N150 or N140 in .308 155's

[farmer7]

Since the Varget shortages up here nearly a year ago I switched to N140 and accuracy wise I'm very happy but I'm unimpressed with the velocities I'm achieving in .308 with 155 AMax before encountering pressure signs.

 

Just wondering is it worth moving over to N150? I wouldn't bother for 30-40 fps but if I could get another 100 that would be great!

 

For people that use both has anyone used them both with the same bullet and recorded velocities? Some sources I've looked at show a decent gain some very little.

 

Also using 178 Amax, 175 SMK and 155 SMK's. I dont want to go to the 5 series VV powders.

 

Any input welcome. Thanks.

[alpha1]

What kind of shooting do you do at what distances. What weight of powder are you using with the 155g A max.

I shoot 155grain A max in my Steyr SSG P1 out to 300 yards with 43.2 grains of N140 with out any problems.

[MJR]

Don't know what velocity you are trying to better but if it helps I use N150 with 175 gn smk's and average 2660fps from a 25" barrel.

[duey]

if your achieving 2850 2900fps then your on the money with your load if you have a 22" to 24" barrel

N140 for than weight of bullet I would expect your charge weight to be in the region of 44 to 46.5grains dependant on your seating depth to achieve those velocities

N150 would be more suited to a heavier bullet 165gr upwards

 

ian

[farmer7]

Thanks for the replies chaps, interesting to see what others are getting. I'm currently loading at 45.3 N140 averaging 2693 fps. Its a 20" Tikka Super Varmint.

 

I know its only 20" but I was still expecting a bit more velocity, any more than that and I'm getting very, very faint ejector marks on Lapua cases ( but no primer flattening or heavy bolt lift whatsoever ). Accuracy is superb but just wondered if N150 would get me a bit more speed.

[Jagged 77]

I use N140 with 168 SMK's and my 1 -300 accuracy load only produces 2500 fps (20" barrel). I then switch to 175 SMK's and N150 and get around 2600 fps which just about keeps me supersonic at 1000. I'm not shooting FTR with it so don't feel the need to stoke it up - I load for accuracy and accept that in order to get significantly better performance I'd need to change hardware.

[farmer7]

I use N140 with 168 SMK's and my 1 -300 accuracy load only produces 2500 fps (20" barrel). I then switch to 175 SMK's and N150 and get around 2600 fps which just about keeps me supersonic at 1000. I'm not shooting FTR with it so don't feel the need to stoke it up - I load for accuracy and accept that in order to get significantly better performance I'd need to change hardware.

Thanks Jagged, I'm not trying to hot rod the .308 either but just wondered if N150 would help get me a bit more. Have you tried the 175's with N140? And I too wont swap speed for accuracy either!

[Jagged 77]

Thanks Jagged, I'm not trying to hot rod the .308 either but just wondered if N150 would help get me a bit more. Have you tried the 175's with N140? And I too wont swap speed for accuracy either!

 

No problem. I don't think you'll get the velocity out of N140 and the 175's. N150 has worked much better for me and seems to be the choice for the heavier 175 / 185 bullets. Having said that Varget with its similar burn rate to N140 is the go to powder for the 175's in the US.

[tisme]

I too have a T3 20" and been trying to get to 1000 yards with it (just to see if I can). So far I tried A max that was accurate out to 850yards but sub sonic soon after that. Then went to Berger 155VLD these went to 920ish ok with Varget 46.4 grains. I was getting pressure signs above and accuracy went down. These were not as accurate as A max, I think this was because I could not seat them near the lands.

I'm now trying 175 SMK with N140. Best load so far 43.6 N140 OAL 2.840, speed 2556 but with the better BC I'm hoping they might do 1000. Just need the time and place to test. I have only tried a sample of N150 I was given and speeds were very similar to N140 but I was left with very dirty cases, No idea why.

[5R-Twist]

Try N135 I use 43gr on Hornady sst 150gr and amax 155 it works great in mine. (Tikka t3 heavy varmint 16in).

 

Its ok in mine but may not be in yours so wise to start a bit lower.

V

[clivej]

deleted

[Laurie]

I've used both in 308 with 155s. I personally prefer N150, but that's for groups and MV spreads not velocities, so it's a short / mid range powder for me. I've had 2,925-2,950 fps from it with 155s seated out in long-throated 30-inch barrels using full case-worth charges in the old 1980s era 160gn Norma brass that has more room in it than Lapua. (Pretty similar capacity to recent Winchester brass.) I had some very good results in 500/600 yard matches a few years back with the Australian 155gn HBC bullet that Brian Fox sells for £300 / 1,000 and N150 in these Norma cases. (I got hundreds of them around 25 years ago from factory ammo sold off cheap and am still using them up as a second string to Lapua which I'm more likely to use in long-range matches.)

