Velocity Spread ?

[jmad_81]

Went out with the STW this afternoon. I was trying to fine tune my 160 AB load. It shoots normally in the .5" range. I knew that my ES, and SD were a bit larger than I would have liked for LR shooting, and I was hoping that tweaking seating depth would tighten groups, but more importantly shrink my ES, and SD numbers as well. The load was developed at a COAL of 3.730. So I loaded from 3.720 up in .005" increments to 3.740". I started at 3.720 and worked up. Things didn't start out all that promising.

3.720"
Shot 1: 3292 fps
Shot 2: 3236
Shot 3: 3300
Group size: 1.055" 2&1

3.725"
Shot 1: 3267
Shot 2: 3281
Shot 3: 3252
Group size: .98" 2&1

3.730"
Shot 1: 3252
Shot 2: 3236
Shot 3: 3244
Group size: .74" 2&1 (the two made a hole and a half)

3.735"
Shot 1: 3284
Shot 2: 3316
Shot 3: 3276
Group size: .64" 2&1 (two cutting and one just left)

3.740"
Shot 1: 3252
Shot 2: 3252
Shot 3: 3252 (not sure what happend here. Fresh batteries in the chrony to start :? )
Group size: .7" 2&1 (two cutting and one about 10 O'clock)

The wind was blowing from right to left 4-10 mph. I don't know how much that would effect a 160 AB going that fast? It was a bit warm to day as well, so the mirage was pretty bad. I let the barrel cool between each shot. I know this load has done five shots in the .4" range in the past, but for shooting 1000 yards I would like it to do a bit better, mostly in the ES and SD department.

This load is on the edge in this rifle I think, all the shells that were over 3280 had extractor marks. All I have tried so far is Retumbo and 215M primmers. I was thinking about dropping a half grain and seeing what happes and reshooting the 3.735, and 3.740 loads. Maybe changing primers as well.

Do you guys have any methods for trying to control ES, and SD numbers? Do you think I would be better off trying RL-25, or H1000 before I retest my seating depths and primer changes with Retumbo?

I'll get a target photo up here shortly.

 

[jmad_81]

View attachment 2012-06-03_16-44-42_795.jpgView attachment 2012-06-03_16-44-20_398.jpg
View attachment 2012-06-03_16-44-33_450.jpg

 

[Ridge_Runner]

try the H-1000, try .015-.030 off the lands, works well in my stw and runs much faster with a max load.
RR

 

[JD338]

Jake,

I would try both H1000 and RL 25 in the big 7.
See what you get with these and then tweek if necessary.

JD338

 

[Guest]

Jake,
I had some issues with my 300 Ultra Mag using Retumbo as is peaks out faster than RL25 and other slow burning powders. I couldn't get close to book max listed with Retumbo in my gun. I switched back to RL25 and it resolved my issues. Definetly make a powder change at least to any one of those suggested by JD338.

Don

 

[usmc 89]

couple of things i would try first of all weigh your brass and make sure that is within a grain of each other, second use a comparotor to measure your coal. i have noticed that retumbo tends to run a little higher in the sd than h 1000 does.

 

[Oldtrader3]

Weigh brass and change primers within the same type (i.e, Large Rifle).

 

[jmad_81]

The brass has all been weight sorted. Trimmed, flash holes deburred, primer pockets squared, and necks turned.

I'll try a load with a 2104 primer and a wlrm primer. Then I'll give the H1000 and RL-25 a shot.

Thanks fellas.

 

[Wis65x55]

Jake,
It is very likely that you could get an additional 150fps velocity; However, It would be very difficult to improve on the SD of 8 fps in load group 3.
Keith

 

[Ridge_Runner]

3.730"
Shot 1: 3252
Shot 2: 3236
Shot 3: 3244
Group size: .74" 2&1 (the two made a hole and a half)

3.735"
Shot 1: 3284
Shot 2: 3316
Shot 3: 3276
Group size: .64" 2&1 (two cutting and one just left)

3.740"
Shot 1: 3252
Shot 2: 3252
Shot 3: 3252 (not sure what happend here. Fresh batteries in the chrony to start :? )
Group size: .7" 2&1 (two cutting and one about 10 O'clock)
.

Before ya do anything, take these loads and try 5 shot groups, if you see a group within a group (3 here, 2 there) try loading a bit longer and see what that does unless you are at max mag length.
RR

 

[jmad_81]

I'm already having to single shot them, and have room to keep moving forward.

I got a pic of a five shot group on my phone I'll get a pic up soon. It's .488" with the 3.730 seating depth. I am very happy with that group. But, I want my dang velocity numbers closer :x

Thanks for the advise, I'll give moving them forward a bit more a shot. What kind of charge weight are you using with the H1000?

 

[jmad_81]

View attachment IMAG0181.jpg

Please pardon the sideways photo.

 

[Ridge_Runner]

my loads for a 160 in the stw are
disclaimer here, they ain't mild loads
81 gr H-1000/fed. 215/160 nosler 3300 fps
95 gr WC872/fed. 215/160 nosler 3340 fps
RR

 

[Ridge_Runner]

I'm already having to single shot them, and have room to keep moving forward.

I got a pic of a five shot group on my phone I'll get a pic up soon. It's .488" with the 3.730 seating depth. I am very happy with that group. But, I want my dang velocity numbers closer :x

Thanks for the advise, I'll give moving them forward a bit more a shot. What kind of charge weight are you using with the H1000?

sounds like an extended mag box is in order.
RR

 

[jmad_81]

Thanks. I'll start low and work my way up. I think I have a fast lot of H1000 sitting on my bench anyways. So I might start around 74gr, and work up doing a ladder test or something like that to help find the max for my rifle. Just wanted a rough idead of were to start looking to issues.

I think with the H1000 loads I'll just start out with them short enough to feed and see what happens. If they need to be longer, your right, and extended mag might be in order.

 

[DrMike]

Very good looking group, Jake. Velocity for that group was what?

 

[jmad_81]

Thanks, Mike. I don't remember the exact numbers, but it averaged out right around 3240. I do remember though that it started out as a 2&1 group, then the last two tore the paper up pretty good. My wood backstop is getting pretty shot up, and needs replaced

 

[DrMike]

That's not a terrible velocity, and the accuracy is excellent. I could live with it.

 

[jmad_81]

I'm almost wondering if part of my problem is not letting my chargemaster 1500 warm up long enough before I start loading. Might have to double check some of my charges on a balance beam scale.

 

[SJB358]

Looking pretty good Jake. That 7STW is rocking it seems..

With my Reloder Electronic Measure, I let it warm up for 30 minutes. Probably doesn't need all of it, but it seems to assist it with being consistent.