Question on Powder Charge Ladder for 308

[DKE34]

Guys, relatively new to reloading. This is the second load I've worked on and the first for 308.

I've got Hornady fired factory brass, H4895 and 168g TMK's. Shooting a Tikka t3x. I set up the ladder based on the book min/max from 41.0-43.8 grains. 3 shots each in .3 grain increments. My shoulder is sore today.

After putting them in charts, there is clearly a plateau/node at 42.2-42.8. The ES for all nine of those shots was 20 fps.

For the highest charge at 43.8, there was clearly no node. It was still a very steep curve on the chart. BUT, all three shots at 43.8 were within 2 fps - 2749, 2748, 2748. There was a scuff on one of the case heads showing a slight pressure sign. I've read all about the soft Hornady brass, but that's what I have and I'm going to use. I know there's better brass out there, but I've been saving Hornady brass for a while now from hunting and shooting and have a couple hundred cases. I don't know if one scuffed case head is enough to say the pressure is too high. There were no signs on the primers.

None of the individual charges in the node from 42.2-42.8 were as consistent as the charge at 43.8. Tighest ES from any one of those three was 12.

Obviously I'd prefer the faster load in 308. It gives me about 100 more yards for effective hunting range.

Should I go with the hotter, more consistent load or go with somewhere in the slower chart node.

I know that the right answer is "Do more experimentation." I'm hoping that somebody has been through this and can save me components and two more 60 mile trips to the range just for more load dev.

Thanks for any input. These forums have saved me a lot of wasted time and components.

 

[Marbles]

Well, I don't think three rounds tells you anything, other than if you have pressure. From experience, you can get 3 rounds without pressure, but have a few that show pressure signs out of 30.

I don't think hot rodding is worth it. I would call pressure at 43.8 gr, drop to 43.3 gr and load 50.

If velocity is more important than reliability, then loading hotter makes sense. I don't think the velocity is worth it though.

I'm doubtful that nodes actually exist and suspect they are an artifact of inadequate sample size.

 

[DKE34]

Well, I don't think three rounds tells you anything, other than if you have pressure. From experience, you can get 3 rounds without pressure, but have a few that show pressure signs out of 30.

I don't think hot rodding is worth it. I would call pressure at 43.8 gr, drop to 43.3 gr and load 50.

If velocity is more important than reliability, then loading hotter makes sense. I don't think the velocity is worth it though.

I'm doubtful that nodes actually exist and suspect they are an artifact of inadequate sample size.

Thank you. I don't care that much about velocity. I was just happy to see an ES of 2 with the high charge. I know it's a small sample size.

 

[Q_Sertorius]

Well, I don't think three rounds tells you anything, other than if you have pressure. From experience, you can get 3 rounds without pressure, but have a few that show pressure signs out of 30.

I don't think hot rodding is worth it. I would call pressure at 43.8 gr, drop to 43.3 gr and load 50.

If velocity is more important than reliability, then loading hotter makes sense. I don't think the velocity is worth it though.

I'm doubtful that nodes actually exist and suspect they are an artifact of inadequate sample size.

I definitely agree with this.

 

[Q_Sertorius]

Guys, relatively new to reloading. This is the second load I've worked on and the first for 308.

I've got Hornady fired factory brass, H4895 and 168g TMK's. Shooting a Tikka t3x. I set up the ladder based on the book min/max from 41.0-43.8 grains. 3 shots each in .3 grain increments. My shoulder is sore today.

After putting them in charts, there is clearly a plateau/node at 42.2-42.8. The ES for all nine of those shots was 20 fps.

For the highest charge at 43.8, there was clearly no node. It was still a very steep curve on the chart. BUT, all three shots at 43.8 were within 2 fps - 2749, 2748, 2748. There was a scuff on one of the case heads showing a slight pressure sign. I've read all about the soft Hornady brass, but that's what I have and I'm going to use. I know there's better brass out there, but I've been saving Hornady brass for a while now from hunting and shooting and have a couple hundred cases. I don't know if one scuffed case head is enough to say the pressure is too high. There were no signs on the primers.

None of the individual charges in the node from 42.2-42.8 were as consistent as the charge at 43.8. Tighest ES from any one of those three was 12.

Obviously I'd prefer the faster load in 308. It gives me about 100 more yards for effective hunting range.

Should I go with the hotter, more consistent load or go with somewhere in the slower chart node.

I know that the right answer is "Do more experimentation." I'm hoping that somebody has been through this and can save me components and two more 60 mile trips to the range just for more load dev.

Thanks for any input. These forums have saved me a lot of wasted time and components.

I load five at 0.5 grain below book max. I shoot them for a group, chronograph them, and check for pressure. If they group well, are about the speed I want/expect, and don’t show pressure, I load and shoot five more. If they still group well (ideally less than 1 MOA), measure decently for FPS/SD/ES, and don’t show pressure, load development is basically done. I will usually load ten or twenty more to check all the factors, but then I consider it done.

If I don’t get good results from the first five, I load five more at 0.5 grain more and try that. If I don’t get good results, I’ll try 0.5 grain less. If I don’t get good results, then I switch powder or bullets.

 

[Hondo64d]

What is your barrel length? That plays a major role in expected velocities. It looks like you’re looking for the most uniform velocities, is that correct? I have found with ten shot or greater sample sizes, single digit SDs are good, most of the time observing 6-12 fps. If you’re getting ejector swipes on the case head, you’re over pressure. If when accounting for barrel length, you’re getting more velocity than the published load, you’re producing more pressure than the published load.

That being said, after years of trying just about every load development method ever proclaimed, I’m not a believer in “nodes.” The number of shots typically used to identify a “node” is statistically irrelevant and not indicative of anything repeatable. If you were doing 20 rounds per charge, your test might identify something repeatable, but who wants to do that?

Nowadays, I’ll load ten round with .2gr between each, maxing at book max. I’ll shoot them all into a single group, usually five at a time, letting the barrel cool between each five, in the interest of saving the chamber’s throat. I’m looking for excess pressure signs, velocity, and group size to determine whether the barrel “likes” that bullet/powder combo. Every barrel is a rule unto itself and not all barrels will like a given combination. If the individual charges are tightly clustered on the target, the barrel likes that bullet/powder combo, and I’ll pick a charge that gives the expected velocity without excess pressure signs and roll with it. If I haven’t reached expected velocity by max charge, I might go up a couple more charges, going up in .2gr increments, again looking for expected velocity and excess pressure signs. Any time you’re getting ejector swipes, you’re likely over 70,000 psi, even with the softest of brass.

If the composite group is garbage, I’ll try a different powder with that same bullet. If that doesn’t produce a desirable result, I move on to a different bullet. If two or three different bullet/powder combinations do not produce acceptable results, it’s new barrel time.

Now for seating depth. With a custom chamber that has a tight freebore diameter, say .0005” over bullet diameter, I have not found seating depth to make a dramatic difference in group size. With a factory chamber that is relatively loose in comparison, it might make a difference, but without groups of a large enough sample size you won’t correctly identify it. And don’t fall for the .003” seating depth increment BS. If a seating depth “node” is that finicky, I don’t want anything to do with it. The throat will erode that .003” in not time at all. If you’re gonna try seating depth test, shoot groups of ten or larger in .025” increments. Generally, I load to max magazine length or .060” off the lands, whichever is shorter and if it produces acceptable results, I roll with it.

John

 

[DKE34]

What is your barrel length? That plays a major role in expected velocities. It looks like you’re looking for the most uniform velocities, is that correct? I have found with ten shot or greater sample sizes, single digit SDs are good, most of the time observing 6-12 fps. If you’re getting ejector swipes on the case head, you’re over pressure. If when accounting for barrel length, you’re getting more velocity than the published load, you’re producing more pressure than the published load.

That being said, after years of trying just about every load development method ever proclaimed, I’m not a believer in “nodes.” The number of shots typically used to identify a “node” is statistically irrelevant and not indicative of anything repeatable. If you were doing 20 rounds per charge, your test might identify something repeatable, but who wants to do that?

Nowadays, I’ll load ten round with .2gr between each, maxing at book max. I’ll shoot them all into a single group, usually five at a time, letting the barrel cool between each five, in the interest of saving the chamber’s throat. I’m looking for excess pressure signs, velocity, and group size to determine whether the barrel “likes” that bullet/powder combo. Every barrel is a rule unto itself and not all barrels will like a given combination. If the individual charges are tightly clustered on the target, the barrel likes that bullet/powder combo, and I’ll pick a charge that gives the expected velocity without excess pressure signs and roll with it. If I haven’t reached expected velocity by max charge, I might go up a couple more charges, going up in .2gr increments, again looking for expected velocity and excess pressure signs. Any time you’re getting ejector swipes, you’re likely over 70,000 psi, even with the softest of brass.

If the composite group is garbage, I’ll try a different powder with that same bullet. If that doesn’t produce a desirable result, I move on to a different bullet. If two or three different bullet/powder combinations do not produce acceptable results, it’s new barrel time.

Now for seating depth. With a custom chamber that has a tight freebore diameter, say .0005” over bullet diameter, I have not found seating depth to make a dramatic difference in group size. With a factory chamber that is relatively loose in comparison, it might make a difference, but without groups of a large enough sample size you won’t correctly identify it. And don’t fall for the .003” seating depth increment BS. If a seating depth “node” is that finicky, I don’t want anything to do with it. The throat will erode that .003” in not time at all. If you’re gonna try seating depth test, shoot groups of ten or larger in .025” increments. Generally, I load to max magazine length or .060” off the lands, whichever is shorter and if it produces acceptable results, I roll with it.

John

Thank you John. Great stuff. It's a factory 22" barrel.

I do plan on playing with seating depth once I settle on a powder charge. Max mag length is significantly off the lands. Mag length is right at 2.800. I did the Erik Cortina jam test several times and got an average OAL of about 2.95. I do have a long mag and bolt stop on order so I can play around with more than 2.8.

I single fed for the powder test at 2.85 with no great reason for picking that length.

Based on that the feedback from you guys, I'll pick a charge around 42.5. How would you recommend I set up the seating depth testing?

I understand I'm probably overthinking this as a hunter and recreational shooter with a factory rifle, but I like it and I want to get good at it. I'm sure there are barrel and rifle upgrades in my future.