First Shot in Magazine has Lower Velocity

Not shooting pistol competively (yet) but I like accuracy and think I have a decent pistol.  A Springfield Range Officer with a Weigand Scope mount, Herter's Grips, and a Match Dot.  I also enjoy reloading ammo for accuracy.

Haven't shot it for quite some time, but recently re-joined my local indoor pistol club and looking for some Winter fun.  For my 45 Auto I would have preferred some 200gr SWC like I have used before, but with the new polymer coat.  Unfortunately those 200gr SWCs are like hen's teeth these days and I have less than 100 in-house of my old ones (uncoated 12 brinnel from MBC).  I was able to find 1000 Berrys plated 230gr RN bullets, so I bought them.  I already had a couple pounds of Bullseye and a pound of VV N330.  So I set out to develop a new load for the Berry's 230g RN bullets using Bullseye in new Starline brass.

Initial goal was 700-750 fps on 5 shots with max spread of 25 fps over a 5-point range of 4.20gr to 5.00 gr Bullseye.  New Starline brass (resized with my dies) was used with WLP primers.  Powder trickled in to nearest 0.02 gr in each individual case.  Light crimp.  1.250 OAL 

I had already started to load a few 200gr SWCs, some with my old Bullseye load, some with N330 to VV minimum, some in old Starline brass, and some in old Blazer ammo brass.  Figured I would shoot it up first to condition the gun a bit.

I shot strings of different weights and measured the velocity using a Beta Chrony.  See attachment.

Procedure for each string was to:
Prepare target
Load 5 shots in magazine
Immediately insert magazine into pistol
Aim and fire first shot within 15 seconds of loading clip
Around 10-15 seconds between each shot.
About 5 minutes between each string.
Temp was around 60 degrees and guns were transported in a warmed vehicle.
I didn't see a huge difference in groups on the targets.

Max spread did not meet expectations at 30.9 fps - 58.76 fps.  I did notice that the low velocity was the first shot on 4 of 5 strings.

Eliminating the first shot of each string gave a max spread of only 5.8 fps - 15.4 fps for 4 of the five strings.  5.8 fps - 30.9fps for all 5 strings.  The 200gr SWC ammo did not show this, but it was shot first.

So I've been thinking about why this was true, in hopes of figuring something out before I load a bunch more the same way.  Any ideas?

I've thought of:
Something about the 230gr bullet itself
Something about the OAL
Something about the way the powder sits differently in case after first shot
Something from shooting the 200 gr SWC beforehand
Temperature effects on powder
???????

Thanks in advance

p.s. I have refinished my deck since the photo!

What chronograph are you using?

rkittine wrote:What chronograph are you using?

Beta Master Chrony w/Competition Electronics lights.  Range has all-LED overhead lighting.

Try shooting one round from a different fun over the chrono and than 5 shot string from the gun in question.

rkittine wrote:Try shooting one round from a different fun over the chrono and than 5 shot string from the gun in question.

Hi, I only have one 45 Auto so I can't shoot same ammo with different gun.  The five strings in question are bracketed with 2 strings beforehand (using different bullets), and the 1 string afterwards uses a completely different caliber gun (first shot was an error on the chronograph).  Did not observe the first shot abnormally low in either of the first two strings.  Did you open the attached spreadsheet?

OK I think I understand what you are saying.  Check the chronograph.  6 shots in string.  First reading from different gun just to get past the first shot and rule out chronograph.  Good idea!

When cartridge loads from magazine (not clip) the first cartridge has more magazine spring pressure to overcome and it can feed differently than the next 4 cartridges. The lighter crimp might be allowing the bullet to seat deeper which changes the pressures. Also some pistols load different from hand (first cartridge) than the following cartridges from the guns cycling from firing.
I would tighten up the crimp to at least 0.465” I would also determine if cartridge is smoothly feeding into chamber or if it seems to have a speed bump causing it to feed rougher; it can make a difference. Might need a new magazine.
Jon

First shot the chamber is colder. 

Also what Jon said, plus the fact that you are hand cycling the slide for the first round, so that also might contribute to the cartridge loading slightly differently.

There's no reason the chrono should measure different speed.

lmyer wrote:I didn't see a huge difference in groups on the targets.

If you can not identify a difference by the group on the target, don't worry about the velocity difference.

SteveT wrote:

Jon Eulette wrote:When cartridge loads from magazine (not clip) the first cartridge has more magazine spring pressure to overcome and it can feed differently than the next 4 cartridges. The lighter crimp might be allowing the bullet to seat deeper which changes the pressures. Also some pistols load different from hand (first cartridge) than the following cartridges from the guns cycling from firing.
I would tighten up the crimp to at least 0.465” I would also determine if cartridge is smoothly feeding into chamber or if it seems to have a speed bump causing it to feed rougher; it can make a difference. Might need a new magazine.
Jon

First shot the chamber is colder. 

