Help me interpret load data - First post

[jtvann]

Hi all,

This is my first post. Forgive the long post right out of the gate. Trying to include all pertinent info.

I'm trying to work up a completely new load. I'm shooting a 300 wsm, just a plain stock Remington 700. I'm using new ADG brass, 175 Barnes LRX bullets, Ramshot Hunter powder, and CCI #34 primers. Rounds are loaded to 2.175 CBTO to make them fit my magazine. That's close to 100 thousands jump.

I went out about 2 weeks ago to try to find pressure signs or where my max charge would be. I stuck with Barnes loading data and tested 1 round at half grain increments from 65-72.5 grains. I never saw pressure signs, but felt the bolt lift a litter heavier beyond 71.5 grains. I was using a magnetospeed sporter chronograph to try and narrow in on a velocity node as well. Here's the data from my first test:

65-2775
65.5- 2828
66-2877
66.5-2899
67-2919
67.5-2980
68-2978
68.5-2987
69-2996
69.5- 3029
70-3065
70.5- 3062
71- 3077
71.5- 3105
72- 3120
72.5- 3167

I tested around 70 grains next. What I didn't factor in, and a major question I have is with temp sensitivity. It was about 55 degrees when I ran my first pressure signs / velocity test.

Next I tested 3 rounds each at the following, but the temperature was around 35-40 degrees.

70.4 - 3009, 3014, 3011
70.6 - 3011, 3023, 3032
70.8 - 3004, 3020, 3024

Today I tested 3 rounds each at the following, with temp close to 60 degrees

69.8- 3059, 3063, 3050
70- 3077, 3076, 3073
70.2- 3091, 3083, 3063

The temp sensitivity has got me stumped. I don't know what to do next.

Dumb question …Is a velocity node specific to a certain velocity? Meaning I will have to learn what the temp swing is and then load various rounds for what the given temp is on a particular day.

Any help would be appreciated.

 

[PddPdd]

I think you picked a portion of the "right" velocity node to investigate further (69.8 - 70.2) but I probably would have extended it to include loads up to 71.2 grains. In your original data your extreme spread (ES) between 70.0 -71.0 is only 15 fps.

From the second set of loads you shot your ES was lowest (4 fps) for 70.0 & 70.4 grains so you could go with 3 shot groups for accuracy in that range or add in the loads up to 71.2 so your aren't leaving anything on the table.

In general, I try to shoot all my loads that I'm comparing to each other, in the same sitting, so I don't have to worry so much about temperature driven velocity changes (especially since the key data from these tests are velocity).

To answer your question, if you pick the best (smallest ES and widest charge weight) you won't need to load temperature dependent rounds. This assumes you are using a less temperature sensitive powders such as the Hodgden extreme line.

Hope that helps.

 

[jtvann]

I think you picked a portion of the "right" velocity node to investigate further (69.8 - 70.2) but I probably would have extended it to include loads up to 71.2 grains. In your original data your extreme spread (ES) between 70.0 -71.0 is only 15 fps.

From the second set of loads you shot your ES was lowest (4 fps) for 70.0 & 70.4 grains so you could go with 3 shot groups for accuracy in that range or add in the loads up to 71.2 so your aren't leaving anything on the table.

In general, I try to shoot all my loads that I'm comparing to each other, in the same sitting, so I don't have to worry so much about temperature driven velocity changes (especially since the key data from these tests are velocity).

Hope that helps.

It helps in hind sight. I guess I'm wondering what good it does to find the perfect load when the powder is that temp sensitive.

Won't my ES and SD be all over the place with a different temp? I mean I could be spot on with a 2 SD and 4 ES when its 60 degrees, but what will my numbers be when its 15 degrees?

Im trying to learn this accuracy/velocity node stuff. Am I just looking for a velocity that seems to be stable? Such as about 3065 fps. Then so I try to vary my powder load for different temps to try to keep hitting as close to that 3065?

 

[ShtrRdy]

Was the brass new for one data outing and then once or twice fired on the other data outing?

 

[jtvann]

Was the brass new for one data outing and then once or twice fired on the other data outing?

Brand new brass never fired.

 

[ShtrRdy]

Brand new brass never fired.

