Groovy twisty question

[Pommy Chris]

Hi everyone,
I shoot up in Ravenshoe, some here may know me and my missus Betta (the new NQRA secretary). I have shot standard for a while and have moved over to FTR, I won FTR in our opm and to be honest I dont find it any more difficult than using a front stand apart making fast wind adjustments. I have ordered a couple of 1 in 10 barrels, but I am wondering if a 1 in 11 might be worth getting too, can you over spin a projectile? With frt I see myself shooting from 155- 185 as in the shorts I have had good success with the 155 hybrids and if I go much over 185 I cant shoot 155 in the same barrel so I cant see myself chambering for much more than the 185 hybrid. My shooting is really coming together in the last 18 months and I want to get the right barrels, I have a Barnard and a Competition Nightforce and my current barrel is an amazing 1 in 12 Border which I will be taking off and saving for big comps as it really really shoots.
Any input is appreciated and hi to everyone
Chris
Almost forget what groove do you guys recommend, 4 groove or 5R?

[Pommy Chris]

Anyone??
Chris

[shooter mcreid]

I think the problem with over spinning is any misalignment between the projectiles centre of gravity any physical centre axis will cause dispersion (group grows). A faster spin will cause more dispersion.
If you use quality projectiles (and a good batch) the effects of over spinning will be neglidgable. If I was you I would get a twist that gives a miller stability of 1.4 for the 185s which should be 1 in 11. Then I would trial this barrel with the 155s which should not be a problem as they come in at about 1.68 (not really over spun). Your 1 in 10 barrel will come in at 2.04, probably still fine.
So I guess in summery both twists will probably work just fine with good projectiles.
As for grooves someone once told me less grooves are easier to clean but wear quicker, not 100% sure though! maybe someone could comment on this.

[Josh Cox]

Well pommy Chris, you could stop being a blouse and shoot TR .

I do not claim to be an expert, although I do have an opinion.

This whole under spin, over spinning etc etc is, IMHO is a load of fairy dust. It either groups or doesn't.

In the shooting sport there are lots of conventions, i.e. shooter XYZ shoots better than me and he uses a 10 twist, well if I use a ten twist barrel, he wont beat me anymore,,,,,,,,,,,,,,,,, usually doesn't work.

The "conventional think " does not always agree with the physics, try it and see if it works, its only money .

Berger give a suggested spin rate for a projectile as " best performance with a XX twist rate or faster", so there it is, "or faster"

Give the 10 a run, I reckon it will work fine.

The plethora of formulas for spins rates etc etc, Greenhills et al are generally "best guess" or in some cases based on hundred year old science and projectiles.

Try this: http://www.bergerbullets.com/twist-rate-calculator/

If that doesn't work for you , try this : http://metro.co.uk/2014/02/18/video-fun-loving-goats-love-life-bouncing-on-metal-sheet-4308437/

[chrisw91]

I run both 155 fullbore's and 185 juggernaughts in a 12 twist. I dont see a need to to go any faster as said by shooter mcreid. The groove configuration is personal preference i'm trying 3 groover's you will never go wrong with a 4 groove kreiger or another border.

[shooter mcreid]

Chris, I didn't say he needed to. He has already ordered some 1 in 10s and was thinking about a 1 in 11. I was simply saying his options would work fine. I'm not surprised the jugganaughts work in your 1 in 12 as that is what burger recommends for them.

[plumbs7]

Hi mate , I once owned a Savage hspfcp 1:10 and shot 155 really well out to 900 and 168's . Didn't try anything heavier .
Also have a three groove Lilya about 800 rounds on it . Still shooting fine . My 26 " has over a thousand and still going well. Just keep the bronze brush well away from them .

(Sorry to my fellow shooters for posting too much of late! )
GS.

[Pommy Chris]

Well pommy Chris, you could stop being a blouse and shoot TR .

I do not claim to be an expert, although I do have an opinion.

This whole under spin, over spinning etc etc is, IMHO is a load of fairy dust. It either groups or doesn't.

In the shooting sport there are lots of conventions, i.e. shooter XYZ shoots better than me and he uses a 10 twist, well if I use a ten twist barrel, he wont beat me anymore,,,,,,,,,,,,,,,,, usually doesn't work.

The "conventional think " does not always agree with the physics, try it and see if it works, its only money .

Berger give a suggested spin rate for a projectile as " best performance with a XX twist rate or faster", so there it is, "or faster"

Give the 10 a run, I reckon it will work fine.

The plethora of formulas for spins rates etc etc, Greenhills et al are generally "best guess" or in some cases based on hundred year old science and projectiles.

Try this: http://www.bergerbullets.com/twist-rate-calculator/

If that doesn't work for you , try this : http://metro.co.uk/2014/02/18/video-fun-loving-goats-love-life-bouncing-on-metal-sheet-4308437/

I could try TR, but I would not want to show you up . On a side note when the new barrels are fitted Betta wants to come down to Cairns and have a play at the long distance, it will be a good test. Also thanks for the scale link it is in the post, scary email title though
I emailed Tripple J and it seems that Border in the 1 in 11 wont be available for quite a while and the 1 in 11 Krieger will be 7 months so I will have to try the 1 in 10 for now. Any other thoughts on grooves?

