Working up a load

[AlieN]

Can I pick the brains of the experts here...

I'm just starting to reload and according to the recommendations here and elsewhere I've been working up from a relatively light load for my .308Win (26" barrel, 1/12 twist), intending to shoot to 600yds.

For a starting point, I've gone with new Lapua brass, Federal 210 primers and Vihtavuori N140 powder behind a SMK 168gr bullet. I determined starting points and maximum loads from three sources (Vihtavuori, Lapua and another).

Wanting to build up slowly, I loaded 35 rounds, 5 each at 39.0, 39.4, 39.8, 40.2, 40.6, 41.0 & 41.4. I shot these on Short Siberia at Bisley at 100yds and was pleased that even the worse performing, gave much better results than the GGG rounds I had been using to date. Throughout the session I kept an eye out for signs of pressure and there were none (and I was well short of the maximum loads from any of the three sources I consulted).

The variations in group sizes were not as large as I had expected, with the worst group around 2", while the best was just over 1". The best group was actually at the second lowest powder charge (39.4gr). So, is this charge likely to be adequate as a 600yd round? I would estimate (based on loading sources) that this might give around 2,350fps, which seems pretty low. I should be able to check actually velocities this weekend.

Can anybody with QuickLoad run the numbers if this will give any more information?

As the charges got higher, to my top charge of 41.4gr, the groups were getting larger. Should I expect them to tighten up again if I went higher still (assuming I could do so safely without showing pressure signs)?

Thanks,

AlieN

[Dannywayoflife]

Those loads look very anemic to me mate. I've found using ramshot powders (different to VV I know) that they shoot best when near max. Personally I would find the max in your rifle and then do an ocw working down from that to find a decent load.

[20series]

i reckon you'd be fine at around 42-43 gns of N140 with no issues.

Alan

[M99]

I run the 168s over 44 gr of n150 for 2700fps

.

[Alpha1]

I use 42.3 grains of N140 in my .308 Steyr with a 168grain bullet with good results.
(This load is safe in my Rifle) Work up to this figure using the usual precautions when re loading.

[ColinR]

I use 43.5 grains of N135 with a 168g SMK. At 300 yds in my AI they virtually go through the same hole. I have to say I always assumed the heavier 168g SMK would be more suitable for long range than the 155g SMK, but I was advised by those that know on this forum that the 168g SMK is designed for shorter ranges. I have to say they are superb at 300 yds so are ideal for McQueen. I have not tried them over 300 yds, but you should be OK out to 600 - as far as I know they are not recommended for much further as I think they might become unstable, but I'm sure someone will correct me if I'm wrong.

[AlieN]

Thanks for the replies, much appreciated.

I'll be shooting the current load (39.4gr) this weekend at 300yds, so it will be interesting to see how that goes, but it does sounds like I want a bit more velocity, so inevitably more development needed. I should have an opportunity to chrono the shots this weekend as well.

Of the groups that I shot using the original set of rounds, the smallest was certainly the 39.4gr, above which the groups got steadily larger until the top load of 41.4gr, where the group started to shrink again, so perhaps I was starting to approach another node at the top end.

I'll report back as things progress...

Thanks again,

AlieN

p.s. If anybody is interested, here is a link to an image showing the results of the initial round of testing.

[rox]

as far as I know they are not recommended for much further as I think they might become unstable, but I'm sure someone will correct me if I'm wrong.

Correct; they were designed for 300m shooting and they excel at it (although the discipline is now dominated by smaller calibres due to recoil). The boat tail angle is the primary cause of problems that occur at long range. This aspect of the design is shared with 'clones' of the SMK such as Speer and Nosler (which is my 300m bullet of choice). It is sometimes assumed that all 168 grain .30 cal bullets have the same problem at long range but this is not the case.

My 300m load is a Nosler 168 (an SMK 'Clone') with 42.0 grains of TR140 (similar to N140). This is deliberately loaded a little soft in order to try and reduce recoil over the long 60-70 shot COF*. For 600 yards I would work up something a bit faster, especially for a shorter COF.

The SMK is forgiving and needs little tuning. I arrived at my 42.0 grain load by shooting a pressure series from a starting load for safety, then a 5 shot group at 42.0 grains, then a 60 shot COF for score. The 5 shots went into 14mm @ 300m (about 1/6 MOA). I've never tried to find 'nodes' and never shot ladder or OCW; maybe I'm just very very lucky. I don't believe that 5 shot groups with different loads produce statistically significant results, even from a machine rest. A good rifle, excellent loading technique, and good shooting should get you to 1/2 MOA or better at short range regardless of any 'nodes' or 'sweet spots'. Maybe when you are trying to shrink the group from 1/3 to 1/4 MOA you might be able to optimise barrel harmonics, or utilise pressure curve flat-spots to accommodate varying charge weights at long range, but until you are shooting well-under 1 MOA with an arbitrary charge that produces any reasonable velocity I don't believe you will see a meaningful difference.


*alpha1: COF = Course of Fire.

..

[Alpha1]

ColinR wrote:

as far as I know they are not recommended for much further as I think they might become unstable, but I'm sure someone will correct me if I'm wrong.


Correct; they were designed for 300m shooting and they excel at it (although the discipline is now dominated by smaller calibres due to recoil). The boat tail angle is the primary cause of problems that occur at long range. This aspect of the design is shared with 'clones' of the SMK such as Speer and Nosler (which is my 300m bullet of choice). It is sometimes assumed that all 168 grain .30 cal bullets have the same problem at long range but this is not the case.

My 300m load is a Nosler 168 (an SMK 'Clone') with 42.0 grains of TR140 (similar to N140). This is deliberately loaded a little soft in order to try and reduce recoil over the long 60-70 shot COF*. For 600 yards I would work up something a bit faster, especially for a shorter COF.

The SMK is forgiving and needs little tuning. I arrived at my 42.0 grain load by shooting a pressure series from a starting load for safety, then a 5 shot group at 42.0 grains, then a 60 shot COF for score. The 5 shots went into 14mm @ 300m (about 1/6 MOA). I've never tried to find 'nodes' and never shot ladder or OCW; maybe I'm just very very lucky. I don't believe that 5 shot groups with different loads produce statistically significant results, even from a machine rest. A good rifle, excellent loading technique, and good shooting should get you to 1/2 MOA or better at short range regardless of any 'nodes' or 'sweet spots'. Maybe when you are trying to shrink the group from 1/3 to 1/4 MOA you might be able to optimise barrel harmonics, or utilise pressure curve flat-spots to accommodate varying charge weights at long range, but until you are shooting well-under 1 MOA with an arbitrary charge that produces any reasonable velocity I don't believe you will see a meaningful difference.


*alpha1: COF = Course of Fire.

Thanks rox

[Jackmanuk]

i used 42 grn of n140 and 155 smk palma and my 308 was a tack driver