f-class 308 where is it going

[coyote]

There seems to be a number of shooters building 308's with faster twists to accommodate the heavies 200+ grainers.
Originally I was going to go with a 12 twist now I'm wondering , if I want to be competitive maybe an 11 twist might be a better choice with the extra ballistic advantage.

We all know there is a limit to how much powder you can stuff in the 308 case and honestly I would much rather be shooting 155's but the trend seems to be changing.

What are your thoughts on this where will it end or will it.

 

[lejarretnoir]

It's all heading towards the 200grs and up these days. If I were building a new one I'd get an 8 or 9" twist so as to give me plenty of room for 230+ grs bullets to try.
I see most are settling on 200 to 215grs, so a 10" twist would be adequate for those.

 

[ARH77]

What kind of speeds are they seeing with 200 or 215 gr projectiles? Are they using extra long barrels to get the speed back up? Or is Moly coating with those projectiles the trick to get them to work?

 

[308BAR]

11t will be able to stabilize a 210 maybe even heavier.

 

[twosmokinspades]

I have a 1-10 and I can shoot 200. Terry Perkins shoots 155 in his rifle, and is way better than I am.

 

[lejarretnoir]

What kind of speeds are they seeing with 200 or 215 gr projectiles? Are they using extra long barrels to get the speed back up? Or is Moly coating with those projectiles the trick to get them to work?

34" barrels.
Actually it's not new. Match Rifle shooters in the UK have been doing it for a long time.

 

[scout]

There seems to be a number of shooters building 308's with faster twists to accommodate the heavies 200+ grainers.
Originally I was going to go with a 12 twist now I'm wondering , if I want to be competitive maybe an 11 twist might be a better choice with the extra ballistic advantage.

We all know there is a limit to how much powder you can stuff in the 308 case and honestly I would much rather be shooting 155's but the trend seems to be changing.

What are your thoughts on this where will it end or will it.

The Miller Stability Formula (see Bryan Litz' books) would indicate that 1x12 is good for mid-weights (155-200 gr) at all competition altitudes and you'll need to go to 1x11 for the heavies (1x10 at sea level).

I've shot 154-210 gr in a 26.5" barrel with 11.25 twist, from sea level to 6800' ASL - my home range is 4800' ASL and why I always talk about altitude when discussing barrel twists and bullet weights (it's important). The 185 Berger LRBT has been my preferred bullet at all distances and altitudes, and I'll experiment with 210s again this year, but keep with the 185s for most of the shooting - I get good competition results with it. The trouble with the heavies gets to be with the recoil - it's still manageable with more torque and jump, but any error in your position is magnified and you might get some fliers. Some shooters are working up new throat configurations to make the heavies work, which means it becomes dedicated to heavies only. Long range is only part of the game - the mid-range also has to be considered for most Canadian shoots, and heavies don't have much advantage inside of 600m.

My thought is for anyone starting out, especially on the East Coast, start with a 1x12 and a mid-weight bullet. By the time you burn it out, you'll have a good idea what to go with next. I believe more people will lose points with the heavies than those that will gain points. There's a learning curve involved.

 

[FTRRookie]

You name it guys are trying it, from 34" barrels, moly, small primer brass and in Canada guys are running bullets up to to 215 at speeds approaching 2700. The guys doing this kinda stuff are putting in a bunch of work testing all sorts of combinations and have reamers designed specifically to accomplish this. If you just want to go out and have fun stick with the 155s, and your 12 twist; imagine the sense of satisfaction when you beat guys shooting the heavies

Speaking for myself I run a 10 twist and shoot 200s at about 2550, which is one of the accuracy nodes for that bullet. It's stout enough to stay over mach 1.2 at 900m, but it's also fairly easy on the brass.

Cheers,

Scott

 

[scout]

You name it guys are trying it, from 34" barrels, moly, small primer brass and in Canada guys are running bullets up to to 215 at speeds approaching 2700. The guys doing this kinda stuff are putting in a bunch of work testing all sorts of combinations and have reamers designed specifically to accomplish this. If you just want to go out and have fun stick with the 155s, and your 12 twist; imagine the sense of satisfaction when you beat guys shooting the heavies

Speaking for myself I run a 10 twist and shoot 200s at about 2550, which is one of the accuracy nodes for that bullet. It's stout enough to stay over mach 1.2 at 900m, but it's also fairly easy on the brass.

Cheers,

Scott

Good points Scott - I should also add that velocity is one concern ... and you need to be safe for all conditions. Gord O has a good point about having different loads for for different temperature conditions.

Going back to a basic IPSC learning - at the winning end, it's not what you do to win, it's what you do to lose that determines the winner. Know what you can do with what you have is more important that experimenting to win.

 

[prairieguy]

The latest development in pushing the F-TR envelope by US shooters at the Berger Sw Nationals is the use of Berger's 230 gr Hybrids out of a 1-9 twist barrel. Not sure about velocities but they are being pushed hard.

 

[Shibby!]

I'm doing 208's out a 24" 1-11.25 barrel with 2500 fps. I have pushed them to 2700. I settled on the slower node because of brass and barrel life. Also it seemed like a "relaxed" node with small grain deviation producing similar results.

 

[Mystic Precision]

If this is any indication, everything is being used but certainly the heavies are being favored.

AT the Worlds team match, many teams shot the 185gr BT Berger (guessing that was the most popular bullet overall). The GB team shot 155.5's. When asked why, the answer was simple - wind coaches have been driving this bullet/similar bullets for decades and know where it goes. GB team did very well.

I am personally shooting the 200gr H and have tested in 12 to 10 twist and the twist really didn't make much difference. I have tested the Berger 185gr to 210gr VLDs in 12 to 10 twist and all stabilised. Due to 1 spin calculation formula, the trend is to overspin a bullet. Another recent formula illustrates that we are using a spin rate of 1 per inch faster then needed.

As to bigger being better, to a degree, it is certainly better on ranges where there is a lot of bumpy air. The more turbulent the air, the "better" the heavies will APPEAR. This doesn't mean higher wind speeds. I mean that there are terrain features that can cause vertical events or local varying gusts to occur.

On a "flat" range even with high winds, lighter bullets can be driven with a high degree of success. A 155.5 was driving to 2nd place in Nokomis, SK a few years back for the Westerns. Winds were fast and crazy fast at times but linear. If you know where to hold, you hit center. Lots of left/right... not a lot of up/down.

Raton, NM where lots of terrain features - hilly and bumpy - with all manner of "jet stream" type winds racing this way and that, the bullet get hammered this way and that going to the target. Here heavy high BC bullets really shine.

Couple of years ago, the European championships was won using a 168gr Hybrid. Pretty sure at the Berger SW, FTR would have been taken with a 215 or 230. Pretty sure the Grand AGG Senior Record fell to a 185gt BT (Go Team Canada) only a few pts behind the overall score.

The middle ground is the 185 and 200gr Bergers at this time for the majority of shooters. 210gr VLDs are being used in several countries cause that is what they can find. The US is definitely the land of bigger better (apparently so is Australia)

The results will still favor the best shooters, wind readers with the best prepped gear. A big bullet can only maintain a better heading if it was launched in the right direction.

And with heavy bullets, there is a lot to be figured out wrt to bipods, recoil management, and proper shooting tech. A lot of stuff is not working out well....

No Free Lunch.
Jerry