Copper or Aluminum

[Larry Gibson]

Larry

I didn't think you were getting accuracy with those checks coming off and whatever is happening to the shanks.

Nobody answered why the pressure in the NRA full power loads (one's in the 50k bracket and over) wasn't deforming the base of the bullets when only paper protected them.

Once the velocity went above 3000 fps the GCs started coming off. They do considerable damage to the SkyScreens which I'll post later. As I've stated and posted numerous time the best consistent HV accuracy of 1 - 1.5 moa (10 shot groups) comes just over 2900 fps. At 3100 fps the 10 shot groups opened to 3.75" with every flyer being also a bullet that lost its GC as seen when the SkyScreens were struck by the GC. Also at 3100 fps the bullet out of the 16" twist is at the front edge of the RPM Threshold.

In the NRA Cast Bullets Supplement Col. Harrison notes in the article starting on page 108 the success with the 160 gr PP'd bullet in the 300 WM with the full load gave an average of 2.6 and 2.2 moa (five 5 shot group average). Unfortunately, the pressure and velocities were only estimates. Also he did not recover any bullets or patches so we don't know whether the patch was "burnt" or not of if the base of the bullet was damaged.

[Larry Gibson]

Thing is Larry did say that the check itself DID NOT MELT, he believes the bullet shank started to melt because he found some form of alloy inside the gas check. I presume it's the tin. Larry does like some extra tin in his alloy blends. Larry chime in if I'm wrong about that.

The bullets were cast of Lyman #2 alloy.

[Larry Gibson]

Larry would be interesting to know if you would do the test, but I ask how would you collect the gas check fragments if it doesn't work? BTW did you recover those bullets that all this happened too and if so was the shank indeed melted?

If I did the test I'm not sure how I would collect the shed GCs. The previous shed GCs are very destructive to the SkyScreens. The fragments shown were found inside the SkyScreen housings. Here you can see the damage done not only by the Hornady GCs shed at 3000+ fps but also from aluminum GCs shed at 22-2400+ fps. Frankly, having replaced and/or repaired several of my SkyScreens I'm no all that keen on doing more repair/replacement. I've already learned at what velocities the checks become separated from the bullets.

No, I did not recover any of the bullets that had shed their GCs. When one screen stopped reading [the fragment was laying on the sensor blocking it from reading] and a support arm was shot in two by a GC I said "enough is enough".

Here's just a few pic's of the damaged SkyScreens;

[Larry Gibson]

Larry I was shooting my Yugo 48 B 8mm Mauser, which is scoped, a few years ago. I was shooting the Lyman 323471 moving along at tad over 2000 fps. Certainly no speed demon as you XCB load. I had a Directv satelite dish up at a measure 500 yards. I was shooting at paper target and I had 4 cartridges left so I shot at the dish. This group isn't in MOA it's in actual inches and as you can see for that distance with a military rifle it's not shabby at all.

Attachment 313753

The 323471 ia an excellent bullet to use at LR out of good Mauser barrels. The bullet itself has several attributes which make it an excellent choice for pushing the RPM Threshold. Additionally thegroove depth of the military 8mm Mauser is .005" deep as opposed to .003 - .004 for most commercial groove depth. The deeper mauser grooves really grasp the long bearing surface of the Loverin style 323471 bullet. That bullet is my favorite LR bullet for use in my own Yugo M24/47. I push that bullet right at 2000 fps also and it hold very well at 500 - 600 yards as you've demonstrated. Well done.

[Larry Gibson]

Back to the thread topic. Probably 15 - 20 +/- years ago I got a GB Lee 6 cavity C326-190-FN mould. I also had a GC maker. I obtained some .012" brass shim from McMaster-Carr (?) and made some 8mm GCs. I decided to make a comparison of them to the Hornady 8mm GCs. I had a lot of Turk primed cases I was using back then so I cast a bunch of the bullets out of COWW +2% tin, sized them at .325, GC'd some with the Hornady's and some with my own GCs, lubed them with Javelina and loaded them over 4895 + a dacron filler in the Turk cases. I used my Yugo 24/47 w/Leupold 6X scope for the test. I shot the Hornady's first shooting two foulers then 10 shots for group. I then let the barrel cool, cleaned it and repeated the test. There was only .01" difference between the groups and given the Turk cases, only visually sorted bullets and no load work up they were close enough for government work.... I then sized, lubed and GC'd the remaining 600+ bullets with my own GCs and loaded them in the Turk cases I had. I've still a couple hundred left as they have prove to be an excellent "walk about" load for use in my Yugo M48.

