Where to go from here? 308 Win with Berger 168 gr Hybrid

[SGK]

I see the same

What makes you think that powder charge only presents itself as vertical on paper?

I find it interesting to compare velocity and POI for each round. Oftentimes the high velocity outliers hit low and vice versa. (See target 1.) On the last group 43.9 gr the rounds had an ES of just 6 fps vs 27 fps for the 43.7 gr charge. ES for 43.3 gr is less than ES for 43.7 yet the former exhibits more vertical. The 'flattening' observed from 43.5 to 43.7 is likely spurious. I would bet that if I shot ten rounds per load the dispersion picture would look rather different and with even more shots each would approach something that looks relatively evenly dispersed in all directions. Hence I think there is merit in tuning powder charge with very good chrono data and tuning seating depth via noting impact on paper.

 

[Nature Boy]

What makes you think that powder charge only presents itself as vertical on paper?

I find it interesting to compare velocity and POI for each round. Oftentimes the high velocity outliers hit low and vice versa. (See target 1.) On the last group 43.9 gr the rounds had an ES of just 6 fps vs 27 fps for the 43.7 gr charge. ES for 43.3 gr is less than ES for 43.7 yet the former exhibits more vertical. The 'flattening' observed from 43.5 to 43.7 is likely spurious. I would bet that if I shot ten rounds per load the dispersion picture would look rather different and with even more shots each would approach something that looks relatively evenly dispersed in all directions. Hence I think there is merit in tuning powder charge with very good chrono data and tuning seating depth via noting impact on paper.

I subscribe to Erik Cortina’s methodology of load development by noting the distance of each group’s center from POA, finding the ones that have the least variation compared to the adjacent groups and calling that the accuracy node.

In the case of your target, and as I read it, that would be 43.7 - 43.9

Here’s the thread

http://forum.accurateshooter.com/threads/long-range-load-development-at-100-yards.3814361/

 

[SGK]

Here's a pic of my 50 jump seated bullet with a bullet aligned next to it. These Berger Hybrid have a long boat tail. Do I have a plenty of bearing surface seated to try seating them shallower for less jump?

 

[Bc'z]

Here's a pic of my 50 jump seated bullet with a bullet aligned next to it. These Berger Hybrid have a long boat tail. Do I have a plenty of bearing surface seated to try seating them shallower for less jump?

Might try a lil more neck tension if you do.

 

[Whit holman]

You can go longer

 

[SGK]

Ok I added 40 thou jump and 30 thou jump to my next test session

 

[SGK]

Here's my thinking. Everyone needs a path or strategy for load development to avoid chasing one's tail. Sure, in the end the only thing that matters is shots on target, on that day, at that distance and in those particular conditions but getting there requires strategy and discipline of which load development is just one small part. So various people have come up with theories and strategies to avoid or minimise going around in circles during load development.

I for one subscribe to the theory that the whole task of shooting a rifle is a random impact generator, largely following normal distribution characteristics (I've not seen compelling evidence to suggest some other sort of distribution assumption is more powerful) with a mean PoI and a dispersion therefrom in all directions which can be described via SD and ES. Fire enough shots and your group will look normal. A lot of factors go into this impact generator but we try to minimise influences like hold, trigger movement, differences in brass prep in order to get down to evaluating the two key variables we are discussing here, powder charge and seating depth. (Unfortunately even these two aren't independent of each other.)

The second thing I believe in is a lack of convergence (and you could add abnormal divergence). So impact on paper at, for example, 100 yards doesn't get better at 200 and further out (all else being equal). If you believe this then accurate measures of velocity velocity variance have value. A good group at 100 with low velocity variance will carry through to 200 and beyond (except, of course, in so far as it is affected by environmental conditions such as wind which is the challenge of shooting at distance) while a good group at 100 with large velocity variance will not. Of course you need to be able to measure velocity variance well and it is now easier than before to do so. It also means load development at 100, with lower externalities (environmental influences), has value for shooting at longer distances. It also means that if you intend to shoot at different distances you need to look at more than just impact on paper at the load development distance or, alternatively, test at every distance which, with environmental externalities, can be a rapid path to madness.

A combination of powder charge and seating depth can produce more consistent muzzle velocity than another. But it may also produce better or worse dispersion. There's an argument for finding the velocity node and then tweaking seating depth to find the dispersion node, recognising that a change in seating depth will cause a shift in the powder required to keep the velocity node. So I think of this as chasing the optimal combination of velocity and dispersion nodes. A gain in one may require a sacrifice in the other.

