30 Cal 260's

[elkaholic]

Your 0.84 is gonna be **** close real world, at muzzle velocity only. As the bullet slows down the BC will decrease, so a velocity bracketed G1 system is fair to use. Or simply use the G7 number... it just doesnt sound as good!

Thanks Nick.......So you don't think I would have a secondary shock wave problem with atmospheric/velocity changes if I went to a longer nose? How far do you think I could push it before I had this problem? That would be one long bullet....Rich

 

[groper]

No No, you keep the same overall bullet length. You sacrifice some bearing surface length to increase the nose length. You will get significantly less wave drag.

However i dont think that aluminium tip will work as its base diameter is quite large and wont fit the larger secant ogive radius... that brass tip should fit tho?

 

[groper]

Or is the aluminium soft enough to change shape and conform to the nose die?

 

[Jon A]

Wait! Don't throw out the old design yet! If the noses get any longer I won't be able to fit them in the magazine for hunting. I don't mind single loading when I'm plinking/testing, but I have to be able to fit them in the magazine for hunting.

 

[elkaholic]

Or is the aluminium soft enough to change shape and conform to the nose die?

I don't think so. I think it puts too much pressure rearward and would cause the jacket to buckle. Ashorter bearing surface would get us a little more velocity too....Rich

 

[elkaholic]

Wait! Don't throw out the old design yet! If the noses get any longer I won't be able to fit them in the magazine for hunting. I don't mind single loading when I'm plinking/testing, but I have to be able to fit them in the magazine for hunting.

DON'T PANIC JON We're going to find out what these do before I move on with anything else...Rich

 

[groper]

And you will always have the existing dies

This is the improved nose i was talking about, it shows the problem with the aluminium tip...

if you can figure out a way to get round this problem, you will have one hell of a long range bullet - even if it is not magazine compatible



With a BC above 0.9 to 1000yds, you should only need one darn shot Jon

 

[elkaholic]

The ballistic tip fix is an easy one. In fact, as you already mentioned, the brass tip might be about right already.....Rich

 

[Jon A]

Yeah, I noticed the base of the aluminum tip was a little too large in diameter such that it formed a slightly different angle than the ogive (a more blunt angle). Fixing that would only add a little length and I can see how it would make a big difference in BC.

 

[groper]

updated the drawing with dimension change... so OAL length will grow .108... will this still fit in your magazine?

 

[Jon A]

An OAL increase of that is fine as long as the nose doesn't grow too much. I'm mainly worried about nose length, I don't mind stuffing them down into the case--I've been doing that for years!

 

[Jon A]

OK, that didn't make sense, I think I was looking at the pic backward. The old profile is in outline and the new profile is solid, increasing the nose .108? That makes more sense. I do think it'll be a bit much for my magazine but would be usable for others. And that would require a new die, right?

I think the easier short term change would be reducing the base diameter of the tip to match the angle of the current ogive more closely. That wouldn't give quite as high a BC but he may be able to do it right now.

 

[elkaholic]

OK, that didn't make sense, I think I was looking at the pic backward. The old profile is in outline and the new profile is solid, increasing the nose .108? That makes more sense. I do think it'll be a bit much for my magazine but would be usable for others. And that would require a new die, right?

I think the easier short term change would be reducing the base diameter of the tip to match the angle of the current ogive more closely. That wouldn't give quite as high a BC but he may be able to do it right now.

Changing the tip "only" without a "NOSE JOB" would make no significant difference. What Groper is recommending is a more angular ogive, maybe from the current .014" offset to an .018" offset or??......Rich

 

[groper]

Im suggesting making the nose longer in relation to the bearing surface, the overall length of the projectile would remain the same.

The new profile i suggested, has its ogive moved .108 further back, which means to seat the same distance from the lands, your loaded round COAL will be .108 longer than what it is now, with .108 less case intrusion.

Additionally, it has a larger radius secant ogive from the current radius and different offset - which provides that more aggressive, pointier profile look - which will give considerably lower drag over the current shape. It may make them more sensitive to tune loads for tho, like other VLD bullets that seem to be seating depth sensitive... although its not a rediculously agressive ogive angle so i wouldnt expect it to be that bad.

The AL tip would need to change to accommodate the longer nose, but the brass tips may work fine as they are already.

Dont touch the boat tail! - if you try to reduce drag this way, you will run into stability problems very quickly....