Copper Fouling and Velocity Questions

[DeadEyeDeadly]

While cleaning my rifle bore tonight, a weird question popped into my feeble brain. Which brand of bullet causes the worst amount of copper fouling?


I surmise that the composition of the jacket material has some bearing on that question. Is a softer jacket worse than a harder jacket, or vice versa? Is the alloy content the main factor? Anyone know of any data available on this brain fart?


On a similar tact, here are the chronograph results for two very similar loads.


204 Ruger, Hornady Case, Federal Match Primer, 27.0 grains IMR 8208 XBR Powder, both bullets seated .02 inch off the barrel lands:


39 grain Sierra Blitzking Bullet – 3733 fps average for 10 Shots
40 grain Hornady V-Max Bullet – 3773 fps average for 10 shots


Despite being one grain heavier, the Hornady averaged 40 fps higher than the Sierra. I now wonder, which load had the highest chamber pressure?


Oops! I guess I'll stop wondering and just go to the range tomorrow and have LOADS of fun!

[Texas10]

You a very punny guyyyyyy

I don't have either of those bullets in my drawers (he-he), but you might try measuring the bearing surface. I'll bet the 39 grain Blitzking has a longer bearing surface and hence, more drag going down the barrel.

Could also have to do with jacket composition too, as you mentioned, or both. That's why the recommendation to back down on your charge when switching bullet mfgs. and work back up checking for pressure.

Are both bullets seated to the same depth into the case and have the same neck tension? That could also be a factor.

[DeadEyeDeadly]

From my rudimentary measurements, both bullets have the same bearing contact length within the bore. The Hornady has a longer boat tail, which results in ~ 1 mm less contact length within the case neck. My guesstimate is that the Sierra has more case neck tension.


I have more neck tension also. When I tell my wife I'm going to the range, she always retorts, “AAAGGGAAAIIINNN!!! You better not drink any beer after you finish shooting!”

[Texas10]

Aahhhh….but are you really ever finished shooting? There's always a next time and the beer is just an intermission.

[darkker]

While cleaning my rifle bore tonight, a weird question popped into my feeble brain. Which brand of bullet causes the worst amount of copper fouling?


I surmise that the composition of the jacket material has some bearing on that question. Is a softer jacket worse than a harder jacket, or vice versa? Is the alloy content the main factor? Anyone know of any data available on this brain fart?


On a similar tact, here are the chronograph results for two very similar loads.


204 Ruger, Hornady Case, Federal Match Primer, 27.0 grains IMR 8208 XBR Powder, both bullets seated .02 inch off the barrel lands:


39 grain Sierra Blitzking Bullet – 3733 fps average for 10 Shots
40 grain Hornady V-Max Bullet – 3773 fps average for 10 shots


Despite being one grain heavier, the Hornady averaged 40 fps higher than the Sierra. I now wonder, which load had the highest chamber pressure?


Oops! I guess I'll stop wondering and just go to the range tomorrow and have LOADS of fun!

Yes the alloy used will have the bulk of the difference. So for an example, Barnes uses dead-soft copper, then heat-treats them to be tough and not explode. This will have a radically different outcome than a more typical 70/30 jacket than used in traditional cup-&-core bullets. Also whether or not they are plated will affect things. So the AMP jackets are a partial deposition/plated style jacket, much like the Deep curl bullets.

Next is the bearing surface area. That I know of, Berger is the only folks who readily publish those numbers.

As to the velocity question, this is a bit envolved.
We have used a Pressure Trace to measure pressure on many different bullets & loads in the same rifle.
On the surface, a different velocity MAY indicate a different pressure; MAY.
We have found thus far that the difference is minor enough that it is essentially irrelevant to the cause, or at least un-detectable to the average joe.
More likely the difference is in the powder, conditions.

Are you measuring jump to lands by the tip of the bullet, or by the actual ogive contact?? Those are different bullets, and measuring to the tip isn't a science, measuring off of the ogive should give you a much more real view of what is happening. Otherwise you may well be allowing more gas to by-pass with one versus the other.

Powder and especially the primers, are affected greatly by the ambient and barrel temps. So is this a ghost caused by things being different?
Also you are dealing with an extruded powder, but you are loading by weight.

Extruded powder has it's burning rate controlled by geometry(kernel size, perforations). It's bulk density(measure of power) and it's geometry have a very closely held relationship. Thus if you only load by weight, you are ignoring any burning rate shift, and further aggrevation of it, by case fill.

[DeadEyeDeadly]

I use a Hornady OAL guage and modified case to measure ogive contact.


I use a Gem-Pro scale for powder measurement.


