My try at HV cast

Ian

Notorious member
The velocity difference is a perfect example of something Fiver mentioned in a PM. The 165A has more bearing surface (at first, anyway), so there's more to engrave right at the start, and it's a little heavier, and the lube is different in this instance, so the powder is working harder during the launch, bumping the pressure up sooner, and putting more energy into the bullet. 4350 is very slow for the .308, especially with cast bullets, but it's obviously working.

Putting this in perspective, Will is getting within 50 fps of the velocity achieved with maximum published jacketed bullet loads, in a barrel two inches shorter than the test barrel's. Yeah, I'm impressed. I've seen cycles of good groups around 2200 fps, 2400 fps, and never made it to the next level, but I think he's there. I consider 2400 fps and 1 MOA for ten shots pretty much a stopping point, never having done much better than that in the .308. 2500 was always a no-man's land in between nodes in my rifles, but that might be changed with the addition of a barrel tuner. Part of the reason the XCB came to be was running out of case capacity in the .308 right at that last node but wanting still to fling 175-grain bullets at 2500 fps and under 45K or so pressure (my concept, anyway, had to have a 57mm case to do it). The .308 doing the same is pedal on the floor with its back against the wall, which is hard on brass, hard on throats, and hard on the shooter, and not usually a good recipe for good groups.
 

fiver

Well-Known Member
yep.
it provided that extra little bit of case capacity the 308 needs.
I figure 2650 with a 165-170gr bullet should be that cases sweet spot.
a 12 twist barrel would be perfect and really make it super simple to achieve.
 

Will

Well-Known Member
My tikka is 1-11” but I haven’t put a cast bullet through it. Yesterday was the first time I ever shot it.
 

35 shooter

Well-Known Member
Will,

One other thing may become very important at the point your at.. Remember i said all t's and i's had to be crossed and dotted after 2500 fps. in the .308?

Brad, Ian, and Fiver have all said time and again through the years that sometimes at higher speeds you may have to adjust seating depth as you go.
With jacketed, i always determined a seating depth and never changed it throughout the loading process, but have had that very thing work well for cast at higher speeds.
Guess it changes things on chamber pressure a bit on the high end of speed?

Anyway, as i said, i got to 2600 fps. with 2"ish moa with the xcb in my .308, but couldn't better that.
Finally i adjusted seating depth just a couple thou. and finally hit a shaky 1.5" moa.
with the same load.
That's the point hunting season caught me at and i stopped load developement.
I believe there may well be another half inch to cut off my groups from there with a bit more experimenting with seating depth and perhaps alloy and hardness?
Don't know yet, but i'm sure watching you and Waco right now.

Btw, i was only shooting 5 shot groups at that point, but they were consistent and hitting the same poi on paper each time.

I would also like to one day reduce my loads back to the starting point and add buffer as Ian did with an 06 years ago and work back up using about a 1/16" compression on the powder and buffer as i go back up the ladder.
I hate using filler because of the extra step, but if it worked, would certainly be worth it on top end.

Not trying to be a "know it all" here(i'm not for sure), but just throwing some things out that helped me once i passed 2500 fps. in my 12 twist .308.
Mine has a 23.5" thin on the end sporter bbl., so kind of whippy on the end, but still think i'll "get there" with it.

Adjusting the seating depth has helped me twice now on the high end of the speed thing.
 

Will

Well-Known Member
Right now the 308 hunting bullet is slightly making contact on the nose.
Any OAL adjustments would be adding jump. I’m not sure how that would work out as far as keeping everything aligned upon ignition with that particular bullet.
 

fiver

Well-Known Member
good points right there.
we are pretty much relating I tried this and it helped stuff here.
it's really, really nice to have an open on track discussion where points and facts are given and helpful.
 
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fiver

Well-Known Member
okay let's look at it like this.
what is keeping everything in line right now?
why?
what else is there to do that instead?
 

Ian

Notorious member
Seating depth is nothing more than a tool for adjusting the initial burn curve via the running start thing. The only problem with it is changing seating depth also changes so much of the fit/alignment dynamics that too much room will destroy groups unless your bullet nose shape and throat are compatible to self-align, and your alloy can take a glancing blow without smearing too much. Bullet shape, alloy, powder burn characteristics, and jump are all variables that affect each other if you change just one of them. Sometimes you have to change all four at once just to keep three that were already working fine the same and change one for the better.
 

Ian

Notorious member
okay let's look at it like this.
what is keeping everything in line right now?
why?
what else is there to do that instead?

I want to see what 35 Shooter and Will have to say about this. You're on the spot, guys, let's talk about it.
 

Will

Well-Known Member
I think what’s keeping things straight now with the 308 hunting bullet is
The bullet is straight in the case to start with.

The nose is engraved every so slightly on a the radius of the bullet which holds it straight, but is not enough engraving that the base rivets before the nose gets moving.