Also what Jon said, plus the fact that you are hand cycling the slide for the first round, so that also might contribute to the cartridge loading slightly differently.

There's no reason the chrono should measure different speed.

Thanks guys!  I corrected my references regarding "clip" to "magazine" - I hate incorrectness too! 

I think the light bulb may have gone on now.  I suppose it makes sense considering the heavier bullet weight and the copper plating on the bullets, that the 230 gr Berry's RN would be more susceptible to moving in the cases.  Maybe the ones that are cycled into place while firing are hitting the feed ramp harder and getting set back further in the case.  Previously I had just heard about recoil supposedly causing it, but hitting that feed ramp hard seems more likely. Not sure how the magazine affects other than the spring tension, but I am now wondering if I changed magazines after the first two 200gr SWC strings and then kept the other one in for the remainder of the session - can't remember for sure.  I can say the magazines have less than 200 rounds through each magazine since new and they have been stored empty.

Gives me some thoughts and info to work with.  The velocity variations I'm seeing probably doesn't make any difference at 50 ft, but I admit I kind of enjoy the diagnostic process in trying to make good ammo.  I think what I'm seeing could start affecting accuracy at 50 yards+.  Previously I have just been primarily loading for bolt action rifles at much longer distances and much faster velocities.  I figure if I'm going to weigh these to 0.02 gr individually, I might as well make them as good as I can during load development.   

One thing though.....  Isn't a 0.465 crimp too much on a 0.452 copper plated lead bullet without any cannelure?  (0.011*2) +0.452 = 0.474   That would be a 0.009 crimp.

Regards,

Les

Hello lmyer,

If your crimp measures 0.474" then you do not have any crimp and could very well lead to your problems.  I would try 0.465" to 0.468".

Also, if you are looking for accuracy, dump the plated bullets.

Jim

A good shortcut to making good ammo is to check out the sticky at the top of this section. Lots of good loads there. And check out some of the topics using the search feature for specific bullets or powders.
CR

spursnguns wrote:Hello lmyer,

If your crimp measures 0.474" then you do not have any crimp and could very well lead to your problems.  I would try 0.465" to 0.468".

Also, if you are looking for accuracy, dump the plated bullets.

Jim

My previous crimp was 0.471.  The 0.474 was the bullet diameter of 0.452 plus 2 x 0.011 for the case.  So I had crimp 0.0015 deep around the bullet.

I had heard the plated ones are not quite as good on accuracy, but was all I could find in non-jacketed bullets at the moment I was looking.  I'm curious what the general consensus is on the polymer coated bullets.  That is what I found for my 38 Special and 357 Mag revolvers.

Thanks

CR10X wrote:A good shortcut to making good ammo is to check out the sticky at the top of this section.   Lots of good loads there.  And check out some of the topics using the search feature for specific bullets or powders.
CR

I saw that!  Good reference.  Thanks!

Right now, reloading supplies are a bit hard to come by!  Just trying to make the most out of what I have now, and what I could get.

For bullets you might try mail ordering them from Brazo's or Bayou bullets, I just recieved 1k of the 180 grain 45 lead SWC from Brazos, I have used Bayou bullets in the past as well.  Ditto on the .465 crimp, even if you are using plated bullets, the crimp is just at the very end of the brass so you should not have any problems.  Also if you don't have one use a taper crimp die.  Good luck and have fun.

troystaten wrote:For bullets you might try mail ordering them from Brazo's or Bayou bullets, I just recieved 1k of the 180 grain 45 lead SWC from Brazos, I have used Bayou bullets in the past as well.  Ditto on the .465 crimp, even if you are using plated bullets, the crimp is just at the very end of the brass so you should not have any problems.  Also if you don't have one use a taper crimp die.  Good luck and have fun.

OK - several have now confirmed the 0.465 crimp.  Looks like it is where to go.  As long as I'm not going to cause a problem with the plated bullets, then that's what I will do.

I'll take a look at the Brazo's and Bayou bullet web sites.

I do have a taper crimp die for sure.

Thanks,

Powder position sensitivity can be a problem with low charge weights using high density powders. Next time out, before each shot fired over the chronograph slowly raise muzzle upward, then lower it to not less than horizontal and fire the shot. If for whatever reason, you dip below horizontal, then raise up again then lower before shooting. Do this exactly the same for each shot. The ES in velocity will tighten tremendously. It may or may not effect the accuracy, depending on distance firing.

Conversely, if you point the gun toward the ground before each shot, then raise it not above horizontal before each shot the ES in velocity will also be tight, but the average velocity will be lower than the procedure above.

