357 reloads velocity variance

Colorado Redneck · June 17, 2009, 10:37 PM

I have reloaded a bunch of 38 spec and 357 over the past few years. Last year I was chronographing some rounds and the reloads were really inconsistent. Some were around 1400 fps and some were only 900 fps. They were all loaded identically. I took some apart after I got home and wieghed the powder and they were dead nuts the same. Same primer. Same cases. All loaded the same.

Does anybody have any ideas? The rounds were stored in the garage, which can get to a hundred degrees in the summer. I would think if the ammo got too hot that all rounds would suffer. I also shot a few factory loads that were on the same shelf, and they shot fine.

I am wondering if my crimp might be the culprit.

Any ideas are deeply appreciated. (As a point of reference, I load lots of 22-250 rounds and have never had a problem with my technique. Not that I didn't screw up....but I ain't a raw beginner.)

Steviewonder1 · June 17, 2009, 10:46 PM

Looks like your Chrono is a bit off on what it reported on the loads of the day they were shot. Nothing else. Loads measured that far off are guilty of the measuring device (The Chrono). I have Never had anything that far off..

Thirdeye · June 17, 2009, 10:50 PM

Could be any number of things. One thing that comes to mind first however is how well you're igniting the powder. That is, are the primers you're using right for the powder you were using? What primers were you using.

Colorado Redneck · June 17, 2009, 11:16 PM

Chrono was pretty consistent with the factory loads, so I am skeptical that it is off that much.

The primers were CCI small pistol. I don't have me book here so can't tell you the exact loads. I know that is important data, but the point is that I had some pretty large difference in velocity.

Any thoughts on crimping? I have never put much crimp on reloads. What do you recommend?

Archie · June 17, 2009, 11:39 PM

Was anyone shooting next to you at the range?

I've had difficulties with my Chrony when the guy next to me was blasting away with a high power, center fire rifle. It appears the shock wave of the muzzle blast affects the Chrony.

Other than that, I would agree, a variation from 900 to 1400 is a bit much.

Next time, chronograph the chambers individually. It could be one chamber is 'bad'.

JFN · June 18, 2009, 06:57 AM

My first guess would be powder position in the case, especially with big cases like the .38/.357, but you didn't mention the powder used.

If it's a high density powder and doesn't fill much of the case volume the position of the powder can make a difference. It can be piled up behind the bullet, in a pile in front of the primer, or scattered in a thin layer the full length of the cartridge. You get the best consistency with a powder that comes closest to filling the case, so powder distribution when the primer ignites is similar from shot to shot.

model14 · June 18, 2009, 07:31 AM

Call the chrony people and see what they say. They are nice people and will tell you what to check. I have chroned a lot of 357 rounds and have never had that much variance.

joneb · June 18, 2009, 07:40 AM

What bullet and powder are you using ?
900 to 1400 fps is quite a spread, that's the difference between 38spl and hot loaded .357 mag. did you notice a difference in recoil and muzzle blast ?
I doubt the crimp is the culprit, but I trim my .357 mag. cases to 1.278" for a consistent roll crimp with cannelured bullets.
Some powders can bridge in powder throws with small apertures giving a occasional partial charge.

Nnobby45 · June 18, 2009, 07:42 AM

Quote:

Any ideas are deeply appreciated.

Yet another question WITHOUT any info on what powder, bullet, etc. Help us help you.

Chrono's can be finicky if not set up right. They need to be all the way in the shade or all the way out, with the sun not too low in the sky.

Quote:

Chrono was pretty consistent with the factory loads, so I am skeptical that it is off that much.

Did you shoot the factory and handloads during the same shooting session to verify that it was your handloads? Or are you talking about handloads on one occasion and factory ammo on another--- when the light conditions could have been quite different.

More info, please.

As JibJab points out, comared to 1400 fps, a 900fps load would sound and feel WAY wrong---as in blooper.

Last: It's not the crimp.

Master Blaster · June 18, 2009, 07:43 AM

what powder, primers, and bullets?

If you were using Bullseye with regular primers its a different story than if you were using 2400...

Doodlebugger45 · June 18, 2009, 11:08 AM

MD Smith (I think that's the name) did some experiments on his webpage where he varied the gun position to shake the powder to the back of the case versus shaking the powder to the front of the case just before firing and measuring the velocities. These loads were some that had a lot of space left over in the case. The velocity variations were quite large as I recall. I don't think they were 500 fps, but they were very significant. It was kind of scary to think about the effect on accuracy.

**Unclenick** · June 18, 2009, 11:51 AM

Like the others, without all the load details and the length of your gun's barrel, I can't guess load details or what velocity you should have expected to see?

