6cm Origin LD issue?

[Whytry85]

Started load development on my origin/proof 6cm the other night. I’m going with the Satterlee method so loaded up 15 rounds starting at 39gr-41.8 of h4350 and 108 eldms in hornady once fired brass and fgmm210m seated between .004-.005. Once fired measured 1.540 and didn’t pass the bolt drop test so resized to 1.5380 and was silky smooth. Velocities are much higher than anticipated and also showing what I think are mechanical ejector swipes starting at 41.6gr. Hornady shows 41.7 max but not what I thought i would find. There’s a few nodes to choose from so more/less just curious. Anyone else ever seen this below max charge? Chalking it up to the “every rifle is different” explanation.

 

[John Glidewell]

Yup. 39.8 to 40.2 + or - a tenth is where it us at. Those are ejector slot marks with mild cratering on the primer. I would call that a safe max. Any higher and you would have heavier bolt lift. You can run hard on these actions, but your money is somewhere around 40 grains. My QL barrel times always line up around 1 to 2 grains off safe max. The speed lines up with what I have seen too. 2990 to 3040 is where they run the best for me.

 

[supercorndogs]

Hodgdon days 41.6 with a 108eldm is max at 3000fps in 24" barrel. Your 41.6 has exceeded that buy 100fps. Are you jammed into the lands.

Single shot Chronograph ladders are choosing you a random.charge weight based on random overlapping deviation in speed.

 

[Whytry85]

Yup. 39.8 to 40.2 + or - a tenth is where it us at. Those are ejector slot marks with mild cratering on the primer. I would call that a safe max. Any higher and you would have heavier bolt lift. You can run hard on these actions, but your money is somewhere around 40 grains. My QL barrel times always line up around 1 to 2 grains off safe max. The speed lines up with what I have seen too. 2990 to 3040 is where they run the best for me.

Kind of what I’m thinking. During initial work up, I’ve seen guys exceed the 41 grain and push them faster with similar pills and powder so I was kind of at a loss.. might even check the 39.3-39.7 to see if there is a slower node to shoot in hotter temps.

Hodgdon days 41.6 with a 108eldm is max at 3000fps in 24" barrel. Your 41.6 has exceeded that buy 100fps. Are you jammed into the lands.

Single shot Chronograph ladders are choosing you a random.charge weight based on random overlapping deviation in speed.

I saw that as well while referencing some data. These were all seated at .025 off the lands. I was also thinking carbon ring might be causing pressure spikes but a quick bore scope proved that to be false.

 

[spife7980]

My proof barrel and Peterson brass and 107s makes 3030 with 37.5 gr of h4350, it goes fast with less powder than recommended on the internet.

Go with your evidence of pressure, not the peer pressure.

 

[Cascade Hemi]

Kind of what I’m thinking. During initial work up, I’ve seen guys exceed the 41 grain and push them faster with similar pills and powder so I was kind of at a loss.. might even check the 39.3-39.7 to see if there is a slower node to shoot in hotter temps.

I saw that as well while referencing some data. These were all seated at .025 off the lands. I was also thinking carbon ring might be causing pressure spikes but a quick bore scope proved that to be false.

There are variances in chambers and barrels. You often here people say they have a fast barrel but what they actually have is more pressure. Whether your barrel is a little tighter or your chamber/throat smaller/shorter, you're building more pressure than the available load data. Your chronograph is an indication of the pressure in addition to the traditional physical signs on the brass and primer. Because of this, I will often correlate velocities with pressure from Hodgdon/Sierra/QL instead of the charge weight with pressure. You're looking for velocity and pressure anyway so your charge weight is largely irrelevant beyond diagnostic value.

The "Satterlee Method" is just a single shot pressure ladder. It's telling where your combination of variables correlate to pressure. It doesn't tell you where nodes are but now you should have a good idea where to start and stop development charge weight.

 

[Hickswr]

Nodes and ladders are myths.

What’s the logic behind jumping .005? In a few hundred rounds throat erosion will have doubled your jump or more. And chasing the lands is no fun, unless you are into that sorta thing.

 

[Cascade Hemi]

Nodes and ladders are myths.

Let's not get carried away. When you add or subtract propellant you increase or decrease pressure. Pressure ladders aren't a myth by any objective metric; more powder does in fact equal more pressure. "Nodes" may not work as many people understand them but cartridges have an efficiency window.

 

[Whytry85]

Go with your evidence of pressure, not the peer pressure.

Ahhhhhhh peer pressure.. haven’t seen her around these parts since high school. But I get where you’re coming from. Honestly not too worried about how many grains etc it takes to make the rifle shoot, just was surprised by my findings.

 

[Whytry85]

The "Satterlee Method" is just a single shot pressure ladder. It's telling where your combination of variables correlate to pressure. It doesn't tell you where nodes are but now you should have a good idea where to start and stop development charge weight.

I guess i should’ve said consistencies in CW instead of “nodes” being as they’re single shot strings. I’ll load up another run to see where it likes the seating depth and move forward.

 

[Supersubes]

Ahhhhhhh peer pressure.. haven’t seen her around these parts since high school. But I get where you’re coming from. Honestly not too worried about how many grains etc it takes to make the rifle shoot, just was surprised by my findings.

But thats just it, the the numbers were screaming at you, but you ignored them. The extra velocity was the result of extra pressure, there’s no free lunch.

 

[Whytry85]

But thats just it, the the numbers were screaming at you, but you ignored them. The extra velocity was the result of extra pressure, there’s no free lunch.

The case pictured is from the 41.8 load. It wasn’t until after testing that I saw a slight and I mean slight, kiss on the brass at 41.6. No other signs besides velocity being higher on anything lower than 41.8 which is why I stopped there. What would you have done in that situation?

 

[Supersubes]

The case pictured is from the 41.8 load. It wasn’t until after testing that I saw a slight and I mean slight, kiss on the brass at 41.6. No other signs besides velocity/pressure on anything lower than 41.8 which is why I stopped there. What would you have done in that situation?

Totally missing the point, dude. The rifle was going fast well short of hornady’s max charge. That velocity wasnt free.

 

[Whytry85]

Totally missing the point, dude. The rifle was going fast well short of hornady’s max charge. That velocity wasnt free.

Nah, I’m with you. Just trying learn my man. All is good. Very good insight across the board. Much appreciated!