Actually, I'd say it has been tested. If you don't know much about Bryan Litz, check out his history (his education and experience is impressive). Here's what he says is one of the thing they do:
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Why might Avg. Velocity change between reloading sessions?
- Thread starter Senor_Barney
- Start date
Actually, I'd say it has been tested. If you don't know much about Bryan Litz, check out his history (his education and experience is impressive). Here's what he says is one of the thing they do:
Depends on the relative humidity in the room. If you've got really low humidity and the hopper isn't sealed, then . . . yes.
I know all about Litz for many years and have read all of his books. I didn't recall seeing that he had done this. Thanks for the link!
He's describing it as an experimental condition in the video. I'd be interested in whether he routinely bothers with humidity packs in each jug of powder.
I see that Boveda "guitar" 70 gram 49% packs are like $4 each on amazon. Maybe I should just be doing this? Try to keep the powder at 50% humidity like it comes from the factory? If it works reliably without complications, it would be way easier than screwing around with Kestrel D2 drops all the darned time.
What's everybody's thoughts on putting a guitar humidity pack directly in your powder?
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If he's not just using such humidity packs, I'd bet he then has a storage space and/or loading room that has controls for the humidity.
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being banished to my garage by my wife, I don't have that luxury.
Have not read the entire thread so someone may have posted this already.
How did you store the powder between loading sessions?
Humidity can play a role in the velocity.
You powder can gain or lose humidity changing the weight of the charge thus changing the MV.
There are a few recent papers out there on this.
How did you store the powder between loading sessions?
Humidity can play a role in the velocity.
You powder can gain or lose humidity changing the weight of the charge thus changing the MV.
There are a few recent papers out there on this.
heat , cold can affect speeds of some or near most powders even temp stable powders like h4350 put a pocket warmer in your pocket and the bullets in your pockets warming the bullets up and the speeds will increase slightly .
That’s not how this works. You do not lower pressures by using 1x sized brass.
Volume vs pressure is determined by the size of the chamber and the wall thickness of the brass, thereby there's really little or not velocity difference due to the brass being virgin or fire formed.
I've noticed my velocity and pressure always going up after the first firing. It doesn't make a ton of sense, but I've checked it several times in different calibers and conditions. I found that my fire formed brass needed about 98% of my new brass charge to get back down to the same velocity.
Flame away on this one.
Could the barrel be "tighter" in warmer temps? Metal expands when heated. I would propose the inner diameter would decrease if the metal expands. The outside diameter would increase and the inner decrease. Maybe very minute, but some effect nonetheless?
Could the barrel be "tighter" in warmer temps? Metal expands when heated. I would propose the inner diameter would decrease if the metal expands. The outside diameter would increase and the inner decrease. Maybe very minute, but some effect nonetheless?
A while back there was a test done where they fired rounds out of a frozen vs ambient vs hot barrel and there was no difference in velocity, so barrel temp does not affect anything as long as you don’t allow the ammo to cook in a hot chamber.
Small sample sizes and shooting over a chrono that has a certain error percentage is probably the issue. Said another way, I doubt there is a difference between the two small samples unless you proved it on target past 600 yards or so to actually see it. I have a cheap optical chrono that lies constantly. I’m getting to the point of not even using a chrono just like I never did before. The target and ballistic solver tells all anyhow and doesn’t lie.
Slightly older post, but i found my old testing excel sheet related to this...
i took loaded ammo that i had been shooting just as a standard for before and after to make sure it's velocity remained relatively the same
then i made 4 different 10 round batches...
1 loaded fresh
1 left the powder in hopper w/ lid on for 3 days
1 left open in a small bowl next to the hopper for 3 days
1 left in a small bowl in the fridge for 3 days
Avg string 1 and 2 are the 6 shots of the standard load pre/post combined
i live on the south tx coast, a block from the bay front, so humidity is always on the higher side even though my garage is A/C'd, it fluctuates a little more than inside the house...it generally stays in the 70-80* range all year
my conclusion...i dont leave powder in my hoppers, and try to leave it exposed as little as possible...only open and pour what i need and return it to the can soon as im done. Im sure that even tho the closed hopper only showed a small drop in the 3 days...id bet it dropped down similar to the open powder over a little more time
2 things ive found that attribute to real velocity differences a lot of people dont realize outside of all the small sample size error/etc mentioned above....powder condition and bore condition even with the exact same load
how the powder is stored and even if the location where it is stored is different from where it was originally obtained...im betting most all of my powder will get slightly slower and slower over the years and multiple can openings because its humid where i live.
bore condition...typically, in my experience, a barrel will gain speed as it fouls...a clean barrel will avg slower than it would 50 rounds later...200 rounds later, faster again (just example round counts)....actual round counts where these changes show up enough to notice depends on the barrel and firing schedule/fouling/etc...you clean it well, it will drop back in speed...and this can repeat/alter things depending on cleaning/firing cycles for the life of the barrel
ive found keeping my barrels mostly clean, generally keeps them inside a 25 fps avg window or so for 100-200 rounds...ive shot barrels from clean to 300+ rounds and gained 75-100 fps with the same batch of ammo before and after 2 day matches, not really ideal
i took loaded ammo that i had been shooting just as a standard for before and after to make sure it's velocity remained relatively the same
then i made 4 different 10 round batches...
