300 grain bullet confusion

[Roblonsberry]

Hello everyone,

Several months ago I had an issue with consistency and thanks to a fellow members help it ended up being my brake. I never would have thought this would cause it but you live you learn. I went from MOA to .3 MOA shooting 300 grain OTM by putting an EC tuner brake on. I’m as surprised as you that worked! My worst group changing the tuner settings with this particular load was .75 MOA.

Being Canadian and being a reloader is a bad combo. I cant get 300 Berger OTM projectiles here. (or much of anything else for that matter)

Since I was able to get Lapua 300 grain scenars I gave them a try. I made up some scenars with the same case, powder charge and primers. I seated the scenars to .002 off the lands like the otm were seated. Velocities were nearly same. Groups were terrible. I checked all my screws on my gun and scope and everything was to spec. Since the velocity is the same I don’t think the bearing surface would cause this.

What could cause the groups to be well over MOA? I tried quite a few settings on the tuner

 

[Dogtown]

You can expect similar velocities between bullets of the same mass, but the bullet profile between the OTMs and the Scenar is different, so there's no guarantee they will group similarly with the same load (especially if seated the same).

Ideally you want to do load dev when you use a new bullet, but in this case I'd just load up some seating depth variation and see if any of those strings show improvement. If not, then start over with powder charge, though you can narrow the range given your previous load.

 

[Roblonsberry]

You can expect similar velocities between bullets of the same mass, but the bullet profile between the OTMs and the Scenar is different, so there's no guarantee they will group similarly with the same load (especially if seated the same).

Ideally you want to do load dev when you use a new bullet, but in this case I'd just load up some seating depth variation and see if any of those strings show improvement. If not, then start over with powder charge, though you can narrow the range given your previous load.

I think this is a good idea. I was hoping to minimize that load development (although I do like it) just becaus of component scarcity. since I have the tuner I expected a little better since my OTM loads improved so much. It goes to show just how deep this rabbit hole really is.
I appreciate your insight sir. Thank you.

 

[spife7980]

A new component = a new load

 

[Roblonsberry]

A new component = a new load

I knew that to a certain degree but I presumed it was weight based with projectiles. The fact that they chrono’d so close further confused me when I saw the crappy groups. Thank you.

 

[Dogtown]

Barrels are also unique from barrel to barrel. Sure, some can trend together to favor certain bullets, but then there are oddballs that just don’t like certain bullets. For me with .338s, I had a barrel that just loved the 250 and 300 Scenar as well as the 300 OTM, but just…would…not…shoot the Hornady 285s. I burned through 200 trying to get a decent load without success. Tried again when I got a new barrel a few years later and it had no problem with them.

 

[Roblonsberry]

Barrels are also unique from barrel to barrel. Sure, some can trend together to favor certain bullets, but then there are oddballs that just don’t like certain bullets. For me with .338s, I had a barrel that just loved the 250 and 300 Scenar as well as the 300 OTM, but just…would…not…shoot the Hornady 285s. I burned through 200 trying to get a decent load without success. Tried again when I got a new barrel a few years later and it had no problem with them.

Mine shoots 250 ok but they don’t do well at distance. Mine too didn’t care for 285s. Too bad since they’re actually available up here

 

[Dogtown]

The 300 A-Tips are another good option, I've found, and have been easy to get in North America on a consistent basis.

 

[Roblonsberry]

I’ll see if I can get my hands on some to try. Thanks.

 

[Fig]

There is more witchcraft than a lot of people (on this forum) want to admit. I'll bet I've taken a half dozen lawnmowers apart trying to figure out what's wrong. Sometimes I would find nothing wrong or broken. I put them back together and they ran fine.
Shooting and reloading machines that are measured down to the thou there's just going to be a lot of aberration that isn't easily explained without millions of dollars testing equipment. I think the best advice is not to dwell on it if nothing obvious is wrong, and just change it up till you find a load that hits. It will take much longer to get there if you ruminate on why something didn't work rather than just accepting it didn't and switching to something different that may work. There are procedures to ladder test and seat bullets to cut down on the time it takes, but there is no substitute for trial and error.

 

[Tempest 455]

Even EC will tell say, you have to tune the load before using a tuner. Likely need to do OCW and seating depth and start at square 1 with a different projectile.

 

[Roblonsberry]

There is more witchcraft than a lot of people (on this forum) want to admit. I'll bet I've taken a half dozen lawnmowers apart trying to figure out what's wrong. Sometimes I would find nothing wrong or broken. I put them back together and they ran fine.
Shooting and reloading machines that are measured down to the thou there's just going to be a lot of aberration that isn't easily explained without millions of dollars testing equipment. I think the best advice is not to dwell on it if nothing obvious is wrong, and just change it up till you find a load that hits. It will take much longer to get there if you ruminate on why something didn't work rather than just accepting it didn't and switching to something different that may work. There are procedures to ladder test and seat bullets to cut down on the time it takes, but there is no substitute for trial and error.

I agree. Some variables just simply aren’t completely controllable. I’d prefer to stick with what I know works for my system for sure. I just can’t get what I need here.

 

[Roblonsberry]

Even EC will tell say, you have to tune the load before using a tuner. Likely need to do OCW and seating depth and start at square 1 with a different projectile.

I agree.

 

[B'N'F]

I’ll see if I can get my hands on some to try. Thanks.

Fellow Canadian here.. you should definitely be able to source the A-Tips, and while Berger bullets haven't had much availability up here lately, they are out there for sure! Powder has become much more available too.

Are you loading a .338 or .300 cartridge?

 

[Roblonsberry]

Fellow Canadian here.. you should definitely be able to source the A-Tips, and while Berger bullets haven't had much availability up here lately, they are out there for sure! Powder has become much more available too.

Are you loading a .338 or .300 cartridge?

I found some A tips but they want nearly $200 for 100 plus shipping etc. I must be signed up for 40 email alerts lol. I’ve even tried calling in favours From gun shop owners. I’m loading for a 338 LM