Viht N550 or N150?

[Dangermouse]

As the title asks,
I am about to finish my stock of N550 which is giving me 2940 fps from a 32" barrel firing a 155 SMK over 49.5 grains, which is definitely a 100% fill if not higher.

I have read that a lot of guys appear to be using N150 but with lower loads, does anyone think that I should swap over now?

Should it make any difference I will be trying to purchase some Berger 155's and maybe something heavier, in the near future,

DM

[sanselm]

Neither - you should be using 540 with a 155gr, you should be able to get > 3000 fps with ease, depending on your barrel you will find that somewhere between 46 & 48 grs will do the trick. I would only use 550 on 185gr bullets and heavier.

[Dangermouse]

Thanks Stuart,

I started out with the 550 last year with a disastrous venture into SMK 190's with a 26" barrel, despite it being recommended it very definitely did not work. Since then I have been using it up with lighter rounds.

I will research the 540 and see what I can find, Should I decide to give the Berger 175 or 185's a go, would it still be suitable?

I have a 1/12 twist,

DM

[sanselm]

Hi DM,

If you go to the 175 / 185 then I would go for the 185 BT and 550, your barrel will take them no problem. MV's of 2750 and above will equal or better a 155gr at 3000 + I think that 540 may be a little too quick for 185's but haven't tried it so I cannot be sure.

If you are sticking with 155's then you may still get the velocity with 140 but I would still use 540 personally.

Regards

Stuart

[rox]

As the title asks,
I am about to finish my stock of N550 which is giving me 2940 fps from a 32" barrel firing a 155 SMK over 49.5 grains, which is definitely a 100% fill if not higher.

I have read that a lot of guys appear to be using N150 but with lower loads, does anyone think that I should swap over now?

Should it make any difference I will be trying to purchase some Berger 155's and maybe something heavier, in the near future,

DM

N140 is a very common choice amongst UK TR shooters (typically shooting a 155 gr at up-to 1000 yards), and it's also used in some popular commercial brands. Loads in the range of 45.0 to 46.0 are used to achieve mv's in the range 2950 to 3000 (in strong, modern, good condition actions designed for target shooting). Peak pressures with N140 may be higher than with 500-series loads developed to the same velocity, but there seems to be a consensus that the double base powders will burn-out barrels more quickly. I expect to get at least 6000 rounds out of a stainless 30" Krieger (1-in-12" to 1-in-14") before binning it, more out of concern that it may be nearing end-of-life than any actual observed degradation in performance. Not sure how this compares with the expectation of double-base/500-series users. I measured one of my chambers yesterday, and the point of engagement into the lands has moved forward about 3 or 4 thou after 1800 rounds since new. A 500 series user reported 7 thou after 1500 rounds on here, but of course this is hardly scientific without knowing any details about the barrel.

I believe that the reason N140 is used more than N150 (in TR) is due to availability, price & metering, otherwise N150 would be technically more suitable.

Naturally, any load details suggested above may not be suitable for your particular circumstances and application, and should not be used directly by others. Follow safe load development procedures.

..

[FilippoMo]

As the title asks,
I am about to finish my stock of N550 which is giving me 2940 fps from a 32" barrel firing a 155 SMK over 49.5 grains, which is definitely a 100% fill if not higher.

I have read that a lot of guys appear to be using N150 but with lower loads, does anyone think that I should swap over now?

Should it make any difference I will be trying to purchase some Berger 155's and maybe something heavier, in the near future,

DM

I would try 150 which should give you slightly less velocity.I shot this powder for many years with
155 scenars it always shot better than 140 in my rifles,even in very hot weather.
sincerely
Filippo
PS I know use Lovex 060 02 for economic reason not performance

[Robin128]

N540.

[Laurie]

N540 will as suggested in previous posts give the highest MVs and in most barrels and chambers very good accuracy. It's the powder to go for with 155s in F/TR at 900 and 1,000yd if you stick to 155s (there are better, heavier alternatives).

Not everybody needs 3,050 fps or more, and there is a barrel life price to pay for this performance, not so much the result of using the only mildly double-base Viht N500 series powders over their single-base N100 series equivalents, much more to do with the increased pressures that give the extra 100 fps over the TR shooter's 2,950 fps.

Personally, if I don't have to whack them out at over 3,000 fps, I'll use N150 as my first choice over N140 and N540 with this bullet weight. A much more flexible powder that usually gives both good groups and small velocity spreads over a fair range of charge weights. For 200-600yd, my current favourite load in a 30" 1-10" Broughton throated for 185s is Fox Firearms 155gn BJD-HBC (Australian) bullet over 47.0gn N150 in old Norma 160gn (thin-walled, VERY roomy) brass and cheapo CCI-200 primers. One-hole 100yd 5-round groups, 2,970 fps MV and single figure spreads. Lapua brass would need some charge reduction, by at least 0.5gn on the max, maybe a full 1.0gn, and the usual caveats about starting a few gn down and working up applies.

To date in many years of loading .308 and 155s covering several rifles and bullets, I've yet to find a bullet in that weight that wouldn't perform with N150, while I've had several that were mediocre performers with the more popular N140. I would never use N550 with this bullet weight.

[Dangermouse]

I will draw a line under this topic.

Thank you to everyone that has taken the trouble to reply and given me the benefit of their experiences.

Unfortunately I have already loaded my ammunition for the Long range comp at the beginning of July, and that will see me using the last of the Viht 550, which I knew was not suitable but it is working and this close to a comp I did not have the time to change.

So after the comp I will be having a brand new start.

I have some Berger 155.5's to test and if anyone is selling something heavier at the comp I will pick up something heavier, possibly the 185's BT as Stuart recommends.
I have a load of 175gn SMK's which I have never got on with, and that is just from a bullet seating point of view, so for the time being I will be saying good bye to the SMK range.

Interesting discussion on primers also running at the moment, I see that the CCI 200's that I am currently using are low down on both charts, as I am coming to the end of the current box I may well move on to CCI BR or if the salesman suggests, the 250's? - the 250's may be too much of a jump.

Again, thanks to all,

DM

[Gun Pimp]

I will draw a line under this topic. DM

Dangermouse - this is one of the best threads we've had on the forum for sometime so please let's not be too hasty to close it.

I've always preferred Vit 140 or 540 to N550 in the 308 with 155's but maybe I need to give 550 another try.

The only time I've experimented with 550 in the 308 was a couple of years ago when I was sorting out a 308 load for someone - who had given me 155gn bullets and 550 and 540 powder.

Charge for charge, the 550 was giving about 80 fps less than the 540 out of the 1 in 14 twist, 32 inch barrel - and the object was to get an accurate load with a 3000 fps plus velocity. Unfortunately, I didn't explore the accuracy of the 550 but the 540 was giving excellent results anyway.

I'll try some 550 next week.

Vince