Ok, I need to hear some opinions from those who are much smarter than me when it come to loading ammo and getting interesting numbers.

This weekend I decided to finally run a seating depth test using 40.0 gr. RL-17 and 140 gr. Federal Fusions, CCI 200 primers and twice fired Starline brass. I am currently loading for a Browning X-Bolt Hell's Canyon Speed 6.5 CM with a SilencerCo Harvester. All brass was processed at the same time and same way.

I have that 40.0 gr of RL-17 will hold a 1 MOA group from .001" from jam point-ish. So I shot a very abbreviated seating test and found the following: 0.002" from jam my group opened to 1.2 MOA and had massive vertical stringing and terrible ES/SD (81/31.2).
0.003" my numbers improved to 0.9 MOA with a bit less stringing (53/25.2). 0.005" however, went to a 0.6 MOA group and (12/5.1).

So my question is this: does seating depth have a roll to play in ES/SD because I may be finding the ideal case volume to powder ratio? Am I getting better ignition conditions in the case? What say everyone?

I have been down that rabbit hole. I too got tighter numbers with a bigger jump. I think small differences from bullet to bullet dimensions combined with small differences in seating with the bullet that close cause the bullet to engage the lands at different stages of the burn, thus altering pressure. Unless I jam the bullet, giving it a bit of jump has resulted in a more consistent burn and tighter numbers for me. I am not a fan of jamming my Bullets. The first time you eject an unfired round and the bullet stays in the barrel while the powder dumps all in the action and magazine, you may feel the same way.

Yep. BTDT. Now every load has 0.010" of jump from the start and then work up a powder weight ladder test.

I definitely do not want to jam my bullets at all. I was seating deeper and going away from the lands with this test. I accidentally jammed a bullet once a few years back and it sucked!!

I think I am going to seat my remaining rounds even deeper and see if my numbers keep improving with a larger jump.

I can’t believe I spelled “role” as “roll”. I amaze myself some days!!

Unless it’s a difference from full jam to jump, it shouldn’t make the difference that your numbers are showing, How are you measuring powder?

I start .003" off the lands, if it will fit in the magazine. I pick an appropriate temperature stable powder for the cartridge, then I go find the tightest shooting load. Almost never do I fool with seating depth after that.

Your powder choice could be your problem. It isn't temp stable, and you are not filling the case. For 6.5 Creedmoor my first preference is H-4350. And it's between 42.0 and 43.0 gr for a 140 bullet, which fills the case more. Alternative burn rate powders are also an option, that fill the case as much, or more.

I don’t doubt what you are saying. I think 40.0 is a low charge but my rifle gets a sticky bolt at 40.3 gr of RL-17. I have a few pounds of H4350 and RL-16 that I will probably play with. Federal data shows pretty anemic velocity with 16 but I’ll work my own data. I’d like these fusion bullets to be around 2700 FPS out of my 22” barrel. Right now I am at 2685 FPS. Also, Browning was very generous with the magazine for this cartridge. I run out of bullet in the neck before I run out of magazine length.

I don't know you're barrel length, but 24" 6.5 Creedmoor, 2800 fps is possible, safely. Right powders, right charge.

Have you worked up any loads with StaBall 6.5? I load that powder in my wife’s 6 CM and it shoot likes a dream.

Have experimented with it in .243. Several factory rifles. The jury is still out for me.

I will try it in my known excellent shooting 6.5 Creedmoor. Need to get on that right now while it's hot weather. Then find out the speed it makes in cooler weather. It would be a 4 month test before I'm satisfied.

My Tikka 6.5 CM runs 140 ELD-M at 2775 fps out of a 24" barrel. I run .030 off the lands. I tried more jump and groups got worse. I tried less and they stayed the same, so I just stick with .030 since I'm up against mag length running much longer.

