BP Conversion Chart

[Cowboy]

Looking for a chart that could Convert 3f to 2f grain size loads?

For example: 60 grains of 2f is equivalent to (blank) grains of 3f. and vise versa.

Looked in my Dixie Catalog, Numerous BP digests that I have. Also looked on line to no avail. I had also touched on this earlier on another member's topic. I want to be able to spread accurate info. when responding to questions.

I know that it definitely has to exist!

I'm just looking in the wrong places!

Would appreciate any help.

Respectfully, Cowboy

 

[coloradoclyde]

Cowboy! the only one I know of is the Lee powder dipper chart..
http://www.google.com/url?sa=t&rct...jFJjFHjJctW6Nhy1g&sig2=pHZIUgBbmc_aLuO7QtRHRw

 

[Cowboy]

Thanks Clyde,

I appreciate your effort and info.

Respectfully, Cowboy

 

[Maven]

Cowboy, That conversion is going to depend on many factors beside grain size; e.g., bbl. length, twist, ball & patch diameter, and powder brand (i.e., how "fast" it burns*). Other things being equal (which they aren't), 60gr. FFg is roughly akin to 50gr. FFFg.


*I was shooting 70gr. Graf's (Wano) FFFg in my .54cal. Isaac Haines last month and found all my shots were 6 - 8" low @ 50 yd. A week later, shooting at the same target, but with 70gr. Diamondback FFg (reduced from 80gr.), it shot to the point of aim, or rather, where it was supposed to.

 

[Cowboy]

Thanks Maven,

I do realize and agree with you about the other variables in play. I also agree that there is a 10 grain reduction when switching from 2f to 3f. At least that seems to be what I've been reading. Seems a pretty high number of shooter's agree with the 10 grain difference between the two.

Respectfully, Cowboy :thumbsup:

 

[Billnpatti]

There are just too many factors in play to come up with an equivalency chart based solely on grain size. The 10 grain reduction when going from 2f to 3f is just a safety factor, not an exact equivalency difference. You may be able to get some sort of equivalency chart from Goex. If they don't have one and you have a chronograph available to you, you could take your powder of choice and load several different loads using 2f and measuring their velocities. Then load up your rifle with several charges of the same brand of powder using 3f and measuring their velocities. You will end up with two charts showing the velocities based upon powder charge. by comparing the two charts, you can see which 3f charge will give you the same velocity as a given 2f charge. Velocity is a pretty good measure of breach pressure. Not exact but close.

I know it is a lot of work but lacking any other charts, this is one way of making your own.

 

[Cowboy]

Thanks for the reply! Unfortunately I do not have access to a chronograph. It's a great idea though. Have to keep your suggestion in mind if ever I run across one.

With all the variables to consider, I can now see why I haven't found anything in print.

Respectfully, Cowboy :thumbsup:

 

[Cowboy]

Goex has a chart on their sight that lists muzzle velocities for a given caliber. Gives RB weight's but no ball diameter . Doesn't give specific charges neither.

Respectfully, Cowboy

 

[BrownBear]

I also agree that there is a 10 grain reduction when switching from 2f to 3f. At least that seems to be what I've been reading. Seems a pretty high number of shooter's agree with the 10 grain difference between the two.

The same "10-grain conversion" works just fine when going up the scale of grains size from 2f to 1f. I've shot a lot of 1f (Goex) over the last few years, and just try to find 1f loads for various calibers! I haven't broken out the chrono to confirm that velocities are comparable, but POI certainly doesn't change much, if at all. It doesn't take actual vel numbers to convince me the relationship is sound and plenty valid for shooting.

 

[Cowboy]

Appreciate the reply BrownBear,

I feel comfortable with the 10 grain rule in reduction from 2f to 3f. Just would have liked to see it printed by the manufacturer.

I just don't feel comfortable mentoring someone else on it if I can't see it in black and white for myself.

Like with the subs, T7 tells you right off in writing to reduce by 15% when using their product. Just would have liked to have seen Goex do the same when switching from 2f to 3f.

I have been shooting Goex 3f using 10 grn less than I would if I was using 2f anyways. I do know it's safe.