 

I reckon there is not a huge lot between the two powders in MVs with this bullet weight, but if it falls either way, it will definitely be N140 that produces more. Above 168gn, N150 takes the advantage as others have said.

[farmer7]

I reckon there is not a huge lot between the two powders in MVs with this bullet weight, but if it falls either way, it will definitely be N140 that produces more. Above 168gn, N150 takes the advantage as others have said.

If thats the case Laurie I'll stick with the N140! Thank you.

[Bianchi]

Since N135 has a burn rate close to the 4895 series powders, I have tested it wirh SMK 168/175s in a semi-auto as an alternative to 4895 with excellent results. Also understand that 4895 is used by some F/TR shooters with 155s. N135 is somewhere between Varget and 4895 in terms of burn rate and can also be a good choice for heavier bullets in .223 Rem (if you own one) for accuracy, at least out to 300 yards.

[Laurie]

Since N135 has a burn rate close to the 4895 series powders, I have tested it wirh SMK 168/175s in a semi-auto as an alternative to 4895 with excellent results. Also understand that 4895 is used by some F/TR shooters with 155s. N135 is somewhere between Varget and 4895 in terms of burn rate and can also be a good choice for heavier bullets in .223 Rem (if you own one) for accuracy, at least out to 300 yards.

 

 

This approach has risks in that it only looks at one aspect of a powder's specification - burn rate. Apart from this factor being an approximation as relative burn rates can and do change in relation to each other depending on the cartridge / calibre characreristics that powders might be used in - that's why every manufacturer's burn-rate chart specifically warns never to use information extracted from it to undertake blind interpolations and/or substitutions - powders have other characteristics that also determine their performance in any given cartridge plus bullet combination.

 

N135 is a handloader's canister version with similar characteristics to one of Vihtavuori's largest bulk sellers, the propellant used in loading standard 7.62X51mm NATO ammunition emplying a 145-147gn FMJBT bullets, and is therefore pretty close to being optimised for this lighter bullet, lower peak pressure variant of the 308 clan.

 

What it is NOT, is a slightly faster burning N140 that therefore suits 155gn bullets better and gives higher MVs. It has a different (lower) amount of specific energy than N140, 3,550J per gram weight compared to 3,700 for the slower burner, a reduction of ~6% in the amount of energy in any given charge weight available to impart velocity to the bullet. It is also a bulkier powder, its bulk density listed by Vihtavuori as 870 grams per litre volume compared to N140's 910 g/l figure, so any particular charge weight sees N135 take up ~4.5% more space in the case. So we have a bulkier powder with less oomph and the OP wants a recommendation for a powder that gives higher MVs! Apart from that, bulk density differences alone result in different fill-ratios of the charge once in the case and different degrees of compression - and that in turn potentially alters combustion behaviour in ways that I for one wouldn't try to to predict. That's an important reason why crude burning-rate comparisons alone often don't work, may even be risky.

 

FWIW, N135 will NEVER EVER produce as high MVs as H4895 in .308 Win with 155s, not safely anyway. H4895 is a much denser powder. To get 100% fill-ratio under the 155.5gn Berger BT seated to 2.900-inch in a 56.0gn water capacity case (typical for Lapua), QuickLOAD calculates it takes 45.9gn H4895, but only 41.7gn N135. H4895 has a nominal specific energy value of 3,930 J/g compared to N135's 3,550, nearly 11% more. This is a real apples and oranges job, as burning rate aside, they have very little in common.

[Bianchi]

Thanks for the expanation Laurie. That explains why I couldn't find one user of N135 at the F-Class Euros. Still consider it to be worth a try for accuracy loads at shorter ranges with 155s though. Farmer7's target distance remains unknown, at least in this thread.

[onehole]

Just for your interest I use Vit140 and 155 Amax,,,only load to 44g giving 2700 fps and is super accurate out to my normal max distances 7/800 yards.Quite a mild load really but half decent velocity probably because my throat is set quite short thus a bit more pressure I would guess.

[Laurie]

Bianchi, I agree 100% on trying it for shorter distance loads. N135 + 155s will likely produce good precision and small velocity spreads and a lower MV doesn't matter a lot if at all. That's why I have used N150 for short-range loads in the roomy Norma brass going at it from the other direction. People sometimes get too hung up on external ballistics comparisons quoting bullet A that beats bullet B by an inch computed wind drift in a 10mph 90-deg wind at 1,000 yards, when they're never actually going to shoot at that distance.

 

I always tell people that group size and flat elevations are paramount up to 600, even 800 yards in most conditions. A rifle + ammo combo that shoots into quarter-MOA beats a faster load with a higher BC bullet that struggles to hold half-MOA and throws odd shots high or low. F/TR at 900 and 1,000 is another matter entirely as you know - everything has now got to be right, velocity, spread, bullet suitability / BC, precision.

