Help with .308 WIN load with Vihtavouri N140

[TQB]

Hi,

I am only shooting up to 300m due to lack of longer ranges in Portugal… I shoot Score Benchrest at 100, 200 and 300m. I know that a factory Sako rifle is not the best suited rifle for it, but it is what I have.

My setup is a factory Sako TRG 22 in .308 WIN with a 26’’ (660mm) barrel with a twist rate of 1:11.

I am using Lapua brass, Vihtavuori N140, CCI BR-2 primers and Lapua Scenar 185gn bullets.

I’m getting 0.5 MOA groups (sometimes a bit smaller – 0.33 MOA) with 2300 fps of average velocity but with ES of about 20 fps, using 39gn of N140.

I have stopped at 39gn of N140 which seems to be the centre of a node.

I have been having some trouble in windy days. I don’t know if that is due to the load, to my wind reading abilities (or lack thereof) or both.

Should I consider a higher load? The Vihtavuori load table states max load at 41.5gn and 2552 fps.

Thank You,
Tiago

 

[JFrank]

Have you tried a lighter bullet ? I have been pleased with 155 scenars in my Tikka 308

 

[OldManTA]

Since you are only going out to 300 meters I agree with SPJ. The 155 Scenars are used by some in long range. Palma matches. The best advice on powder charge is the old tried and true; work up slowly in small increments watching for pressure indicators. The burn rate for N140 is SIMILAR, not exactly the same, as Varget and 46-47 grains with the Sierra 155 SMK Palma and Berger 155's is a typical load using the brass and primers you are using for Palma competition. I mention that ONLY as a comparison as you must be mindful of the high pressures involved. I hope that gives you something to work with.
Tom Alves

 

[TQB]

I have some 155, some 167 and even some 100gn bullets to test.

Thank you.

 

[Ned Ludd]

If you shoot at a range where the wind is an issue, it can wreak havoc on your score at 300 m, even though that is not an exceptionally long distance. The reason for this is the small size of the target (less room for error), and the fact that the shorter distance effectively reduces group spread for all the competitors, meaning the competition is usually even tougher. For many years, I shot in a local 300 yd F-Class match. In F-TR, if you dropped more than a couple points, you probably weren't going to win. A missed wind change of 2 mph was enough to put a shot from a typical F-TR rifle (.223 Rem/.308 Win) out of the 10-ring (2.85" diameter) at 300 yd. The top shooters in F-TR were generally running 185-200 gr high BC .30 cal bullets. So for your intended purpose, accuracy/precision, as well as using a high BC bullet capable of better resisting wind deflection are both critical. Determining what can be loaded optimally in your Sako is an additional part of the equation.

The Lapua Scenar 185 is a good design, but there are certainly higher BC designs. Whether they are too long to load optimally in the Sako is something I can't directly address. If you are wed to using the 185 Scenars, which is understandable, especially in the current shortage climate for reloading supplies, I would make a couple suggestions regarding your current load. The first would be that 2300 fps is pretty slow for a 26" barrel. F-TR shooters using 30" barrels throated appropriately would easily be getting somewhere around 2750 fps from that bullet/powder combination. Even commercial ammunition with 175 gr bullets fired from 24" test barrels ought to generate somewhere in the 2650 fps range, which translates to about 2550 fps for a 185 gr bullet.

Let me make it clear that I'm am not advocating velocity for the sake of velocity. That would be a mistake. Nonetheless, if you're running the 185s at around 2300 fps, you're likely giving up from around 200 to 250 fps, which is not marginal. In fact, giving up somewhere in the neighborhood of 100 fps velocity or so will be the point at which you can start readily detecting the effect on the target in terms of wind deflection. The real question is exactly where your load is in relation to "MAX pressure"? I can't tell with any certainty from the information you posted, but my feeling is that you're running a slower node. Sometimes those slower nodes can show exceptional precision, and there would certainly be a reduction in felt recoil, which should make gun handling easier. However, it is also possible that a faster node would have every bit as good precision, and be more resistant to wind deflection. The only way to know for sure will be to work up a little higher in terms of charge weight and see if you can hit the next faster node without going over pressure. I suspect you might find something between 2500 and 2550 fps. The Berger reloading manual lists 40.5 gr as a "MAX" load for N140 and their 190 gr bullet, with a predicted velocity of 2470 fps from a 24" test barrel. With a 5 gr lighter bullet, a bit more case volume, and 2" more barrel length, I would anticipate you should be able to hit the 2500-2550 fps range without pressure issues using N140, but that's something you'll have to determine for yourself. If you try to hit a faster node, just be aware you may have to work a bit harder on gun handling, due to increased felt recoil. It shouldn't be huge, but may be noticeable.