[TD1886]

I feel like you still don't get what I'm saying. And I'm fine if you don't agree, but I wish you got it, first.

The base of a boolit doesn't melt (the side does). So the check, which covers the base, should not only not melt, it shouldn't reach the temperature that would even melt lead. The only way it reaches that temp, demonstrated by Larry's boolits, is because it sucked out heat from a jet of gas that would have otherwise contributed to melting the side of the boolit.

Oh I get what you are saying. Now I'm wondering if that jet of gas got ahead of the check and sprayed it with molten alloy that it gas cut, rather then the base of the bullet melting.

[TD1886]

The 323471 ia an excellent bullet to use at LR out of good Mauser barrels. The bullet itself has several attributes which make it an excellent choice for pushing the RPM Threshold. Additionally thegroove depth of the military 8mm Mauser is .005" deep as opposed to .003 - .004 for most commercial groove depth. The deeper mauser grooves really grasp the long bearing surface of the Loverin style 323471 bullet. That bullet is my favorite LR bullet for use in my own Yugo M24/47. I push that bullet right at 2000 fps also and it hold very well at 500 - 600 yards as you've demonstrated. Well done.

Thank's Larry. That Mauser is exactly as you described and mine was a brand new unissued one. I think the 8x57 Mauser is one of the best cartriges and it certainly has stellar performance with cast bullets.

[TD1886]

Back to the thread topic. Probably 15 - 20 +/- years ago I got a GB Lee 6 cavity C326-190-FN mould. I also had a GC maker. I obtained some .012" brass shim from McMaster-Carr (?) and made some 8mm GCs. I decided to make a comparison of them to the Hornady 8mm GCs. I had a lot of Turk primed cases I was using back then so I cast a bunch of the bullets out of COWW +2% tin, sized them at .325, GC'd some with the Hornady's and some with my own GCs, lubed them with Javelina and loaded them over 4895 + a dacron filler in the Turk cases. I used my Yugo 24/47 w/Leupold 6X scope for the test. I shot the Hornady's first shooting two foulers then 10 shots for group. I then let the barrel cool, cleaned it and repeated the test. There was only .01" difference between the groups and given the Turk cases, only visually sorted bullets and no load work up they were close enough for government work.... I then sized, lubed and GC'd the remaining 600+ bullets with my own GCs and loaded them in the Turk cases I had. I've still a couple hundred left as they have prove to be an excellent "walk about" load for use in my Yugo M48.

Job well done Larry. I have tested my checks along with Hornady and they are the equal and sometimes beat them, not all the time.

[gloob]

Larry's data is quite convincing. At 3100 fps, the copper checks started falling off and more importantly started throwing fliers. The aluminum checks started doing that at 2400 fps.

Bringing this back to the topic of "copper vs aluminum," I said it in my first post. Copper > aluminum. But sometimes aluminum is good enough for your gun and load. Then there's no difference as far as you're concerned!

[TD1886]

Larry's data is quite convincing. At 3100 fps, the copper checks started falling off and more importantly started throwing fliers. The aluminum checks started doing that at 2400 fps.

Bringing this back to the topic of "copper vs aluminum," I said it in my first post. Copper > aluminum. But sometimes aluminum is good enough for your gun and load. Then there's no difference as far as you're concerned!

Well let me tell you that MY aluminum checks DO NOT fall off at 2400 fps and I've fired them much faster then that out of a 30-06 with a MUCH faster twist then what Larry is using on his XCB rifle. This is not to infer anything negative to what Larry is saying. I believe what he's telling us here. It just doesn't happen to me.

[gloob]

What's "much faster?" I believe my Lyman cast data load info lists ~1800-2200 fps for maximum loads in 308.

