Starting Charge Calculation For a New Rifle

[Art Caputo]

Calculated without barrel length are bogus numbers.
The 45 cal is way under powered for my 42 inch barrel, using the davenport formula the MAX that will burn in my barrel is 75 grains. Above that charts numbers.

My go-to accuracy charge in my 44”, 45 with LRB is 70gr FFFG. Falls right in the charts listed charge ranges… as do my 50, 54, and 58 cal loads.

 

[FishDFly]

Where did you find this formula?

Calculating for the bullet weight is correct.

But is seems like something is off with the other parts of the formula.

Thanks.

Cannot remember where I got it.

It may have been the ALR site, I found it theother day when looking for something else in my notes.

 

[Dale Allen Raby]

So.... how much powder for a 16" naval gun? I know it's technically a breech-loader, but it uses black powder...

 

[FishDFly]

Two scoops.

 

[64Springer]

So.... how much powder for a 16" naval gun? I know it's technically a breech-loader, but it uses black powder...

2,637,706.9 grains.

Rounding up could produce significant overpressure.

 

[tenngun]

2,637,706.9 grains.

Rounding up could produce significant overpressure.

Problem with that is you need a wagon to carry the charger.
Well I guess those guns were only carried on rag wagons

 

[ETipp]

Using the same powder charge volume as your bore diameter is much easier than crunching the numbers.

Indeed, that's a good overall method. Works on .50 and .54 calibers for a fact.

However, that puts me over the maximum on my .32 Crocket rifle, which is 30.0 grains. Perhaps that's the odd duck rifle?

Then again, that's for 3F, not 2F, so that might make the difference, eh?

Not stating which method is correct for a beginning powder charge. However, when I used the formula Fish posted, for my .32 Squirrel rifle, it equates to 19.157 grains. 20 grains just happen to the the recommended charge for best accuracy, which it is.

Using the formula Fish posted for my .54 I came up with 95.87 grains. Round to 96 grains. My guess is most folks use 2F in .54 caliber.

Indeed, ball park figures.

 

[Shawrco]

Sometimes folks asks where to start with a load.

Bullet diameter cubed X 1502.6 = Bullet weight in grains

Bullet weight (in grains divided 7 X 3 = starting charge

For a .40 rifle

.395 X .395 X .395 X 1502.6 = 92.82 grains

92.82 divided by 7 X 3 = 39.78 grains of powder or 40 grains.

Being somewhat of a frustrated wanna be engineer I like formulae... and I appreciate that this probably isn't the place to go through a derivation . Wish you could remember the source so we who might like to could see how it works. To me, something cubed is volume and there is a constant 1502.6 that relates to powder (?)... then I get lost at 7 x 3
I printed the table @Art Caputo posted (thanks!). The number from your formula matches up with 30+ barrel length in table for 2Fg, a little on the high side for 3Fg. I bought my used TC Hawken 50 on GB and it didn't come with a manual, so I downloaded one from TC website. It has a recommended charge table int the back - 50gr 2F up to 110 max...

 

[Johnny Tremain]

Where did you find this formula?

Do I search for Davenport Formula on this server, Ive posted it several times ands so did the original folks many moons ago.