The second suggestion I would make will hold true regardless of whether you stay with the ~2300 fps load, or try to hit the next higher one. Seating depth is a big deal when it comes to optimizing precision. I would advocate thoroughly testing seating depth with thew 185 Scenars over a range from close to touching (-.003" or so), to as much as .030" to .050" off the lands. Having the optimal seating depth means tighter groups, something that is absolutely essential for shooting winning scores at 300 m. It sounds to me like there may still be a little more precision to be wrung out of your load, even if you don't decide to try for the next faster node. So a little more testing may be in order. When you have something you think is the best it can possibly be, the next step would be to practice shooting in various wind conditions as often as possible. The more you can learn in practice, the more it can help you when you apply it in matches.

 

[TQB]

Thank you Ned Ludd, that was very insightful.

I will do a ladder test again and try to detect a higher node. I don’t think the current load does well in the wind.

My current seating depth is about 0.010 into the lands, but still able to extract the round with ease without marring the bullet a lot.

My neck tension is 0.0015 and usually, I’m getting soot in the shoulder and sometimes even in the body area. Therefore, I have indications that the pressure is low.

Here is a GRTools image of the load.

I set my neck tension with a L.E. Wilson bushing die and afterwards I use a L.E.Wilson .30 cal expander.


One more question please.

I have bought a tuner. With my current load and some very limited testing I think I have adjusted it somewhat.

For this new ladder test should I set the tuner to zero and do the test or should I leave it as it is adjusted?

Thank You,
Tiago

 

[mgunderson]

I would check the seating depth as others have suggested. You may find a node that is a little more forgiving in the wind.

 

[Ned Ludd]

Thank you Ned Ludd, that was very insightful.

I will do a ladder test again and try to detect a higher node. I don’t think the current load does well in the wind.

My current seating depth is about 0.010 into the lands, but still able to extract the round with ease without marring the bullet a lot.

My neck tension is 0.0015 and usually, I’m getting soot in the shoulder and sometimes even in the body area. Therefore, I have indications that the pressure is low.

Here is a GRTools image of the load.View attachment 1283814

I set my neck tension with a L.E. Wilson bushing die and afterwards I use a L.E.Wilson .30 cal expander.


One more question please.

I have bought a tuner. With my current load and some very limited testing I think I have adjusted it somewhat.

For this new ladder test should I set the tuner to zero and do the test or should I leave it as it is adjusted?

Thank You,
Tiago

I would suggest keeping the tuner set on zero while testing charge weight and/or seating depth, then re-optimize the tuner setting last.

 

[Juppe12]

I would try changing powder to N150, works better with 185gr Scenar.
Other thing to consider, Sako promises 0.5 MOA at 100m accuracy for TRG rifles, so you might be at limits with that rifle. But with TRG you have best barrels manufactured by Sako, barrels are hand picked and also bolt is manufactured with tighter tolerances.

 

[coolbox]

My friend uses N140, and he loads at 43.5 gr for an MV of ~2720 fps with 185 juggernauts, 32" bartlein, 1:11.

I have to agree with Ned Ludd. The smaller 300mtr target size makes it quite challenging. And the MV of 2300fps is slow. You should load up gradually, and keep looking for pressure signs.

I have shot with the TRG a few times, its an exceptionally accurate rifle.

 

[Capt. Oblivious]

Try some 168gr Berger Hybrids and N540

 

[6bra1k]

soot on the body is a clear indication of low pressure, i think the velocity says the same.
i shoot the 185, but not for 300.
168 150 155 still good with n140, maybe try a fed primer
( 3 185 at 300 .68")

 

[JFrank]

I would increase neck tension and add powder.

 

[TQB]

Today was testing day at the range.


I tested :

• Lapua HPCE 100gn with Vihtavouri N130
• Lapua Scenar 167gn with Vihtavouri N140
• Lapua Scenar-L 175gn with Vihtavouri N140
• Lapua Scenar 185gn with Vihtavouri N140

I couldn't test de Lapua Scenar-L 155gn with Vihtavouri N140, because I made them to long...

Here are the results:

and:


Your advice is wellcome.

Thank You,
Tiago

 

[JFrank]

Shoot this one