Flat Base vs Bevel Base

[Savvy_Jack]

Uncknick,

Is there much difference, if any, in flat base vs bevel base (not boattail) ballistics between 100-300 yards in the 44 cal range? I would think the overall design of the 44 bullet would diminish performance before the bullet base design would effect performance?

 

[Unclenick]

Your assumptions are correct. In order for a boattail reduce drag, the angle of the tail can't be too great or the air is peeled off its surface rather than following its slope so its drag is as great as a flat base. McCoy's Modern Exterior Ballistics has a plot of the effect, and IIRC, it peaks at about 7.5°, where it is close enough to the 9° number the military settled on for the 172-grain M1 Ball bullet back in the early 1920s, which is a compromise between best drag and how long the boattail has to be to cut the base area significantly. About the steepest boattail is the 13° boattail on some MatchKing bullets, like the 30 cal 168-grain bullet, but that is intended to help get the bullet to go to sleep (damp out initial yaw) faster to improve accuracy at shorter ranges. It's not good at long ranges, where it can cause overcorrection that results in tumbling.

The bevel bases on cast pistol bullets I have are at close to 30°, so that will just behave like a flat base for drag. But even if the angle was right, the improvement in BC would be small because it would decrease such a small percentage of total drag on the relatively blunt pistol bullet.

 

[std7mag]

As was said.
Think not of a beveled case as a boattail, but for ease of loading.
Much easier to get a beveled bullet started in the case mouth, even with expansion.

 

[Savvy_Jack]

Thanks!!

 

[GaCop]

Handgun wise, I have found that I get better accuracy overall using flat base cast bullets instead of bevel base. It's not a big difference but is noticeable.

 

[mikld]

I agree with all the above posts; the bevel base on a handgun bullet (44 caliber), is not a designed accuracy consideration, but to make casting and seating easier. I only have one bevel base bullet mold and it's for 45 ACP. Yep, the bullets fall out of the mold quite easily, and they are set in the case mouth quickly for seating. All my other molds are flat base or gas check base, I just wanted a particular shape bullet for my 45 ACP carbine...

 

[gwpercle]

Bevel based cast handgun bullets became popular with commercial caster's , the automatic casting machines had a higher rate of production with them...
They don't add a thing to accuracy. Looking at all the old Lyman mould designs , I find only one with a bevel base #452630 all the rest are flat base , gas check and 5 that have a zinc washer cast on the base.
If a bevel improved accuracy I'm sure more than 1 would have that feature....
but they don't.
Gary

 

[rodfac]

Handgun wise, I have found that I get better accuracy overall using flat base cast bullets instead of bevel base. It's not a big difference but is noticeable.

Yep that's my experience as well. Uncklenick may chime in here, but I'd attribute better accuracy, in part, to the longer bore bearing surface of the flat base types. What say you Nick?

Too, in my own casting operations, I've had more problems getting full mold fill-out, (without fins and imperfections) with bevel based designs than with flat based ones. Also sprue cutoff anomalies. YMMv, Rod