Best powder for & expected velocity for the 208gr Amax in 32-34" barrel 308?

[Fordnutter]

Hi Guys,
A mate is looking at putting together a 308 for FTR class & is looking at building it to suit the 208gr Amax. The barrel would likely be a 32 or 34" trueflite 1-11" twist. What sort of speeds are people getting from this barrel length & projectile combo & what are the best powder choices for maximum velocity while still retaining best accurracy at the 1000yd mark.
Any information, links or advice would be greatly appreciated.

 

[navyrad8r]

ok Ford...
lot of folks have read it but nobody commented.... i shoot 190's (SMK and Bergervld) out of an M1 Garand for the 1K. 44gr~~ of IMR4320 LC brass fully processed (all the tricks), wolf primers .007 in the lands. i would think somewhere in the neighborhood would be a good place to start with your amax efforts. 2700-2750 ish for speeds. i am sure more bolt gunners will chime in shortly. send pm to German Salazar and or Brian Litz and ask for their opinion. Both shoot have hsot the palma exensively. At the very least maybe this will help out by triggering some responses. good luck to you and please work oyur load up safely.
cheers,
Doc

 

[usmc1986]

Ford,

There are guys elsewhere using RL17 with 20-24" barrels getting 2700 FPS with 1:10 through 1:12 twists. I'd stick closer to a 1:11 or 1:10 twist.

 

[bulldog284]

2700 fps with a 24 inch tube,,i find that hard to belive what loads are they using?

 

[ZechG]

I use 44 grs of Varget and CCI large rifle primers with this load and it shoots about 2 1/2" at 600yds if i do my part. .010 into the lands. I can send you a pic of the groups if you like. They shoot around 3/4" at 300yds. Velocity according to my chrony is almost 2550. 24" barrel.. I use a .331 bushing.

 

[DukeDuke]

N550 or RL-17

 

[allen529]

There is a post on Snipershide detailing this very bullet and Re17 and the post about 2700 is correct. They are shooting the bullets moly'd behind a max charge of 51 grains. They are using Winchester brass and drop tubes to get all the powder into the case. Of course they are seating the bullets long too.

Most of them are starting around 43 grains and working up slowly. Almost to a man they see a spike in velocity around the 49 to 51 grain area.

Allen

 

[Laurie]

N550 + Re17, maybe IMR-4007SSC too. The barrel must be chambered with a lot of freebore to suit the bullet, so it becomes a long/heavy bullet only set-up.

If you want a more flexible rig that lets you use 155s to 210s, you need less freebore and will lose 50-100 fps MV.

I would caution you to think hard before committing yourself here, irrespective of how good a 208/210gn VLD at 2,700 fps looks on paper. A 34" barrel with max (probably over max) pressure loads can create its own problems with harmonics making it very fussy. You haven't said what action you plan to use, but a free-floating barrel that length puts a lot of strain on the action and its tenon threads. The extra 4" over the 30s that nearly everybody uses in F/TR adds weight and it's frightening how quickly you hit that 8.25 Kg overall weight limit including bi-pod. If you go for these lengths, you'll likely find you have make significant weight savings in the stock, scope or bi-pod - or all three. (Don't consider shooting 210s at 2,700 fps off a Harris type bi-pod unless you're a heavily built ex-Marine used to shooting .338 LM rifles or similar and enjoy the experience!)


British and Brtiish Commonwealth Match Rifle shooters are getting higher MVs with 190-220gn bullets from their 30" barrels than nearly all F/TR competitors do even with 32" or longer tubes. Also MR shooters have found the 1-11" twist is ideal for 210s. 1-10" loses you velocity due to the energy loss in spinning the bullet up faster.

Finally, after a short-term flirtation in UK F/TR with 210s, there has been a big move back to 155s. The norm now is 1-11" twist, a compromise chamber, and two ammunition lots for big matches. 155s are invariably shot in steady winds, 210s in 'difficult' conditions. The heavy bullet generate a LOT of recoil and torque in an 8.25 Kg rig at around 2,600-2,650 fps MVs even on a wide-set big foot bi-pod making it much more difficult to handle the rifle consistently on the bi-pod / rear bag. Whether it is due to this or some other factor, almost all 210 converts have complained of dropping points thanks to 'increased elevation' at long ranges. In rough conditions, the improved wind-bucking abilities are reckoned to outweigh this disadvantage hence keeping it as an option.