Same brand and same lot # for each of the outings?

 

[waveslayer]

It helps in hind sight. I guess I'm wondering what good it does to find the perfect load when the powder is that temp sensitive.

Won't my ES and SD be all over the place with a different temp? I mean I could be spot on with a 2 SD and 4 ES when its 60 degrees, but what will my numbers be when its 15 degrees?

Im trying to learn this accuracy/velocity node stuff. Am I just looking for a velocity that seems to be stable? Such as about 3065 fps. Then so I try to vary my powder load for different temps to try to keep hitting as close to that 3065?

There is no such thing as a repeatable velocity flay spot. Try to replicate it and it won't happen.
With new Brass it will shoot different than once fired etc. Brass length. Internal volume will have some effects.

Pick a velocity and test test test. Learn how your rifle performs under different weather, shooting positions will change POI too, for example test this out:
Zero with one load, for example your 70 gr load. Zero prone, now shoot same load off a bench, then kneeling, then standing etc. Your POI will shift and you may need to settle on the medium Zero.

But pick a velocity you want, then seating depth and track this load in all weather patterns, you may need to adjust powder charged.
Or try to find a more stable powder to use.

 

[Plinker147]

If it's strictly a hunting gun just do the
Load development at the average temperature of when and where you hunt. This way you don't need to worry yourself about big temp swings.

If it's a Gun your going to shoot in all different conditions then you will have to shoot the loads in different temp and see what the real world difference is going to be. If your shots are 500-600yards and under the temp difference likely won't make enough point of impact difference to worry about for hunting. Further than 600 yds the temp/ velocity difference will start to be more noticeable the further you get.

I've shot allot of animals with temp sensitive powders inside of 600 yards without any issues

 

[jtvann]

Same brand and same lot # for each of the outings?

Yes. I bought 200 brand new ADG brass when it released last week. All from the same lot.

 

[jtvann]

There is no such thing as a repeatable velocity flay spot. Try to replicate it and it won't happen.
With new Brass it will shoot different than once fired etc. Brass length. Internal volume will have some effects.

Pick a velocity and test test test. Learn how your rifle performs under different weather, shooting positions will change POI too, for example test this out:
Zero with one load, for example your 70 gr load. Zero prone, now shoot same load off a bench, then kneeling, then standing etc. Your POI will shift and you may need to settle on the medium Zero.

But pick a velocity you want, then seating depth and track this load in all weather patterns, you may need to adjust powder charged.
Or try to find a more stable powder to use.

Sounds good. I liked the looks of my 70 grain load. I'll probably just stick to that for a while and play with it.

It is a hunting rifle and nothing else.

I'm using StrelokPro, which can estimate velocity for given temps if I don't already know what it is from experience.

I was just surprised at how temp sensitive Ramshot Hunter seemed to be. Close to 2 feet per second per degree.

Nothing wrong with making an average summer load and an average winter load if the speed bothers me that much. Just need to watch for over pressure in the summer if I'm running a hot load in the winter. I don't think I am though.

 

[waveslayer]

Sounds good. I liked the looks of my 70 grain load. I'll probably just stick to that for a while and play with it.

It is a hunting rifle and nothing else.

I'm using StrelokPro, which can estimate velocity for given temps if I don't already know what it is from experience.

I was just surprised at how temp sensitive Ramshot Hunter seemed to be. Close to 2 feet per second per degree.

Nothing wrong with making an average summer load and an average winter load if the speed bothers me that much. Just need to watch for over pressure in the summer if I'm running a hot load in the winter. I don't think I am though.

I'm not too familiar with Ramshot. But also keep in mind your velocity may be off too depending on your chrono, even the best chronos can be off.

 

[Bob Wright]

Tag

 

[SteveBurton]

Do yourself a favor and download this handy tool called Chronoplotter. It will plot your ladder test on a graph which makes visualization easier. Looks like you have some good advice already.

Chronoplotter

 

[waveslayer]

For sake of this thread I won't go into details about Ladder tests. Basically they can be very unreliable, especially with shooter error, natural dispersion in velocity, BC, environmental factors. Not very reliable , thus the OCW is a tad more reliable . But OP. You're on the right track