The reason why I started this topic was in hope of seeing it in black and white. Just don't feel right if I intend to pass this info along and not have anything to back up what I say, even if I know it's safe.

Respectfully, Cowboy

 

[BrownBear]

I just don't feel comfortable mentoring someone else on it if I can't see it in black and white for myself.

I'm about 90% certain I got the info from the Lyman black powder loading manual. Haven't double checked that cuzz my manual is buried somewhere, but it would be a good place for you to check.

 

[Cowboy]

:haha: I think I also have a Lyman Blackpowder& Loading manuel( 2nd Edition). Like you, I'm gonna have to dig it out from somewhere?

Respectfully, Cowboy :thumbsup:

 

[Rifleman1776]

Goex has a chart on their sight that lists muzzle velocities for a given caliber. Gives RB weight's but no ball diameter . Doesn't give specific charges neither.

Respectfully, Cowboy

Forget charts. :nono:
While forums like this can be helpful you cannot learn muzzle loading at a key board. :shake:
You already own a bp testing machine. It is called a rifle. :shocked2:
Load safely and go out and shoot targets. A fun afternoon at the range will answer your questions. Then you can help others by posting your results. :v

 

[George]

Here's a thought you might want to investigate. A simple rule such as using 10 grains less of 3F than 2F will work over some range of loads, but not so much for others. If you are using a 20 gauge smoothbore with .600" balls and charges of powder in the 70-90 grain range, then it's probably OK. But what happens if you are shooting a .32 caliber rifle with powder charges in the 20-30 grain range? A decrease of 10 grains will definitely not work.

The "rule of thumb" I've always heard of and used is about a 10% difference, not a flat 10 grains. Doing it that way, the difference will be a sliding scale, larger with large loads, smaller with small loads.

Spence

 

[Cowboy]

Great Advice. Thank you!

When using Goex 2f in my.50's on an average I've been using 70 grain. With my .45's been using 60 grains of 2f.

Just recently started using 3f and have been reducing my loads by 10 grains.

I definitely understand what you have said and will adopt your method of reducing by 10% instead of 10 grains. Makes perfect sense!

I appreciate it!

Respectfully, Cowboy

 

[BrownBear]

Good catch.

I use the "10 grain" rule of thumb for simplicity with the course adjustments on powder measures. That works because most of the time I'm flopping back and forth, it's with charges up in the 80-120 grain range.

In fact I'm betting the recommendation is for "10%," which would accommodate the full range of calibers and charges. A 10% reduction in charge for a 36 or 40 cal makes a lot more sense than a 10 grain reduction.

 

[George]

It may be the case that the difference is significantly greater than 10% with larger loads. Here's a photo of a page from the 1975 edition of the Lyman handbook explaining a comparison of velocity and pressures between G-O 3F and G-O 2F. In case you can't read it all, here's an example for high-end charges.

Charge-------- - Velocity-----Pressure
140 grains 2F----1779 fps----8500 LUP
100 grains 3F----1740 fps---11700 LUP
-----------------------------------
40 grains-----------39 fps------3200 LUP



Spence

 

[Cowboy]

Spence, I appreciate your research as well as the references that you have provided for us.

Thank you for the education!

Respectfully, Cowboy

 

[BrownBear]

That's comparable to the charts in the Lyman manual showing charges, velocities and pressures with assorted powders and projectiles.

I think we're on pretty safe ground whether using 10% or 10 grains if he was firing 180 grains in a 54 caliber. I'm going to stick with using 10% in small bores and 10 grains in the bigger stuff. A 10 grain change to my pet 15 grain 32 caliber load is like bringing a gun to a knife fight, while a 10% change should I ever decide to use 2f (not) will hardly make a difference. Along the same lines, adjusting my 54 cal load 9 grains up or down rather than 10 grains isn't going to raise any ballistic eyebrows. Heck, I can't even measure 1 grain with the bigger measure I use for larger cals. But it's easy to get as close as 2 grains with the little adjustable 25 grain measure I use with the small cals.

As for charts to make the conversion? Meh. Maybe I could fold one up and keep it in my patch box just in case. :wink:

 

[hanshi]

What Spence said.