I can tell you that errors that big can occur on a chronograph if it isn't far enough from the gun's muzzle. Bits of unburned powder and whatnot can trip one of the screens ahead of the bullet's actual arrival. I have seen a Doppler radar trace of a .40 cal pistol bullet being accelerated 35 fps by muzzle blast after it left the muzzle. The standard G1 projectile needs 50 yards to lose 35 fps, so I multiply my pistol bullet B.C. by 50 yards to see how far out the chronograph should be for my bullet to lose 35 fps and set the chronograph there. Usually about 10-15 yards out, which is three times more than most people use, but which can only help reading consistency (if you don't shoot the chronograph).

I will mention that Father Frog's site has a discussion of primers in which it says they can fail after as little as one summer spent in the trunk of a car. If the garage maybe got a good bit warmer some days than you are allowing, that might be a source of erratic ignition? 100 degrees shouldn't be a problem, though. Assuming you have no chronograph issues, I would take some of your pull-downs and put fresh primers (if you can find any) into the cases and put the same powder and bullets in and see if that clears it up?

kraigwy · June 18, 2009, 12:26 PM

assuming the components were constant, check over all lenght. Measure the shells and seperate them by lenght, Even a couple thousands can make a differance. Just one of a million things that can affect the velocity.

Personally I dont care about velocity, I'd shoot them from a bench at a target 25 or 50 yards (50 is better) and see how they group. If they group well, dont worry about it.

Pocketfisherman · June 18, 2009, 12:29 PM

Sometimes the Chrony is too close and it picks up either gases from the gun, or the cloud of unburned powder pieces. Try moving the Chrony further from the muzzle. When I see big variances like that, it's the first thing I do and it usually fixes it.

Colorado Redneck · June 18, 2009, 11:28 PM

Hey folks---sorry to not be as specific as I should have. I will get the data and post it soon. Too little time, too little sleep, and too many years of hard living are pushing me towards the bedroom.

Thans for everybody's input. Hope you don't ignore my sorry arse after this snafu.

Redneck

ps...gotta get some sleep cause there are some disrespctful prairie dogs that need to meet eternity tomorrow and I am going to help some of them out. Supposed to be 80 degrees and sunny and I can't wait!

Nnobby45 · June 19, 2009, 01:23 AM

Quote:

ps...gotta get some sleep cause there are some disrespctful prairie dogs that need to meet eternity tomorrow and I am going to help some of them out. Supposed to be 80 degrees and sunny and I can't wait!

And to think PETA admonished the President for killing a fly, and sent him a live trap.

June 17, 2009, 10:37 PM	#1
Colorado Redneck Senior Member Join Date: January 7, 2008 Location: Northeast Colorado Posts: 2,006	357 reloads velocity variance I have reloaded a bunch of 38 spec and 357 over the past few years. Last year I was chronographing some rounds and the reloads were really inconsistent. Some were around 1400 fps and some were only 900 fps. They were all loaded identically. I took some apart after I got home and wieghed the powder and they were dead nuts the same. Same primer. Same cases. All loaded the same. Does anybody have any ideas? The rounds were stored in the garage, which can get to a hundred degrees in the summer. I would think if the ammo got too hot that all rounds would suffer. I also shot a few factory loads that were on the same shelf, and they shot fine. I am wondering if my crimp might be the culprit. Any ideas are deeply appreciated. (As a point of reference, I load lots of 22-250 rounds and have never had a problem with my technique. Not that I didn't screw up....but I ain't a raw beginner.)

June 17, 2009, 10:46 PM	#2
Steviewonder1 Senior Member Join Date: February 16, 2009 Location: John's Creek, Georgia Posts: 328	357 Load Varience?? Looks like your Chrono is a bit off on what it reported on the loads of the day they were shot. Nothing else. Loads measured that far off are guilty of the measuring device (The Chrono). I have Never had anything that far off..

June 17, 2009, 11:39 PM	#5
Archie Senior Member Join Date: May 27, 2000 Location: Hastings, Nebrasksa - the Hear Posts: 2,209	Colorado... Was anyone shooting next to you at the range? I've had difficulties with my Chrony when the guy next to me was blasting away with a high power, center fire rifle. It appears the shock wave of the muzzle blast affects the Chrony. Other than that, I would agree, a variation from 900 to 1400 is a bit much. Next time, chronograph the chambers individually. It could be one chamber is 'bad'.

