chronograph and velocity

[YORKTOWNE54]

Was planning on checking some velocities soon through a chronograph. I never used it for the flintlock yet. I'd like to see where the point of no return is and to see how the velocities change according to powder charge. Does anyone have any experiance here to offer some tips?

[roundball]

Hopefully yours have cables long enough that you can set it up a good 15 feet away so the billowing smoke doesn't interfere with the start stop pickup of the projectile;

Probably overkill, but I put a strip of 2" wipe clear heavy duty scotch brand packing tape over each sensors on mine to keep them from possibly getting damaged from handling, and/or accumulating any grunge (easy to wipe off the tape if need be)
 
If your Chrono accepts an AC adapter and you have electricity where you'll be shooting suggest you get an AC adapter or take plenty of spare batteries.

And stay focused on each shot to ensure you're aiming through the center of the screens each time.

Enjoy

[Buzzard]

In the past, i've had trouble with the patches hitting the sky screens. I don't use them anymore. Setup on cloudy days or under an umbrella or canopy.

[northmn]

I have chronographed several loads and had no problem, but my chronograph sets behind a steel angle iron guard.  I have always set it up like, Roundball suggests, about 15 feet from the muzzle.  A couple of things you may notice is that the first shot out of a clean barrel will probably be lower velcoity than the rest.  Sometimes quite a bit.  Once fouled they tend to stabilize.   I hit the point of diminishing returns for my 50 percussion at about 80 grains of 3f.  Every barrel has its own quirks.  When I drilled the 54 vent out to .070 from 1/16 or .0625 I had a very slight loss in velocity.  One issue that a chronograph does not show for me was that while Graf's powder was consistantly slower in more than one gun, in my 25 I got more shot to shot consistancy and easier loading between shots.  Since the difference was about 70 fps but the Grafs still gave 1680 fps, I use the Grafs for the 25.  Another difference is that 2f gave less shot to shot variation in my 54 over 3f.  Interested in your results.

DP

[Daryl]

I set up normally, then take the overhead diffusers off as well as the wires. I then find a 'spot' on the dirt bank to aim at that will line up and clear the 'screens'.  I used to cover the screens as Roundball does, bit found it to be a waste of time.  If the 'eye's get smudgy, a Q-tip wipes them clean with a swipe.  Different chronographs have different set-ups, of course. When we used Taylor's chrony, with the card screens and front readout, we merely set it on a stump and went for it - no problem.

When chronogrpahing loads that have wads, ie: shotguns, I put an angled defletcor of steel or wood in front of the first screen to protect it from flying wads or stray pellets.

[longcruise]

What is "the point of no return"?

[roundball]

What is "the point of no return"?

Its probably pretty safe to assume he's referring to the point of diminishing returns when discussing chronographing loads, wouldn't you think?

[YORKTOWNE54]

point of no return would refer to, once the maximum velocity is achieved say at 110 FF powder and you keep increasing charge without seeing any more velocity increase. Some have stated of potential velocity decrease after such a point.

[Mad Monk]

Some chronographs are sensitive to how high above the screen the ball is when it passes over them.  With both of my .50's with patched balls.  The Pact allowed the ball to be seen up to a foot above the screens.  The CED Millennium I replaced it with has a maximum height of about 6 inches above the screens.

I used both at 15 feet from the muzzle.  How far out the patches carry may be affected by the lube you use.  When I used a water based lube the #40 cotton drill patches would fall short of the first screen.  With a sticky "grease" lube some would carry through the first screen and give an error reading.  This got to be a real problem in cold weather with the "grease" lubes if they got very stiff or hard down near freezing or below freezing.

[Daryl]

Good point Bill.  As to the point of no-return - it does exist, but you will never shoot that much powder.

The point of little or less return is easily found somewhere below 125gr. and maybe even 100gr. in a .50, depending on barrel length.

Higher velocity flattens trajectory over unknown ranges - sometimes necessary even though it isn't as efficient as a 'plinking' load.

Velocity rise per grain of powder to 80gr. is higher per grain than from 80 to 120gr., but the lesser, more efficient load is not a 125 yard moose load in a .50, whereas the 120gr. load can be.