The above conditions will not be as pronounced with low density powders or hotter loads, since the empty space in the case does not permit powder position variation as much.

Coming from Action Pistol (Bianchi) background this condition is well documented, especially in .38 spl where there is often much empty space in the cartridge. Powder position sensitivity can be a huge problem, especially on the first shot on the moving target. Interesting that the variation doesn't effect accuracy too much but on the moving target the first shot having been fired from the holster, would trail the rest of the group, because velocity was lower. Without having the need to shoot on a moving target, this condition would not jump out so much. 

Before you disbelieve this try it. Again, most prevalent with high density low charge weight powders, in big volume cases. It is also more prevalent with slower burning powders.

A random thought -

In the rifle world, velocity will vary based on one's hold and how one manages the recoil. For my service rifle, I have measured different velocities when slung in tightly prone, and when shooting unsupported standing.

Is it possible you are holding more loosely for the first shot (more free recoil = lower velocity) and then tightening up your hold / leaning in for following shots?

Allgoodhits wrote:Powder position sensitivity can be a problem with low charge weights using high density powders. Next time out, before each shot fired over the chronograph slowly raise muzzle upward, then lower it to not less than horizontal and fire the shot. If for whatever reason, you dip below horizontal, then raise up again then lower before shooting. Do this exactly the same for each shot. The ES in velocity will tighten tremendously. It may or may not effect the accuracy, depending on distance firing.

Conversely, if you point the gun toward the ground before each shot, then raise it not above horizontal before each shot the ES in velocity will also be tight, but the average velocity will be lower than the procedure above.

The above conditions will not be as pronounced with low density powders or hotter loads, since the empty space in the case does not permit powder position variation as much.

Coming from Action Pistol (Bianchi) background this condition is well documented, especially in .38 spl where there is often much empty space in the cartridge. Powder position sensitivity can be a huge problem, especially on the first shot on the moving target. Interesting that the variation doesn't effect accuracy too much but on the moving target the first shot having been fired from the holster, would trail the rest of the group, because velocity was lower. Without having the need to shoot on a moving target, this condition would not jump out so much. 

Before you disbelieve this try it. Again, most prevalent with high density low charge weight powders, in big volume cases. It is also more prevalent with slower burning powders.

not so random i think. Heard of this before. Definitely something to check.
Thanks .

pgg wrote:A random thought -

In the rifle world, velocity will vary based on one's hold and how one manages the recoil. For my service rifle, I have measured different velocities when slung in tightly prone, and when shooting unsupported standing.

Is it possible you are holding more loosely for the first shot (more free recoil = lower velocity) and then tightening up your hold / leaning in for following shots?

This was off of a rest, with me sitting down so i would think more consistent. Thanks!

I will have to try powder position in a handgun case, verses velocity one day. I never thought that would make a serious difference in a pistol case or at the yardages we shoot, but I understand the premise. 

I shoot 1,000 yard bench rest and the winningest cartridges in even short range bench rest are pretty much all wild cats, with one of the parameters being short squat cases that are completely filled, some times compressed, so the there is no difference in the powder ignition. Giggle a factory .30-06 round and listen to the powder move around as compared to a .308, which is basically .30-06 Short. You see .308s in Palma, FTR etc, but not .30-06s any more.

Bob

I'm not saying it made any difference in my case (50'). In fact I previously claimed it didnt appear to make any difference at 50', but that it might start mattering at 50 yards+. I just noticed the low velocity on each first shot out of the clip only with the plated 230gr RN bullets and asked why in the hopes of producing better ammo. The two predominant working theories seem to be powder position and bullet getting set back from too little of a crimp. These are both things I can design experiments to investigate for during my next range session. I thank everyone who responded.

Greetings,

When using my barrel tester, I quite often experience Round #1 as the low velocity.

This is using a PACT chronograph.

I verified the results with a borrowed LabRadar.

Never did learn what was causing it. I thought it might be the barrel cooling down while changing targets.

It seemed to happen with the Speer HBWC bullets with the "Moly" coating. My home swaged bullets with Lee Liquid Alox did not always record shot #1 as the low.

More stuff to ponder, where are all the Ballisticians when we need them?

Cheers,

Dave

Let's say your average velocity is 750fps, and ES is 725-775 (delta=50fps).

A quick calc. says the 50 fps extreme spread yields a difference of +/- 0.5" of bullet drop at 50 yds.  You all are welcome to confirm my calcs.

While I appreciate the interest in reducing ES in velocity and its benefits, please understand that it alone makes only a minimal difference in group size at 50yds., and I wouldn't waste too much time trying to find the lowest ES.  Many other factors are more important for increasing our scores on the target.

Good luck!