More importantly, what happened when you maxed out and suffered failure? If you haven't found that point on both types of checks, then you really don't know which one works better, do you? I admit I haven't done this, and that I don't know from my own experience. I'm going with Larry's data.

It takes a lot of time and range trips to do this kind of thing. I tried to shoot 2400 in 223, once, with a load some shooter had been cooked up for cycling an AR. The boolits ended up coating my flash hider. I just went back to lyman data at 1900 fps, which I found works with aluminum or copper. But that doesn't prove aluminum = copper.

Even if I tried, the difference might not be much if any in 223 with the 10 thous check. I would expect there might be a bigger difference in boolits with thicker checks.

[TD1886]

What's "much faster?" I believe my Lyman cast data load info lists ~1800-2200 fps for maximum loads in 308.

More importantly, what happened when you maxed out and suffered failure? If you haven't found that point on both types of checks, then you really don't know which one works better, do you? I admit I haven't done this, and that I don't know from my own experience. I'm going with Larry's data.

It takes a lot of time and range trips to do this kind of thing. I tried to shoot 2400 in 223, once, with a load some shooter had been cooked up for cycling an AR. The boolits ended up coating my flash hider. I just went back to lyman data at 1900 fps, which I found works with aluminum or copper. But that doesn't prove aluminum = copper.

Even if I tried, the difference might not be much if any in 223 with the 10 thous check. I would expect there might be a bigger difference in boolits with thicker checks.

Don't know why you mentioned loads for the 308, I did say the 30-06. They were a tad over 2800 fps.

Well if you are asking me what happened when "I" maxed out, well I didn't max out and nothing happened. I was pushing the 06 with that cast load to see what it would do. The one thing I don't like about my CZ550 is the groove is .309 . The second thing I don'w like is it's a hammer forged barrel and although some hammer forged barrels shoot very well, many don't.

I once tried to strip a 7mm cast bullet in a 7x57 Mause and the bullet was cast of lead. I couldn't do it and it really didn't lead the barrel. I'm not sure you can get a cast bullet to turn 360 degres plus in a barrel. Revolvers I've seen it happen.

[Larry Gibson]

Keep in mind many push cast bullets faster because of PPing and PCing. Both are a form of a "jacket" and do alloy higher velocity while maintain accuracy. My data refers to ternary alloy naked cast bullets that are just GC'd and lubed.

I have pushed PC'd GC'd cast bullets to 2800 fps and maintained usable accuracy at 100 yards. That was out of .223s and a 308W with 12' twists. However, with ternary alloyed naked, GC'd and just lubed bullets I've yet to see such. Yes, it is easy to get 2800 fps out of any '06 with any cast bullet. However, maintaining accuracy is another thing.

gloob, what are the specifics of that 2800 fps load, number of shots and what accuracy at what range(s)?

[gloob]

Don't know why you mentioned loads for the 308, I did say the 30-06. They were a tad over 2800 fps.

Just because the 308 numbers are the ones I looked at, when I last knew where my Lyman manual was. 30-06 has a bigger case and can theoretically get higher velocities with a lower pressure (like with jacketed bullets), but I would have guessed max cast velocity would be pretty much the same thing between the two, using the ideal powder for either.

You got 2800 fps in 30-06 with aluminum checks, first try, no experimenting with powders and alloys needed? Are you PC'ing, too? Is this your regular load? If not, did you put it on paper to make sure they're going straight?

edit: ^LArry, that was TD's post. I've yet to get a normal checked boolit to exit in one piece above 2200 fps.

I once tried to strip a 7mm cast bullet in a 7x57 Mause and the bullet was cast of lead. I couldn't do it and it really didn't lead the barrel. I'm not sure you can get a cast bullet to turn 360 degres plus in a barrel. Revolvers I've seen it happen.

TD, was that with a gas check? I don't think you can leave fouling in the barrel when using a gas check. Even when my cast 223 were leaving the barrel in a blast of molten lead, the bore was clean.

Boolits getting "stripped" by the rifling is something I don't really believe, yet. How do you know? Do you recover the boolit, after? And by the time rifling "stripped" a boolit, wouldn't it get gas cut all to heck and completely messed up beyond recognition? I imagine only half the boolit would make it out in a solid piece.

