Help Me Understand My Data

[briscoetab]

My experience with new brass is limited compared to some, but neck tension has been all over the place. I have been running it through an expander mandrel, chamfering and deburring, then using imperial dry lube on inside of the necks and bullets. Even better if you shoot all your virgin brass 1X before you start load development.

I resize and run expander mandrel on new brass just to make it consistent. Don’t have any evidence it helps anything but when seating bullets you can feel the neck tension is more consistent. If I didn’t size them you could feel a bullet seat hard every one in awhile.

When doing load work up I will use new brass for the initial parts of my load work up but I only try to use the fires brass to fine tune and seems to work well for me.

 

[Harvey_NW]

The reason is decided to load more rounds at 40.5 was because it was the most accurate of my ladder. As I increased over 41, things really widened up. Should I mess with OAL next?

If anyone wants to develop a load for me and is near Missoula, MT let's talk time and mental energy are not things I have much excess of.

I'm no expert but I have an opinion on this, I've noticed on a lot of barrels that aren't heavy contour that my Magnetospeed changes harmonics and will not only shift POI but also change group pattern so I only use it for velocity data. When shooting a ladder I don't look for accuracy at all, I'm specifically looking for a velocity node because usually accuracy can be tuned in with seating depth. I combine a few different methods that usually works well for me, FWIW here's my process:

1. Run new brass over an expander mandrel or expander ball to straighten out any neck inconsistencies, load a ladder in .3 gr increments. I load all rounds for a ladder at .010 off the lands and never closer with hunting rounds so I don't risk getting a stuck bullet in the field.

2. Shoot to pressure (if you've loaded high enough), and look for the flat spots in velocities. I always hope for 3 charges that have a spread preferably less than 20.

3. I pick a charge at the higher end of the flat spot because usually load development is done in the off season in more reasonable or higher temperatures. Theoretically this should help stabilize the load for lesser temperatures, but I always try to verify. Load 4 rounds each at .010, .030, .050, .070, .090, and .110 off the lands.

4. Shoot groups.

If you want to spend the time or geek out further you can throw an OCW test in there, or do a seating depth test on different charges within that velocity node, but this usually gets it dialed in relatively fast for me.

 

[N2TRKYS]

I’ve never had issues getting low SD numbers with my factory RCBS dies, Chargemaster combo, or measuring the COAL. Also, there’s nothing wrong with finding a load with virgin brass. I do this all the time and find it easy to duplicate with fired brass.

 

[Boomer51]

I've got a few Tikkas and the barrels seem a bit slow. I've been able to work up to factory velocities, or a bit above, without pressure signs. My Tikka 6.5 CM has an accuracy node at 2,759 fps with a 143 ELD-X, using H4350. I got higher velocities with RL 26, but with reduced precision. I don't mind the slow barrels a bit, given the accuracy they give.

Jim

 

[slowelk]

I am definitely expecting some improvements after the first firing of the brass. I'm going to try to do some of the easy stuff first - lube necks and get a head space gauge. Down the road will be an auto dispenser of some kind and a better scale.

@Boomer51 - how far off the lands are you in your tikka? I hear different things with about how much tikkas like to jump.

 

[mvrk28]

Is that load compressed? I’m .02 off the lands with 140 hornAdy and bergers and start to compress at 46, I do the stupid toothbrush and buzz it down but still crunching, 47 is compressed big time. I’m 2760 with the Hornady I haven’t chronod the bergers yet. RL 26 and lapua small primer

Im .04 off the lands with hammers and I don’t believe the load is compressed, I’m using Alpha Munitions brass. I don’t feel any crunching. No toothbrush needed with a long drop tube.

 

[Boomer51]

Slowelk. My 6.5 likes 0.020 off of jam.

 

[Don Qui Puncher]

Im .04 off the lands with hammers and I don’t believe the load is compressed, I’m using Alpha Munitions brass. I don’t feel any crunching. No toothbrush needed with a long drop tube.

If you shake the loaded round you’ll hear it if it’s not compressed, 46 gets me to the base of the shoulder 47 goes passed the beginning of the shoulder , I use a vibe toothbrush and it settles the kernels down and I get a tiny bit more space, I have to go real slow with the press to hear/feel it compress

 

[briscoetab]

Thanks for the replies everyone. There are some terms thrown out there that I need to look up, sounds like I need some better gear too.

To answer some questions that came up:

new brass, I did no prep after reading that some of the premium brass didn’t need prep. CCI 250 magnum primers.

rifle has 177 rounds through it as of yesterday. I think a better scale might be the first order of business.

Other questions:

What are reasonable expectations for standard deviation and extreme spread? If you could assume that charge weights were precise, what else contributes to velocity variation?

I’d really like to get 2,700 FPS out of this combo. That isn’t asking too much is it? I read over on snipershide that due to Peterson’s lower case volume, it actually produces lower muzzle velocities due to lower average pressure, despite higher peak pressure. Is there any truth to that?

I started looking back at some of my old load work up data and my max load before I started seeing pressure signs was around 2870fps. That was with alpha brass, h4350, 143eld-x in a 26” barrel. I would guess going to a 21.5” barrel you would loose 60-100fps and 10-20fps maybe with the heavier bullet. So I would guess a reasonable top end speed would be a max of 2700fps without really pushing it but each rifle is different so could be a little more or less.