How low can you go? - Page 2

Tsquared · February 28, 2016, 08:57 AM

Going with a minimum bullet load in a revolver makes me nervous.

I have used magnum primers in 44 brass and twisted it into colored gulf wax to shoot my 44mag in my basement. The only cost was the primers and wax. I taught my son proper gun practices with this method.

briandg · February 28, 2016, 02:57 PM

frankenmauser , you are an expert,gimme a hard thinking about this.

His revolver will have a tiny amount at free bore, then the forcing cone,and by the time it encounters the rifling, it will have a pressure drop when the bullet passes the cylinder gap.

This isn't like firing through a semiautomatic barrel in a bunch of ways. I don't really know what those effects would be. This is something that has bugged me since the first post. Free bore at first may build enough inertia to pop it into the rifling,but then the gap will cut into the pressure and may take the thing down too far to continue and let the gas leak away. For that matter, that bit of free bore may choke down the necessary pressure for the powder to continue burning.

I don't recall seeing this addressed. It could be that nobody could answer it, and the. Only way will be to experiment until it fails.

FrankenMauser · February 28, 2016, 03:53 PM

I'm no expert; just a guy that spends a lot of time thinking, talking about, and messing with ammunition and firearms.

---

CAUTION: The following post includes loading data beyond or not covered by currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assume any liability for any damage or injury resulting from use of this information.

I don't know if the estimates would translate well to low pressure 9mm, since they're generally based on mid-range .38 Special or full pressure .357 Magnum, but most estimates that I have seen claim 8-12% of pressure is bled off by the cylinder gap of a revolver.

However, that isn't as bad as it sounds. Most 9mm loads will reach maximum pressure within just 0.25" to 0.4" of bullet travel, which will still have the base of the bullet well within the cylinder of an LCR.

My own 122 gr LFP load, for example (1.090" COAL, 0.515" bullet length, 0.025" bevel base, 1.600" cylinder working length), works out to having exactly 1.000" of bullet travel (with a "perfect" bullet) before the base of the bullet breaks the seal at the cylinder gap.
By that point in time, pressure has already reached maximum and dropped back down to about 2/3 of maximum (the same happens for nearly any 'standard' load), and the bullet is already traveling at 70-75% of muzzle velocity (653 fps, in this case).

In the LCR you have another two inches of barrel to further boost velocity, so long as pressure isn't insanely low.
But the fact that the revolver has a short barrel means there is less time for the cylinder gap to bleed off pressure, and the overall impact should be negligible.

As long as the bullet is moving fast enough before the base jumps the cylinder gap, it should be just fine.

(For some real world examples: Ballistics By The Inch did some velocity-vs-cylinder gap testing a while back, with .38 Spcl and .357. Overall, they lost just 20-80 fps; and the shorter the barrel, the lower the impact of the cylinder gap.)

If you're wondering "how slow can you go?" I really don't think there is a good answer to that question, given the variability of barrel quality, bullet selection, powder lot consistency, and effect of different primers on individual loads.
But I do know that I have reliably taken certain .32 caliber revolver cartridges, in 4.2" and 5.5" barrels, down to as low as 400 fps with predictable results - as far as bullets exiting the barrel. Ignition was spotty, due to the insanely low powder charges and choice of powder, but when the powder ignited, the bullet always left the barrel.
After some tweaking, I did end up with one load that is 100% predictable and reliable at 480 fps.

For the record...
If I wanted to practice with a 9mm LCR, I'd just use standard pressure 9mm ammo loaded with 120-147 gr bullets.
There isn't a whole lot of muzzle blast or recoil that needs to be avoided, and practice with something closer to "SD" loads would be beneficial.

cecILL · February 29, 2016, 08:28 AM

OK, Started at the 3 grains. Stopped at 2.5 grains.

No performance problems. Guessing 5-600 fps. A pleasure to shoot.

Recoil similar to a .38 target load in a full size revolver.

TimSr · February 29, 2016, 08:51 AM

This is one of those cases where understanding WHY a certain minimum or maximum is published.

38spl published minimums are arrived at with stuck bullets in mind.

9mm published minimums are arrived at with actions failing to cycle in mind.

This leaves you with some trial and error, and forming unsupported opinions while looking over a variety of load data.

I would start with published data, and a powder that reduces well, and using a chronograph, reduce until you hit about 700fps, to leave a healthy margin of error. As with anything else, some lead bullets will get you there with a smaller charge.

**Unclenick** · February 29, 2016, 08:53 AM

Glad that worked out. I would expect it to, as your powder space is small. Should behave about like a 38 Special Wadcutter, except your bullet is lighter. You will get cleaner burning with Clays if you try it.

griz · March 1, 2016, 08:02 AM

Well, I clearly missed that it will be fired in a revolver when I dashed off a reply. It sounds like the OP has already worked down to a light load, but I will reiterate all the cautions about how it is easier to stick a bullet in a revolver compared to a bottom feeder. Or at least it's easier to fire another round behind it with another trigger pull. Sorry, I would edit my first post if I could figure out how.

FrankenMauser · March 1, 2016, 04:57 PM

griz, you're past the grace period. Posts can only be edited for 5 days. After that, only a moderator can edit a post.

griz · March 2, 2016, 08:32 AM

OK. That's understandable and I wasn't complaining about it. I just hadn't checked in for a while and was embarrassed to have given sketchy advice.