I fired the test loads in the following sequence: 5 Sierra, 5 V-Max, 5 Sierra, 5 V-Max -
so my guess is that barrel temperature should not have contributed significantly to the observed velocity differences.

[darkker]

Barrel temp is the killer in the variable, as it really affects the primer.
https://www.shootingsoftware.com/tech.htm

[DeadEyeDeadly]

darkker - Thanks for the link, and making my mind reel even more than I can tolerate!

[bigedp51]

Below the throat and bore of a brand new button rifled Savage barrel.





Below before and after fire lapping the Savage barrel.



Below the same fire lapped image enlarged.



Below a brand new custom made hand lapped barrel.



The real question is which "type" barrel collects the most copper. I collected old milsurp rifles and many of them used corrosive primers and many of the rifles had frosted and pitted bores.

Bottom line, button rifled barrels and old milsurp barrels are better off using foam bore cleaner and minimum cleaning rod time.

Below a 1943 No.4 .303 British Enfield rifle with a two groove frosted bore and one shot of foam bore cleaner.

[darkker]

MZ5 had one of those sewer pipes as well!

[MarkTC]

Yes the alloy used will have the bulk of the difference. So for an example, Barnes uses dead-soft copper, then heat-treats them to be tough and not explode. This will have a radically different outcome than a more typical 70/30 jacket than used in traditional cup-&-core bullets. Also whether or not they are plated will affect things. So the AMP jackets are a partial deposition/plated style jacket, much like the Deep curl bullets.

Next is the bearing surface area. That I know of, Berger is the only folks who readily publish those numbers.

As to the velocity question, this is a bit envolved.
We have used a Pressure Trace to measure pressure on many different bullets & loads in the same rifle.
On the surface, a different velocity MAY indicate a different pressure; MAY.
We have found thus far that the difference is minor enough that it is essentially irrelevant to the cause, or at least un-detectable to the average joe.
More likely the difference is in the powder, conditions.

Are you measuring jump to lands by the tip of the bullet, or by the actual ogive contact?? Those are different bullets, and measuring to the tip isn't a science, measuring off of the ogive should give you a much more real view of what is happening. Otherwise you may well be allowing more gas to by-pass with one versus the other.

Powder and especially the primers, are affected greatly by the ambient and barrel temps. So is this a ghost caused by things being different?
Also you are dealing with an extruded powder, but you are loading by weight.

Extruded powder has it's burning rate controlled by geometry(kernel size, perforations). It's bulk density(measure of power) and it's geometry have a very closely held relationship. Thus if you only load by weight, you are ignoring any burning rate shift, and further aggrevation of it, by case fill.

Ok just figure I'm not very educated in powders how would extruded powders be measured?

[darkker]

ALL loaded by volume, FOR volume; weight is completely irrelevant to them. Specifically I'm not sure if they use mL or CC.
Loading extruded powder by volume will take advantage of the relationship between the BD & BR. So when the BD shifts a corresponding inverse burn rate change happens. As a wonderful side benefit, you always have a singular volume, so your cases don't have a moving case fill, which will further aggravate a change in burning rate.

[pbmax84]

Maybe it's self defeating, but I set my measure to throw around 2 tenths light. Throw the volume charge in the pan, then trickle up to weight. My possibly flawed thinking is that it cant hurt to have both volume and weight near correct.

[FW Conch]

And what I'm hearing, if I am proficient in their use, I can load more accurate ammo using my LEE Dippers than weighing and trickling??

[darkker]

Yes.
Using a volume to get a weight, then trickling up to the final weight; isn't volume, since you are looking for a weight. What that can allow for is a shifting case capacity, and thus a moving burning rate. Only loading the case to a volume prevents that.

I think where most people run afoul of the idea is the reference tie. So remember, just line data in any manual, the info is ONLY a reference and not supposed to be copied.
For loading by volume, since few sources list any data, here is the reference. Remember this tie to weight is ONLY a reference, you aren't looking for a weight.
Use your measuring device (whatever it may be) in this case your Lee dippers. They are calibrated in a unit of volume (CC's). So how ever you fill them, always do it the Dane. Fill them, then weigh the amount. Take the average, and do the following math: again this is an example.
3.8cc ÷ 48 gr = 0.0791667. This is your VMD, for this lot only! So if your data says a start loads is, 35gr: 35×.0.07916667=2.77cc

Remember data is only a reference, your lot isn't the Dane as was tested, and your VMD is only for the tested lot of powder, in the conditions tested. So if you take several months/years to use it, the moisture content will vary. This also aggravates the burning rate.