Once you have a theory or strategy to follow you need a disciplined approach to understanding just what conclusions - or the level of confidence you can have in such conclusions - can be drawn from observations of impact on paper and velocity recordings. An entire science is dedicated to such things and it's called statistics. It can help. It can help, for example, you determine whether, based on the sample shots you have fired, one group is statistically different from another. It's worth deploying it. **

Of course none of the above prevents one encountering crossroads such as I did - whether to pause and check seating depth, recognising its impact on pressure, or continuing to hold seating depth constant and pushing further with powder charge. Albeit only based on 3 observations, it did seem that I might have hit a velocity node at or near 43.9. **



**

We can use my sample set of three shots fired with 43.9 gr as an example. As ES of 6 and an SD of 3.21 seems pretty cool at first glance but it is more sobering to understand that, given we only have 3 samples, at the 95% confidence interval we can only be sure that the SD is somewhere between 1.7 and 20.2 fps. Ugh - doesn't feel as good as looking at 3.21. (At a 90% confidence interval the range falls to 1.9-14.2.) We can do the same for the 43.7 charge and find that we can only be 95% confident the SD for that sample set is between 7 and 90! Ugh!! But we can then consider if there is a statistically significant difference between what I observed with 43.7 vs 43.9. At the 95% confidence interval we can only conclude they're the same - ugh. More positively, however, we can conclude there's a 90% change they are different. That's enough confidence for me at this stage.

As for the maths, well I don't like dragging out a calculator and trying to remember formulae. So I just use this handy online page from Adam MacDonald. https://www.autotrickler.com/stats-calculator.html Just click on the 'calculator' and enter your shot velocity data.

 

[SGK]

Just vs me. And there's no math really. Just an understanding of average, SD and ES and confidence intervals. Most people understand the first 3 anyway. Only requires doing load development over a good chrono. So when I go to the range I simply plonk down the Two Box - I only do a rough alignment between muzzle and target as I'm only using it for shot to shot variance - and shoot. It takes about 20 seconds to take out of the bag and set up. I just note the velocities as I go (as it is easier than going back through the data saved in the Two Box later). As I have a Shotmarker that gives me group size info and velocities at target (the latter can be used for imputing muzzle velocity and ballistics profile etc). Adam's online calculator makes using the velocity (or other) data easy. Keying the velocity readings into it only takes a few seconds and there's no need to worry about the math. The Two Box doesn't do any 'string' data calculations such as average, ES and SD and so I use his calculator for this anyway. The handy benefit of doing so is I can properly compare two shot strings easily.

If the Shotmarker provided variance from group centre for each shot in a group you could use the same method for dispersion. It does, however, produce group height and width info in MOA.

To emphasise the point, I think it comes down to whether, for example, you believe an equally spaced shot string (assuming no wind etc) that is vertically strung provides different information than one that is horizontal (or diagonal) of the same width/length. If you take a view that they're just random samples around a centre then both sets have identical information. They're the same. However, if you think, for example, that the vertical one must have more velocity dispersion than the horizontal one then you begin to draw different conclusions from each. But is that the case? Shooting over a good chrono and comparing velocity data with impact on paper is the only way to test either hypothesis. (And either way, you still need to understand what confidence you can have in 3 shot or whatever groups/sample sets.) If I took all the numbers off the target page (and my first post) would you think 43.7 gr had less or more velocity variance than 43.9 gr? Now compare 42.7 gr and 43.7 gr. With either load 43.7 or 43.9, would you think shot 1 had the highest or lowest velocity or somewhere in the middle?

In the scheme of things related to shooting a Two Box is cheap (and the calculator is free) and it can be a useful tool. (A Labradar is probably as good but more expensive. A Magnetospeed not.)

 

[SGK]

Thx. I'll report back after the next trip to the range. BTW for anyone a little unsure about statistics I recommend reading Adam's two blog articles at the link above.

 

[Bc'z]

Just vs me. And there's no math really. Just an understanding of average, SD and ES and confidence intervals. Most people understand the first 3 anyway. Only requires doing load development over a good chrono. So when I go to the range I simply plonk down the Two Box - I only do a rough alignment between muzzle and target as I'm only using it for shot to shot variance - and shoot. It takes about 20 seconds to take out of the bag and set up. I just note the velocities as I go (as it is easier than going back through the data saved in the Two Box later). As I have a Shotmarker that gives me group size info and velocities at target (the latter can be used for imputing muzzle velocity and ballistics profile etc). Adam's online calculator makes using the velocity (or other) data easy. Keying the velocity readings into it only takes a few seconds and there's no need to worry about the math. The Two Box doesn't do any 'string' data calculations such as average, ES and SD and so I use his calculator for this anyway. The handy benefit of doing so is I can properly compare two shot strings easily.

If the Shotmarker provided variance from group centre for each shot in a group you could use the same method for dispersion. It does, however, produce group height and width info in MOA.

