What does this mean? (help with load development)

[Big_Bear]

I loaded up my first batch of 308 and tested it at the range a few days ago (I have experience reloading for 45-90 and 45-70 but that's it). I was expecting a more definitive result. Using IMR 3031, I loaded up ten rounds of each load beginning at 39 gr (Hogdon's starting load) and increasing by 0.5 gr up to 41 gr (Hogdon's listed max is 42gr). Wondering how I should interpret this. What should be my next step? Should I test closer to the max? Should I try to narrow in around the 39.5 gr range? Maybe try a different powder? Any insight would be much appreciated.
Thanks!

Here are the details:

RIFLE:
Remington 700P 26" barrel in a B&C stock
Bushnell Elite 6-24x40
Shot from a bench rest with adjustable front rest and rear bag

LOADS:
F/L sized R-P brass (was fired once in an M14)
Primer pockets uniformed
flash hole deburred
trimmed to 2.08"
Hornady Match 168gr BTHP
COAL=2.90"
CCI LR primers
IMR 3031 powder

All groups 10 shots. Targets shot at 100 yards with minimal wind at an exterior temp of 2 degrees C





In the 40.5 gr group I remember there was more than normal resistance when closing the bolt for the flyer shot.

 

[skypilot]

What is the intent of your development? Long range grouping at 600+ yds? Or a nice group at 100 yds?

I never load develop @ less than 300 yds and usually try to develop at the distance I plan to shoot most of the time.

It is almost impossible to see vertical stringing and other issues in close(like 100 yds), yet they are very evident at distances of 300 yds or more.

If you wish to only shoot @ 100 yds for bugholes, perhaps take the best group and its load and try adjusting the bullet seating depth.

Consider reloading some Sierra Match Kings or shoot some factory 165-168gr Federal Game Kings and Nosler Trophy Accubonds just to get an idea of how the gun shoots.

Mine will shoot factory SGK and Accubonds almost in the same hole at 100 m and about 1.5"@ 350m(383 yds) from prone, bipod and with popcorn filled sock for rear bag.

 

[Pr589]

One thing you could try is moving out to 200 yards and trying the same loads using an Optimal Charge Weight OCW approach (http://optimalchargeweight.embarqspace.com/#/ocw-instructions/4529817134).

That said, without knowing much about how consistently you shoot (i.e. are the flyers you or the gun/ammo) or how consistent is your loading technique, it seems to me that you may have a node around 40.5 to 41 grains for that bullet/powder combination. I'd load up some tests at and between these two charge weights and re-test. When you find the best load you can then try different bullet seating depths. It can make a significant difference.

In my experience, you should also try different bullet and powder combinations to find what works well with your rifle. I am currently in load development with a rifle that shoots well with 75 Amax (~ .5 MOA) and Varget; however 80 Amax shoots down into the 0.3 MOA range using the same powder (Varget). It's hard to believe that 0.5 grains of bullet weight makes that much difference. Incidentally, it also hates Hornady 75 BTHP and 77 Sierra MKs.

Although 3031 is a great powder it is on the fast end of the spectrum for 308. You may want to try Reloader 15, Varget, or 4064.

 

[Cleftwynd]

Forget about wind drift or horizontal errors and watch the vertical. If the vertical tightens up in a certain powder weight pay more attention to that load or just above or below.

As others suggested, try moving out to 200 yards for more definitive results.

 

[nowarningshot]

One thing you could try is moving out to 200 yards and trying the same loads using an Optimal Charge Weight OCW approach (http://optimalchargeweight.embarqspace.com/#/ocw-instructions/4529817134).

That said, without knowing much about how consistently you shoot (i.e. are the flyers you or the gun/ammo) or how consistent is your loading technique, it seems to me that you may have a node around 40.5 to 41 grains for that bullet/powder combination. I'd load up some tests at and between these two charge weights and re-test. When you find the best load you can then try different bullet seating depths. It can make a significant difference.

In my experience, you should also try different bullet and powder combinations to find what works well with your rifle. I am currently in load development with a rifle that shoots well with 75 Amax (~ .5 MOA) and Varget; however 80 Amax shoots down into the 0.3 MOA range using the same powder (Varget). It's hard to believe that 0.5 grains of bullet weight makes that much difference. Incidentally, it also hates Hornady 75 BTHP and 77 Sierra MKs.

Although 3031 is a great powder it is on the fast end of the spectrum for 308. You may want to try Reloader 15, Varget, or 4064.

Well said. I would suggest that the two most likely issues are COAL and powder choice. The 700p is renowned as a good shooter, this is a premium product from Remington, barrels and accuracy are most often head and shoulders above the vanilla "SPS" model 700.

Try popular sites like reloaders nest, looking for what projectile the successful shooters are using, but the ones you are using should do better. Pay attention to what COALS they are having success with in your rifle. Pitch the M1A brass, that system is known to be brutally tough on brass, differences caused may be part of the spread in your groups. Old brass from your bolt gun would be ok for the M1A, but probably not the other way around. My first thought is that 3031 is a powder you use for your other calibers. My go to powder in any original military case is IMR4895, i would think other powders that should be good would be Varget, and either H or IMR in either 4350 or 4831. It can be hard to source components, but these are among the most popular and common components available. Buy by the pound and small lots of projectile until you narrow down a pet load.

That rifle, stock....straight out of the box and with your optics should be capable of .5 moa. Individual differences could be attributable to the shooter, but some of those groups should be flirting with .5moa; whereas, more of yours are 1-1.5.

Finding the solution is the fun. Let it be fun, not frustrating.

 

[Big_Bear]

Thanks for all the great advice! So I've picked up some IMR 4064 and some Varget. I'll leave the 3031 for my 45-70. Also picked up a box of 168gr SMKs which seems to be the go to bullet for my gun. Gonna try out a new batch of loads at 200 this time. Although I'd like to be shooting at longer ranges, most places in the area don't go past 200. I've looked into the OCW method, thanks for the tip, Pr589. For now I'll stick with the recommended COAL and play with that once I get my powder charge figured out.

Again, thanks for the feedback.