Velocity VS Pressure

[Phlytyer]

:huh:A NuB question; how can one change from BP to Pyro to 777 to Mag3, and get different velocities and still have 'safe' loads?

Being new to BP, I am a bit confused. In studying the various powder options, I found that equal measures of different powders appear to achieve significantly different results. Now, I am not a physicist but it seems to me that there is some room for concern. The manufacturer of my rifle (CVA) states maximum load of 100 gr. of BP. This seems to be a fairly common industry standard. However, in studying load tables at Hodgden, Goex and Magkor, I was surprised to find the following data.

.490 Ball and Patch------90 GR.---increase
---------------------------------------------
Black Powder (FFG)--------1712------0------0%
PYRO RS & SELECT (FFG)--1787-----75------4%
Triple 7 (FFG)-------------1925----213-----12%
Triple 7 (FFFG)------------1945----233-----14%
BlackMag3 (FFG)----------1997----285-----17%

Now, if all of these are safe loads, does that mean that I could safely increase my BP load by 17 percent and achieve the same velocities? (I rather doubt that is acceptable). On the other hand, these various companies appear to indicate that I can achieve greater velocities with equivalent volumes of their product.

But, to get greater velocity, one must have greater pressure. This would then, potentially exceed the safety limits of my gun. If CVA states the maximum velocity of my gun is 1712, how can I get higher velocity WITHOUT greater pressure? Is there some characteristic of BP and BP substitutes that I am not comprehending? :hmm:

 

[Rat]

I believe the relationship between pressure and velocity is not exactly linear. Burn rate and burn charactoristics have a lot to do with it also. Some smokeless powders will produce higher velocity at the same or even less pressure than others.

What you may be seeing with the BP and the subs are different burn charactoristics, different types of pressure curves.

I would guess that there is enough "fudge factor" in the safety margins that you are not seeing exact comparisons as far as pressure goes...and there are no SAMMI specs for muzzle loading rifles, per caliber, as far as I know. Still, if you fired all those powders in a pressure barrel, and adjusted the charges so that pressure was identicle, you still might/would see different velocities.

Well that's my best guess anyhow.

Rat

 

[Phlytyer]

Rat:

Thanks for the response. I will just have to get some powders and see what happens in my gun.

 

[Slamfire]

Hogdon states on the 777 label that you should reduce the maxim load by 20% as there is greater pressure involved. My problem with it is that my accuracy goes all over the board when usin' the danged stuff. It cleans up great though so if hittin' what you aim at ain't important its great stuff.

 

[Stumpkiller]

I believe the relationship between pressure and velocity is not exactly linear.

What he said. The curve of velocity vs. powder charge has a pronounced "dogleg". It climbs relatively fast, and then begins to level out and increase much more gradually.

Going from 70 to 80 gr may pick you up 150 fps, while going from 90 to 100 may only gain you 50 fps.

 

[HardBall]

The "pressure vs. velocity" thing is something I'm always a student of, be it BP rifles or smokeless metallic reloading.

Generally with a given powder, Black Powder or substitutes, as you increase the powder charge, pressure increases. Now, velocity and pressure are proportionally related, but they are not necessarily linearly proportional. With smokeless pistol powders; some powders have a sweet spot where they render good velocity and uniformity for a given powder charge. Exceed their sweet spot and pressure can really spike, with little gain in velocity. Other smokeless powders, Alliant Unique being a good example, are loved for their (usual) linearity; meaning, as you gradually increase the powder charge in your reloads, velocity and pressure seem to rise together without unusual spikes- all the way to the firewall.

From what I've seen of the limited pressure data that

 

The data I saw for Black Mag 3 showed higher velocities with less pressure than real BP or the other replacements.
: T-7 is supposed to be reduced by 15% to 20% approximately. Is this done by having a lower specific gravity, or does the volume have to be reduced? Equal pressure between the sustitutes and BP 'should' produce the same velocity - theoretically.
: These are questions that should to be answered.
: There is no such thing as a maximum velocity for your gun. CVA merely showed the velocity they got with the maximum combination they used. There is such a thing as a maximum pressure, though, which shouldn't be exceeded.
: Is the CVA max load for 2FG, 3FG or for 1FG powders? Spanish and Italian mfgr's in the 70's listed only pressures as max, in .36, 44,45 and .58.
: Most mfgr's. list 2F for calibres .45 and larger, including G.R.R.W., H&R, Numrich Arms, & T.C.- these are from the Lyman BP Handbook as listed on Lyman's Table of Proofs and MFGR's Load Suggestions, pg. 86

 

[Phlytyer]

May thanks to all who have contributed to my BP education. I think I'm starting to understand. In searching this website, I found the Links Section and found a lot of good information.

A GOOGLE search took me to Chuck Hawk's site where this article helped immensely.

Again, thanks for all of the great advice and input.

 

Thanks for showing the article. I found it very interesting indeed, for it stated that BlackMag-3 does indeed produce more pressure than it's volumetric BP load. This makes sence, but now shows 1 of each - so to speak- one yea, one nay.
: As the BM3 isn't suitable for the flinter, I'll just continue using it in the Model 71 Mauser where it does an excellent job. I found the actual fouling to be soft and very little of it, though, on par with Pyrodex.
: My load was 76gr. actual, about equivalent to 100gr. in the .45 bore, delivering 1,500fps with 505gr. bullets, which is well in excess of what BP or Prodex will do.

: Thanks Phlytyer

 

[robinghewitt]

I have here a card of 1/2" Remington Golden Balls, on the back it tells me that 90 grains of FFg will give 1197 ft.lbs of energy.

Assume a 3 foot barrel and you don't need a degree in rocket science to calculate an average pressure around 2000 psi.

Peak pressure will be way up on that, but if you could achieve the perfect burn then 2000 psi would suffice.

Black powder has a high start pressure but it can't hold useful pressure as the ball moves up the barrel. By using other propellants you could achieve higher velocities while actually reducing the peak pressure.

Unfortunately, alternative propellants just don't smell like the real thing ::

 

The article also stated that 100gr. of PyrodexRS with a light 240gr. sabot bullet produced over 20,000PSI and that some loads used by lots of shooters today, produced pressure almost up to 30,000PSI.
; Numbers this high, should produce some nervous shooters.
; It is unfortunate everyone who shoots BP isn't required to read that article.
: It is peak pressure that blows breeches and/or barrels.

 

[sse]

I suggest that rollingb should read that article since its by his favorite author. :: ::
:: ::

Regards, sse

 

[RussB]

I suggest that rollingb should read that article since its by his favorite author. :: ::
:: ::

Regards, sse

Send it to him...I double dog dare ya! That'll get that "pot licker" (your words) fired up, and mixin his words fer shore! :crackup: :crackup:


Russ

 

[sse]

Whale, if yer gonna dubble dog me...naw only a "rat" would do that. :no: :no:

Regards, sse

P.S. What the heck, I can be as good a rat as the next guy. :haha: :haha: