Curious chrono results

[Muddly]

My elder .50 flint Renegade flintlock gave some very curious results 'tuther day. The charge was 70 grains of 3f Swiss, the projectiles I can not mention, but weigh 200, 230 and 250 grains.
The 200s did 1528 fps with a high/ low of 14 fps
The 230s did 1448 fps with a high/ low of 14 fps
The 250s did 1407 fps with a high/low of 7 fps.
This from a HARD ramming 26 inch factory barrel.
My Hawken with the same 250 grain load does 1610 fps. Modest ram.
My 24 inch unmentionable does 1575 fps with tje 250s. It also gets 1630 fps with the 230s. Almost easy ram.
The point of impact difference, elder Renegade, with all 3 loads is 3/4 inch at 50 yards.
My other, not so hard ramming flintlock Renegade, has a point of impact difference between the 200 and 250 grain of 4 &5/8ths inches at 50 yards. Got to chrono this one!
I expected some velocity difference between percussion and flint, but this is a bit much. I also wonder if the tight ram is a factor?
Forgive the projectiles, but has anyone noticed such disparity in velocity between flint/ percussion ignition and or tight/ loose ram with patch ball or conical?
Maybe I just have a " different " barrel...

 

[EC121]

You need a Kadooty for a consistent ram.

 

[64Springer]

You need a Kadooty for a consistent ram.

A Kadooty doesn't work as well as a Dikfer when ramming.

 

[Muddly]

With 14 fps ( 2 loads) and 7 fps actual variations, not calculated, I don't think my swab/ ramming is an issue.

 

[olskool]

i have been handloading since 1967 and shooting BP since the 70s, i have never owned a chronograph, as long as i hit the spot every time, i couldn't care less about the speed, just me,,,,,,,,,,,,,,,,,

 

[Nav]

You can't really compare two different guns and expect anything. I've had two of the same model guns that shot very different and wanted different loads for precision. Every gun is like a woman. It's usually not going to be readily apparent what makes them tick. You have to figure them out.

 

[Greenjoytj]

The flintlock is going to loose some chamber pressure through the vent. I have read it could require 5 grains more powder in a flintlock to equal MV from a sealed percussion lock gun. With all other load parameters being the same.

If it is hard to ram the projectile down it is going to be hard to get out too, work effort will be needed and will present as reduced MV, this would be as expected.

Perhaps smoothing the rough hard to ram barrel with some JB Bore Paste, or change projectile diameter.

Ramming pressure on the seated load is a non issue as in it won’t make a difference.
No ramrod can exert pressure on the powder like a reloading press can pack powder into a metallic cartridge case. It is the quantity mass weight of powder that provides the power of the load not how firmly it’s rammed/seated.

You would likely see higher MV using 2fg powder particularly with the heavier projectiles.

 

[Johnny Tremain]

When I chrono my 45 cal, never thought the 180gr ball would do over 2000fps.
Your are cooking right along.

 

[longcruise]

If it is hard to ram the projectile down it is going to be hard to get out too, work effort will be needed and will present as reduced MV, this would be as expected.

That actually works the other way around. It's counterintuitive but it's the way it works. An easy proof is to compare identical RB loads in the same gun with two different patch thicknesses. The tighter patch will shoot faster. Or, same patch but balls that vary .005. Larger, even though slightly heavier, will shoot faster.

 

[Absoroka]

Barrel length will make a difference in velocity. The short Renegade flintlock may not be consuming all of the energy generated by the gas expansion produced by ignition. Three FFF does have a fairly quick pressure curve compared to 2FF. Shooting one of the funny bullets which weighs more will take more energy to get it going down the barrel, thus the slower velocity. The condition of the barrel bore may be different as well. The resistance due to bullet design can also have an effect. You might also want to 'mike' land to land and groove to groove measurements. Your Hawken may have a slightly larger bore. You are getting good consistency in velocity so accuracy should be pretty good. Figuring it all out is half the fun.

 

[Muddly]

Did finally chrono the easier ramming barrel. Results were interesting.
Same projectiles and charges.
200 grain 1665 fps. High/ low 14 fps.
Tight barrel-1523 fps. H/L 14 fps
230 grain 1602 fps H/L 16 fps.
Tight barrel 1448 fps. H/ L 14 fps
250 grain 1545 fps. H/ L 14 fps
Tight barrel 1407 fps. H/ L 6 fps.
It's interesting that 2 barrels, and not too far apart in serial numbers, from the same manufacturer can differ this much with the same loads. I understand every barrel is a rule unto itself, but DANG. Both barrels have excellent consistency. The high/ lows are not calculated, they're the actuals.
I've found that Holy Black, Swiss 3f in this case, gives velocity consistency that " more efficient " powders dream of. In my percussion rifles, if my variations get above 15 fps, I'm doing something wrong. I would've expected higher variations in the flintlock due to that big hole in the barrel. I'm happy to be disappointed in this regard.