[Bianchi]

Laurie, entirely correct in a nutshell. Can't believe what some folk do to squeeze a few more fps out of their rigs with a loss in accuracy and inconsistent MV, loose primer pockets etc.

 

I am coming from the other end with a .308 Win barrel on my F/O rig - 125 grain SMK FB with N133 in an ultra-tight chamber with 13" RR profile specifically for 300m. N135 seems like the next logical step if I will ever compare my best load against 155 grain bullets.

 

Thank goodness Vithavouri powders will still be around in the foreseeable future.

[baldie]

I,m getting 2683 fps with 45.6 grains of 150 with a 167 grain scenar from a 20" AX. Stupidly accurate too.

[farmer7]

You know your onions Laurie, saves a lot of research!

 

As for target distance Bianchi I am mostly shooting steel plates out to a maximum of 1000 yards on the farm, and I know there are much better bullets than the 155 AMAX for long range (and a 20" .308 for that matter!) but I have quite a number of them to use and they do double duty on vermin very successfully so I can use the same bullet for targets/vermin. And can buy via post also which is very useful where I live.

 

With my present load I've only shot for group size on paper to 300 yards and is holding 1/2 moa very consistently from a stock Super Varmint in a GRS stock loaded to magazine length which is just over 2.800 which I'm very happy about.

 

As for my quest for more speed its purely for increased range and reduced windage with the above combination.

 

I've not tried seating out to the lands in this rifle as I wanted to magazine feed so dont know how much freebore it has but if I restart load development using the same components seated to the lands with the extra case capacity am I likely at all to achieve higher MV before encountering pressure?

 

I believe chamber pressure is highest loaded to touch the lands dropping as its seated deeper but I presume it must increase again as the case capacity is reduced significantly????

 

Any further opinions gratefully received!

 

ETA: I'm a slow typer, another 3 replies since I started to type this post!

[Laurie]

I am coming from the other end with a .308 Win barrel on my F/O rig - 125 grain SMK FB with N133 in an ultra-tight chamber with 13" RR profile specifically for 300m. N135 seems like the next logical step if I will ever compare my best load against 155 grain bullets

 

 

That's an excellent, interesting approach. Please tell us one day how it works out in practice!

[Laurie]

Farmer 7, yes it's the available freebore that is the key factor affecting things rather than what the bullet is actually loaded to in order to make magazine COAL. If your rifle does have the freebore to let you load the bullet out another tenth of an inch say, maybe even two tenths, unless you go for a jam into the lands COAL, you won't increase (or decrease) pressures other than marginally.

 

What the longer COAL does do potentially is let you put more powder into the case without a cramming-in heavily compressed status. Depending on bullet length / shape, seating it further out may see its base at a better - or worse - position vis a vis its position against the case neck to shoulder junction and that can affect groups and velocity spreads, well in theory anyway.

 

I'm reading Mic McPherson's new book Metallic Cartridge Handloading .... Pursuit of the Perfect Cartridge at the moment and he's a great fan of swirl pouring using a fairly long tube on the powder funnel. This is something I've done for years as a matter of habit and Forster makes the ideal funnel - plastic funnel bit at the top, five-inch small diameter metal tube with a multi-calibre belled bottom end that suits .22 to .30 case-mouths. Hold the assembly slightly canted and pour the charge in from the scale pan at an angle so it swirls around the funnel sides before dropping into the tube. This set-up and procedure sees another grain, couple of grains of many powders go into the 308 case comfortably. McPherson says it's not just about maximising charge weights (within safe loads of course), but the way the kernels lie in the case-body gives a superior more consistent burn.

 

Believe it as krank rubbish theory or as 'the gen', but McPherson has been in this game a long time and as an engineer / gunsmith has been instrumental in some very innovative designs, wildcats and so on. He's the nearest thing we have to a 21st century P O Ackley gunsmith come serious experimenter, so I always take his views very seriously. It may be worth your while adopting this technique if you don't do it now - the 308 is quite space constrained when you're searching for maximum performance.

[farmer7]

Farmer 7, yes it's the available freebore that is the key factor affecting things rather than what the bullet is actually loaded to in order to make magazine COAL. If your rifle does have the freebore to let you load the bullet out another tenth of an inch say, maybe even two tenths, unless you go for a jam into the lands COAL, you won't increase (or decrease) pressures other than marginally.

 

What the longer COAL does do potentially is let you put more powder into the case without a cramming-in heavily compressed status. Depending on bullet length / shape, seating it further out may see its base at a better - or worse - position vis a vis its position against the case neck to shoulder junction and that can affect groups and velocity spreads, well in theory anyway.

I've just measured the distance to the lands, my current load measures 2.203 to ogive. When loaded to touch the lands they measure 2.278 to ogive.

 

If I take .010 off that measurement to keep me clear of the lands thats leaving me 0.065". Is that enough extra to bother with?

 

Also how marginal pressures are we talking?!