Point of impact change?

[Travis Gregory]

How much if any can I expect my POI to change by switching from 2f to 3f black powder and using the same charge. BTW I have been using 70gr 2f in my .50 and want to use 70gr 3f.

 

[Mountainman56]

I can only think of one way to find out. Might be 60 or 65 grains of 3f would give the same results. Might be it'll work fine at 70. Chances are you'll have to re-sight your rifle. :2

 

[jdixon]

I have done this experiment and usually found that the POI drops as you increase the powder charge, to a point anyway. This seems counterintuitive but, it was explained to me by an old timer this way:

The 3F charge will produce slightly more velocity than your 2F charge of the same weight. This will result in the ball leaving the barrel sooner ”“ duh right? On ignition, the barrel immediately begins to rise ever so slightly and continues to do so until the energy of the recoil has dissipated. With a higher velocity charge, the ball will leave the barrel sooner, therefore be less affected by the rising barrel and strike lower than the lower velocity ball would at the same point of aim. Now I am not talking about much here and in some cases, it may not even be noticible but, in theory the higher velocity charge will hit lower.

Someone else may have another idea on this but; this explanation seemed to me very plausible.

 

[Zonie]

That depends on a lot of variable things like barrel length, patch thickness, ball size, the distance to the target, etc.

Just guessing that your gun is similar to the one Lyman used to test loads for their "BLACK POWDER HANDBOOK & LOADING MANUAL" it would have a 28 inch barrel with a 1:48 twist shooting a .490 diameter ball with a .015 patch.

Using GOEX powder their 70 grain powder charges their 70 grain 2Fg charge delivered a muzzle velocity of 1471 fps.
The 3Fg 70 grain charge delivered a muzzle velocity of 1657 fps.

In order to get a change in impact number I set the range in my roundball trajectory calculator to be aimed at 100 yards and looked at the change in trajectory between the two velocities at 30,50 and 70 yards.

At 30 yards the difference in trajectory was 0.6 inches. At 50 yards the difference was 0.5 inches and at 70 yards the difference was 0.4 inches.

Hope this helps answer your question.

 

[nw_hunter]

You do know, that after all is said and done, you will have the terrible task of finding out for yourself :wink:

A man has to do these things to justify going to the range over, and over, and over again.

Let us know the results!..........You know you won't sleep until you know! BG