Design Rule For SWC Meplat Size

[Good Cheer]

Is there a reliable rule for "good" design of a SWC on how big the nose flat can be made?
As a percentage of diameter or of area?
Keith is said to have said 65% of diameter and later 70%.

[Guesser]

It seems they go from "pointy" to nearly full diameter. Compare 360302 and 360344. I cast and shoot both. Sized .360 for 38 S&W and .358 for 38 Special.

[Outpost75]

Keith was right.

If you don't shoot your handguns past 40-50 yards, then a full wadcutter has more smash up close, but don't try to hit a groundhog at 100 yards with it...

[OS OK]

There is a few fellas on this forum that I pay close attention to, I think I remember one of them saying something about the 60% number...sort of a good percentage that'll give the best of both aspects...good energy transfer into a target and not so handicapped in longer flights and accuracy.

Good question Good Cheer...we have been in need of a post like this for days now!

[white eagle]

I though that the meplat size was 62% but that is rite in there with what others have posted

[RobS]

dependent upon caliber

[wv109323]

I will sent you a PM.

[Outpost75]

Anywhere from 0.6 to 0.7 of the bullet diameter works pretty well. I like somewhere in the middle. My experience has been that very large meplats, greater than about 0.7 of bullet diameter, begin to act more like full wadcutters, and low-velocity dynamic instability becomes a problem beyond about 50 yards.

Some users, like 44Man claim that the big meplats can give good long range accuracy when they are driven hard enough. This may be a case of the bumblebee not having studied aerodynamics, but I have not been able to make that happen.

I can tell you that firing Accurate 31-077B flatnosed bullets, which has a meplat of .2" or .64 of bullet diameter, fired at supersonic velocities loaded with 3 grains of AutoComp in a .32 ACP rifle, gives me 2," 5-shot groups at 100 yards fired from a reworked Remington 580 bolt action, off sandbags with a 4X hunting scope. The 31-090B of similar shape also shoots very well, as do the 31-087B and 31-087T, which have smaller meplats. All the .32 ACP bullets I tested below.

Bullets having meplats no larger than 0.7 of their diameter show dispersion which is linear, being in proportion to the range. The 50 yard dispersion of the two large meplat 090V and 095T bullets is about FOUR times their 25 yard dispersion, and at 100 yards more than TEN times their 25 yard dispersion.

200995200991200996200992200994200993

When I tested the Accurate 31-090V or Accurate 31-095T, both having .25" meplats, 0.8 of the bullet diameter, from the boltgun with scope, either would shoot sub one-inch bug holes at 25 yards, but their dispersion is nonlinear and neither do better than 3-4" plinking groups at 50 yards and might stay on the 4 ft. target backer at 100.

My two cents. I'm still waiting for .44Man to post pictures of those minute of angle 5-shot 200 yard groups he shoots with full charge wadcutters in his revolver, but I haven't seen them yet, I am still waiting...

[GLynn41]

I have two so called Keith molds-- one is a Lyman 410459 --it has .255 meplat, the other is a Saeco .411 230 and it has a 275 meplat
on impact with a target --the 410459 acts like a wad cutter,, in deer it cuts the same wad cutter type hole in the hide. One I took had thumb size hole in the heart- then a wad cutter out This one has a 60 %something
Saeco is around 70%
I have not taken any thing with the Saeco but on paper it acts like a LFN-- and nothing like a wad cutter
the difference is not the meplat at least on paper--- but the base of the nose where it joins the shoulder is smaller on the 410459 than the Saeco which is much larger at its base-- as to meplat i like these two older Keiths
I was told by Mr.Veral Smith that a .41 cal needs around 75% so i will go with him if I ever get another keith mold. This works out to be about.308 meplat