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Speed increased, powder charge is the same.

2

260Girl

Private
Minuteman
May 16, 2018
34
11
#1
I'm shooting a 6.5 x 47 Laupa round. Over the past two months I've picked up 30 fps. without making any changes to my load. Two things that have changed: the weather is much hotter, and my barrel now has almost 700 rounds down it.

I'm all for gaining speed, but I've noticed that my groups have opened up out past 150 yards. I try not to get too hung up on "group size" but I this is a competition gun I really want to keep things as tight as possible. Right now I'm noticing that out of 3 rounds, I'm gettng a flyer on a fairly consistent basis. I'm not sure if I should try adjusting the load, or not. I don't want to wear out my barrel by tweaking a load without knowing what to tweak. Does anyone have suggestions?
 
#2
Well your barrel could have finished the “break” in per say. Also what powder? Hotter temp usually means faster burn.

Could also be a carbon ring in the throat causing a little bit more pressure.
 
#3
I'm using Varget. I was wondering if the barrel "break in" was part of it. Now here's where I show my ignorance, I don't know how to identify a carbon ring, or how to correct it.
 
#4
You should be able to feel the constriction with a tight fitting patch/jag, if it's bad enough. As for cleaning, there a whole thread somewhere on this board (powder solvent, ATF, brake cleaner, etc.)...

I'd wager you've just broken the barrel in, and the increase in velocity pushed you into another accuracy node.
 
#5
MarinePMI said:
You should be able to feel the constriction with a tight fitting patch/jag, if it's bad enough. As for cleaning, there a whole thread somewhere on this board (powder solvent, ATF, brake cleaner, etc.)...
Click to expand...
Thanks for bringing the carbon ring possibility to my attention. I'll check out my barrel, and I'll research the tread too.
 
#6
MarinePMI said:
You should be able to feel the constriction with a tight fitting patch/jag, if it's bad enough. As for cleaning, there a whole thread somewhere on this board (powder solvent, ATF, brake cleaner, etc.)...

I'd wager you've just broken the barrel in, and the increase in velocity pushed you into another accuracy node.
Click to expand...

Can I reduce the powder charge slightly to get back to the previous node. Does it work like that?
 
#7
You can try to go back to your previous node by backing down on powder, I would want to figure out the why of it though before just backing down. You can try putting the ammo in a cooler to drop its temp before firing and seeing if its just the temps or something else.

When is the last time you gave it a good cleaning? When you chamber a round do you notice that some are tight? And if so can you eject an unfired round and see any scuffs on the bullets? If so then thats a good indication of a carbon ring if you havent seated the bullet out longer since developing the load. A carbon ring is basically a build up of hard carbon deposits in the throat/freebore. If you havent cleaned it for 700 rounds it sounds like youre about due for one.
 
#9
spife7980 said:
You can try to go back to your previous node by backing down on powder, I would want to figure out the why of it though before just backing down. You can try putting the ammo in a cooler to drop its temp before firing and seeing if its just the temps or something else.

When is the last time you gave it a good cleaning? When you chamber a round do you notice that some are tight? And if so can you eject an unfired round and see any scuffs on the bullets? If so then thats a good indication of a carbon ring if you havent seated the bullet out longer since developing the load. A carbon ring is basically a build up of hard carbon deposits in the throat/freebore. If you havent cleaned it for 700 rounds it sounds like youre about due for one.
Click to expand...

I've put 70 through the barrel since the last cleaning. Rounds have been chambering without tightness. Everything with the load is the same. I'm very - I'll call it "detail oriented" - with my loading procedures, so nothing is different there. My SD's are rarely above 6. Today the chrono was 2724 fps, where the same Lot (I loaded 100 rounds in this Lot for a match) 30 rounds ago was 2717 fps. I'll try the cooler next time I go out.
 
#10
Could be the ambient temperature around the ammo. I’ve seen elevation changes between strings at 600 from leaving the ammo in the sun.

The other possibility I’ve been told is that barrels speed up over the break in. However, you are way past that point at 700 rds. If you said 100-200, I would be leaning more towards that explanation
 
#11
Or, just maybe, and I'm just throwing this out there, you really don't know for sure what your MV is or was. All we know for a fact is your shooting has clearly gotten worse over time. Nodes, flyers, and break-in are just common buzz words.
 
#12
Culpeper said:
Or, just maybe, and I'm just throwing this out there, you really don't know for sure what your MV is or was. All we know for a fact is your shooting has clearly gotten worse over time. Nodes, flyers, and break-in are just common buzz words.
Click to expand...

So maybe I'm just shooting like shit; the more I practice the worse I get? Yes, that's always a possibility, but with this particular rifle, I have kept data on every round I've put through it, with notes on each trip to the range. I'm inclined to believe that I do know how to use my Magnetospeed well enough to get a somewhat accurate MV. I also know how to read the data I've collected and can see that there has been a change in speed that correlates to a change in accuracy. After reading the responses that people have posted I'm also inclined to believe that, regardless of the reason for the increase in MV, I may not be in the same node I was previously in.

