Load development advice for my .308 - What's the next step?

[bluto77]

Thank you in advance to anyone that reads through all of my post and provides insight and advice. I do appreciate it and place a high value on the knowledge I gain from this website.


I am new to reloading and relatively new to long range shooting, and this is the first load development I have done for a rifle. I started by trying various factory loads at various weights, and my .308 definitely liked the FGMM 175gr the most so I'm using those bullets and Varget powder. The Hodgdon loading manual shows a Min - Max charge for Varget of 42.0 - 45.0. Based on a number of things I've read, I left out the lower portion of the range and loaded enough to shoot 3, 3 shot groups at each charge from 43.0 to 45.0 in .2 increments. I realize 99 rounds may be overkill, but the more practice I get behind the rifle and at the loading bench the better I will get. I started at 43.0, shot all 3 groups, and proceeded through each charge weight the same way. There was no round robin. All shooting was done from a bench off of an Atlas bipod with rear bags. Below are my targets and results.

I am looking for help analyzing the targets, identifying nodes, and advice on the next step. I didn't exactly follow the OCW Test or Ladder test, but I will likely go back and do both of them just to compare what I find doing it this way. The 3 pictures are of all of the charges going top to bottom, and I found the "best" charge weights based on a combination of the lowest average group size of the best two groups (excluding the worst group to allow for shooter error) and most consistent POI. I will list the measurements for each charge weight above the corresponding picture. It should be noted, although relatively "new" to long range shooting, I am capable of consistently shooting 5 shot group 1 MOA and under with my 5.56 gas gun and .5 MOA 5 shot groups with a bolt gun.

I took the following measurements at each charge weight which is shown in the same order on the right side of the target:
- Average of 3 groups: Labeled "Avg"
- Average of 2 smallest groups: Labeled "2 best Avg"
- Variance or spread between largest and smallest group: Labeled "Var"
- Variance or spread between 2 smallest groups: Labeled "2 Var"
- Smallest group size: Labeled "Best"


Charge Weights 43.0 - 43.8

43.0 grains
- Avg .598
- 2 Avg .532
- Var .321
- 2 Var .248
- Best .408

43.2 grains
- Avg .407
- 2 Avg .347
- Var .235
- 2 Var.105
- Best .294

43.4 grains
- Avg .675
- 2 Avg .540
- Var .418
- 2 Var .024
- Best .528

43.6 grains
- Avg .565
- 2 Avg .532
- Var .152
- 2 Var .106
- Best .479

43.8 grains
- Avg .425
- 2 Avg .264
- Var .565
- 2 Var .163
- Best .182

Charge Weights 44.0 gr to 44.6 gr

44.0 grains
- Avg .485
- 2 Avg .441
- Var .214
- 2 Var .161
- Best .360

44.2 grains
- Avg .508
- 2 Avg .457
- Var .160
- 2 Var .025
- Best .446

44.4 grains
- Avg .416
- 2 Avg .256
- Var .661
- 2 Var .362
- Best .075 ***LOWEST***

44.6 grains
- Avg .530
- 2 Avg .436
- Var .298
- 2 Var .032
- Best .420

Charge Weights 44.8 gr to 45.0 gr

44.8 grains
- Avg .498
- 2 Avg .402
- Var .320
- 2 Var .066
- Best .369

45.0 grains
- Avg .374
- 2 Avg .229***LOWEST***
- Var .499
- 2 Var .127
- Best .165

I put the nodes in bold. They were at 43.2, 43.8, 44.4, and 45.0. All .6 gr apart. The "best" charge weight appears to be 45.0 gr. While it doesn't have the smallest group, it does have the smallest average of the best 2 groups in its charge weight, with both of those groups looking like they have nearly an identical POI. The only problem is I was getting sticky bolt at 45.0 gr. To me, the next logical step would be to load up 15 - 20 rounds at each of those charge weights and then shoot either 2 different 10 shot groups or 4 different 5 shot groups at each one to see which is most consistent. But that sure is a lot of shooting to narrow down the OCW.

Additional information
Rifle Info:
- .308 Win
- Rem 700 action trued
- Krieger 26" barrel with 1:12 twist
- Krieger #17 contour
- Huber 2 stage trigger with 2.5 lb break at 2nd stage
- AICS 1.5 chassis
- Vortex Razor 5 - 20 with Seekins rings
- Atlas bipod

Load info:
- 175 gr SMK
- Varget
- FGMM brass and various Lake City brass (all charge weights were shot with the same headstamp)
- Fed 210

 

[K_4c]

Know that your higher charge weights may be fine for the winter months but pressure issues will arise during the summer (I run to nodes, a summer and winter for each). I personally don't play the velocity game, especially with a .308. Instead, I find a node that offers good velocity with no pressure signs (premature failure in primer pockets, cracked necks, etc can all be avoided).

Overall, you did a fine job and the work shows just that. Look into doing a ladder test when time allows.

Best of luck bud and good job.

