optimum barrel length for

[rsc1960]

 

2 rifles in question.

 

I have 2 rifles being sent to my rfd on approval they are mentioned below, I have been shooting for a while but not out past 200 250 yards (not on live quarry) so may i ask for your thoughts.

 

1, a Tikka t3 in 243 for deer and medium range shooting, this has a 1/10 twist

 

2, a Tikka 6mmbr for deer and for longer range shooting than the 243 above.this has a 1/9 twist

 

I am looking to run bullets from 86 to 105 gr if the above rifles will hold them steady.

 

thank you

 

RSC

[az1]

I have a t3 hunter in 243 but think it might be 1 in 12 ? But I use 87gr vmax with 37.3gr of n140 COL 2.685

It a little warm but I know a few using it and got second opinion from more experienced shooters

I have used it up to 1040 yard with very good results

[Swamp Donkey]

I have a t3 hunter in 243 but think it might be 1 in 12 ? But I use 87gr vmax with 37.3gr of n140 COL 2.685

It a little warm but I know a few using it and got second opinion from more experienced shooters

I have used it up to 1040 yard with very good results

1 in 10" is your twist

[Laurie]

It's not bullet weight per se that determines the twist rates needed to stabilise bullets properly, but their length in relation to calibre. The more a bullet measures in calibres, the faster it must be rotated. In fact, a short heavy bullet (like round-nose flat base types) manages with a slower twist rate than a same weight or even lighter - but longer - version. We tend to talk weights as a shorthand, as the heavier a bullet is the longer it also usually is.

 

You'd be very lucky to get good and consistent results with long range bullets weighing 100gn and above in either twist rate, and really there's no chance with the 1 in 10 barrel. The optimum design for LR target type shooting currently on the market is the 87gn Berger Hunting VLD, and expanding deer bullet whose alternate function is target shooting in slower twist barrels. Unfortunately for most British target shooting 6mm shooters, its expanding status puts it out of bounds.

 

The recommended minimum SG (gyroscopic stability function) is 1.4, although in practice 1.3 usually works fine in most temperature and atmospheric conditions.

 

Here are approximate SG values for a selection of 6mm bullets in 10-inch / 9-inch twist rates. (Exact values depend on MVs and ambient / environmental conditions)

 

Berger

87gn Hunting VLD .......... 1.26 / 1.55

90gn BT Target ............... 1.38 / 1.71

95gn Target VLD ............. 1.06 / 1.31

100gn Target BT ............. 1.04 / 1.29

105gn Target BT ............. 1.07 / 1.32

105gn Target VLD ........... 1.00 / 1.24

 

 

Sierra

95gn MK ......................... 0.98 / 1.21

107gn MK ....................... 0.99 / 1.22

 

 

Nosler

90gn B. Tip ...................... 1.37 / 1.69

95gn Partition .................. 1.46 / 1.81

 

 

Hornady

87gn VMax ...................... 1.26 / 1.56

87gn HPBT ..................... 1.63 / 2.02

100gn BTSP ................... 1.33 / 1.64

105gn AMax .................... 0.95 / 1.17

 

Lapua

90gn Scenar ................... 1.12 / 1.38

105gn Scenar ................. 0.92 / 1.13

 

 

Plastic tip bullets will usually work with a slower twist than the maths suggest as the lightweight tip section expands the length more than it increases the need for a faster rotation. So the 87gn Hornady VMax will work well in a slower twist than the formula says and 1-10" is fine. Likewise, some HPBT Match designs, especially the lighter Lapuas have much longer jackets than their internal cores with a large airspace in the nose / tip section. They'll work too with a maybe 0.1 lower SG value than is normally desirable. Even so, this makes the 90gn Scenar marginal in a 1-10" twist barrel.

 

The other factor to bear in mind is factory barrel twist rate accuracy. if you buy a Krieger or Bartlein etc 1 in 9, that's the twist you get. Factory rifles' nominal rates are sometimes 'out' by a quarter inch or so, and this can make the difference at the margin, so a factory Remy shoots a bullet while a Winchester doesn't or vice versa even though they're both listed as having the same twist rate.

[Laurie]

It's not bullet weight per se that determines the twist rates needed to stabilise bullets properly, but the their length in relation to calibre. The more a bullet measures in calibres, the faster it must be rotated. In fact, a short heavy bullet (like round-nose flat base types) manages with a slower twist rate than a same weight or even lighter - but longer - version. We tend to talk weights as a shorthand, as the heavier a bullet is the longer it also usually is.

 

You'd be very lucky to get good and consistent results with long range bullets weighing 100gn and above in either twist rate, and really there's no chance with the 1 in 10 barrel. The optimum design for LR target type shooting currently on the market is the 87gn Berger Hunting VLD, and expanding deer bullet whose alternate function is target shooting in slower twist barrels. Unfortunately for most British target shooting 6mm shooters, its expanding status puts it out of bounds.

 

The recommended minimum SG (gyroscopic stability function) is 1.4, although in practice 1.3 usually works fine in most temperature and atmospheric conditions.

 

Here are approximate SG values for a selection of 6mm bullets in 10-inch / 9-inch twist rates. (Exact values depend on MVs and ambient / environmental conditions)

 

Berger

87gn Hunting VLD .......... 1.26 / 1.55

90gn BT Target ............... 1.38 / 1.71

95gn Target VLD ............. 1.06 / 1.31

100gn Target BT ............. 1.04 / 1.29

105gn Target BT ............. 1.07 / 1.32

105gn Target VLD ........... 1.00 / 1.24

 

 

Sierra

95gn MK ......................... 0.98 / 1.21

107gn MK ....................... 0.99 / 1.22

 

 

Nosler

90gn B. Tip ...................... 1.37 / 1.69

95gn Partition .................. 1.46 / 1.81

 

 

Hornady

87gn VMax ...................... 1.26 / 1.56

87gn HPBT ..................... 1.63 / 2.02

100gn BTSP ................... 1.33 / 1.64

105gn AMax .................... 0.95 / 1.17

 

Lapua

90gn Scenar ................... 1.12 / 1.38

105gn Scenar ................. 0.92 / 1.13

 

 

Plastic tip bullets will usually work with a slower twist than the maths suggest as the lightweight tip section expands the length more than it increases the need for a faster rotation. So the 87gn Hornady VMax will work well in a slower twist than the formula says and 1-10" is fine. Likewise, some HPBT Match designs, especially the lighter Lapuas have much longer jackets than their internal cores with a large airspace in the nose / tip section. They'll work too with a maybe 0.1 lower SG value than is normally desirable. Even so, this makes the 90gn Scenar marginal in a 1-10" twist barrel.

 

The other factor to bear in mind is factory barrel twist rate accuracy. if you buy a Krieger or Bartlein etc 1 in 9, that's the twist you get. Factory rifles' nominal rates are sometimes 'out' by a quarter inch or so, and this can make the difference at the margin, so a factory Remy shoots a bullet while a Winchester doesn't or vice versa even though they're both listed as having the same twist rate.