I have to admit that I do like the idea of saying it's just bad shooting on my part, because that means I would need to spend less time at the loading bench, and more time at the range - shooting! ;)
 
#15
If you have the range, why don't you shoot yourself a ladder at 500? I've asked myself a lot of headache doing this because I was shooting tight groups at 100 with loads that were mediocre at distance
 
#16
260Girl said:
So maybe I'm just shooting like shit; the more I practice the worse I get? Yes, that's always a possibility, but with this particular rifle, I have kept data on every round I've put through it, with notes on each trip to the range. I'm inclined to believe that I do know how to use my Magnetospeed well enough to get a somewhat accurate MV. I also know how to read the data I've collected and can see that there has been a change in speed that correlates to a change in accuracy. After reading the responses that people have posted I'm also inclined to believe that, regardless of the reason for the increase in MV, I may not be in the same node I was previously in.

I have to admit that I do like the idea of saying it's just bad shooting on my part, because that means I would need to spend less time at the loading bench, and more time at the range - shooting! ;)
Click to expand...

Do what has been suggested and ignore culpeper

Barrels usually do speed up and it usually can change things
 
#17
Well you narrowed it down to yourself or a finicky rifle that acts like an off the line 700. Get some Match grade ammo and keep it on hand as a benchmark. Or check your aiming parts and make sure your bipod is on tight. Why does everybody think the load they wasted all that time on suddenly went to shit? Make sure all your shit is wired tight.
 
#18
I have access to a 200 yards max. at the present time. I did have access to 1000 yards for several months. I've taken this rifle and load out as far as 1000 with a 4.5 inch group on a perfect day with no wind. 1 inch consistently at 300 yards. (Thanks to Joe Walls of Exodus Rifles).

I may need to work on a ladder test soon.
 
#20
Then you know you can shoot and your equipment works. Need a tuning for whatever reason. Mine was that all my original load work was done on virgin brass, and some was done at 100 yards.
 
#22
Culpeper said:
Well you narrowed it down to yourself or a finicky rifle that acts like an off the line 700. Get some Match grade ammo and keep it on hand as a benchmark. Or check your aiming parts and make sure your bipod is on tight. Why does everybody think the load they wasted all that time on suddenly went to shit? Make sure all your shit is wired tight.
Click to expand...

It's guys like you that remind me to make sure my shit's not wired too tight. Gotta roll with it!
 
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#25
Culpeper said:
Less brass capacity
Click to expand...
yup. Lower volume. Pressure and volume are inversely proportional in a closed system. On the second time around, the brass now has a higher volume (how much depends on the chamber), and the same charge used for the virgin brass may produce a different pressure profile, which may put the charge out of its original "node". Theoretically, increasing the charge marginally should straighten it out, but sometimes you need to find a new depth as well. Gotta figure it out experimentally
 
#26
mijp5 said:
yup. Lower volume. Pressure and volume are inversely proportional in a closed system. On the second time around, the brass now has a higher volume (how much depends on the chamber), and the same charge used for the virgin brass may produce a different pressure profile, which may put the charge out of its original "node". Theoretically, increasing the charge marginally should straighten it out, but sometimes you need to find a new depth as well. Gotta figure it out experimentally
Click to expand...

So the first time the brass is fired it forms to the chamber which increases it's volume. Does the volume stay the same after that? The brass grows in length, but is that just the necks, or is the whole case thinning out over time?
 
#27
Yes, the brass should remain the same volume (assuming consistent resizing/shoulder bump), once fired in your chamber (which slightly increases the volume).

As to the length, the whole case is essentially extruded each time is is sized, forcing the brass to "flow" towards the path of least resistance...which is the neck/case mouth. So, what is measurable in difference is the length of the neck, but in fact the whole case is stretching/thinning (to some degree) when sized. This is where case head separations occur (assuming the primer pocket doesn't give out first).

Clear as mud? :)
 
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#30
I never put it together before - pressure can be impacted by what's happening inside of the round itself, and also by what's happening inside of the chamber/barrel, ie: carbon ring.
 
#31
spife7980 said:
When is the last time you gave it a good cleaning? When you chamber a round do you notice that some are tight? And if so can you eject an unfired round and see any scuffs on the bullets? If so then thats a good indication of a carbon ring if you havent seated the bullet out longer since developing the load. A carbon ring is basically a build up of hard carbon deposits in the throat/freebore. If you havent cleaned it for 700 rounds it sounds like youre about due for one.
Click to expand...
Barrels are usually done speeding up long before 700 rds, I doubt you have an anomaly.
I'd follow this advice from spife. Varget is a dirty powder, and even though you have to have a complete burn going on running this fast of a powder, it can still buildup in your bore causing exactly the symptoms you've described. The more you fire a gun, the harder the carbon deposits get, clean it good, then go chrono a few of your original load.
 
