OCW test: 308 with 175 SMK & IMR 4064

[michaelnel]

Yesterday I shot an OCW series (Optimal Charge Weight, see: http://optimalchargeweight.embarqspace.com/) from my Savage 10FCP HS Precision using the following components:

Bullet: Sierra 175gr BTHP MatchKing (SMK)
Brass: Lapua, new, full length sized
Powder: IMR 4064
Primers: CCI 200
COAL: 2.235 (at the ogive, with comparator)

I loaded sighters at 39.7, 40.5, and 41.3 grains. I had previously tested and found 44.3 grains to be max for my rifle before adverse pressure signs started showing up, so I used that as max in this test.

I shot these loads at these numbered targets:

Target Grains
--------------
#1: 41.6
#2: 41.9
#3: 42.2
#4: 42.5
#5: 42.8
#6: 43.1
#7: 43.4
#8: 43.7
#9: 44.0
#10: 44.3

Observations.... extremely tight groups at #2 and #6 but I realize that is not what OCW is all about. Nonetheless, nice groups.

Note that #8 only has two holes, and the group sizes for those two is only .103" according to the OnTarget software. Problem is, when shooting the third rotation of the round robin I mistakenly shot #3 of the target 8 group into target #9. I did see which one it is, (it is the second from the bottom), which if that had been shot at #8 would have made for another tiny group.

So, what kind of analysis can we make from this? I think there may be a node in the #4 to #5 range. Not sure, this seems a difficult one to analyze.

Here's the target:

 

[wapiti25]

you need to go to longer range (300 or more), look for small verticle in the groups. I would shoot #6 and #8, then try changing the seating depth.

 

[michaelnel]

Thanks. This is an Optimal Charge Weight series, not an Audette ladder test. OCW stuff is generally shot in round robin fashion at 100 yards.

 

[Keith Glasscock]

I'd reshoot 6-8. I'm thinking the 7 might have been rifle or shooter spreading them out.

 

[bsumoba]

If this were my group, this would be my thought process:

* looks like I might have 2 nodes, one around 42.5-43 grains. It also looks like I have one around 43.8-44 gr. Being that 44.3 gr is my max charge and that I am using IMR4064 and with it being known to be a little temp sensitive, I would work around 42.5-43 grain range.

* I would tighten the charges and extend slightly beyond my range to determine if it is a true node, so I would load 3-5 rounds of 42.3, 42.5, 42.7, 42.9, 43.1, and maybe 43.3. I would shoot this and see if the shot pattern is consistent. If it is, I go to seating depth.

* Once I determined that it is a true node, I would then either try to shoot this at 300+ yards to validate or I would take the middle charge of the range (so I would choose maybe 43gr and then start creating rounds with seating depths in 0.010" increments to finalize my load.


as a point of reference (and ONLY a point of reference), my friend is using 42.5gr 4064 and 175gr SMK in his 19" bolt action.

 

[teele1]

Busdriver, I think you're rite on track reshoot 6-8

 

[michaelnel]

Thanks for the inputs folks! Gives me some ways to go for more testing.

 

[jo191145]

If it were me.
Shoot some groups, if that vertical doesn't disappear increase comparator length to 2.240" and try again.
Even though it's only 100 yds I see some great potential from that gun once it's dialed in. Enjoy.

 

[Piotrowski]

Didn't read beyond looking at your comments about 2 & 6...

Newberry has notes posted somewhere about 41.9 and 43.1 (high node) with IMR4064 in Lapua brass. I've also been using 41.8 and 43 in Federal GMM brass. (42.2 and 43.4 in Winchester brass.) He is right... those loads do shoot well in many rifles (2 for me) without doing any testing.

I am looking forward to getting back to the Range to try some more of the testing described by Cortina.

 

[JamesnTN]

My load in my accuracy international is 42.3 grns Varget Fed 210m primers Lapua case and a Sierra 175 MK this load will shoot sub 1/2" anytime I want to. If my memory serves right FGMM is 43.2 grns of IMR 4064

 

[amlevin]

My load in my accuracy international is 42.3 grns Varget Fed 210m primers Lapua case and a Sierra 175 MK this load will shoot sub 1/2" anytime I want to. If my memory serves right FGMM is 43.2 grns of IMR 4064

Thumbs up on this load for my rifle as well. Have a whole target full of "30's" I shot yesterday morning, a couple even "20's".

Only difference is that I use Wolf/Tula primers rather than Fed's. In my rifle and brass they work the same as the Fed's and for a lot less money.

 

[Forum Boss]

This rifle seems to have the potential for good accuracy. However, the variance in vertical spread from one group to the next suggests that something is wrong with the gun mechanically or with the shooting set-up.

If everything is set up right, and the barrel is not moving in the action, I would expect that something in the .75" range (for 3 shots) would be your worst result, no matter what the load.

When I see something like #7 (1.651"), I am thinking mechanical problem, scope issue, funky rest or something else. We've seen Savages that produced erratic groups like this because the tenon threads were oversize and off-axis.

The groups #6 and #8 are impressive -- I would certainly keep testing in that range, or just do repeated groups at 43.7, your #8 load.

However, your target is telling you that something is wrong that has nothing to do with powder.

 

[chapstix97]

I have been working up loads BC of the reloading supplies famine we had in the last 2 years and I have been shooting hornady which I never used I found an interesting article from berger. In that sweet spot ogive to land.

http://www.bergerbullets.com/getting-the-best-precision-and-accuracy-from-vld-bullets-in-your-rifle/

 

[rap36case]

I am late to this discussion, but I am conducting similar experiments now with 175g Mk moly coated. I am shooting a CZ550 308Win with 26" barrel, Votex Viper ffp and 20MOA ss from Murphy. A few ideas:

1. Dirty bird targets from Birchwood Casey help visualize shots at 300yards.
2. A good chronograph helps confirm and flag possible overpressure.
3. I have shot 43.5gn and found no signs of overpressure.
4. What you see at 300 is amplified at 500 and sometimes confounded.
5. I have jump set at .005 but plan to go 0.005 jam to 0.015jump in view of loads posted here.

Anyone else try this with 308 moly coated?

 

[amlevin]

1. Dirty bird targets from Birchwood Casey help visualize shots at 300yards.

Theyre fine unless you get a group that drops under 1/2" like I did a couple times. Then the "splatter effect" tends to make it hard to discern which shot was which.

A terrible problem to have, 1/2" groups @300 yards

 

[gaboon]

With 4064 i found somewhere around 42.5gr is the best nodes and with a jump of .015. I would differently check torques on scope and action screws make sure they are even. Do the test over and make sure the natural aim is the same there is too much vertical in the shots to say its the powder charge.