June 18, 2009, 11:51 AM	#12
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,742	Like the others, without all the load details and the length of your gun's barrel, I can't guess load details or what velocity you should have expected to see? I can tell you that errors that big can occur on a chronograph if it isn't far enough from the gun's muzzle. Bits of unburned powder and whatnot can trip one of the screens ahead of the bullet's actual arrival. I have seen a Doppler radar trace of a .40 cal pistol bullet being accelerated 35 fps by muzzle blast after it left the muzzle. The standard G1 projectile needs 50 yards to lose 35 fps, so I multiply my pistol bullet B.C. by 50 yards to see how far out the chronograph should be for my bullet to lose 35 fps and set the chronograph there. Usually about 10-15 yards out, which is three times more than most people use, but which can only help reading consistency (if you don't shoot the chronograph). I will mention that Father Frog's site has a discussion of primers in which it says they can fail after as little as one summer spent in the trunk of a car. If the garage maybe got a good bit warmer some days than you are allowing, that might be a source of erratic ignition? 100 degrees shouldn't be a problem, though. Assuming you have no chronograph issues, I would take some of your pull-downs and put fresh primers (if you can find any) into the cases and put the same powder and bullets in and see if that clears it up? __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

June 18, 2009, 11:28 PM	#15
Colorado Redneck Senior Member Join Date: January 7, 2008 Location: Northeast Colorado Posts: 2,006	Sorry for the incomplete info Hey folks---sorry to not be as specific as I should have. I will get the data and post it soon. Too little time, too little sleep, and too many years of hard living are pushing me towards the bedroom. Thans for everybody's input. Hope you don't ignore my sorry arse after this snafu. Redneck ps...gotta get some sleep cause there are some disrespctful prairie dogs that need to meet eternity tomorrow and I am going to help some of them out. Supposed to be 80 degrees and sunny and I can't wait!

June 17, 2009, 10:50 PM	#3
Thirdeye Member Join Date: June 16, 2009 Posts: 17	Could be any number of things. One thing that comes to mind first however is how well you're igniting the powder. That is, are the primers you're using right for the powder you were using? What primers were you using.

June 17, 2009, 11:16 PM	#4
Colorado Redneck Senior Member Join Date: January 7, 2008 Location: Northeast Colorado Posts: 2,006	Chrono was pretty consistent with the factory loads, so I am skeptical that it is off that much. The primers were CCI small pistol. I don't have me book here so can't tell you the exact loads. I know that is important data, but the point is that I had some pretty large difference in velocity. Any thoughts on crimping? I have never put much crimp on reloads. What do you recommend?

June 18, 2009, 06:57 AM	#6
JFN Member Join Date: July 4, 2007 Location: Virginia Posts: 45	My first guess would be powder position in the case, especially with big cases like the .38/.357, but you didn't mention the powder used. If it's a high density powder and doesn't fill much of the case volume the position of the powder can make a difference. It can be piled up behind the bullet, in a pile in front of the primer, or scattered in a thin layer the full length of the cartridge. You get the best consistency with a powder that comes closest to filling the case, so powder distribution when the primer ignites is similar from shot to shot.

June 18, 2009, 07:31 AM	#7
model14 Member Join Date: November 15, 2008 Location: Grass Lake, Michigan (75 miles West of Detroit in beautiful farm country. Posts: 44	Call the chrony people and see what they say. They are nice people and will tell you what to check. I have chroned a lot of 357 rounds and have never had that much variance.

June 18, 2009, 07:40 AM	#8
joneb Senior Member Join Date: December 10, 2005 Location: Central , OR Posts: 1,888	What bullet and powder are you using ? 900 to 1400 fps is quite a spread, that's the difference between 38spl and hot loaded .357 mag. did you notice a difference in recoil and muzzle blast ? I doubt the crimp is the culprit, but I trim my .357 mag. cases to 1.278" for a consistent roll crimp with cannelured bullets. Some powders can bridge in powder throws with small apertures giving a occasional partial charge.

June 18, 2009, 07:43 AM	#10
Master Blaster Senior Member Join Date: October 12, 1999 Location: One of the original 13 Colonies Posts: 2,281	what powder, primers, and bullets? If you were using Bullseye with regular primers its a different story than if you were using 2400...

June 18, 2009, 11:08 AM	#11
Doodlebugger45 Senior Member Join Date: April 15, 2009 Location: Wyoming Posts: 1,717	MD Smith (I think that's the name) did some experiments on his webpage where he varied the gun position to shake the powder to the back of the case versus shaking the powder to the front of the case just before firing and measuring the velocities. These loads were some that had a lot of space left over in the case. The velocity variations were quite large as I recall. I don't think they were 500 fps, but they were very significant. It was kind of scary to think about the effect on accuracy.

June 18, 2009, 12:26 PM	#13
kraigwy Senior Member Join Date: June 16, 2008 Location: Wyoming Posts: 11,060	assuming the components were constant, check over all lenght. Measure the shells and seperate them by lenght, Even a couple thousands can make a differance. Just one of a million things that can affect the velocity. Personally I dont care about velocity, I'd shoot them from a bench at a target 25 or 50 yards (50 is better) and see how they group. If they group well, dont worry about it.

June 18, 2009, 12:29 PM	#14
Pocketfisherman Member Join Date: June 2, 2009 Location: Central TX Posts: 92	Sometimes the Chrony is too close and it picks up either gases from the gun, or the cloud of unburned powder pieces. Try moving the Chrony further from the muzzle. When I see big variances like that, it's the first thing I do and it usually fixes it.