unusual Trailboss findings with small blackpowder era cartridges...

Magnum Wheel Man · February 21, 2010, 08:33 PM

admittedly, my testing is limited, to a couple cartridges, & in this Minnesota winter weather...

Temp's in the 20's* distance to target is 30ft, chrono readings taken about 4ft from the muzzle...

cartridges are 32 & 38 S&W...

barrel lengths tested 2", 3", & 5"... sorry about the missing data

these are 5 shot average velocities... using roundball loads, for lower chamber pressures & less barrel resistance... I'll have some cast bullets to try but expect similar results ???

32 S&W...

Barrel length... 0.5 grains... 0.7 grains... 1.0 grains
2".................255 fps.......317 fps.....................
3".................247 fps.......316 fps........521.4 fps
5"..................................241 fps........385.6 fps

38 S&W...
Barrel length... 0.3cc.........0.5cc...........0.7cc
2"
3".................279 fps.......546fps...........515.6 fps
5".................155.5 fps....302.2 fps........302.2 fps

it appears as if the maximum velocities are coming from the shorter barrels...
looks like 1.0 grain, & 0.7 cc are maximum loads for the 2 cartridges, & perhaps once a maximum load is achived, the velocity stays the same for certain barrel lengths... of course my findings are all taken in the cold weather... but I'm curious if anyone else has documented similar results...

thoughts ??? Comments ???

Magnum Wheel Man · February 22, 2010, 07:23 AM

1.0 grain of Trailboss is nearly maximum case capacity without compressing the powder on the 32 S&W ( which is a no-no with Trailboss ), likewise 0.7 cc is maximum for the 38 S&W

my results seem kinda goofy, with the longer barrels definately throwing lower velocities... but also some larger charges throwing lower velocities ( like the 3" barrel 38 results )

these are all 5 shot averages, & extreme spreads were not excessively large indicating either combustion or inconsistancies with the chrony... related to the cold...

my cast bullets for the 32 should be here today, & maybe I can get a few loaded for next weekend... but I find the results with the roundballs strange, as accuracy is good, & all shots consistant ( a 30 round group from all shots, form a pretty good 12-14" circle on my target backer, not bad IMO, considering the extreme spread of charges & various barrel lengths used ) I'm not getting excessive barrel leading, I guess I'm at a loss to explain this... any suggestions ???

SL1 · February 22, 2010, 08:16 AM

I'll start by saying that I have never used Trailboss, so all I can offer is some speculations.

One that comes to mind immediately is that different revolvers can have major differences in velocities with the exact same load. Things like different throat diameters, different chamber volumes and different cylinder-to-barrel gaps are usual contributors and are easy to measure in your own guns. But, the relationship of barrel groove diameter to chamber throat diameter(s), alignments of cylinder chambers with the barrel bore, and variations in the bore diameter along the length of the barrel can also make differences, and they are harder to measure. So, it is quite possible for a gun with a longer barrel to shoot "slower" than a gun with a shorter barrel. If your guns shoot other loads in the same order of velocities, then that is probably part of the answer. If they shoot other light loads in different velocity order, then maybe there is something strange about Trailboss.

My QuickLOAD version doesn't have Trailboss in its powder database, so I can't check how fast your loads burn 100% of their powder. It occurs to me that, if it is quite fast, then the barrel-to-cylinder gaps could be limiting how long the gases get to push on the bullets as they travel down the barrel by bleeding the pressure away pretty early. That could go a long way toward limiting how much velocity you are getting as you increase barrel length,and maybe even charge weight. The velocity could be coming mainly from acceleration while the base of the bullets are still in the cylinder throats. Whatever velocity is being added by residual pressure in the barrel while the bullet transits, is also being worked against by the addditional friction in the barrel.

Still, I would think that additional powder in a specific load with a specific gun would show some pressure increase and some velocity increase, unless powder burning-rate isn't changing as we expect when loading density increases. High-power cartridges sometimes show velocities leveling-off or even slightly decreasing as max charges are exceeded, so that isn't an unheard-off behavior. And, it really hasn't been explained well, that I know of. So, maybe Trailboss has a similar behavior at much lower pressures. It would be intersting to me to see if others have seen similar behavior.

SL1

Magnum Wheel Man · February 22, 2010, 08:38 AM

just an FYI... Trailboss falls in the powder burn rate chart close to PB, Green Dot, & #5...

it is unique in that it is shaped like little doughnuts, & is very sensitive to being compressed & breaking those doughnuts... I think the shape allows for alot of "air" mixed in with the charge, probably reduces initial chamber pressures, because of the volume of air mixed in with the powder ???

lower chamber pressures are evident by sooting of the cases at the lower charge levels, by mid charge levels, the brass is clean, but none of the cases comes even close to showing high pressures, even at maximum charge... it's a very bulky powder with it's unique shape...

... I understand different guns have different charictoristics that can control the velocities ( barrel cylinder gaps, bore diameter, etc. ) but to see a universal slowing of the balls with longer barrels, & some at a very large percentage, seems strange to me...

... I have run into the added charge & no additional velocity before in my reloading, but to see a marked drop in velocity ( again could be contributed to the gun )... & of course these are all 100 year old guns, so there is more chance for variance with less standardized manufacturing between guns... but atleast outwardly, they all seem in good enough shape to fire... I think I'll have to check / measure the barrel cylinder gaps on the fired guns ???