Tikka factory barrels are notoriously slow and I'm using H-4350 instead of RL-16, so I think 2800 should be easily achievable if you use RL-16 and have a Bartlein or Shillen. I just happen to have a barrel node right at the top end of what H-4350's max charge limit is. I think most Tikka shooters with 24" CTR's end up running closer to 2,725-2,760 out of their factory rifles with H-4350 and then everyone speeds up when it's rebarrel time, or when you figure out that RL-16 does the same precision but with some free speed.

I have tried a small seating depth test with my my 308 and have found that it makes some difference but it was no where near the order of magnitude you are seeing. For example, I ended up changing my seating depth by about 0.090" with the same powder charge (308 with varget) and the ES/SD numbers were probably less than 10-15% different. There was a depth within that broad range that shot noticeably better but again wasn't as wide a margin as your, something like went from shooting 0.8moa to 0.6moa. I too suspect there is something else at play here instead of solely just the seating depth variation. My little test showed me seating depth is a very fine tuning adjustment.

I must have been smoking something good yesterday! My original post should have read 0.01", 0.02" and 0.05" respectively.

An educated guess from past experience is measuring those speer bullets from base to ogive will reveal a dimensional difference of .002-.003 which is where the inconsistency is manifesting.

You are probably correct. My shots aren't much over 300 yards max so I am pretty happy staying under an inch with a fluted sporter barrel and decent numbers for deer hunting. I was really curious if anyone else here had ever experienced such crazy numbers with after playing with seating depth.

I do feel like switching powders may get me better velocity and possibly better accuracy.

Yup

Yes...it's all about pressure. You're directly effecting pressure by pushing a bullet in and out of the case.

If fine tuning...I'll 100% do a seating depth test.

Just to screw with people's minds...I have developed loads where I have start with seating depth....then move to powder charge. Nothing says you have to do powder charge first...I've also hit a powder charge that didn't shoot the greatest but had really good es/sd numbers and I've been able to tighten that group up significantly by changing seating depth.

Like most everything in the rifle world...you just have to try it and the next barrel will likely be different.

I am no expert, but I do have pertinent info. I reload for a Savage model 12 with a 24" barrel. My load is .5gr over what hodgdon shows as book max, but I have been told by many that 6.5CM is safe up to 43 gr of H4350 with a 143gr ELD-X, and I worked up to it. I am at 42.4gr, and that shows no pressure signs in my gun. In testing, I went up to 42.7 gr and still showed no pressure, but 42.4 gr had a better group of .438 inches. It has continued to shoot .5 MOA since. Over the Chrony, I averaged 2775 fps. Those Chrony readings were taken in December with temps in low 50's.

You experience is par for the course.

Hodgdon lists 40.0 gr as max. I haven't tested a rifle with a charge that low in over 10 years.

However, some of Hodgdon's maximum charges, for various cartridge/powder/bullet combos are in fact to be believed. What they say is maximum, you might find pressure before, or at their listing.

Since Federal only gives data with Alliant powders on the card that comes with the bullets, where would you start with H4350 and Fusion bullets. I am sticking with the bullets because I like their performance on game and they don't shoot half bad. They almost act like they want to build pressure quicker than most bullets.

I see data for the 140 Gold Dot and I believe the bullets are the same except the gold dots have are coated which in theory makes them more slippery.

Any cup and core 140 data will work. Start low and work up looking for pressure signs is standard operating procedure. Advertised data is a no more than a starting guide to work from.

Agreed.

Except for the "any" word. There are some bullets with different bearing surface lengths. Longer bearing surface can mean seeing pressure earlier than a shorter bearing surface. Just a general caution for anyone else viewing.

I believe these Fusion bullets fall into the "earlier" pressure category from my experience.

I have six manuals I cross reference data between. There is commonly significant differences. Within a given manual such as speer since the OP is loading fusions, there will be multiple projectiles of the same weight with different profiles where the bearing surface varies, yet only one set of data. It is up to the loader to determine what the actual maximum is for his particular components in the rifle he is loading for. That is clearly stated in each manual I own. Starting low and working up to create your own data the first time you load with a new set of components in a given rifle accounts for that.

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