Yes, it is easy to get 2800 fps out of any '06 with any cast bullet.

- Larry
Interesting. I thought the boolit was the limit, at some point, rather than case capacity. Hence the rise of larger and larger case capacity with smaller/faster bullets going hand-in-hand with the introduction of jacketed bullets. I've entertained the thought of a 22 Hornet, as potentially shooting just as fast as 223 with cast boolits but with less powder. But then the reality of more expensive cases makes that moot. Case capacity is potentially a bigger component than I thought. Now I really want to find my Lyman manual.

However, maintaining accuracy is another thing.

Yes, this is what I meant. I mean, if you don't count accuracy, you can make any rifle shoot cast at least as fast as jacketed. Dunno how accurately you can chronograph a spray of lead droplets, though.

[TD1886]

Just because the 308 numbers are the ones I looked at, when I last knew where my Lyman manual was. 30-06 has a bigger case and can theoretically get higher velocities with a lower pressure (like with jacketed bullets), but I would have guessed max cast velocity would be pretty much the same thing between the two, using the ideal powder for either.

You got 2800 fps in 30-06 with aluminum checks, first try, no experimenting with powders and alloys needed? Are you PC'ing, too? Is this your regular load? If not, did you put it on paper to make sure they're going straight?

edit: ^LArry, that was TD's post. I've yet to get a normal checked boolit to exit in one piece above 2200 fps.


TD, was that with a gas check? I don't think you can leave fouling in the barrel when using a gas check. Even when my cast 223 were leaving the barrel in a blast of molten lead, the bore was clean.

Boolits getting "stripped" by the rifling is something I don't really believe, yet. How do you know? Do you recover the boolit, after? And by the time rifling "stripped" a boolit, wouldn't it get gas cut all to heck and completely messed up beyond recognition? I imagine only half the boolit would make it out in a solid piece.

First the 7x57. Yes with a gascheck. It should have been severely leaded, but wasn't. If it was leaded the gascheck wouldn't have take every bit of it. Also there was no grey wash or leading at the crown.

On the 06 I had been shooting gaschecks all along so can't really say first try. I was using RL22 powder. The accuracy was good enough for deer, but it wasn't what I wanted. I wanted an inch or below. So not the bullets weren't PP'ed. To tell you the truth I don't care a lot about PP bullets.

[Shopdog]

If you're having issue with them coming off;

Cpl ways to stop it dead in it's tracks are... roll crimping,is an easy enough process that you'll have to cut the shank off before it can be removed. The other isn't quite as "forever" but durn close.... use a 5C collet/closer and turn in the upper edge.

Good luck with your project.

[TD1886]

Okay I have done some tests to prove to you all that auto extracted fired cases are hotter then manually extracted cases. Test Rifle: M1A Springfield Nation Match Stainless barrel. Rifle Temp: 65 degrees. Ammo LC primed cases loaded with IMR 4064 powder and topped with Hornady 168 grain match bullets. First Shot Semi Mode: Case temperature was 110 degrees and that's after it flew through the air and landed on the ground and I walked over to it to gauge it. So it had some cooling time. Screwed the gas plug out of the rifle as it doesn't have a gas shut off system. Second Shot: Case temperature was 76 degrees and that's after I manually ejected it and gauged it as it was laying on the ground.

Our you fellows believing me now that semi or full auto extracted cases are hotter then manually extracted cases because the friction of them getting violently extracted and ejected from the chamber?

This is about all I can do to prove this to you all. I will be testing other firearms and calibers if you are interested.

[TurnipEaterDown]

The semi auto or full auto gun extracts the case from the chamber much faster than anyone can manually. Residual case temperature has a strong relationship to dwell time in the chamber and heat transfer from the brass casing to the chamber walls. Not so much about friction. The case does have higher residual chamber pressure during extraction in a semi or full auto than a typical manually operated gun like a bolt, pump, or lever, but then I never saw anyone run a bolt, pump, or lever at 1000+ rpm either.