Personally, I like the 185gn Berger BT Long-Range at around 2,800 fps from a 30" heavy-contour Broughton and haven't found anything that performs better for me to date

Laurie,
York, England

 

[Rustystud]

N-550 gave me the best velocity with Berger 210s, but it also gave me pressure issues over 80 degrees. A 32" Broughton 1:10 gave me 2700fps but fried the brass. Slowing them down to 2600-2650 kept them supersonic at 1000 yards and was easier on the brass. These rounds have plenty of recoil compaired to lighter bullets. I think the 185 berger is a better choice for the 308.
Nat Lambeth

 

[Heavies]

What twist would be optimal for 185 Berger BT LR 11, 12, 13?

 

[Laurie]

N-550 gave me the best velocity with Berger 210s, but it also gave me pressure issues over 80 degrees. A 32" Broughton 1:10 gave me 2700fps but fried the brass. Slowing them down to 2600-2650 kept them supersonic at 1000 yards and was easier on the brass. These rounds have plenty of recoil compaired to lighter bullets. I think the 185 berger is a better choice for the 308.
Nat Lambeth

+ 1 on that Nathaniel. I'm currently doing load development with 208s/210s and N550 (other powders later) for eventual publication in the UK online magazine www.targetshooter.co.uk, and even in our cool spring temperatures am finding this a distinctly finicky combination in standard (large primer) Lapua brass in my compromise-throated chamber.

0.2gn charge weight steps at the top end of the charge range didn't stop me blowing a primer last week in only 12 degrees C (54 F) temperatures with no significant warning signs from the previous batch. Trying these loads off the bench in full BR rest/bag type shooting is a bitch too, recoil wise - not a pleasant experience at all. Perhaps thanks to this factor, I'm finding it hard to get 5-shot 100yd groups below the half-inch mark from a rifle that regularly shoots in the threes and fours with lighter bullets.

The GB F-Class F/TR guys using heavy loads with these bullets (nearly all using the Berger 210gn VLD) mostly use small primer Lapua Palma brass. MVs in the 2,650 to just over 2,700 fps range are being reported without pressure signs using case-filling loads of N550, but when I've tried 185-210 bullets over N550 in these cases, I've found that MVs are well down on what others are claiming. After a certain weight is reached in each combination tried to date, I've found that MVs (and pressures too?) plateau and won't get up to those available from large primer brass. I suspect that's why many of my countrymen are getting away with the loads they quote, but even then, I wonder what's going to happen if we have a warm summer over here by our standards. With four miserable cool wet summers in succession, many national level F/TR competitors here have likely never shot their rifles and current loads in really hot conditions, say 85 degrees F and above plus the heating effect of ammunition boxes sitting in full sun on the firing point. (Temperature effects are so little known / regarded here that hardly anybody keeps their ammunition in the shade, never mind using cool boxes and similar ploys.)

 

[Laurie]

What twist would be optimal for 185 Berger BT LR 11, 12, 13?

11 or 12 - take your pick. 13 works but is marginal for this bullet. 12 is probably optimal, but 11 likely works just as well in practice and gives you the option of trying the 208gn A-Max and 210s from Sierra and Berger.

 

[Heavies]

What twist would be optimal for 185 Berger BT LR 11, 12, 13?

11 or 12 - take your pick. 13 works but is marginal for this bullet. 12 is probably optimal, but 11 likely works just as well in practice and gives you the option of trying the 208gn A-Max and 210s from Sierra and Berger.

Thank you Laurie ;D

 

[allen529]

Not to hijack this thread but Laurie provided me with some load data for 185's with N550. I don't think I have posted anything yet about it but in my 28" barrel I found that at 38 degrees I can load up to 46.8 grains with NO pressure signs. Two weeks later same lot of components but temp around 49 degrees I was getting some pressure signs at both 47 and 47.2 grains. Obviously more so with the 47.2 grns. I will not shoot above 46.8 grains now in temps above 50 degrees with 185's, winchester fully prepped brass, and wolf LR primers.

Now fast forward to yesterday. I loaded 5 rounds each of 46- 46.2- 46.4 - 46.6 grains. Temp: 87 degrees. Everyone single case (20 in all) had swipe marks on the case heads from the bolt and ejector however bolt life was smooth as glass and no flattening of primers at all. I havent measured them to see how much growth has taken place. Funny thing though I had more scuff marks on the lower filled cases and less as it went up. Thoughts????

I will not shoot above 46.2 grains above 87 degrees with 185's and N550. This powder is very temperature sensitive. But it sure did shoot nice. ;D

As for 208+? I have two boxes and my rifle wont load them out where they need to be. I can get no more than 45 grains of RE17 in my winchester cases with a drop tube before I am compressed.

Allen

 

[Fordnutter]

Wow thanks for all the replies guys...I had been away for a while & hadn't checked this thread. I'll pass on this information to my mate - Thank you for all the helpful information, it is greatly appreciated.