Load development procedure?

[jrw1976]

Is there anyone out there that finds the seating depth that their rifle likes before they find the sweet spot powder load? It might just be dumb luck on my part but I bought a used savage 7mm rm this summer and just decided to load up a few rounds at 68.5 gr H1000 WLR primers and 162 gr amax at .020 off the lands just to get it shooting. That load gave me 2 inch groups at 225yrds. Since then I have really free floated the barrel and bedded the action using the factory stock. Then I loaded up 5, 3 shot groups only varying the seating depth, from the lands out to .050 off. The .050 off rendered a group of .772" at 100 yrd. Then today I shot at 225 yrds and I shot an average of .660" out 0f 4, 3 shot groups. So is this dumb luck or is finding the seating depth first the ticket? I guess after christmas when I run a ladder and work up a powder load the story will play out. But between now and then I am cautiously happy.


Thanks, JRW

 

[SBruce]

I don't know that it really matters, but I always found the OCW and then used seating depth to fine tune.

They both have effects however, so I don't know that anything is "written in stone".

 

[johnnyk]

I first determine the overall length for the bullet I am loading, subtract .010" from that number and that is my seating depth. I don't vary the seating depth again.
In over 25 years of reloading the only time I have had to vary the seating depth was when trying to get the 168gn VLD Berger to shoot accurately in a 700P in 7Mag. I tried .010, jammed, .005, .020, .030. I tried four or five powders and two or three primers. I never did get those darn things to shoot and shot the whole box trying! I gave up. JohnnyK.

 

[jrw1976]

I ran the test because I have always wanted to know how seating depth effected accuracy and I found that it had great effects. Now I am very curious what the outcome of my load test will be.


JRW

 

[Nalgi]

You hit the nail on the head!!!

you found out our secret! we use a starting charge of about 80-85% of max load. From there, figure out the seating depth. It really shows itself .003, .005, .007 off lands. There will be a sweet spot. once you find that work the charge up til it starts to spread (not to exceed Max. load)

It should give you good results. We found this out because we had to switch all our loads to non lead. Switching bullets alone didnt work.

 

[bigngreen]

I start with seating depth with them all, establish at what COAL I'm touching the lands then work back like the Berger guys say to do but I go in .010 increments then down to .005 increments for the last one. So far once I establish the spot it remains that spot till I have to chase lands. Weatherby cases have been the exception, I load them to max box length and make them work by tweaking everything else.

 

[jrw1976]

Finding the seating depth first before I find the powder charge just makes sense to me. Because if I was to just pick a random depth of say .010-.020 off the lands like most guys seem to do to start with and that depth isn't the one the gun likes. Then I continue on to work up a powder load with this faulty depth, my theory is that I would be getting faulty pressure spikes at ignition. I am going with the opinion that seating depth is the constant in the process because as we all know the distance of the bullet away from the lands effects the ignition pressure spike which in turn also effects barrel vibration. Well this is just a theory that has perplexed me since I started reloading a year ago and so far this is the answer I have came up with.


JRW

 

[RockyMtnMT]

I start at or just off the lans depending on what type of bullet I am using. Increase from start load in .5g or 1g increments (singles) to find max load using a chrony. After that I adjust seating depth if needed to fine tune groups. This method will use the least amount of resources. Almost always have a load done inside of 25 rounds.

Steve

 

[Gene]

I use Steve's method and find it works well. Always change just one element at a time. Both OAL and charge are critical. But even miniscule seating depth changes can affect accuracy, MV, ES, etc.

I would not recommend choosing one seating depth and failing to try others.

 

[ScottB]

I run the ladder test, find the 'node' or 'sweet spot' and then fiddle with COAL. Unless the 'node' is already sub-MOA, which is usually is really close.....then I leave well enough alone and work on sending projectiles downrange with the perfect practice method.




Scott