Surviving the transonic barrier.

[elkaholic]

That has been a long time theory of mine. The problem is that it would be hard to make a bullet with a very high BC and have a nose heavier than the rear. I am also of the opinion that bullets with a super high Sg factor can potentialy have more trouble making it through as any defects or concentricity issues could create a minor amount of imbalance during it's flight which when subjected to the effects of making the transition could aid in the bullet starting to destabilize faster whereas a bullet that is truely asleep may start to wobble a bit less than one that is already down that path.

Understand that the above is ALL theory and I am not saying that this is how it is. I have no evidence to back any of it up.

It wouldn't be too hard to imagine heavier forward if you are using a thicker based jacket with a thin nose section and using a heavier ballistic tip than the plastic ones. You wouldn't necessarily be the "heaviest" at the tip, but you could easier be heavier in the front half of the bullet as opposed to the rear half. I think I have such a bullet...Rich

 

[Buffalobob]

I believe it is Nosler who has a tungsten core in the rear of their bullet to increase the weight and integrity. It would be interesting to see if it flips at the transition and travels backwards.

Another interesting geometry is the HAT bullet which has so much aluminum displacing lead in the front half that it probably has a severe weight to the rear problem also.

 

[cstilt]

My guess is niether. If high BC had anything to do with surviving it the 300 would have a better chance. If higher than average Sg and shorter bullet had anything to do with it the 250 would. However, based on past experience using a 1.9 stability factor with a shorter than average bullet, they still destabilized at the transonic range. So either it was over spinning them that did it or it was other factors. Regardless, a very high Sg didnt save it. However, it would be very interesting to see if one or the other survived. Best case, they both do. Worst case niether do. Better yet, one or the other. This would give us an indication as to whether it was a higher BC or a higher Sg that did the trick as using your example would show that. The 250 would have a conciderably higher Sg which if it wouldnt make it would show that too high an Sg would cause destabilization. If it survived it and the 300 didnt it would show that a lower Sg regardless of BC isnt the answer where the higher Sg is the answer. If only I had a place to shoot 2000 yards

I'm not expert here, but why do you need 2000 yards? Would it be possible to find an area say 600-1000 yards and use a reduced load? I don't have any ballistic calculators handy but I'd think you could use it to figure out at what range the bullet would go subsonic and set your target a given distance past that. That way the bullet that's groups opened up more than the other's would be the less stable of the two. I'm sure there's gotta be something wrong with an idea so simplistic though.

(I'd love to test this, but I don't have that much range or skill to make it valid. BTW, this is an interesting post)

 

[bigngreen]

Most of Black Powder Cartridge shooting is done in or through transonic and slower. There maybe some answers there.

 

[elkaholic]

I'm not expert here, but why do you need 2000 yards? Would it be possible to find an area say 600-1000 yards and use a reduced load? I don't have any ballistic calculators handy but I'd think you could use it to figure out at what range the bullet would go subsonic and set your target a given distance past that. That way the bullet that's groups opened up more than the other's would be the less stable of the two. I'm sure there's gotta be something wrong with an idea so simplistic though.

(I'd love to test this, but I don't have that much range or skill to make it valid. BTW, this is an interesting post)

The problem, as I see it, with a reduced load is lower rotational velocity which also affects stabilization.....Rich

 

[Topshot]

I'm not expert here, but why do you need 2000 yards? Would it be possible to find an area say 600-1000 yards and use a reduced load? I don't have any ballistic calculators handy but I'd think you could use it to figure out at what range the bullet would go subsonic and set your target a given distance past that. That way the bullet that's groups opened up more than the other's would be the less stable of the two. I'm sure there's gotta be something wrong with an idea so simplistic though.

(I'd love to test this, but I don't have that much range or skill to make it valid. BTW, this is an interesting post)

cstil,
Not a bad idea but you would still need a very long range. This would be needed to let the bullets do their thing after they go through to sound barrier.

When I shot both the 300 gn SMK and the 250 gn Hornady, they went through the sound barrier at about 1900 yards. As the target was at 2285 yards there was still plenty of distance left for the bullets to go nuts in if they wanted to.
This extra distance sure shows up any stability issues if they are there.

 

[Michael Eichele]

I'm not expert here, but why do you need 2000 yards? Would it be possible to find an area say 600-1000 yards and use a reduced load? I don't have any ballistic calculators handy but I'd think you could use it to figure out at what range the bullet would go subsonic and set your target a given distance past that. That way the bullet that's groups opened up more than the other's would be the less stable of the two. I'm sure there's gotta be something wrong with an idea so simplistic though.

(I'd love to test this, but I don't have that much range or skill to make it valid. BTW, this is an interesting post)

I am no expert either but I dont think the forward velocity to gyroscopic stability ratio would be the same with a reduced load at 1K than it would be at a full load at 2K.

 

[cstilt]

Thanks guys,

Thats the kind of knowledgeable replies I was looking for. I figured there would be something wrong with my idea because the answer seemed too easy. Although now I have to do a search and find out exactly what "gyroscopic stability ratio" is and how it works.lol I learn something everyday on this site. I'm glad I joined.

Thanks,

Chris

 

[elkaholic]

Thanks guys,

Thats the kind of knowledgeable replies I was looking for. I figured there would be something wrong with my idea because the answer seemed too easy. Although now I have to do a search and find out exactly what "gyroscopic stability ratio" is and how it works.lol I learn something everyday on this site. I'm glad I joined.

Thanks,

Chris

Rotational (gyroscopic) velocity is the mv x twist rate and tends to maintain at a higher rate than forward momentom. If rotational velocity gets to low for the given bullet, stability suffers.......Rich

 

[Bginvestor]

I was doing some research on "mcgyro" program and saw this thread.

Question, does mcgyro algorithms do a good job with hollow points with different mass CG's?