To emphasise the point, I think it comes down to whether, for example, you believe an equally spaced shot string (assuming no wind etc) that is vertically strung provides different information than one that is horizontal (or diagonal) of the same width/length. If you take a view that they're just random samples around a centre then both sets have identical information. They're the same. However, if you think, for example, that the vertical one must have more velocity dispersion than the horizontal one then you begin to draw different conclusions from each. But is that the case? Shooting over a good chrono and comparing velocity data with impact on paper is the only way to test either hypothesis. (And either way, you still need to understand what confidence you can have in 3 shot or whatever groups/sample sets.) If I took all the numbers off the target page (and my first post) would you think 43.7 gr had less or more velocity variance than 43.9 gr? Now compare 42.7 gr and 43.7 gr. With either load 43.7 or 43.9, would you think shot 1 had the highest or lowest velocity or somewhere in the middle?

In the scheme of things related to shooting a Two Box is cheap (and the calculator is free) and it can be a useful tool. (A Labradar is probably as good but more expensive. A Magnetospeed not.)

So by looking at the targets,are you saying you wouldn't load 43.8 and proceed with seating then fine tune charge?

 

[SGK]

I'd say I don't have a reason to load 43.8 at this stage. The testing thus far was an estimated 60 thou jump. 43.9 gr (or thereabouts) has promise as a velocity node - based on measured velocity data - but I think I need more work on seating depth before fine-tuning powder further. (I'm not saying that 43.8 won't be better but I don't see anything on paper, or in the recorded velocity data, that suggests I should try it just now.) I hope that makes sense. Perhaps I just have a lot to learn!

 

[Bc'z]

Ok look at these targets I shot out of my 06'.
By looking for poi on targets there is a flat spot with a lil bit of vertical.
Load is lapua brass, h4350, wlrp, 185vldI chose to load 56.4 gr h4350 a d moved to seating in .003 increments.
I chronographed load after development and lost velocity from my switch from RP brass but gained in accuracy.
So by looking at targets in original post I see 43.8 gr as a good starting point.
Not being argumentative just reading targets.
Always looking at different way to skin the cat.

 

[SGK]

Nice. How's the velocity consistency? You might only shoot at that distance and so not care but if you want the group to hold over a longer distance you'd need it.

But I don't follow the rationale for trying 56.4 rather than doing your seating depth test with 56.5. What I'm saying is that I don't think you can take comfort from the perceived 'flat spot' of 56.5 and conclude something between the two will be better. It is why I asked Nature Boy the question in post 22. You have just 3 samples of underlying behaviour. A couple more shots might have, for example, rounded out the shape of the group. Dunno. I just don't see the logic behind the decision. I asked the question of Nature Boy with a genuine interest in understanding the rationale behind the conclusion drawn.

But hey, we all try to have some sort of methodology rather than spurious/random testing. For now I lean towards Adam's working approach: use a good chrono to find a velocity node and look at groups on paper for seating depth (recognising that they aren't independent and it may well be the case that gaining one may mean a loss of the other and so a tweak is required).

I'm a bit chicken and seek guidance here when I'm loading well above listed max powder charge and I still haven't tried seating bullets deeper/shorter. (Or it looks like only a very small amount of bearing surface is seated in the case neck and I'm wondering if I can trying seating longer.)

I'm hoping the Hybrids live up to their marketing and are less sensitive to seating depth such that my 10 thou increments cover a lot of bases.

 

[SGK]

Thx. I'll report back after the next trip to the range.

Well I'm not sure what I learnt from today. Except maybe I'm crap at shooting my 308.

I decided to try a seating depth test with 43.90 gr of Varget.

o 30 thou jump => 2.246” 4 rounds (3x loaded)

o 40 thou jump => 2.236” 4 rounds (3x loaded)

o 50 thou jump => 2.226” 5 rounds (2x loaded; 5 rounds to finish of 2x loaded brass)

o 60 thou jump => 2.216” 4 rounds (2x loaded)

o 70 thou jump => 2.206” 4 rounds (3x loaded)

o 80 thou jump => 2.196” 4 rounds (3x loaded)

With 50 thou jump I can clearly hear the powder in the case when shaking the cartridge. Not so by 70 thou jump.

