Plastic tips?

[edge]

Obviously plastic tips make bullets longer, but what is their effect on required twist?

Intuitively I would think that a heavy nose is better for stability. After all a plastic tip added to a hollow point bullet moves the CG rearward causing more instability...but I have heard that this is not the case.

edge.

 

[royinidaho]

edge,

Here are my unscientific observations based on the repointing project... Opinions only

Plastic tips seem to have been developed to prevent point deformation of cartridges in the magazine after the first shot. This then caught on as they are pretty sexy looking and caught on with shooters

Plastic tips are simple to form and incorporate into bullet forming. They are very light and my opinion is that they contribute very little to bullet weight or stability considerations.

Plastic tips are very uniform thus bullet to bullet bc should be very consistent.

Plastic tips are relatively blunt thus bc will be lower than if the same weight hollow point bullet had a meplat diameter of 0.025"

The the repointing project trims the jacket back a specific amount, removes the plastic stub and inserts a brass tip with a meplate less than 0.030" and a weight of around 11 grains with a significant increase in overall length length.

The final bullet weight is increased a few tenths under 10 grains.

BC is increased by a published and real world tested just under 0.500 to a calculated estimate 0.660. Field testing is sporadically underway with definite indications of significant bc increase.

Out of my 8 twist barrel @ 3500 MV stability doesn't appear to be an issue.

However, process tolerances definitely make a difference.

Here's a pic to feed your mind processing a bit.

The 159.8 grain repointed bullet compared to the 150 Ballistic Tip and a 195 grain Wildcat.

 

[edge]

Wow, how cool are those

My problem is selecting a bullet for a rifle with a slow twist.
If I use a Miller stability program I need to know if the plastic tip is included in the OAL or do you only use the copper portion OR do I need to actually add some factor to the tip length to figure the correct twist?

edge.

As an afterthought, have you tried to reshape the Accubond tip in the lathe?
Make a sharper point by shaving the tip and jacket back and leaving the OAL unchanged?

 

[Mikecr]

It's a good question edge, and I agree with your reasoning.
It does seem like plastic tipped bullets would be less stable(given CG to CP). But they are actually a bit MORE stable(somehow).
They don't seem to be any lower in drag either, as their BCs are same or worse than non-plastic-tipped..

Maybe Bryan Litz would help with understanding of this.

 

[royinidaho]

As an afterthought, have you tried to reshape the Accubond tip in the lathe?
Make a sharper point by shaving the tip and jacket back and leaving the OAL unchanged?

Yes I reshaped the tip on the lathe but none of the variations I tried panned out. They were not pleasing to look at, bc calcs said it wasn't worth the effort.

The brass tips make a definite change. Plus they perform terminally as identical as I can determine as the original NABs and BTs.