 

[northmn]

There are two aspects of diminishing returns with a round ball.  One is the amount of powder used and the amount of increase in velocity.  There seems to be a point in which the gain is minimal with powder increase.  Also a roundball will lose velocity very quickly at higher velocities.  Some claim that about 1800 fps is a good high point because over that and the losses tend to increase such that a 200 fps gain at the muzzsle will mean a 70 fps gain at 100 yards.  One reason that if you want more power go to a bigger bore as they tend to have better retention.  At 80 grains of 3f my 50 gave about 1870 fps which is pretty good.  If I need more punch I will use a 54 or bigger.

DP

[Daryl]

But, if you don't have a .54, you use a bit more powder, sight for it and go hunting and kill a moose. 

[YORKTOWNE54]

I heard moose meat is quite delectable, wish we had them in Pennsylvania.Sounds like setting up 15 foot back seems to be the preferred distance, so as to not have issues.

[Buzzard]

My 62cal fowler will only do about 5-6" @ 50yds. My 54cal smooth rifle will do about 4-5" @ 50 yds.

[longcruise]

Hopefully yours have cables long enough that you can set it up a good 15 feet away so the billowing smoke doesn't interfere with the start stop pickup of the projectile;

Probably overkill, but I put a strip of 2" wipe clear heavy duty scotch brand packing tape over each sensors on mine to keep them from possibly getting damaged from handling, and/or accumulating any grunge (easy to wipe off the tape if need be)
 
If your Chrono accepts an AC adapter and you have electricity where you'll be shooting suggest you get an AC adapter or take plenty of spare batteries.

And stay focused on each shot to ensure you're aiming through the center of the screens each time.

Enjoy

What is "the point of no return"?

Its probably pretty safe to assume he's referring to the point of diminishing returns when discussing chronographing loads, wouldn't you think?

Heh heh, you and I both know that, but was just trying to encourage the OP to put a more precise definition on his question.  And, that he did!

So, here is some real world chrono data that I did with a .45 TC in a 28 inch barrel.  Most shooters are not going to go this high with charges in shooting a .45 and will probably not go, proportionally speaking, this high in any of the larger bores either.

Shot on 05/30/10 with TC .45, goex 3f, wally duck patch, spit lube

50 grains
1517

70 grains
1680 +163

90 grains
1865 +185

120 grains
2031 +166

[Daryl]

Mike - to keep 20gr. intervals, shouldn't the last charge be 110gr.? That looks about right. Good post.

In testing my big gun(14 bore rifle) years ago I started at 82gr. 3F for 1,225fps.  At 100gr. 3F, I started losing patches(burns), so I switched to 100gr.2F and was rewarded with 1,250fps.  At 125gr. I recorded approximately (data lost) 1,325fps.  150gr. gave me close to 1,425fps and I stopped at 165gr. for 1,525/1,550fps.

 As I knew at that time the US Military thought they were getting 1,700fps from their muskets with 165gr. of musket powder, I deided to see with what charge of today's powder (1990) I had to load to get that velcity.  That charge turned out to be 225gr. for 1,700fps.

I went back to targeting and filing in my sights, when I accidently double charged with powder - 330gr. ie: 12 drams, the normal 'light' 4 bore charge, instead of my normal 165gr., 6 dram charge.  The recoil picked me up off the chair, and the chronograph recorded 1,770fps.  70fps gain over the previous 225gr. charge giving 1,700fps, ie: 105gr. more powder for 70fps, but the velocity was still climbing - not receeding.

There are some smokeless powders used in small cases that will actually reduce speed with increased loads that are stil winthin the prressure specs for that round - however with black powder, it would take a horendous amount of powder, much of the barrel's length, to show a reduction in speed.  The increase ratio will decrease, but the speed continues to increase with any charge we are likely to use.

[longcruise]

Mike - to keep 20gr. intervals, shouldn't the last charge be 110gr.? That looks about right. Good post.

Yes, but my can was near empty and I did want to shoot the 120 charge.  The other powder I had with me that day was Scheutzen 3f.  I compared it a 120 too and it came in just a few fps diff from the goex.

[WaterFowl]

 

 Mount a protective screen to protect the chronograph screen




80 fff-goex=1287     FPS  flatlined at 130 gr
135 fff-goex=1608

62 cal 33'X1" Rice flint barrel..shoots best 105-100 gr FFF.