Lede/Throat/Freebore and the cast boolit

[sthwestvictoria]

I just would like to check a few things with the hive mind of CastBoolits. I understand that with boolits we are happy to have boolits and OAL that engrave the rifling slightly, as long as the cartridge ejects without leaving the boolit behind. This is different to jacketed where there is a preference for a jump to the lands.

How much rifling engraving is best? This is my new 250grain GC boolit from Jim at Cast Bullet Engineering for my Mauser 98k in 35 Whelen, 1:14 twist:
LedeFreeBore.jpg

In the picture, OAL is 84mm (3.307"), this leads to the engraving shown. This OAL fits well in the magazine well (mauser 98k rebored. 8x57mm OAL is 82.00 mm (3.228")) with 4-5mm spare. Official .35 Whelen OAL is 84.8 mm (3.340")

Is this a safe amount of engraving? The cartridge with this OAL loads from the magazine well, chambers and extracts. Is there anything to be gained by going shorter or longer?

The load will be 40-42grains AR2206H (H4895), case capacity as pencil line below:
40grains.jpg

Edit: I confused SAAMI spec and my OAL - my OAL that chambered well with slight engraving was 80.0mm

[Larry Gibson]

That amount of engraving is fine as long as the round chambers easily and extracts when unfired w/o leaving the bullet stuck in the thraot/leade. Best to double check that with a well fouled chamber as throat/leades get "gritty after a few rounds have been fired. Additionally it is safe if the load has been worked up to with that amount of engraving. Appears you want a top end load(?) but I suggest backing off to 30 gr, use a 1/2 - 3/4 gr dacron filler and work up to your projected 40 - 42 gr load of H4895 under the 250 gr bullet.

Larry Gibson

[runfiverun]

if you try to go longer, chambering the round will probably seat it there for you anyway and break your static neck seal when it does.

I think you are in good shape.
you have what you want as far as a useable round, now to work up a load.

[sthwestvictoria]

Thank you for the excellent replies. Perhaps the load is a little stout. It was based on two sources for extrapolation:
Lee_250graininformation.jpg
Lee's Modern Reloading and the 1grain reduction method to arrive at a velocity of 2000fps
And ADI's reloading data for 35 Whelen:
ADI_250grain.jpg
Which did correlate with the velocities that Lee's 1grain method was suggesting. Unfortunately neither the Lyman 3rd or 4th have loads. The Lyman 4th only has 198grains and 204grain loads.
Using the Hodgdon reduced load 60% of max rule with H4895, this informs that I could go down to (53grainsx0.60) 31.8grains.
The goal is 1800-2000fps with oven treated boolits, annealled at the nose for hunting.

[sthwestvictoria]

My worries about having too much engraving of rifling were from the Hornday Handbook 3rd Ed:
Hornady3rdEd_p17.jpg
Hornady3rdEd_p18.jpg
Hornady3rdEd_p19.jpg
And from my chamber cast I thought the lede was rather short. I should cast my .243 chamber as I know it likes really long OAL, it may be interesting to see what that is like.

[geargnasher]

Jaxketed and cast are two different things completely. Cast doesn't raise pressure much at all when seated to touch the lands because it has much lower engraving resistance.

It isn't necessary to engrave the rifling or even touch it, in fact some guns shoot better with the boolit seated off the lands a bit when the cartridge and boolit are properly fitted, but most people don't accomplish adequate cartridge fit, so an accuracy advantage is typically realized when achieving a good, solid "pilot" condition with the boolit's nose upon chambering.

Gear

[sthwestvictoria]

in fact some guns shoot better with the boolit seated off the lands a bit when the cartridge and boolit are properly fitted, but most people don't accomplish adequate cartridge fit, so an accuracy advantage is typically realized when achieving a good, solid "pilot" condition with the boolit's nose upon chambering.
Gear

I was wondering if I should seat a bit deeper to clear the riflling but as per the above chamber cast if I go much deeper the GC will be below the neck. So I'll stay around the 84mm OAL.

Edit: I confused SAAMI spec and my OAL - my OAL that chambered well with slight engraving was 80.0mm

[runfiverun]

try what you have before you worry about what ain't happening yet.

[cbrick]

In your picture of the boolit, dummy round & chamber cast the rifling on the chamber cast looks good but I can see only one land engraving on the dummy round. Does the chambered round engrave all the way around the boolit nose or in just one or two places? If there is boolit run out that causes the boolit to engrave only one side accuracy will be effected. Engraving of the nose is fine as long as a chambered round can be removed but it should be engraved evenly all the way around the boolit nose.

Rick

[sthwestvictoria]

There is rifling engraving around the nose of the boolit. This was actually a non-heat treated boolit as a dummy round so I'll see if the harder boolits engrave and eject as well.

[sthwestvictoria]

Very happy! I was able fire off a few rounds yesterday:
38grains2206H_small.jpg
39grains2206H_small.jpg
39_5grains2206_small.jpg

The caveat being these were at 50metres, not the usual 100m as I was also get used to a new scope (1.5-5 tasco pronghorn). And four shot groups rather than usual 5. However still very happy. These were the first 16 rounds fired of this 250grain boolit from CBE and it has worked a treat. Recoil was present but not uncomfortable. I don't have a chronograph but using the Lee 1grain reduction ratio suggests just under 2000fps, which is perfect, maybe a bit fast for hunting. Projectiles were oven heat treated, lubed with my own pan lube (BW/vaseline/lanolin/crayon) and there was no leading and lube star at the muzzle.

Larry did suggest a filler but I have to suggest I am a wimp and have some sort of irrational fear of putting something other than powder in the case. I'll read up about it and trial.

[felix]

For a huntin' gun, group size means zilch! 50 yards is plenty also for testing ammo/gun. 4 shots are perfect when shot for POA/POI, as one shot each for each combination of temperature and humidity ever expected. Overlay each target, and the 4 holes should touch one another. ... felix

[runfiverun]

your first target shows the classic vertical stringing which calls for a filler to fix.
once you got into a better fill/powder burn with just one more grain of powder you see how things tightened up.

now if you will be taking extreme uphill and down hill shots then a filler is recommended to keep the powder in a consistent position [against the primer] and you would then revisit that lower load.

looking good though.

[sthwestvictoria]

Well I will look into fillers and gird my loins for a trial of polyester filling.
Other things to try are whether the ACWW 2%tin actually needs heat treating or not and also what ACWW:Pb 50:50 would work like.
Thanks for all the advice, couldn't have done it without the forum.

[runfiverun]

there is a lot of those answers right in the hunting section.
goodsteel has a thread in there on the 358 win with a very good discussion on alloy and performance.

[MBTcustom]

This one:
http://castboolits.gunloads.com/show...e-in-the-world

[runfiverun]

Tim.
you might as well make that your sig line.
it is a classic.

[waksupi]

When I get vertical dispersion in a group, I first try a slightly larger boolit, as sometimes the heating of the barrel will let a marginally sized boolit gain velocity and shoot higher. I also try reducing the load just a smidge.

[kir_kenix]

When I get vertical dispersion in a group, I first try a slightly larger boolit, as sometimes the heating of the barrel will let a marginally sized boolit gain velocity and shoot higher. I also try reducing the load just a smidge.

I usually do the oposite. I will stick with the same projectile, same size and bump the load up a little bit. I've always found that a slight bump in load density/velocity will frequently bring vertical dispersion under control. Well of course there are different ways to get things done, thats part of the fun I guess.

[runfiverun]

they both work too.
the bigger boolit will raise initial ignition pressure.
the load bump gives better case fill for the same affect.
the targets above prove it.