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Lower velocity on 1st revolver round

This is a discussion on Lower velocity on 1st revolver round within the Reloading forums, part of the Firearm Forum category; I have been reloading for about a year and shoot weekly on my property, 99% reloaded ammo that I make. I have noticed that while ...


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Old November 12th, 2013, 09:19 AM   #1
 
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Lower velocity on 1st revolver round

I have been reloading for about a year and shoot weekly on my property, 99% reloaded ammo that I make.

I have noticed that while shooting my LCR .38special that my first round will have a significantly lower velocity and felt recoil than the subsequent 4 rounds. If I immediately follow with another 5 rounds, again the 1st round is much lower in velocity.

I do not notice this with my carry factory ammo.

It is very noticeable when I use Autocomp (5.9 grains) with a 125 gr plated bullet (Berry's Flat Point). The readings were something like 610, 730, 740, 735, 750 (I'm at work now and don't have my data with me, but I think that's close).

I did notice that 5.9 gr Autocomp didn't fill the case as much as Unique but I'm operating on memory there, and not totally sure of that.

I was suspecting powder not being at the back of the case on the 1st round?? I didn't think to hold the gun up before firing each round.

What do you think could be causing this?



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Old November 12th, 2013, 10:26 AM   #2
 
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Wow! Have you used different chambers for the first shot? Did you shoot them over a chrony?, and if so, how much spread? (oh yeah, I see your readings now). What about temperature? Have you experience this with any other powder/load?

This is an odd one to me...
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Old November 12th, 2013, 10:50 AM   #3
 
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I agree about trying different chambers. Maybe some crud in one and you happen to have that one first each time...?
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Old November 12th, 2013, 10:58 AM   #4
 
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Just a wild guess here - perhaps something to do with "position sensitivity" of Autocomp.

With the first shot, you have just finished holding the gun in a barrel down position to load it, causing the powder to gather up toward the "bullet" end of the casing. On all the subsequent shots, recoil has shifted the powder around to be more evenly distributed. Maybe even up against the "primer" end if there is enough recoil to cause the revolver to rotate to a more vertical position.

Here are two experiments to try. First, hold the revolver muzzle down before each shot (all of them) to get powder down toward the "bullet" end.

Secondly, try the reverse - hold the revolver muzzle up before each shot.

Compare velocities between the two strings and see if any thing pops out.

Let us know how it goes.
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Old November 12th, 2013, 11:08 AM   #5
 
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Try a different powder, like Bullseye, if you can find load data for your desires.
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Old November 12th, 2013, 11:45 AM   #6
 
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Quote:
Originally Posted by NewportNewsMike View Post
Just a wild guess here - perhaps something to do with "position sensitivity" of Autocomp.

With the first shot, you have just finished holding the gun in a barrel down position to load it, causing the powder to gather up toward the "bullet" end of the casing. On all the subsequent shots, recoil has shifted the powder around to be more evenly distributed. Maybe even up against the "primer" end if there is enough recoil to cause the revolver to rotate to a more vertical position.

Here are two experiments to try. First, hold the revolver muzzle down before each shot (all of them) to get powder down toward the "bullet" end.

Secondly, try the reverse - hold the revolver muzzle up before each shot.

Compare velocities between the two strings and see if any thing pops out.

Let us know how it goes.
Thanks. I will try this. Also, I'll make sure I'm using different cylinders on the first shot. I'll post again, after I shoot this weekend. I may have to load some more so that I can make the proper comparisons.
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Old November 13th, 2013, 08:47 AM   #7
 
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Quote:
Originally Posted by NewportNewsMike View Post
Just a wild guess here - perhaps something to do with "position sensitivity" of Autocomp.

With the first shot, you have just finished holding the gun in a barrel down position to load it, causing the powder to gather up toward the "bullet" end of the casing. On all the subsequent shots, recoil has shifted the powder around to be more evenly distributed. Maybe even up against the "primer" end if there is enough recoil to cause the revolver to rotate to a more vertical position.

Here are two experiments to try. First, hold the revolver muzzle down before each shot (all of them) to get powder down toward the "bullet" end.

Secondly, try the reverse - hold the revolver muzzle up before each shot.

Compare velocities between the two strings and see if any thing pops out.

Let us know how it goes.
Sounds like a plan to me!
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Old November 17th, 2013, 07:27 AM   #8
 
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Results from Saturday

Thought I would post the chronograph results from NewportNewsMike's recommended trial:

1st String (Shooting gun as I normally do, walking up to the line and firing 5 shots): 492, 593, 591, 571, 559 (Ave - 561; Es - 101; Sd - 41)

2nd String (Holding gun muzzle down before each shot):
476, 462, 482, 516, 496 (Ave - 486; Es - 54; Sd - 20)

3rd String (Holding gun muzzle up before each shot):
759, 736, 746, 702, 741 (Ave - 736; Es - 57; Sd - 21)

4th String (Shooting gun as I normally do)
590, 637, 621, 617, 585 (Ave - 608; Es - 46; Sd - 20)

1st 4 strings shot with LCR .38 special

5th String Shooting as I normally do with my son's S&W 642, which had 5 rounds shot through it a few minutes before I shot these 5.
463, 616, 625, 715, 618 (Ave - 607; Es - 252; Sd - 90)

My initial post was concerning the use of Autocomp at 5.9 grains, using a Berry's Plated FP 125 gr bullet. Well, I am out of bullets and didn't have enough loaded with Autocomp to do this trial. So the data above was using the same bullet, but with 5.1 gr of 7625 powder.

