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Dromia

Dave, the game is up.

Everyone knows about the selectiveness of your memory "loss".

What did you say your name was.

No need to over tax the forgetery Dave, just use the ignore button.

maybe he has forgotten where it is...

If magnum powders burn slowly so as to give plenty of time to build up pressure, does that indicate that a hard lead cast bullet could be used at quite high velocities? If the acceleration up the bore was gentle, and the bullet quite hard, then perhaps leading would be minimal and the risk of bullet failure eliminated?

No quite sure what you mean by magnum powders?

Hard cast lead boolits are not a good idea at any velocity.

If you want to shoot cast at higher velocities then slower powders do work better, giving you the velocity you want at less than maximum pressure. This is the same for cast as for condom.

My full stoke 303 cast boolit load uses IMR 4350.

Ideally when shooting cast at high velocities you want the boolit to be fully supported by the rifling and bore before peak pressure is reached.

With good boolit fit, a suitable, not hard, alloy and appropriate lube then leading won't happen even at high velocity. What you need to be careful about with cast at the higher velocities is boolit deformation during the jump from case to bore as deformation will give poor accuracy but not leading.

This is as much about good boolit alignment with the bore as it is about slow powders.

We were pondering if it would be possible to develop two loads for our 7mm Rem Mag.

One full power load based on nice sleek boat tailed condom bullets for long range shooting from 600 to 1000 mards

One load based on cast boolits for use at 300mards, occasionally out to 600 mards.

Our thinking with the cast boolits was that they would need to be relatively hard to avoid being worn away in the bore

dromia wrote:No quite sure what you mean by magnum powders?

Hard cast lead boolits are not a good idea at any velocity.

<Eyes boxes of GM hardcast boolits I've been loading for light .44 loads/cabinet full of said loads suspiciously>

For 600 yrd shooting with target accuracy then you don't really need any special alloy.

For these loads I use range scrap cut with roof flashing for a brinnel hardness of around 12.

Boolit fit is the key, also you don't need slow powders for this as the velocity will be in the 1600-1800 fps range, powders in the range of N120 work well here.

Again I refer you to Ed Harris's article on cast bullets in military rifles, lodged in the library.

zanes wrote:

dromia wrote:No quite sure what you mean by magnum powders?

Hard cast lead boolits are not a good idea at any velocity.

<Eyes boxes of GM hardcast boolits I've been loading for light .44 loads/cabinet full of said loads suspiciously>

Hard cast boolits with hard waxy lubes are that way so that the boolit manufacturers can ship them loose without special packaging so the boolits don't get damaged so much or spread the lube in transit, they are also usually easier to cast with good fill out. Hard cast boolits benefit the manufacturer not the shooter.

In saying that they usually perform adequately at pistol velocities.

meles meles wrote:We were pondering if it would be possible to develop two loads for our 7mm Rem Mag.

One full power load based on nice sleek boat tailed condom bullets for long range shooting from 600 to 1000 mards

One load based on cast boolits for use at 300mards, occasionally out to 600 mards.

Our thinking with the cast boolits was that they would need to be relatively hard to avoid being worn away in the bore

whilst I see your reasoning I think your adding complication ? i'm very much signed up to the K.I.S.S principles ie find a load that works at 1000 and then just use it at all ranges ? you will only need to learn one set of data then !

also (and i'm sure dromia will know for sure) but I think there is issues when swapping between lead and jacketed and the rifle will need a good clean between strings of different types?