February 21, 2010, 08:33 PM	#1
Magnum Wheel Man Senior Member Join Date: July 26, 2006 Location: Southern Minnesota Posts: 9,333	unusual Trailboss findings with small blackpowder era cartridges... admittedly, my testing is limited, to a couple cartridges, & in this Minnesota winter weather... Temp's in the 20's* distance to target is 30ft, chrono readings taken about 4ft from the muzzle... cartridges are 32 & 38 S&W... barrel lengths tested 2", 3", & 5"... sorry about the missing data these are 5 shot average velocities... using roundball loads, for lower chamber pressures & less barrel resistance... I'll have some cast bullets to try but expect similar results ??? 32 S&W... Barrel length... 0.5 grains... 0.7 grains... 1.0 grains 2".................255 fps.......317 fps..................... 3".................247 fps.......316 fps........521.4 fps 5"..................................241 fps........385.6 fps 38 S&W... Barrel length... 0.3cc.........0.5cc...........0.7cc 2" 3".................279 fps.......546fps...........515.6 fps 5".................155.5 fps....302.2 fps........302.2 fps it appears as if the maximum velocities are coming from the shorter barrels... looks like 1.0 grain, & 0.7 cc are maximum loads for the 2 cartridges, & perhaps once a maximum load is achived, the velocity stays the same for certain barrel lengths... of course my findings are all taken in the cold weather... but I'm curious if anyone else has documented similar results... thoughts ??? Comments ??? __________________ In life you either make dust or eat dust... Last edited by Magnum Wheel Man; February 21, 2010 at 09:02 PM.

February 22, 2010, 07:23 AM	#2
Magnum Wheel Man Senior Member Join Date: July 26, 2006 Location: Southern Minnesota Posts: 9,333	to add to the data I entered yesterday... 1.0 grain of Trailboss is nearly maximum case capacity without compressing the powder on the 32 S&W ( which is a no-no with Trailboss ), likewise 0.7 cc is maximum for the 38 S&W my results seem kinda goofy, with the longer barrels definately throwing lower velocities... but also some larger charges throwing lower velocities ( like the 3" barrel 38 results ) these are all 5 shot averages, & extreme spreads were not excessively large indicating either combustion or inconsistancies with the chrony... related to the cold... my cast bullets for the 32 should be here today, & maybe I can get a few loaded for next weekend... but I find the results with the roundballs strange, as accuracy is good, & all shots consistant ( a 30 round group from all shots, form a pretty good 12-14" circle on my target backer, not bad IMO, considering the extreme spread of charges & various barrel lengths used ) I'm not getting excessive barrel leading, I guess I'm at a loss to explain this... any suggestions ??? __________________ In life you either make dust or eat dust...

February 22, 2010, 08:38 AM	#4
Magnum Wheel Man Senior Member Join Date: July 26, 2006 Location: Southern Minnesota Posts: 9,333	thanks for the reply... just an FYI... Trailboss falls in the powder burn rate chart close to PB, Green Dot, & #5... it is unique in that it is shaped like little doughnuts, & is very sensitive to being compressed & breaking those doughnuts... I think the shape allows for alot of "air" mixed in with the charge, probably reduces initial chamber pressures, because of the volume of air mixed in with the powder ??? lower chamber pressures are evident by sooting of the cases at the lower charge levels, by mid charge levels, the brass is clean, but none of the cases comes even close to showing high pressures, even at maximum charge... it's a very bulky powder with it's unique shape... ... I understand different guns have different charictoristics that can control the velocities ( barrel cylinder gaps, bore diameter, etc. ) but to see a universal slowing of the balls with longer barrels, & some at a very large percentage, seems strange to me... ... I have run into the added charge & no additional velocity before in my reloading, but to see a marked drop in velocity ( again could be contributed to the gun )... & of course these are all 100 year old guns, so there is more chance for variance with less standardized manufacturing between guns... but atleast outwardly, they all seem in good enough shape to fire... I think I'll have to check / measure the barrel cylinder gaps on the fired guns ??? __________________ In life you either make dust or eat dust... Last edited by Magnum Wheel Man; February 22, 2010 at 08:46 AM.

February 22, 2010, 08:16 AM	#3
SL1 Senior Member Join Date: November 8, 2007 Posts: 2,001	I'll start by saying that I have never used Trailboss, so all I can offer is some speculations. One that comes to mind immediately is that different revolvers can have major differences in velocities with the exact same load. Things like different throat diameters, different chamber volumes and different cylinder-to-barrel gaps are usual contributors and are easy to measure in your own guns. But, the relationship of barrel groove diameter to chamber throat diameter(s), alignments of cylinder chambers with the barrel bore, and variations in the bore diameter along the length of the barrel can also make differences, and they are harder to measure. So, it is quite possible for a gun with a longer barrel to shoot "slower" than a gun with a shorter barrel. If your guns shoot other loads in the same order of velocities, then that is probably part of the answer. If they shoot other light loads in different velocity order, then maybe there is something strange about Trailboss. My QuickLOAD version doesn't have Trailboss in its powder database, so I can't check how fast your loads burn 100% of their powder. It occurs to me that, if it is quite fast, then the barrel-to-cylinder gaps could be limiting how long the gases get to push on the bullets as they travel down the barrel by bleeding the pressure away pretty early. That could go a long way toward limiting how much velocity you are getting as you increase barrel length,and maybe even charge weight. The velocity could be coming mainly from acceleration while the base of the bullets are still in the cylinder throats. Whatever velocity is being added by residual pressure in the barrel while the bullet transits, is also being worked against by the addditional friction in the barrel. Still, I would think that additional powder in a specific load with a specific gun would show some pressure increase and some velocity increase, unless powder burning-rate isn't changing as we expect when loading density increases. High-power cartridges sometimes show velocities leveling-off or even slightly decreasing as max charges are exceeded, so that isn't an unheard-off behavior. And, it really hasn't been explained well, that I know of. So, maybe Trailboss has a similar behavior at much lower pressures. It would be intersting to me to see if others have seen similar behavior. SL1