I have ordered a Shiloh 1863 .54-caliber cap lock rifle with 30-inch barrel. Its rate of twist is 1:48 - as is Pedersoli's version of this breech-loading cap lock. Pedersoli offers a ringtailed plain base bullet [mold] whose cast length is a nominal 1.195 inches. This bullet has stable flight-to-target to [at least] 200 yards, the farthest distance at which I have tested it.

This is a very long projectile for 1:48 in .54-caliber. Since my 1863 Sporting Rifle is being built to be a hunting rifle that I will be capable of shooting accurately to 175 yards, I am concerned that the bullet will lose stability during penetration when used on game animals larger than deer - the same instability exhibited by circa 1960s 5.56 mm 55-grain bullets in M16 rifles with 1:12 twist.

One obvious solution is to shoot shorter bullets. This solution does not really address my concern. How can I test any bullet for impact-and-penetration at the longest distance I might shoot? In this instance 200 yards allows me a fudge factor.

I fear shooting into wet or dry newsprint, or any other uniform medium (ballistic gelatin) will not tell me what I want to know. It's easy to determine whether a bullet will penetrate as far as I want. But such penetration testing may not account for the bullet yawing during penetration - that is, shorter than anticipated penetration plus random penetration direction.
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Ruling out Thompson-Lagarde type testing on live animals, ruling out buying sides of beef or pork, please describe in as much detail as you are able how to test my Sharps bullets.

There is a valdidated formula for determining the distance it would take in target for a ogived projectile to overturn.

The formula assumes a number of prerequisites.

1. The projectile must remain intact and must not deform. This thus negates the use of a lead bullet

2. The target must have a homogenous consistancy with the same mass density as Gelatine or muscle. Wet paper does not fit this criterium.

3. You have to know or assume a small value for the projectile impact angle of attack. This in itself is an imporant value and more recent study has shows that this value is stochastic and not a static number and likely accounts for the differences between true values vs calculated values.

4. You have to know the critical data values of your chosen bullet. ie position of the centre of gravity. The transverse moment of inertia of the projectile as well as the transverse moment of inertia.

With this data is is possible then to calculate the distance it takes in target from impact to a point where overturning is deemed inevitable.

There is a variance between the actual value and the calculated value but the difference is not big enough to invalidate the formula.

The formula reads:

Lnc = 31.6 x (Lg:Jq ) > - 0.212