Shot on Saturday 18 May 2019. Here's the data. Pic of target attached. Brass seems ok re excess pressure signs.

o 30 jump: 2607, 2594, 2601, 2573 Avg 2593.8 SD 14.82 ES 34. Group: W 0.42 MOA, H 0.60 MOA. Avg vel at target 2432, SD 11.3

o 40 jump: 2588, 2588, 2581, 2577 Avg 2583.5, SD 5.45, ES 11. Group: W 0.64 MOA, H 0.87 MOA. Avg vel at target 2430, SD 3.1

o 50 jump: 2576, 2599, 2595, 2587, 2606 Avg 2592.6, SD 11.55, ES 30. Group: W 0.30 MOA, H 0.79 MOA. Avg vel at target 2446, SD 9.9

o 60 jump: 2580, 2619, 2596, 2590 Avg 2596.3 SD 16.54 ES 39. Group: W 0.21 MOA, H 0.85 MOA. Avg vel at target 2448, SD 15.7

o 70 jump: 2604, 2586, 2608, 2621 Avg 2604.8 SD 14.45 ES 35. Group: W 0.49 MOA, H 0.6 MOA. Avg vel at target 2442, SD 11.0

o 80 jump: 2620, 2611, 2619, 2592 Avg 2610.8 SD 12.97 ES 28. Group: W 0.47 MOA, H 0.70 MOA. Avg vel at target 2458, SD 3.9

Best groups were 30 jump and 70 jump. (I knew I pulled one shot of the latter right.) Lowest velocity variance was from 40 jump. Previously I had done 3 shots at 43.90 and an estimated 58 jump (see post 1) and gotten very encouragingly low velocity variance. 60 jump today wasn't anywhere as encouraging.

Suggestions? I'm thinking a little more powder with 30 jump and maybe trying seating a little longer. Either that or just shooting my .223!!!!!

(Velocities recorded by the Two Box Chrono aren't comparable one day to the next due to box placement. The avg velocity at target from the Shotmarker should be however. As a reference, 43.90 gr of Varget at last outing was producing 2464 fps at 100 yd target.)

 

[Bc'z]

If you don't have heavy bolt. Stay @ .0030 jump and shoot another OCW in .1gr increments up to 44.5gr

 

[David101]

@sjk I agree with you and have had similar discussions with Adam. Powder Charge is all about velocity seating depth will change the grouping. Only thing I would slightly dissagree with you on is the 100 and 200 yard comment about grouping. 100 yrds can be a bit to close and the bullet can still be unstable before it goes into its sleep mode. 140 yrds would be a better close range indicator.
Then on the flip side the Current world champion an Australian who I have spoken with a fair bit and competed with is a firm believer in barrel tuners even on 1.25 parallel barrels and dont be surprised if the Australian Team to South Africa all have barrel tuners. So they certainly believe in barrel harmonics.

 

[Billy 30-06]

At this point I would stop load development with these components and go to something else." Like 168gr SMK and H-4895." Your gun is telling you it doesn't like what you're feeding it. I have found Varget not to be the best powder for the 168gr bullet in the .308 with a 26" barrel. It's OK to experiment with seating depth after you found a good load but it's going to be hard to beat .010" from the lands. I found if it won't shoot @ .010" jump you need to work with a different powder or bullet. With a good load .010" difference one way or another won't make any difference that you can measure.
Billy

 

[SGK]

@sjk I agree with you and have had similar discussions with Adam. Powder Charge is all about velocity seating depth will change the grouping.

I don't think they're independent but the philosophy isn't a bad one. Everyone needs some sort of strategy/theory/plan to work to else decisions have no basis and you've got noting to compare results with.

Only thing I would slightly dissagree with you on is the 100 and 200 yard comment about grouping. 100 yrds can be a bit to close and the bullet can still be unstable before it goes into its sleep mode. 140 yrds would be a better close range indicator.

Brian Litz did quite a bit of work in this area for Modern Advancements in Long Range Shooting vol II. Worth reading.

 

[SGK]

Dang’
Where’s all that vertical comin from?
Have you considered a Sierra 168 bthp? Much easier to tune in fact you could probably get a great shooting recipe in one or two trips to the range.

At this point I would stop load development with these components and go to something else." Like 168gr SMK and H-4895." Your gun is telling you it doesn't like what you're feeding it. I have found Varget not to be the best powder for the 168gr bullet in the .308 with a 26" barrel. It's OK to experiment with seating depth after you found a good load but it's going to be hard to beat .010" from the lands. I found if it won't shoot @ .010" jump you need to work with a different powder or bullet. With a good load .010" difference one way or another won't make any difference that you can measure.
Billy

Hmm. My HPS ammo is 168gr Sierra MK (Viht N540 powder). I have several hundred of these Bergers though and I thought the Hybrids were meant to be easy to tune (at least with respect to seating depth). And my 8lb jug of Varget isn't even half gone. Ugh.

 

[Billy 30-06]

Hmm. My HPS ammo is 168gr Sierra MK (Viht N540 powder). I have several hundred of these Bergers though and I thought the Hybrids were meant to be easy to tune (at least with respect to seating depth). And my 8lb jug of Varget isn't even half gone. Ugh.

They may be easy to tune but if your rifle doesn't like them or Varget you don't want to burn up your barrel trying to get them to shoot. Some barrels don't like the new lots of Varget. I have a 8lb lot of Varget that won't with anything in my .308.
Billy