New load question

[PopCharlie]

If you start with new brass for a new load, and start with the determining powder primer node, how much will the velocity node move once the brass has been fired? Given using the same brass throughout the load development process.

I'm working on loads for a new 6br. I'm starting with 30 pcs of new Lapua brass. I plan to load these with a fireforming, barrel break in, sighting load. Then, using the same 30 pcs, start working on the velocity node.

TIA
PopCharlie

 

[piie]

The last time I started with a new box of Lapuas for my 6.5CM, I told myself before hand that I would not consider the rounds fully fire formed until 3x firings. It turns out - by way of measurements - that 2x was sufficient in my case. In any event - I decided that I would then just use the 3x firings to get to a good seating depth with a "middle of the line" load in terms of powder, so that - by the time the cases were properly fire formed, and I would start bumping shoulders back - I could only concentrate on powder charge and not worry about seating depth anymore. Whether right or wrong ( I think I read it on these here forums a while ago that seating depth can be determined regardless of powder charge) - it actually worked quite well for me... YMMV... The new brass will have less case capacity than fired rounds - hence the "logic" that I wouldn't start playing with powder charges in non fire formed brass...

 

[PopCharlie]

The last time I started with a new box of Lapuas for my 6.5CM, I told myself before hand that I would not consider the rounds fully fire formed until 3x firings. It turns out - by way of measurements - that 2x was sufficient in my case. In any event - I decided that I would then just use the 3x firings to get to a good seating depth with a "middle of the line" load in terms of powder, so that - by the time the cases were properly fire formed, and I would start bumping shoulders back - I could only concentrate on powder charge and not worry about seating depth anymore. Whether right or wrong ( I think I read it on these here forums a while ago that seating depth can be determined regardless of powder charge) - it actually worked quite well for me... YMMV... The new brass will have less case capacity than fired rounds - hence the "logic" that I wouldn't start playing with powder charges in non fire formed brass...

Makes sense. At least, by finding the seating depth before powder/primers, you can create more fire formed brass. BTW, 3X Firings seems to be right for my 6.5x47L. My .223 likes 4x to 5x before it gets consistent.

PopCharlie

 

[K22]

I can share my procedure that has worked for me but it's not high tech or "rocket science." I'm just trying to obtain a load that will give me the desire precision with the least amount of load development.

Some preliminaries - If you are seeking ultimate precision, the rifle should have a good bedding system and the barrel free floated. There are some rare exceptions on the free floating issue but I won't go into that here. Select a day for load testing with no to little wind and no mirage. If not, you're just peeing in the wind as the saying goes and wasting components. Also, I do all the load testing with a fouled barrel, about 3 shots.

On a new load which means to me a new bullet / powder I've never tested I start with published data from the bullet mfg. I set the cartridge length at .020" from the lands provided I have one bullet diameter inside the neck and the cartridge will fit the magazine. I begin with the starting published load, fire a five shot group allowing the barrel to cool between shots.

Depending the case capacity I move up about 5% or so and fire another five shot group always checking for pressure signs. Once I find a load that meets my standards, I'll fire a couple of confirming 5 shot groups to verify. I avoid compressed powder charges and never exceed published data maximum and if fact stay below the max. I also prefer "stick" powders rather than ball powders. The former is more temperature forgiving.

After a two or three firing I recheck the adopted load but rarely have I've experience radical changes in precision because of case wear issues.

If I'm not obtaining the results I desire the first change I make is another bullet assuming you are using a suitable powder. For most established cartridges, there are a group of powders that are known to work the best. Pick one of them. Manual often have recommendations on powder - a good place to start.

In my experience, the bullet is the single most influential factor affecting precision. Before moving to another bullet you can experiment with seating depth but in my experience it won't make much difference if the rifle doesn't like the bullet you've selected.

 

[Ned Ludd]

I work up loads in virgin brass regularly. Because the neck tension (interference fit) of brass straight out of the box can vary widely, I usually size it down with a FL bushing die and a bushing that will give neck tension ~.001" to .002" smaller than I ultimately want. Then I open up the necks with the appropriate diameter mandrel as the final neck sizing step. If set appropriately, the bushing die does not move the shoulders on virgin brass, it only sizes the necks down to where all the brass is ever so slightly under the diameter to which the mandrel will expand it, allowing the mandrel to generate much more uniform neck tension. When virgin brass is properly prepared, these loads can shoot very, very well.

Once the brass is fire-formed, it usually only takes a slight adjustment of charge weight to bring the load back to where it was in the virgin brass. Typically, dropping the charge weight from somewhere around 0.1 to 0.3 gr will usually be sufficient to re-establish the original velocity of the load as determined with virgin brass. Regardless of the amount of charge weight adjustment necessary (different cartridges will likely require different adjustments based on their internal volume before/after fire-forming), if you re-establish the original velocity, the load should end up very close to what it was in the virgin brass. Although I always determine optimal seating depth empirically after the brass is fire-formed, it often does not change once the velocity has been re-established.

I have always thought of putting hundreds of fire-forming rounds into the dirt to be a waste of time, effort, and reloading components, which as everyone knows are rather difficult to come by these days. I want to get something out of the fire-forming process, so I use loads in virgin brass as a learning tool, for practice, and also shoot them in club matches. Because the adjustments to bring a load using fire-formed brass are relatively minor as compared to virgin brass, I feel like the fire-forming and load development process with virgin brass is not a wasted effort. YMMV.