As you can see, holding the muzzle up or down before shots had a definite effect, however string 4 also showed that having a heated up barrel apparently made the shots more consistent (I am assuming this is why). Granted, I only had a sample size of 5 for each string. As a side note, my backyard range doesn't have a high berm, so I shoot at a slightly downward angle. I am sure this makes a difference and is probably why more people haven't experienced this.
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Old November 17th, 2013, 08:06 AM   #9
 
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Thanks for posting your results. Very interesting! I didn't think there would be that much "position sensitivity" in reloads with a modern powder...
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Old November 17th, 2013, 08:33 AM   #10
 
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The findings are a surprise to me too. Seems if one gets into reloading one needs to do some digging on different powers......

Way informative and cool. Thank you!
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Old November 17th, 2013, 03:39 PM   #11
 
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String 3 kinda tells the main story I think.

I've read on reloading sites about using a filler of some sort to keep the powder at the rear of the case to avoid this issue.
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Old November 17th, 2013, 03:45 PM   #12
 
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I have been using Titegroup in my three calibers, 9mm and 38/357 that I reload. I understand it is not position sensitive and have not felt any difference in rounds.
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Old November 18th, 2013, 03:51 AM   #13
 
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I've occasionally noted a lower first round velocity from my hand loads as well. It usually occurs with lead alloy bullets of my own casting efforts as well as commercially cast ones. I attribute it to cold bullet lube in the bore creating a different friction component to the shot....but I've wondered why it was lower; thinking that more friction (cold lube), it would result in higher velocity. Nevertheless, it's there, and not always...cold days, warm days about the same but I've not kept a watch out for it, then collated the environmental factors against the low speed shot. A cypher to be sure.

I don't think hand gun loads would be position sensitive enough to cause that kind of difference...but bullseye in .45 Colt cases might be....don't know.

You're using plated bullets, I see, so the bullet lube idea might not be valid, unless you were shooting lubed cast round just before switching to the plated ones. In truth, I don't remember a slow first round with jacketed bullets...but I'll keep a watch out for it.

One other idea is the chrono itself. I do know that I get some strange readings from my PACT when the battery is low, and too, if the screens are being jiggled by wind. Just one more variable to run down...

HTH's and Good question/post. Rod

Last edited by Rodfac; November 18th, 2013 at 03:53 AM.
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Old November 18th, 2013, 06:22 AM   #14
 
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Quote:
Originally Posted by clintnc View Post
Thought I would post the chronograph results from NewportNewsMike's recommended trial:

1st String (Shooting gun as I normally do, walking up to the line and firing 5 shots): 492, 593, 591, 571, 559 (Ave - 561; Es - 101; Sd - 41)

2nd String (Holding gun muzzle down before each shot):
476, 462, 482, 516, 496 (Ave - 486; Es - 54; Sd - 20)

3rd String (Holding gun muzzle up before each shot):
759, 736, 746, 702, 741 (Ave - 736; Es - 57; Sd - 21)

4th String (Shooting gun as I normally do)
590, 637, 621, 617, 585 (Ave - 608; Es - 46; Sd - 20)

1st 4 strings shot with LCR .38 special

5th String Shooting as I normally do with my son's S&W 642, which had 5 rounds shot through it a few minutes before I shot these 5.
463, 616, 625, 715, 618 (Ave - 607; Es - 252; Sd - 90)

My initial post was concerning the use of Autocomp at 5.9 grains, using a Berry's Plated FP 125 gr bullet. Well, I am out of bullets and didn't have enough loaded with Autocomp to do this trial. So the data above was using the same bullet, but with 5.1 gr of 7625 powder.

As you can see, holding the muzzle up or down before shots had a definite effect, however string 4 also showed that having a heated up barrel apparently made the shots more consistent (I am assuming this is why). Granted, I only had a sample size of 5 for each string. As a side note, my backyard range doesn't have a high berm, so I shoot at a slightly downward angle. I am sure this makes a difference and is probably why more people haven't experienced this.
I am not an expert, but whether you hold the gun up or down, you would think that would affect all rounds, not just the 1st. one.
What do you use for a OAL for these loads? Also, how do you measure your powder? I ask because in my Hodgdons guide you should be at about 1000 fps. with 5.1 gr of 7625. even taking into account they use a longer barreled revolver, your numbers seem low to me.
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Old November 18th, 2013, 07:58 AM   #15
 
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I think

Quote:
Originally Posted by moakes58 View Post
I am not an expert, but whether you hold the gun up or down, you would think that would affect all rounds, not just the 1st. one.
What do you use for a OAL for these loads? Also, how do you measure your powder? I ask because in my Hodgdons guide you should be at about 1000 fps. with 5.1 gr of 7625. even taking into account they use a longer barreled revolver, your numbers seem low to me.
I think the suggestion here is that holding the gun down while loading results in the powder in all the rounds to shift toward the front of the case and when the gun is raised gently to firing position and fired the powder, which doesn't completely fill the case, is skewed such that the primer may not ignite the powder as intended affecting the rate of burn and thus the pressure.
After the first shot the recoil and muzzle flip redistributed the powder in the remaning rounds.
The test involving holding the gun upward or downward was intended to determine if the distribution of powder within the cases affected the ignition/burn rate/pressure. Based on the results that does seem to be the case.
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