F = 30
__________
mod. 2:
A = 1,250
B = 1,000
C = 0,900
D = 7,000
E = 9,500
F = 30

So, as you can see, in mod1 the idea is increasing thenon length and muzzle diameter. In mod2 it only thenon length.
The main question is will the changing of default(by barrel makers) heavy palma contour dimensions negatively affect on accuracy ? Which mod is better ? And as you understand, I don't have any more blanks to make a comparison

Best,
Ilya S.

 

[DaveTooley]

You won't be able to shoot the difference between the two barrels.

 

[Doug Beach]

I don’t think you’re going to tell the difference in recoil due to a 1.4% weight difference. Back of napkin math says something like 10.1 vs 10.2 ft/lbs of recoil.

 

[marazzi59]

My thoughts are if you turn a barrel on a lathe and take to heavy of a cut you can mess up accuracy potential. Very light cuts and very slow infeed.

 

[Ilya S.]

My thoughts are if you turn a barrel on a lathe and take to heavy of a cut you can mess up accuracy potential. Very light cuts and very slow infeed.

Thank you. I have read old gunsmiting book about barrel blank turning job, author says initial turning cuts off must be without springing.

 

[Sniper338]

Find a speedy contour barrel. See how that matches up with what you want.

 

[Ilya S.]

Find a speedy contour barrel. See how that matches up with what you want.

If I understand correctly, it is heavy varmint with 1,000 muzzle diameter ? Too heavy. But I see the same idea to icreasing muzzle diameter. In my mod.1 will be a straight 1.000 cylinder part of barrel with 22,5" length. Is it bad for harmonics and accuracy ? I dont know.

 

[Dusty Stevens]

Get a lv and cut it to length to make weight. Start on the big end. No need to reinvent the wheel your gunsmith should do this a lot.

 

[Edd]

If I understand correctly, it is heavy varmint with 1,000 muzzle diameter ? Too heavy. But I see the same idea to icreasing muzzle diameter. In my mod.1 will be a straight 1.000 cylinder part of barrel with 22,5" length. Is it bad for harmonics and accuracy ? I dont know.

Is there a reason you are wanting a Palma style contour instead of a straight taper target style?

 

[Liven The Dream]

HV Palma Finish at 30” shank end 5” straight to Taper . More room to work with and to set back if you want ?

 

[Ilya S.]

Is there a reason you are wanting a Palma style contour instead of a straight taper target style?

"straight taper target style" like heavy varmint - too heavy, "light varmint" - interesting idea.

HV Palma Finish at 30” shank end 5” straight to Taper . More room to work with and to set back if you want ?

No, its about weight and stiffness.

 

[Liven The Dream]

"straight taper target style" like heavy varmint - too heavy, "light varmint" - interesting idea.

No, its about weight and stiffness.

Guys Win Palma Matches with Med. Palma Contour all around the World ?
HV Palma will be so stiff you will be jealous .....

 

[Will Henry]

Your "mod 1" would be fine and would give you a barrel which is heavy toward the muzzle and would, theoretically, vibrate at a slower frequency (we are pretending we could tell the difference here).
"Mod 2" would, of course, move the balance point to the rear and would produce a barrel which, theoretically, vibrates at a higher frequency.
In my opinion (which carries less weight than either barrel), the difference in balance matters only when the rifle is held in the hands. For an "F" or FTR rifle, it means much less as long as the rifle isn't balanced ahead of the bipod.
When shooting from unsupported positions or even prone with a sling, the amount of weight on your front hand can affect your hold a lot. From a rest or a bipod, not so much.
Mod 1 would, in theory, produce a barrel which is less sensitive but I suspect the difference might be more in the mind of the shooter than anything. WH