Muzzle velocity question???

[186thFCo]

A couple quick question. when working up a load for a long range hunting/PRS rifle what is a good SD muzzle velocity to aim for. I would like to get zero but right now I'm getting around 15/16 SD according to my magnetospeed.

2) When preforming a ladder test how important is barrel temp?

3) why do i have such a big deviation in MV when the primer, powder charge and seating depth are all as identical as i can get them, is there something i'm not accounting for?

thanks for your help

 

[Kopfjager1]

A good SD to aim for is under 10fps, 15-16 is still in an acceptable range to be in. Where youre going to notice the SD is longer ranges, greater than 800 generally. With 15fps SD youre looking at a estimated 5" vertical uncertainty at a grand. I would try to keep your barrel temp as low as possible, just to reduce any variables. I would strive for less than 1 round every 10-15 seconds. Honestly I would worry about the powder temperature more, such keeping all your rounds in the same place, either all of them in the shade or all in the sunlight.

Primer depth consistency and neck tension, and case capacity are going to be the biggest factors after powder charge and seating depth. To get into single digit SDs you need to be pretty consistent with your handloading process.

 

[spife7980]

Every 10-15 seconds? That barrel is going to be scorching by the end! I stick to one every four minutes testing. If I can't hold my palm to it in front of the scope without too much sensation then I think it needs to cool a bit. Keep it warm, not hot.

If you think you have it all dialed in start weighing brass, turning necks, annealing etc.

Shoot your targets and see see what they have to say as well. Some stuff can be finicky sometimes but the paper doesn't lie.

 

[Citius7]

To answer number 3. Even when everything is perfect it won't be. Your barrel will have nodes. Pockets of velocity where the barrel 'likes' to be shot at. When you shoot a ladder for visual you will see the nodes flatten out vertically and will be side to side of one another. You will be able to confirm this when you use a chrono. It will be a flat spot where things look like the point of impact did not shift. These tend to be where you want to load at. And they are forgiving for a handloader. SDs tend to be the best in nice big nodes. Clear as mud?

 

[Kopfjager1]

Every 10-15 seconds? That barrel is going to be scorching by the end! I stick to one every four minutes testing. If I can't hold my palm to it in front of the scope without too much sensation then I think it needs to cool a bit. Keep it warm, not hot.

If you think you have it all dialed in start weighing brass, turning necks, annealing etc.

Shoot your targets and see see what they have to say as well. Some stuff can be finicky sometimes but the paper doesn't lie.

Yep, my mistake, just woke up, I was thinking of no more than 4-5 rounds per minute, and break between each string of 10 rounds.
Honestly though, Ive shot upwards of 20 rounds in rapid succession and never noticed a POI shift where it can be blamed on MV alone.

 

[186thFCo]

Sweet thanks guys, I'll be doing ladder testing on two of my rifles this weekend, hopefully.

 

[Supersubes]

Post your gun/load details, might help us suggest a direction to move in.

 

[impactaddict]

Try to get velocity readings on every shot when you do your testing. Citius7's instructions will come into play with that data. You're looking for "flat spots" in velocity which often correlate to the node of your barrel. Finding those flat spots and throwing powder charges in the middle will allow the hand loader a little breathing room for slight variations.

Ideally you'll have 2 plateaus with sharp velocity increases between them, one slower plateau and one faster. I usually load to the faster and play with seating depth to fine tune.

This video should help explain the concept
https://www.youtube.com/watch?v=ACyfeeBHVOA

Good luck and please share results!

 

[Deleted member 10043]

True cold bore shot is the first shot of the day. Waiting 15 minutes is not a cold bore shot.

As, for SD, you want singe digit and the smaller the spread the better. I shoot a 10 shot string and I don't wait between shots. It is a rifle and not some woman that needs an hour of attention to reach an orgasm.

 

[186thFCo]

Try to get velocity readings on every shot when you do your testing. Citius7's instructions will come into play with that data. You're looking for "flat spots" in velocity which often correlate to the node of your barrel. Finding those flat spots and throwing powder charges in the middle will allow the hand loader a little breathing room for slight variations.

Ideally you'll have 2 plateaus with sharp velocity increases between them, one slower plateau and one faster. I usually load to the faster and play with seating depth to fine tune.

This video should help explain the concept
https://www.youtube.com/watch?v=ACyfeeBHVOA

Good luck and please share results!

So doing it this way you don't even need to put rounds on paper you just look at the velocities your getting from the magnetospeed and that correlates with the nodes in your barrel, am I getting that right? If this is true it would be a big help for me cause it is sometimes hard for me to find a range that is 300 yards or better to do a ladder test. All the ranges here in New England are at best 200 yards.

 

[Deleted member 10043]

Nodes are just the point somebody gets some good groups on that particular day.

 

[impactaddict]

So doing it this way you don't even need to put rounds on paper you just look at the velocities your getting from the magnetospeed and that correlates with the nodes in your barrel, am I getting that right? If this is true it would be a big help for me cause it is sometimes hard for me to find a range that is 300 yards or better to do a ladder test. All the ranges here in New England are at best 200 yards.

This is correct. You can do this testing at 100yds or shoot directly into the berm for that matter. Based on this method, we are ONLY interested in velocity plateaus.

 

[186thFCo]

Thats good to know. I will try that out on my .308. I just did a ladder test on two of my rifles at 350 yards, my 7mm has a node I will work off of that is clear as day, but my .308, not so much.

 

[DynamicAccuracy]

I usually shoot for 4-7 fps SD in my 6.5x47.

 

[DynamicAccuracy]

Idk if barrel temp makes a difference when doing load development. I would suspect is depends on barrel contour. A light weight sporter barrel eill have vertical stringing as it heats up but my heavy varmint hasn't shown signs of stringing yet