How to improve SD?

[exx1976]

Here's a string from a load I worked up.

String 10
1) 2444.0 -16.9
2) 2447.0 -13.9
3) 2453.0 -7.9
4) 2441.0 -19.9
5) 2433.0 -27.9
6) 2486.0 25.1
7) 2471.0 10.1
8) 2517.0 56.1 f
9) 2467.0 6.1
10) 2480.0 19.1
11) 2475.0 14.1
12) 2456.0 -4.9
13) 2453.0 -7.9
14) 2450.0 -10.9
15) 2455.0 -5.9
16) 2454.0 -6.9
17) 2461.0 0.1
18) 2462.0 1.1
19) 2471.0 10.1
20) 2442.0 -18.9
21) 2468.0 7.1
22) 2453.0 -7.9

High: 2517.0
Low: 2433.0
E.S.: 84.0
Ave.: 2460.9
S.D.: 17.9
95%: ±8.3

All the brass has been weighed and sorted in 1.0 gr increments, bullets are 185gr Berger Hybrids, powder is 41.9gr from a Chargemaster. FGMM primers, Redding Type S bushing FL sided (bumped .001"), Forster Ultra Micrometer seater, seated to .020" jump.

Speeds look low because it's a 20" barrel.

How can I improve SD on these loads?

Thanks!

 

[FLIGHT762]

Try another brand of primer. You never know.

 

[Name Enough]

Try another brand of primer. You never know.

+1 = ran out of my usual primers and had to try another brand = SD was the significantly improved. This was with my standard pet load. Suprised me as they were less expensive than the premium primers I was using

 

[Hasgun Willtravel]

Bullet seating length. VLD's are extremely picky, in my experiences, where they are seated off the lands for consistent SD's, without spikes and pressure. Back off in increments, the golden spot for me has been about .025 or .030 back. But could be other variables, are you measuring OAC lengths off bullet tips instead of the ogives?

 

[exx1976]

I'm measuring from the ogive, and they are all DEAD on to one another.

I have some Winchester primers here, I'll give those a shot next. Hard to find much else right now...

 

[runngun]

Is this a max load? You may find that the powder will burn more consistently at a higher or lower pressure.

You may also try a different coronagraph, double check the charge master accuracy using another scale, clean your rifle barrel, or try a different bullet of a similar weight to see if it makes a difference.

If it becomes more consistent when you back the bullet off a bit, it may be because you are loading them long enough that some bullets are actually touching the lands.

 

[Suasponte]

Uniform the flash holes and check your weights with another scale coming off the chargemaster.
Place a the load you tossed back onto the scale after you have it weighed. I bet is does not read
41.9gr.

Once I started weighing my charges with a Lyman M5 tuned by Scott Parker my ES and SD #'s have improved
100%. When I chrono my loads they are never more than 50fps ES. This is with multiple powders, primer mfg's, and brass
makes.

Get yourself a set of Grain check weights that you can verify your scales accuracy at. If your tossing 41.9 have 41.9 grains
of verified weight to check your scale at. The chargemaster scale I had failed at repeatable verifiable weights.

Terry

Lyman Shooters Scale Weight Check Set | eBay

 

[Rapidrob]

How hot did the barrel/chamber get?
Did the light change over the chronograph?
Was every shot fired over the exact same place in the chronograph?
How was the ammo stored at the range/car?
A super low SD means nothing if your rifle does not like the load.
I have seen sub-10 SD's that were like shooting buck shot. 100 fps SD's shoot like a house-of-fire.
a 17.9 is well within anyones acceptable range.

 

[SavageLapua]

Just curious, what powder are you using? I ask because I want to switch powders in my 6.5x55, I'm not a big fan of RL22. Which is the powder in the recipe I was given by the previous owner. It shoots very well (0.4 MOA). I tested this load out for myself, and this is what I found.

April 7, 2013:
32F, 72%RH, 26.45inHG. 100y
RL22
10 shot sting
min: 2620 max: 2691 ave: 2644 SD: 21 ES: 71 MAD: 15
0.4MOA

April 26, 2013:
66F, 48%RH, 26.4inHG. 100y
RL22
10 shot string
min: 2676 max: 2738 ave: 2703 SD: 21 ES: 62 MAD: 17
0.4MOA

Since RL22 has become very hard to come by, I decided to try some different powders that are a little easier to find (here). Results as follows.

H4350
10 shots
min: 2720 max: 2742 ave: 2730 SD: 7 ES: 22 MAD: 6
0.4MOA

H1000
10 shots
min: 2720 max: 2785 ave: 2753 SD: 17 ES: 65 MAD: 13
0.3MOA

All using same bullets, same primers, same scale... yada yada yada... I'm very pleased with H4350.

SL

 

[milo 2.0]

How hot did the barrel/chamber get?
Did the light change over the chronograph?
Was every shot fired over the exact same place in the chronograph?
How was the ammo stored at the range/car?
A super low SD means nothing if your rifle does not like the load.
I have seen sub-10 SD's that were like shooting buck shot. 100 fps SD's shoot like a house-of-fire.
a 17.9 is well within anyones acceptable range.

+1 on what this guy says.
Powder charge, seating depth, and neck tension uniformity will all help. A load with the worst numbers was my best load ever, wish I still had that chamber!!

 

[l115a3]

Have to look with Primer , Nk Tension

 

[normbal]

How many nodes did you get on OCW testing before you started showing high pressure signs?

You might work around that 41.9 number .2 gn +/- or work with another node at a heavier charge.

Generally your most accurate groups will give you the lowest SDs. Think about it.

Also, are you using a Stony Point/Hornady OAL gauge or measuring the bullets to the TIP, not the ogive? Makes a difference.

 

[msiebert]

"A super low SD means nothing if your rifle does not like the load."

Truer words were never said...well maybe about something else, but not in this case. For certain that statement is golden. Once upon a time I had this same problem {numbers almost identical}and it took me a while to get it but what worked for me was annealing the necks. I tried everything and nothing improved or changed much until I annealed the cases. Just remember as above...super close SD doesn't necessarily equal super tight groups. Good luck.

 

[Aimsmall55]

Have you tried the br2's? Only reason I say this is I had the same problem. Groups were good at 100 using fgm210m but when I tried the br2 my groups were just as good and sd and Es went way down. Only thing was I lost about 20 to 25 fps. But at a 600 yard ftr match I want my numbers to be as low as possible before I shoot in it. My load ( and all the other guys shooting for the most part) was over power pro 2000 mr. What powder are you using. I never saw...

 

[deanq]

SD isn't really telling you much with only 20 rounds fired. Work on getting ES down into single digits (hi/low velocity).