 

[K_4c]

Also, perform your ladder test at distance (300 meters). This will show even more detail....


Ultimately, you'll be chasing a dragon (always searching for the best components/load data)

 

[bluto77]

Ha! Right! It'll never be "good" enough will it?!?!? But that's what drives the obsession. Thanks for the input. Btw, which charge weight/weights do you think are looking the "best" right now? I know I can get consistent .5 MOA out of this rifle at the very least with a solid load, and then I'll really start chasing the dragon. But right now I'm just trying to get it down to a consistent .5 MOA. I can already do that somewhat consistently with FGMM 175's.

 

[Graham]

Load development advice for my .308 - What's the next step?

Within a few grains of max charge weight I would be surprised if you can tell the difference in accuracy of a .308 Varget load.

 

[K_4c]

Any idea what your muzzle velocities are with the said nodes? If you can get 2700- 2750 fps out of a midrange node I'd stick with that. There's a ratio that needs to be understood (or should I say an efficiency standard). 45 grains looks great but is the extra powder used worth the notable gains (i.e muzzle velocity).

Personally, I'd settle on 43.8 (summer node) and 44.4 (winter node) until you get more time behind the rifle... If you got less then 300-400 rds down the tube, expect your velocities to drop as your bearing surface will be established.

 

[bluto77]

Within a few grains of max charge weight I would be surprised if you can tell the difference in accuracy of a .308 Varget load.

Would you mind elaborating on that to help me understand why? Thanks for the response.

 

[bluto77]

Any idea what your muzzle velocities are with the said nodes? If you can get 2700- 2750 fps out of a midrange node I'd stick with that. There's a ratio that needs to be understood (or should I say an efficiency standard). 45 grains looks great but is the extra powder used worth the notable gains (i.e muzzle velocity).

Personally, I'd settle on 43.8 (summer node) and 44.4 (winter node) until you get more time behind the rifle... If you got less then 300-400 rds down the tube, expect your velocities to drop as your bearing surface will be established.

I have a Magnetospeed that I haven't used yet, but plan on using on the next range trip. I'll post the results. What is the ratio? I do get what you're saying though about probably not needing to go to the higher end at 45.0 grains if I'm already getting 2700 - 2750 fps at the lower charge weight. But why is that? I'm assuming that relates to the ratio/efficiency standard you're referring to. And how would I go about determining whether it would actually be worth the extra powder/barrel erosion to use the 45.0. I'm pretty sure I have at least 300 - 400 rounds down the tube as I've put at least 250 -300 down it myself, and I'm the 2nd owner.

 

[waveslayer]

If I understand right , you are asking about why the two loads in different temps?... If that is what you are asking then it's because the heat will change the pressure of the rounds. Change your POI. Stick with the 43.8 or 44.4 loads. Do those and you are golden from the pics. Nice groupings

 

[bluto77]

Thanks, but they're only 3 round groups, so they don't count for anything.

I understand about the temperature difference effecting the powder. I was asking why I would use the lower charge weight just because they're in the 2700 - 2750 fps range. Is that considered an optimal velocity for the 175gr SMK or something? As far as determining if the 45.0 grains was worth the extra powder, after re-reading what he said, I guess that was more of a rhetorical question. Sorry...I've read so much about reloading as I've taught myself how to do it, that I probably read too far into things now. So much conflicting information out there. For instance, the reason I didn't do the OCW Test to begin with is because on his website, Dan Newberry talks alot about doing the test with a freshly cleaned barrel, and the importance of cleaning the barrel throughout the test (like every 20 - 30 rounds at the very least). Being a student at Snipershide U, I learned in barrels 101 (from Graham actually) that you shouldn't clean the fouling out of your barrel that often and only when accuracy starts to degrade, which would be after hundreds of rounds. I realize that's also "conflicting" information, but I started doing it that way and I saw improvements in my accuracy. So I'm sticking with it. Makes me wonder about everything else on the OCW test.

 

[sinister]

First, wonderful job -- bravo and kudos!

Consistent sub-minute/sub-halves performance with a long range (vice flat-base benchrest) bullet. And you want smaller groups. We'll measure you for the strait jacket in a moment.

The chock-full 45.0 charge (do you use a drop tube?) works on giving you maximum case efficiency by eliminating airspace -- it reflects with your tightest groups.

Try 10-shot groups, and groups at 300 yards...then start nailing targets out to 1,000 yards.

 

[weshowe]

Blutto77,

Nice report and work up! It looks like your rifle is very consistent...as is the shooter.
I settled on 44.3 grains of Varget for my go to load. This in Lapua Brass, Fed 210 M primer under a 175 gr. SMK

Keep up the good work...you've got a nice rifle and good loads. With more range time your all set.

Wes

 

[Graham]

Load development advice for my .308 - What's the next step?

Yes, what Sinister said, above.