[Pommy Chris]

Cool metal sheet link
Chris

[RDavies]

I am no guru on twists or 308s but don't think you will have too many problems accuracy wise by using a 10" twist with 155s and many people have done well with this combination. Due to the limited speed of 308s, you wont be having problems with bullets blowing apart from excessive rotational speeds.
With the good quality bullet jackets, the likely reduction in accuracy with the faster twist will likely be only marginal, maybe not noticeable, as will be the reduced velocity or increased pressure. (but still theoretically likely)

If it was myself though and I was going to get another barrel anyway, I would prefer to have a slower twist, around 12" for the 155s for the following reasons.
Slower twist will cause slightly less rifle torque, causing your bipod to torque less if it is the type with pivoting arms.
Slower twist will likely copper foul slightly less
Most of your shooting in FNQ will either be in relatively warm weather or at slight altitude (less dense air) so it is likely that you can get away with slightly slower twists than the rest of us.
You are lucky in that in your local area you have some people who have much more of an idea than I do about twists etc so they will be good to have a chat to.

[Josh Cox]

I could try TR, but I would not want to show you up

Geez, talk about setting the bar low.......................

[Pommy Chris]

I could try TR, but I would not want to show you up

Geez, talk about setting the bar low.......................

If only Josh,
If I ever shoot TR I will be asking you for a lesson.
Off topic but I cleaned my OPM cases today and it had been bugging my about my low 4 that cost my the first day aggregate. Yes I won FTR grand agg but I hate unexplained highs and lows. I had one case with a concave inward primer ie low pressure in other words low load so it seemed that my Charge master threw a very very low load indeed so I am very happy that scale you recommended is on its way.
Cheers
Chris

[Pommy Chris]

I am no guru on twists or 308s but don't think you will have too many problems accuracy wise by using a 10" twist with 155s and many people have done well with this combination. Due to the limited speed of 308s, you wont be having problems with bullets blowing apart from excessive rotational speeds.
With the good quality bullet jackets, the likely reduction in accuracy with the faster twist will likely be only marginal, maybe not noticeable, as will be the reduced velocity or increased pressure. (but still theoretically likely)

If it was myself though and I was going to get another barrel anyway, I would prefer to have a slower twist, around 12" for the 155s for the following reasons.
Slower twist will cause slightly less rifle torque, causing your bipod to torque less if it is the type with pivoting arms.
Slower twist will likely copper foul slightly less
Most of your shooting in FNQ will either be in relatively warm weather or at slight altitude (less dense air) so it is likely that you can get away with slightly slower twists than the rest of us.
You are lucky in that in your local area you have some people who have much more of an idea than I do about twists etc so they will be good to have a chat to.

I sort of agree and I have been looking for a barrel with maybe a 1 in 11 as a half way house but the Border are our of stock and the Krieger will be 7 months which is too long. I am half thinking about getting my Archer 12.5 twist rechambered for the Barnard as a club barrel but I would prefere to sell the Omarks with the barrels.
Chris

[Frank Green]

To fast a twist? I tell everyone this......I error on the faster side of the twist than vs. running the twist on the ragged edge of being stable. Being on the ragged edge of being stable if you shoot at different elevations, temperatures etc...you can run into stability problems.

To fast a twist can give you accuracy problems but this is usually linked to to much run out in your bullet/loaded ammo or shooting a poor quality bullet. A poor quality bullet or ammo with excessive run out the faster twist will amplify the run out. This is caused by the bullet not starting more in a true center line of the bore of the barrel. The more run out and when the bullet makes the jump to the rifling the more of a premature the wobble is going to be from the faster twist.

If your shooting good quality bullets/ammo with little run out I don't see a faster twist being a negative thing then.

You have to start the twist rate needed based on the longest/heaviest bullet you intend to shoot.

The number of grooves in my opinion has no bearing on accuracy or barrel life. I do believe though the 5R style rifling does help fight bullet failure. The lands don't directly oppose one another and in conjunction with the angles on the sides of the lands the 5R will distort/upset the bullet jacket less.

Later, Frank
Bartlein Barrels

[Pommy Chris]

To fast a twist? I tell everyone this......I error on the faster side of the twist than vs. running the twist on the ragged edge of being stable. Being on the ragged edge of being stable if you shoot at different elevations, temperatures etc...you can run into stability problems.

To fast a twist can give you accuracy problems but this is usually linked to to much run out in your bullet/loaded ammo or shooting a poor quality bullet. A poor quality bullet or ammo with excessive run out the faster twist will amplify the run out. This is caused by the bullet not starting more in a true center line of the bore of the barrel. The more run out and when the bullet makes the jump to the rifling the more of a premature the wobble is going to be from the faster twist.

If your shooting good quality bullets/ammo with little run out I don't see a faster twist being a negative thing then.

You have to start the twist rate needed based on the longest/heaviest bullet you intend to shoot.

The number of grooves in my opinion has no bearing on accuracy or barrel life. I do believe though the 5R style rifling does help fight bullet failure. The lands don't directly oppose one another and in conjunction with the angles on the sides of the lands the 5R will distort/upset the bullet jacket less.

Later, Frank
Bartlein Barrels

Thanks Frank,
So for a rifle that I want to shoot 185 hybrids in and maybe 155 hybrids what twist would you choose?
I ordered the 4 groove barrels for now as it is all I can get but I do want to get another barrel.
Cheers
Chris