#32
What has been your cleaning procdure for the last 700 rounds? At this point I would scrub the carbon out and then the copper. There are a lot of ways to achieve this.

EDIT: sorry Milo. I posted just after you
 
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#33
260Girl said:
So the first time the brass is fired it forms to the chamber which increases it's volume. Does the volume stay the same after that? The brass grows in length, but is that just the necks, or is the whole case thinning out over time?
Click to expand...

There is such thing as brass flow. The walls of the cartridge get thinner as the brass gets shot and resized over and over. This will increase volume but I haven't seen any tests that conclude how much.
I took 4 times fired Hornady brass and split it with a wire edm. The wall thickness at the taper/shoulder junction was only .007".
 
#34
Jay McLean said:
There is such thing as brass flow. The walls of the cartridge get thinner as the brass gets shot and resized over and over. This will increase volume but I haven't seen any tests that conclude how much.
I took 4 times fired Hornady brass and split it with a wire edm. The wall thickness at the taper/shoulder junction was only .007".
Click to expand...
What does a new piece measure?
 
#36
Culpeper said:
What has been your cleaning procdure for the last 700 rounds? At this point I would scrub the carbon out and then the copper. There are a lot of ways to achieve this.

EDIT: sorry Milo. I posted just after you
Click to expand...
I've never used anything to clean out the carbon. I just learned, through this thread, that carbon build up is a thing. It looks like I can use an abrasive or a chemical cleaner to get the carbon out. I use a bore guide when I clean my barrel. I'm starting to wonder if that leaves an area that doesn't get cleaned. As in the place where the guide contacts the chamber/barrel.
 
#37
260Girl said:
I've never used anything to clean out the carbon. I just learned, through this thread, that carbon build up is a thing. It looks like I can use an abrasive or a chemical cleaner to get the carbon out. I use a bore guide when I clean my barrel. I'm starting to wonder if that leaves an area that doesn't get cleaned. As in the place where the guide contacts the chamber/barrel.
Click to expand...
No, unless you have a custom bore guide, the nose of the bore guide will stop at the shoulder in your chamber, it's way bigger than the neck of your case.
 
#38
That makes sense. I up until now I have cleaned my barrel every 200 rounds. Some people have told me they clean their bore after every trip to the range, some say they wait until they see a degrade in accuracy. There doesn't seem to be a general consensus on how it should be done, not even between rifle builders, or pro shooters. I picked 200 rounds, because I started with 200 rounds of new brass. I cleaned and prepped the brass, cleaned the rifle and the cycle started again. No scientific reason. What I find odd is that in all the time that I've been shooting and talking to people about guns, copper build up is the only thing that I've heard can cause problems. I've never heard of a carbon ring. Glad I finally decided to post on SH.
 
#40
260Girl said:
That makes sense. I up until now I have cleaned my barrel every 200 rounds. Some people have told me they clean their bore after every trip to the range, some say they wait until they see a degrade in accuracy. There doesn't seem to be a general consensus on how it should be done, not even between rifle builders, or pro shooters. I picked 200 rounds, because I started with 200 rounds of new brass. I cleaned and prepped the brass, cleaned the rifle and the cycle started again. No scientific reason. What I find odd is that in all the time that I've been shooting and talking to people about guns, copper build up is the only thing that I've heard can cause problems. I've never heard of a carbon ring. Glad I finally decided to post on SH.
Click to expand...
Things tend to get simplified, if you have a copper buildup, carbon is present too, and vise versa. Where a copper solvent will remove softer carbon, but not all, where theoretically a carbon dissolver if let sit long enough to get to bare metal, so when you finally jag it out should push the copper out with it. But it does not work that easy. This is where a borescope is handy.
 
#43
260Girl said:
If you fill the void with powder insead of the end of the bullet doesn't that increase the velocity, because you have more powder, basically exploding?
Click to expand...
Not necessarily. You are decreasing the empty volume of the case either way. You have to fine tune it using either method. It’s all about pressure profile. 45 gr of powder in a 308 case will push a bullet out at a respectable speed, while 45 gr in a 338 Lapua will be subsonic or a squib (provided you are somehow able to pack it evenly in the case).
 
#45
260Girl said:
I realize my knowledge of pressure and how it works is zip. I haven't had to do much load development in the past. I've reached a new level with my shooting, and now a need to step up to the next level of knowledge with my loading.

I understand the basics of barrel harmonics and nodes. Does pressure determines velocity. Are they directly related: reducing pressure will reduce MV?
Click to expand...

You are over thinking it. Just try to re work your loading by trying powder charges a little above and below your last loading
 
#49
260Girl said:
I'm curious, because I really want to know how this works. Is that to raise or lower the pressure in the case - which will raise or lower the velocity?
Click to expand...
It could be either. All that matters is that you’ve lost your precision somehow and have to get it back. By changing pressure profile in either direction, you are hoping to end up at a new reliable “node”
 
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