The UK's Finest Independent Forum for Shooters and Gun Owners. Est 2010.

Hi all
I have a .308 target rifle and shoot 155gr factory (supplied) match rounds,i would l like to have a go at F/TR shooting.
The rifle has a Barnard P action,30" barrel and a 1/13 twist.The velocity i get is approx 2900 f/ps.
The distance i currently shoot is out to 900 yds with these rounds but would like to shoot out to 1100meters.
Would 175gr TMK bullets be a better choice for longer distances and will they stabilise in the barrel i have??
Any recommendations would be appreciated.
Andrew

The issue you have is the twist rate.

If you want to be competitive in F/TR out to 1000 yds and beyond, you need to optimise everything and unless you're confident at wind-reading, you'll want to use a heavier bullet.

Even the 175 is going to have marginal stability out of a 1 in 13 barrel, but I'd always suggest giving something a try before dismissing it just because someone like me has said it won't work very well

If you want to get serious, I'd think about a re-barrel to something like a 32" 1:10, throated to take the heavier bullets (ie 185-215 Bergers).

The issue around stability and twist rate is the length of the bullet rather than its weight.

I'll see if I can dig out my calculator ...

OK, Bryan Litz has these figures for the 175gn SMK stability Factor in a 1:13 twist barrel:

Worst Case: 1.26 (sea level, 0% humidity, 0 degF, 2600fps)
Nominal: 1.46 (sea level, 50% humidity, 59 degF, 2800fps)
Best Case: 1.67 (1000ft, 100% humidity, 100 degF, 3000fps)

Anything below 1.4 is marginal so I think you'd need to try it.

I don't have data on the TMK but will keep looking.

A heavier bullet invariably means a longer bullet.

Here's a calculator: http://www.bergerbullets.com/twist-rate-calculator/

Thanks for the link JSC. Here are the results for the TMK and they don't look promising. Although greater than 1.0 is in theory stable there's not enough margin and 1.4 is a better goal.

JSC wrote:If you want to get serious, I'd think about a re-barrel to something like a 32" 1:10, throated to take the heavier bullets (ie 185-215 Bergers).

^^ This is good advice if you can afford it.

My .308 has a 26" Lothar Walther barrel with 1:11 twist and gets excellent results at 1,000 yards with 185gn Berger Juggernauts.

@nd wrote:Hi all
I have a .308 target rifle and shoot 155gr factory (supplied) match rounds,i would l like to have a go at F/TR shooting.
The rifle has a Barnard P action,30" barrel and a 1/13 twist.The velocity i get is approx 2900 f/ps.
The distance i currently shoot is out to 900 yds with these rounds but would like to shoot out to 1100meters.
Would 175gr TMK bullets be a better choice for longer distances and will they stabilise in the barrel i have??
Any recommendations would be appreciated.
Andrew

You can stick with the 155s if they work in your rifle. 2900+ fps is OK.

Heavy bullets (185) could be marginal in a 1 in 13. It's worth noting that the GB FTR Team will be using 155s at the World Championships in Canada this year.

The Gun Pimp wrote:It's worth noting that the GB FTR Team will be using 155s at the World Championships in Canada this year.

Interesting. That's for the team matches only or individual matches too?

What's the story behind that decision and was it a unanimous one?

JSC wrote:

The Gun Pimp wrote:It's worth noting that the GB FTR Team will be using 155s at the World Championships in Canada this year.

Interesting. That's for the team matches only or individual matches too?

What's the story behind that decision and was it a unanimous one?

I'm not on the Team so I've no further information. But, the 155.5 Bergers have always been a superb bullet with many long range victories on both sides of the pond. Yes, there is a swing towards the 'heavies' but maybe the 155s are a bit more forgiving.

Thanks For the replies all.I will try out the 155gr bullets that i have and see how i get on before any major outlays.
Andrew