Building a precision load and ladder testing

[fairchaser]

If you were building a new load for a long range rifle, what would be the few most important elements in building and testing loads? After I select my bullet, powder, case and primer and size them to fit my rifle, I would ladder test powder charges until I found a node and then fine tune from there at long ranges. Is this the right approach?

 

[DaveB]

I would say that is exactly the process with one exception. I don't choose a powder. I let results choose the powder.

With Your initial loads you want accuracy and muzzle velocity. This is why some folks use the newer Chrono technology because FPS is a big factor.

A tight group at 100 stretched out to 2/3/400 and you should start to see the drop. You should have predicted the drop based on your ballistic chart. If you are performing at expected levels you can begin to stretch it out in increments.

And sadly it is at the longer distances where gremlins like wind and mirage and even humidity can play a part.

Best of success.

 

[fairchaser]

I would say that is exactly the process with one exception. I don't choose a powder. I let results choose the powder.

With Your initial loads you want accuracy and muzzle velocity. This is why some folks use the newer Chrono technology because FPS is a big factor.

A tight group at 100 stretched out to 2/3/400 and you should start to see the drop. You should have predicted the drop based on your ballistic chart. If you are performing at expected levels you can begin to stretch it out in increments.

And sadly it is at the longer distances where gremlins like wind and mirage and even humidity can play a part.

Best of success.

DaveB, what standard deviation is acceptable in FPS? And what would make you give up on the powder and try another? Thanks for the feedback.

 

[DaveB]

A large SD indicates some kind of problem....Powder charge light/heavy. Primer too strong results in over-combustion results in variances (think small rifle primer and what the real pro's use) Case mouth tension (anneal-some folks do it after every firing) You can address it by rotating case as you seat...this is marginal and not a method to avoid annealing. Shoulder setback is too much/not enough. Your barrel is too dirty/too clean.

As an objective, a SD of less than 20 is probably too large....I would die for that on a consistent basis

As for powder change: You need something that TENDS to be temperature insensitive (I don't think any of them are totally stable). Lets say RL7 returned a SD of 4 and velocity of 3200 FPS but bullets would not group. You change Jump up to contact with lands and back to SAAMI specs. Still no accuracy despite near perfect chrono results. Change bullet weight to longer...if not in plan to do so then move down the burn rate chart.

I still use an RCBS 10-10 scale and measure every charge and take other precautions to insure than 59.5 grains is EXACTLY 59.5 grains. If I get flyers I know this is most likely neck tension. If I cannot get a powder to group I drop that powder and move on to the next. Because of my experience with the Browning BOSS I know barrel vibrations actually change the flight of a bullet. The BOSS allows you to minimize this effect. Since you cannot use the BOSS at long range contests, you have to change the powder burn rate to get the barrel vibrating the same way every time. Its why you sometimes see me ask which bullet is 1, 2, etc. Residual heat allows the barrel to flex (think bull barrel).

Every step needs to be focused on repeating the steps exactly.

My BIL is a maniac but I have watched him send 5 downrange at 200 yards through the same hole more than once. He neck turns. He weighs brass. He weighs bullets. He anneals after one shot. He measures set back. He seats to + or - .0002. This probably describes a lot of folks on TNDeer.

 

[fairchaser]

DaveB, thanks for the decision tree on hand loading. That rabbit hole can get deep and it's also bottomless. But there is a point of diminishing returns. I read an article awhile back that tested rounds shot in a controlled environment. What they found was certain things that were thought to be important to consistentency were not as important and others were more important. I wish I could remember all the details but one thing I remember was that primer seating pressure was big and things like powder charges down to the grain were not. I have two Browning Boss rifles; so I understand barrel vibration and harmonics. I think one of the main things ladder testing does is find that sweet spot where the rifle wants to settle in for a certain FPS. The trick is to find where you get consistent speed and accuracy. Thanks again for the help! I'll start with chronoing at shorter ranges and once I get something I like, I'll stretch it out. I'm thinking that I'll start with 168 gr Sierra match kings and varget in my savage 10 .308. I'll probably start around 41.4 grains and work toward the max. until I see some pressure issues. Once I find something close I'll tune it and ladder test. Wish me luck, I'm jumping into the rabbit hole!

 

[mr.big]

what do you consider long range?? I have seen some really good loads with tight ES numbers fall completely apart after about 4-500 yards,,,,my best shooting 1,000 yard load in my 6.5x47L just shoots pretty good at 100 yards and has ES of 13-15 fps depending on the weather,,but it will stay on a 5x8 inch steel plate at 1,000 yards

 

[fairchaser]

what do you consider long range?? I have seen some really good loads with tight ES numbers fall completely apart after about 4-500 yards,,,,my best shooting 1,000 yard load in my 6.5x47L just shoots pretty good at 100 yards and has ES of 13-15 fps depending on the weather,,but it will stay on a 5x8 inch steel plate at 1,000 yards

Shooting 600 yds and no farther Mr. Big. So are you saying don't trust your 100 yd groups or be sure to test them at your max range before counting them good?

 

[mr.big]

if 600 is your max range ,,I would want to start my testing at at least 300 yards,,if you dont have anywhere to shoot except at 100 yards then you will have to but I would want to test it at 600 the first chance I had,,



there is a monster thread on accurate shooter about testing for long range at 100 yards that has lots of relative info in it,,,there are a few world class LR FClass shooters that do test at 100 yards,,

http://forum.accurateshooter.com/thread ... t-36221455

 

[fairchaser]

if 600 is your max range ,,I would want to start my testing at at least 300 yards,,if you dont have anywhere to shoot except at 100 yards then you will have to but I would want to test it at 600 the first chance I had,,



there is a monster thread on accurate shooter about testing for long range at 100 yards that has lots of relative info in it,,,there are a few world class LR FClass shooters that do test at 100 yards,,

http://forum.accurateshooter.com/thread ... t-36221455

Thanks Mr. Big. I plan on load testing at 300 too. I can shoot at 100, 200, 300 and 600.

 

[user 14220]

Bullet shape and seating depth can have a huge influence on accuracy.

 

[DaveB]

I spent over a year on my 308 to get it to group at an inch or better. I counted spent brass.....85 rounds.

My AR is an M&P. Until the factory fixed a bolt problem it would not group and still is never going into the deer woods.

My 280 fired a 5-round group and although I had 5 other ladders to shoot I stopped right there.

I have a Model 70 that won't group 180's. Does 150's just fine. Over 200 rounds trying to get this Win to group.