February 28, 2016, 03:53 PM	#28
FrankenMauser Senior Member Join Date: August 25, 2008 Location: In the valley above the plain Posts: 13,424	I'm no expert; just a guy that spends a lot of time thinking, talking about, and messing with ammunition and firearms. --- CAUTION: The following post includes loading data beyond or not covered by currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assume any liability for any damage or injury resulting from use of this information. I don't know if the estimates would translate well to low pressure 9mm, since they're generally based on mid-range .38 Special or full pressure .357 Magnum, but most estimates that I have seen claim 8-12% of pressure is bled off by the cylinder gap of a revolver. However, that isn't as bad as it sounds. Most 9mm loads will reach maximum pressure within just 0.25" to 0.4" of bullet travel, which will still have the base of the bullet well within the cylinder of an LCR. My own 122 gr LFP load, for example (1.090" COAL, 0.515" bullet length, 0.025" bevel base, 1.600" cylinder working length), works out to having exactly 1.000" of bullet travel (with a "perfect" bullet) before the base of the bullet breaks the seal at the cylinder gap. By that point in time, pressure has already reached maximum and dropped back down to about 2/3 of maximum (the same happens for nearly any 'standard' load), and the bullet is already traveling at 70-75% of muzzle velocity (653 fps, in this case). In the LCR you have another two inches of barrel to further boost velocity, so long as pressure isn't insanely low. But the fact that the revolver has a short barrel means there is less time for the cylinder gap to bleed off pressure, and the overall impact should be negligible. As long as the bullet is moving fast enough before the base jumps the cylinder gap, it should be just fine. (For some real world examples: Ballistics By The Inch did some velocity-vs-cylinder gap testing a while back, with .38 Spcl and .357. Overall, they lost just 20-80 fps; and the shorter the barrel, the lower the impact of the cylinder gap.) If you're wondering "how slow can you go?" I really don't think there is a good answer to that question, given the variability of barrel quality, bullet selection, powder lot consistency, and effect of different primers on individual loads. But I do know that I have reliably taken certain .32 caliber revolver cartridges, in 4.2" and 5.5" barrels, down to as low as 400 fps with predictable results - as far as bullets exiting the barrel. Ignition was spotty, due to the insanely low powder charges and choice of powder, but when the powder ignited, the bullet always left the barrel. After some tweaking, I did end up with one load that is 100% predictable and reliable at 480 fps. For the record... If I wanted to practice with a 9mm LCR, I'd just use standard pressure 9mm ammo loaded with 120-147 gr bullets. There isn't a whole lot of muzzle blast or recoil that needs to be avoided, and practice with something closer to "SD" loads would be beneficial. __________________ Don't even try it. It's even worse than the internet would lead you to believe.

February 29, 2016, 08:53 AM	#31
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	Glad that worked out. I would expect it to, as your powder space is small. Should behave about like a 38 Special Wadcutter, except your bullet is lighter. You will get cleaner burning with Clays if you try it. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

March 1, 2016, 04:57 PM	#33
FrankenMauser Senior Member Join Date: August 25, 2008 Location: In the valley above the plain Posts: 13,424	griz, you're past the grace period. Posts can only be edited for 5 days. After that, only a moderator can edit a post. __________________ Don't even try it. It's even worse than the internet would lead you to believe.

February 28, 2016, 08:57 AM	#26
Tsquared Senior Member Join Date: January 26, 2016 Location: NE Atlanta Posts: 337	Going with a minimum bullet load in a revolver makes me nervous. I have used magnum primers in 44 brass and twisted it into colored gulf wax to shoot my 44mag in my basement. The only cost was the primers and wax. I taught my son proper gun practices with this method.

February 28, 2016, 02:57 PM	#27
briandg Senior Member Join Date: May 4, 2010 Posts: 5,468	frankenmauser , you are an expert,gimme a hard thinking about this. His revolver will have a tiny amount at free bore, then the forcing cone,and by the time it encounters the rifling, it will have a pressure drop when the bullet passes the cylinder gap. This isn't like firing through a semiautomatic barrel in a bunch of ways. I don't really know what those effects would be. This is something that has bugged me since the first post. Free bore at first may build enough inertia to pop it into the rifling,but then the gap will cut into the pressure and may take the thing down too far to continue and let the gas leak away. For that matter, that bit of free bore may choke down the necessary pressure for the powder to continue burning. I don't recall seeing this addressed. It could be that nobody could answer it, and the. Only way will be to experiment until it fails.

February 29, 2016, 08:28 AM	#29
cecILL Senior Member Join Date: August 13, 2001 Location: central IL Posts: 769	OK, Started at the 3 grains. Stopped at 2.5 grains. No performance problems. Guessing 5-600 fps. A pleasure to shoot. Recoil similar to a .38 target load in a full size revolver.

February 29, 2016, 08:51 AM	#30
TimSr Senior Member Join Date: March 8, 2013 Location: Rittman, Ohio Posts: 2,074	This is one of those cases where understanding WHY a certain minimum or maximum is published. 38spl published minimums are arrived at with stuck bullets in mind. 9mm published minimums are arrived at with actions failing to cycle in mind. This leaves you with some trial and error, and forming unsupported opinions while looking over a variety of load data. I would start with published data, and a powder that reduces well, and using a chronograph, reduce until you hit about 700fps, to leave a healthy margin of error. As with anything else, some lead bullets will get you there with a smaller charge.

March 1, 2016, 08:02 AM	#32
griz Senior Member Join Date: July 31, 2000 Location: Middle Peninsula, VA Posts: 1,588	Well, I clearly missed that it will be fired in a revolver when I dashed off a reply. It sounds like the OP has already worked down to a light load, but I will reiterate all the cautions about how it is easier to stick a bullet in a revolver compared to a bottom feeder. Or at least it's easier to fire another round behind it with another trigger pull. Sorry, I would edit my first post if I could figure out how.

March 2, 2016, 08:32 AM	#34
griz Senior Member Join Date: July 31, 2000 Location: Middle Peninsula, VA Posts: 1,588	OK. That's understandable and I wasn't complaining about it. I just hadn't checked in for a while and was embarrassed to have given sketchy advice.