 

[K_4c]

I have a Magnetospeed that I haven't used yet, but plan on using on the next range trip. I'll post the results. What is the ratio? I do get what you're saying though about probably not needing to go to the higher end at 45.0 grains if I'm already getting 2700 - 2750 fps at the lower charge weight. But why is that? I'm assuming that relates to the ratio/efficiency standard you're referring to. And how would I go about determining whether it would actually be worth the extra powder/barrel erosion to use the 45.0. I'm pretty sure I have at least 300 - 400 rounds down the tube as I've put at least 250 -300 down it myself, and I'm the 2nd owner.

You stated in your first post a sticky bolt was present at the higher node (45 grains). That's a clear indication and one should back off the throttle. Many, including myself have found the 175 smk to be right at home in that 2700's fps range (you achieve the highest BC noted and this can be proven throughout your ballistic algorithm). One thing is for sure, your gun smith did a great job. I've been told by a pretty prominent smith, that if a gun is put together right, it'll shoot a variety of loads well... and your rifle does just that.

Take care bud

 

[sinister]

You stated in your first post a sticky bolt was present at the higher node (45 grains). That's a clear indication and one should back off the throttle. Many, including myself have found the 175 smk to be right at home in that 2700's fps range (you achieve the highest BC noted and this can be proven throughout your ballistic algorithm).

Dang -- missed that. Good point.

A sticky bolt will also hamper your cycling speed as it hangs up and keeps you from smoothly working the action.

 

[bluto77]

This is great news. Sounds like I don't really have any more searching to do for OCW, and I can start loading and shooting. I'll probably do the ladder and OCW test just for grins, but nice to know I can run with 44.6 gr for now. Time to shoot some real groups and see what she (and I) can do. I like doing the 6 group challenges that Elfster1234 sets up in the semi-auto forum, and will be doing the bolt action one at 300 yards in the near future. The rifle already runs sub-MOA at 300 yards with the FGMM 175's, and i can't wait to see what it does with handloads. I bought this rifle used on here from JoeMusso, and he said the gunsmith was Matt Babb at Bentwood gun smithing in Henderson, NV.

Here's a pic of the rifle before I swapped out the scope with a different rifle and put the Vortex Razor on it. Haven't had a chance to shoot it with the TBAC on yet. Sure going to make for a pleasant shooting experience in the future!

 

[K_4c]

Well done, and enjoy your rifle. Looks like your fundamentals are good to go.

 

[MoBoost]

First, wonderful job -- bravo and kudos!

Consistent sub-minute/sub-halves performance with a long range (vice flat-base benchrest) bullet. And you want smaller groups. We'll measure you for the strait jacket in a moment.

The chock-full 45.0 charge (do you use a drop tube?) works on giving you maximum case efficiency by eliminating airspace -- it reflects with your tightest groups.

Try 10-shot groups, and groups at 300 yards...then start nailing targets out to 1,000 yards.

This.

The rifle obviously "shoots" with anything you throw at it. But if you are doing a load development in 0.5% increments, you should use bigger samples, otherwise you are just picking up background noise. You can try and overlay the three groups you already shot into one 9-shot group and make sense out of it this way.

What I look for in the ladder or OCW is the sudden average POI change, find two charges that cause the jump and load right between the two. This way any variance in temperature, neck tension, brass volume will not make your load jump into the next nod.

 

[bluto77]

I find it interesting that different charge weights cause the POI to shift around the center, yet some of them still group well at their particular POI and some do not. It seems to me that as you went up in powder, using the same bullet, said bullet POI would go higher and higher as the bullet is getting pushed faster, thus getting to the target quicker, thus having less time to drop, thus a higher POI. I guess that's all theoretical though. I've also read about the charge weight changing the exact point of the muzzle that the bullet leaves the barrel, and that being what causes the POI shift.

 

[K_4c]

I believe your referring to the harmonics of the barrel when the rifle is fired.... I would concur with this observation.

I say it's time to stretch her legs and really see what your rifle/hand loads are capable of

 

[MoBoost]

I find it interesting that different charge weights cause the POI to shift around the center, yet some of them still group well at their particular POI and some do not. It seems to me that as you went up in powder, using the same bullet, said bullet POI would go higher and higher as the bullet is getting pushed faster, thus getting to the target quicker, thus having less time to drop, thus a higher POI. I guess that's all theoretical though. I've also read about the charge weight changing the exact point of the muzzle that the bullet leaves the barrel, and that being what causes the POI shift.

At 100 yards velocities don't affect POI that much. It's all about barrel harmonics - and that's why you need to stay away from the "nod jump" loads.

 

[bluto77]

I say it's time to stretch her legs and really see what your rifle/hand loads are capable of

Here's a pic of a 300 yard target from a few months ago with the FGMM 175gr. This is the benchmark for what will be considered worst case for the hand loads.

 

[elfster1234]

It appears that your ocd has fully developed and my training is finally complete. The padawan learner has now become the master. The circle is now complete.

http://m.youtube.com/watch?v=EZD1f9RTEJU