300WM ES/SD Issues

[Matchgrade]

Fellow Hide members,
I am Looking for some help lowering my SD/ES on my 300 Win Mag. My Current Load is preforming with a consistent, unimpressive ES of 80 FPS and a double digit SD.

210 Berger Hunting VLD, .005 off the Lands
71.9 Grains of H4831SC, Charged and Weighed with FX120I
Sig Fireformed cases (weight sorted), AMP Annealed (Every Firing), shoulder bumped .002, Neck tension .001 using Redding bushing die. Giraud trimmed. Cleaned with SS Tumbling media.
Federal 215M Primers
I am testing the loads in 10 round batches.
Barrel is a 1/10 24" Bartline Heavy Palma

I have tried a variety of different powders and charge weights in this rifle , including N165, H-1000, and Retumbo. As well as different bullet combinations and seating depths (212, ELDX, Berger 208, Berger 230, 220SMK) all with almost the identical results over a magneetospeed V3 Chrono.

I have had success with other calibers, .338LM, .308, .260, and 6.5 achieving a sub 10 SD but after a year of chasing my tail with this 300 Win mag any help would be appreciated.

Thanks

 

[Rocketmandb]

What did you do to arrive at the powder charge you're using?

 

[Matchgrade]

@Rocketmandb Over 3 grains 70-73 of powder I selected the the charge weight with the best ES, followed by the smallest group. After some research this evening I suspect I may need to find a wider velocity node that is more forgiving.

 

[918v]

You prolly over annealed and now the necks do not hold the bullet well enough to ensure proper combustion.

 

[MtnCreek]

005 off lands and 001 tension is most likely the problem(s)

 

[Schw15]

I would say try tighter neck tension at least .02 and play with seating depth a little.

 

[Feniks Technologies]

Just for extra info on what people are suggesting.

If you are jammed into the lands, then things like annealing and interference fit (what most people call neck tension) aren’t that important for consistent velocity. The reason being that your bullet is already against steel. So, it will be consistently held in place while pressure builds.

Consistent pressure = consistent velocity. Consistent velocity is what keeps sd/es low.

When you are jumping bullets, there is an initial “push” or pressure build up that unseats the bullet from the neck and into the lands. Then the lands hold it until pressure builds to push it down barrel.

So, annealing an interference fit are now important.


That’s why people are suggesting increasing it. You’ll likely find that with more interference fit and/or more friction in the neck, your velocity will be more consistent.


If all else fails, buy some Lapua brass. Most problems people have are solved via better components.

 

[918v]

Try your load with 1x fired brass that you did not anneal ever. Report back with the ES.

 

[Rocketmandb]

If all else fails, buy some Lapua brass. Most problems people have are solved via better components.

I've never used Sig brass, so have no clue about how good it is, but the above advice seldom fails. My adage is: if Lapua makes brass for what you're shooting, you shoot with Lapua.

With that said, @Matchgrade , here are some additional points:

- What @918v says is true. If you've over-annealed brass, it's sort of done. You have to work it a lot to get it back into line, and my belief is that it's simply not feasible once it's toasted.

- It would be helpful if you post your work-up data. What is not clear is why you landed on the load you did. I like to pick a velocity that delivers the best SD, then tune for seating depth to get group size down. SD is important to me in most rounds I shoot, as I do a lot more ELR than not.

- You don't mention using a mandrel or neck lube. Since you're tumbling the brass and removing carbon in the necks, some neck lube is in order. I had a thread where I measured the difference in using mandrel/not and neck lube/not, and all combinations. It was very clear that using a mandrel and neck lube has a significant impact on SD. https://www.snipershide.com/shooting/threads/mandrel-musings.7075612/#post-9476761

- The impact of not using mandrel/lube gets amplified when you have crap brass. Sig might not be "crap", but it might not be as uniform as you would think. As an example, ADG is regarded as high-quality brass. I used it for quite a while with my 300 PRC, but didn't get as good results from when I made my own cases out of RWS (same or better quality than Lapua) 8x68S cases. My seating force consistency (correlates to muzzle velocity SD) was poor - on the order of 15-20 lb spread. When Lapua finally came out with 300 PRC, my spread dropped down to mid-single digits. It was night and day.

- I'm going back to what @Feniks Technologies said: "buy some Lapua." Unfortunately, Lapua is hard to come by, but RWS is available. Get some of that, run a new ladder, get a mandrel/die, use neck lube.

 

[Matchgrade]

@Rocketmandb @Feniks Technologies @Schw15

Thank you guys for your input.
Went .003 Neck tension W/ mandrel, graphite lubed, changed powder charge from 71.9 to 72.5, backed the seating depth to .010 off the lands. shot a 6 round string at a 7.4 SD and another 4 round string at 7.6, both near 1/4 MOA.

I will confirm with a larger test lot tomorrow, but the numbers are defiantly manageable now. Lapua Brass Next.

 

[Rocketmandb]

@Rocketmandb @Feniks Technologies @Schw15

Thank you guys for your input.
Went .003 Neck tension W/ mandrel, graphite lubed, changed powder charge from 71.9 to 72.5, backed the seating depth to .010 off the lands. shot a 6 round string at a 7.4 SD and another 4 round string at 7.6, both near 1/4 MOA.

I will confirm with a larger test lot tomorrow, but the numbers are defiantly manageable now. Lapua Brass Next.

Dang, that was quick - and good results!

 

[99mpower]

WOW... small changes, little tweak, and BAM, in there.. cant wait to see what you end up with after Lapua Brass