1 loaded fresh
1 left the powder in hopper w/ lid on for 3 days
1 left open in a small bowl next to the hopper for 3 days
1 left in a small bowl in the fridge for 3 days
Avg string 1 and 2 are the 6 shots of the standard load pre/post combined
i live on the south tx coast, a block from the bay front, so humidity is always on the higher side even though my garage is A/C'd, it fluctuates a little more than inside the house...it generally stays in the 70-80* range all year
my conclusion...i dont leave powder in my hoppers, and try to leave it exposed as little as possible...only open and pour what i need and return it to the can soon as im done. Im sure that even tho the closed hopper only showed a small drop in the 3 days...id bet it dropped down similar to the open powder over a little more time
2 things ive found that attribute to real velocity differences a lot of people dont realize outside of all the small sample size error/etc mentioned above....powder condition and bore condition even with the exact same load
how the powder is stored and even if the location where it is stored is different from where it was originally obtained...im betting most all of my powder will get slightly slower and slower over the years and multiple can openings because its humid where i live.
bore condition...typically, in my experience, a barrel will gain speed as it fouls...a clean barrel will avg slower than it would 50 rounds later...200 rounds later, faster again (just example round counts)....actual round counts where these changes show up enough to notice depends on the barrel and firing schedule/fouling/etc...you clean it well, it will drop back in speed...and this can repeat/alter things depending on cleaning/firing cycles for the life of the barrel
ive found keeping my barrels mostly clean, generally keeps them inside a 25 fps avg window or so for 100-200 rounds...ive shot barrels from clean to 300+ rounds and gained 75-100 fps with the same batch of ammo before and after 2 day matches, not really ideal
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Interesting. Have you read the chapter about barrel life in Litz's most recent book?
Pretty much. I don't have the book in front of me at the moment, but there's a chapter on the characterization of barrel life. Covers both changes in MV as the round count increases, and how it changes as the barrel fouling builds up, with the subsequent 'reset' from cleaning back to bare metal using abrasives. Pretty cool stuff.
Still 40fps swing isnt a sample size thing. 20 maybe or sd numbers. You should have a pretty accurate average velocity in 5 shots. Every pro level shooter i know chronos less then 10 before every match. Ive lost 20fps out of nowhere before but it stayed there and the barrel is still at that speed so idk
This is an old thread but analyzing the OP's original issue I see several things. In reloading and shooting on different occasions any number of things can change. Obviously components didn't and if you are taking care of your powder humidity is not the issue. One of the issues may actually be the Magnetospeed. Its mounting may or may not be an issue and I have not seen anyone test its repeatability from one installation to the next. This is something that might need to be tested. Taking it off and remounting it a couple of times during a session.
If comparing brass not in the same condition that may be the issue. Unfired brass absorbs energy on firing that doesn't make it to the bullet. Once resized and full length sized it will absorb a different amount. Necked or bumped brass will absorb almost none.
For the 23 deg change in temperature assuming the rounds were at those temps it would be reasonable to expect the rounds to be 10 to 20 fps different. (estimating a .5 to 1 fps per degree rate of change). That would leave about 20 to 30 fps as the issue. This would mean a powder deviation of about 0.5 grains which is highly unlikely to be the issue with the Fx. However, it is important to calibrate the scale prior to each use or to use check weights as a minimum to verify the accuracy in the load range to be used.
He did mention the 8 and 10 shot group and with the 4 SD (not a true number due to MS error) it means the loading process is consistent so I would not expect this difference to be due to anything prep wise
The bottom line is that I would work to rule out errors associated with the Magnetospeed.
If comparing brass not in the same condition that may be the issue. Unfired brass absorbs energy on firing that doesn't make it to the bullet. Once resized and full length sized it will absorb a different amount. Necked or bumped brass will absorb almost none.
For the 23 deg change in temperature assuming the rounds were at those temps it would be reasonable to expect the rounds to be 10 to 20 fps different. (estimating a .5 to 1 fps per degree rate of change). That would leave about 20 to 30 fps as the issue. This would mean a powder deviation of about 0.5 grains which is highly unlikely to be the issue with the Fx. However, it is important to calibrate the scale prior to each use or to use check weights as a minimum to verify the accuracy in the load range to be used.
He did mention the 8 and 10 shot group and with the 4 SD (not a true number due to MS error) it means the loading process is consistent so I would not expect this difference to be due to anything prep wise
The bottom line is that I would work to rule out errors associated with the Magnetospeed.
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