[gloob]

you fellows believing me now

I figured you'd have deleted that post, by now. I never did quote it, so as to give you that chance after giving it 10 more seconds of thought.

You, yourself posted this, right after.

By the way one gram of powder produces about 3700 joules energy from high energy gun powder. There's is only one powder manufacturer that releases this type of data that I know of. You figure out who it is. While you are at figure out what the C or F degree of 3700 Joules is!!

Yes, you can start a fire by rubbing two sticks together. But if you do that at the same time as burning 10 grains of smokeless powder under your tinder, you might want to give some credit to the powder.

Measure the temp of your chamber while you're at it. Notice it heats up, too, but it will never get as hot as a freshly auto-extracted case. The chamber cools the case.

You could also try extracting an empty case out of your gun over and over. Tell us how hot it ever gets.

Giving physics lessons always goes wrong, on a gun forum. I know better than to try, but here I am:

Barring some potential extra friction from early/sticky extraction, the total amount of heat created by extracting a case slowly versus quickly is the same. This is the reason boolit friction can't make an entire boolit turn to mush, no matter how fast you shoot it (keeping barrel length constant). Faster velocity just means that same amount of heat from friction is dumped into the skin of the boolit in a shorter time, potentially softening/melting the skin before that heat is shared deeper into the core, and then allowing gas to jet past and melt the entire boolit. Higher psi will more likely force a leak and higher psi means the jet is faster, thus hotter (replaced by more hot gas as fast as that heat is absorbed by barrel/boolit).

I.e., if a substantial enough portion of the boolit melted/eroded to cause accuracy issues, that boolit leaked, period. And the portion of the boolit that was lost was due to a gas jet down the side. Unless you made a special gun with a 24 foot long barrel in order to melt a boolit through friction.

[TD1886]

I figured you'd have deleted that post, by now. I never did quote it, so as to give you that chance after giving it 10 more seconds of thought.

You, yourself posted this, right after.


Yes, you can start a fire by rubbing two sticks together. But if you do that at the same time as burning 10 grains of smokeless powder under your tinder, you might want to give some credit to the powder.

Measure the temp of your chamber while you're at it. Notice it heats up, too, but it will never get as hot as a freshly auto-extracted case. The chamber cools the case.

You could also try extracting an empty case out of your gun over and over. Tell us how hot it ever gets.

Giving physics lessons always goes wrong, on a gun forum. I know better than to try, but here I am:

Barring some potential extra friction from early/sticky extraction, the total amount of heat created by extracting a case slowly versus quickly is the same. This is the reason boolit friction can't make an entire boolit turn to mush, no matter how fast you shoot it (keeping barrel length constant). Faster velocity just means that same amount of heat from friction is dumped into the skin of the boolit in a shorter time, potentially softening/melting the skin before that heat is shared deeper into the core, and then allowing gas to jet past and melt the entire boolit. Higher psi will more likely force a leak and higher psi means the jet is faster, thus hotter (replaced by more hot gas as fast as that heat is absorbed by barrel/boolit).

I.e., if a substantial enough portion of the boolit melted/eroded to cause accuracy issues, that bullet leaked, period.

Gloob let's go after this at a different angle. Let's take a 45-70 case and resize it. Maybe you never paid a lot of attention to resizing cases other then how hard or easy they were to size and also hoping you don't stick a case. Well not that, but how warm the case gets sizing and extracting it. Get your 45-70 lubed and ready to resize and line it up to the die mouth. What I want you to do is ram it into the dies and extract it right away and fill the case and tell me if it's warm or not. Remember the dies is cold, it isn't buning any powder, and you're not shucking the case out of the die as fast as semi auto or full auto action.

On the joules of energy I never once said that powder didn't burn hot.

On your loading a case and extraction it over and over isn't going to do much because their isn't much friction since the case is loose in the chamber. I don't think that was a very good analogy on your part.

If you don't want to believe that the majority of the heat in an extracted case from a semi or full automatic weapon is from friction, well then that is your prerogative. To be sure I'm not talking about a 06 30 caliber machine gun running non stop in a Jap banzai attack on Iwo Jima in WW2 where the machinegun is so hot it's cooking off rounds.