The free bore section in front of my case is .3095” and the bullet is .309” in that area so there’s not much room for it to move around.

It’s hard to explain. I need to get a pic of the pound cast beside my loaded round. It makes a lot more since then. The 308 hunting bullet design matches my chamber really well. The only problem with it is there is very little of it in the case.

I believe that’s what I can’t get the SD’s down. There is just not enough bullet neck tension to get any kind of consistency. I know the SD’s don’t seem crazy but when you see the shot to shot changes it’s a wonder they hit within a foot of each other.

I know I drifted off topic some there at the end
 

Ian

Notorious member
Trying to steer a bullet from the back end is folly unless you either have down around 1-2 thousandths total loaded neck clearance, or have more supporting surface on the front AND middle than at the rear. In your instance you don't have much at the rear, which can be a good thing because powder gas pressure acting on the bullet base also acts to expand the case neck before the bullet moves, and that expansion will never happen the same way twice or happen exactly all the way around every time, particularly if engraving resistance is high.

Neck tension affects the initial part of the powder burn curve and the volume expansion ratio. Bullet pull is infinitesimal compared to engraving resistance, and while it does affect burn curve and powder ignition consistency (indirectly, by volume expansion vs. pressure build rate), it doesn't mean you have to have neck tension to get the powder up to a good "staged" start before the neck turns the bullet loose. Regarding boosting the ignition curve, you can accomplish the same thing as having more neck tension (or having more bullet in the case for the neck to grab) by simply pushing the bullet out farther into the throat when chambered and substituting initial engraving resistance for neck tension. This won't make your fixed ammunition any more pocket-friendly or robust with just the gas check in the neck, but it might make it shoot better.
 

fiver

Well-Known Member
I'm gonna throw in what I just done with my last loads.
my neck ID is set to .309, my bullet diameter is .310.
my oal [isn't really since I don't remember it right off] is like 2.780 but after I chamber the round it is 2.755
there is engraving of the nose but closing the bolt actually seats the bullet.

I'm going to use this same sizing/seating method throughout the test, but what I'm going to do is keep using a slower and slower powder.
somewhere along the line I should find a point where I hit almost 100% load density, a lower pressure, and keep my velocity.
any slower and I start going the other direction.
so what then?... stop [shrug] boost the powder? go back the other direction and work on other stuff.
I don't even know if I am going to find any accuracy doing this, but there has to be a balanced point in there somewhere.
 

35 shooter

Well-Known Member
I only adjust seating depth when all else is failing. Kind of a last ditch thing to try before going to another powder.

Once you've reached speeds over 2500 with cast, I think it can work in some cases in a way you normally would'nt think it would.

Things are starting to happen at that point and small changes can make a big difference...... Or not.
 

Will

Well-Known Member
Fiver that’s pretty much what I’m doing. I have very little neck tension after running my .309” RCBS expander through the neck.

The 47gr load of 4350 is starting up into the case neck and the bullet is pushed down on it when chambered.
 

Ian

Notorious member
Will, you might try loading by volume at that point, rather than weight, so the gas check is actually touching the powder the same in every cartridge when you load them, and slightly crunching it back when chambered.
 

Will

Well-Known Member
I have a few things to figure out when I switch over to the thicker lake city brass. I’m not sure how case capacity is going to work out but hopefully I’ll be crunching powder. I’ve always shot my best groups with 100%+ load density.
 

Ian

Notorious member
Make sure you turn the high side off the LC necks, there will be about half to one thousandth thickness variation, then cycle them back through the expander, FL sizer, and expander again to get them back on center with the case body. Or just consider the first firing after turning to be a brass forming operation, then neck size afterward.
 

Will

Well-Known Member
Well that would be nice Ian but a neck turning tool is something I have yet to invest in. That’s one of those items on my to buy list.
 

35 shooter

Well-Known Member
Wow, busy day at work for me today, hardly had time to even take a break.

One thing i mentioned (adjusting seating depth) seems to have been taken as seating deeper into the case to create more "jump"?
I actually had seating more into the rifling in mind for the first try to help with the neck tension thing you've mentioned.
Maybe just a couple thou. to see if there's an improvement...if so, then another thou., while watching for pressure signs of course.
I always start out with a bit of contact with the rifling, but sometimes(with cast), i've found out at the top end of what the powder is able to give me in speed, that a bit more contact can bring the accuracy back in too....sometimes.

I've had it work by backing off to only bare contact with a bore rider before in my 35 whelen. It cut a 2" moa load at the speed i wanted to a 1 moa load with the exact same powder charge.
That one really surprised me, but i guess there's more than one way to skin a cat lol.
There wasn't much more to try in either case other than trying another powder.
I was being hard headed about just changing to another powder and wound up making it work for me with the seating depth.

Looks like lots of good tips have been posted today...any one of them could be the magic formula for where you are now.

Gonna try cast in that Tikka?