Opinions on pressure signs for a specific load workup - Page 2

schmellba99 · April 26, 2013, 08:57 AM

Quote:

1. The OP said "coated bullets". Maybe the barrel was not coated with the same coating when the first batch was fired, but became coated as they were fired. Perhaps that reduced pressures with the later batches?

Combined Technology bullets are not "coated" in the sense like moly coated projectiles we are generally used to.

Winchester uses a cupric oxide coating on the projectiles, but it is strictly a marketing ploy. While an argument could be made that the coating is for corrosion protection, the reality is that the lubalox coating makes the projectile stand out, but provides no lubrication properties. *

*Loyal user of Combined Technology projectiles here

My guess, and it looks like it has been answered already, is that the starting load with that powder is providing too much air space in the cartridge, and is allowing almost a detonation type combustion as a result instead of a controlled burn you get from a normal round.

243winxb · April 26, 2013, 03:38 PM

That would rule out the "coated bullets" if not like moly.

reynolds357 · April 26, 2013, 08:51 PM

lubrilox might not be moly, but it definitely reduces pressure. I did extensive work with the lubrilox coated vs non coated bullet in my 7WSM. With same powder charge, coated bullet much slower.

**Unclenick** · April 26, 2013, 09:38 PM

…and, if he got an old box of CT, there was moly on it. The old box I've got has it and you can rub it off on your finger.

I am starting to wonder if something else is going on. If the pressure builds too slowly the case won't stick to the chamber before it gets slammed back into the bolt face. It lacks normal growth in that instance. Are those 40 grain charged cases needing trimming after sizing?

WESHOOT2 · April 27, 2013, 05:54 AM

I have observed similar signs testing handgun ammo. As the charge increased, there may be charge weights that show distinct pressure signs, but as one moves upward in charge weight those signs disappear, and the load 'acts' normally.
Sometimes along the charge weighnt curve one will find lowered velocity with a charge increase, or a disproportinal increase in velocity.
And as we move past, velocity becomes progressive in gain with its charge increase.

What I think the OP saw was exactly that: An increase in charge weight gave proper results, once past that wackadoo charge.

reynolds357 · April 27, 2013, 07:10 PM

unclenick, I am neck sizing with a Lee Collet die. I only shot the brass one time each piece with the 40 grain charge, but it did not need trimming. It actually got a slight bit shorter the first time it was fired and neck sized. I have shot the brass I am load developing with six times. After the sixth firing it had grown to the max length. I full length sized it, which put it well over the full size length and then trimmed it. I will probably start playing with the rifle again Monday. I am going to get the chronograph out and try to figure out what is going on with the rifle. Its favorite load is H 1000 compressed to the point the bullet gets pushed back out and being jammed so hard into the rifling that the bolt is very hard to close. That load is not practical, so I will keep looking for a reasonable load it likes. I guess I could try crimping, but I have never had any luck in the past crimping a Nosler ballistic tip.

SL1 · April 28, 2013, 10:10 AM

It sounds like you are quite possibly getting "secondary explosion effect" with the 40 grain load.

If so, then it might not be a vry consistent effect. ONE round might gie you much higher pressures in the future than you have seen in the past.

So, I would urge caution. Working DOWN with the chronograph might be a better idea than working up, since you have already worked the load up and know that the higher charges are safe in your gun. Working down would allow you to spot the differences early on when you get to the 40 grain loads, so you can stop if things look really bad, before shooting enough loads to get a decent average.

But, before shooting them at all, I suggest that you talk to the folks who produced the load data that you are using. If it is new data shot with a transducer, they should be able to give you some good advice. If it is old data shot with a crusher, that would be good to know. But, I seriously doubt that the pressure-testing folks would knowingly publish a load that looked "spikey" to them while testing.

SL1

**Unclenick** · April 29, 2013, 10:08 AM

Hodgdon's data is all by copper crusher, unfortunately. 39-42 grain load range is their recommendation. And old transducer data may not help, either, as the 1992 standard for conformal Piezo transducers just calls for a peak value detector, offering no way to view spiky behavior. You'd need someone with not only a transducer but specifically one with a more modern graphical output display to discern that, and I don't know who is using which instrument setups? Also note that the kind of event Brian showed will only appear on strain gage measurements, since the transducers are tied to and move with the barrel, and so can only spot pressure at the transducer, but not a transverse wave in the steel that echoes an event local to the bore further down, as those seem to be.

Reynolds357,

Can you report the case water capacity of one of your fired cases taken just before it needs FL resizing? That is, weigh the case with the fired primer still in it, fill it level to the mouth with water (no meniscus, no air bubbles, no water drops on the outside) and weigh it again. Report the weight of the empty, primed case and the weight filled with water. Preferably, use a case that is of average weight and length.

Additionally, before filling with water, fill the same case level to the mouth with 760 from your lot and report that weight, too. (Then get all that powder back out before filling with water.)

What I noticed in the Hodgdon data is the difference between the top and bottom load is less than the usual 10%. It's about 7%. It makes me wonder if that powder is sensitive to ignition conditions with less than some certain percent of case fill. One possible indicator for this would be to see whether a 40 grain load produces the same pressure signs in a full length resized case (or, better yet, in a new case) than it does in the neck-sized-only cases, in which the % case fill would be smaller.

Despite conventional wisdom on the Winchester Ball powders, I would also try a mild primer if you can find one. A Tulammo KVB7, for example, or a Federal 210.

reynolds357 · April 29, 2013, 08:32 PM

I will have to fire form some more brass because I full length sized it all. I will get you the water capacity of full length sized and fire formed. I am confident it will be a significant difference based on what I saw when loading compressed loads with H 1000 and based on how rediculously hard the brass was to full length size. I am sure Ruger has cut a chamber on the high side of SAAMI spec.

April 26, 2013, 09:38 PM	#29
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	…and, if he got an old box of CT, there was moly on it. The old box I've got has it and you can rub it off on your finger. I am starting to wonder if something else is going on. If the pressure builds too slowly the case won't stick to the chamber before it gets slammed back into the bolt face. It lacks normal growth in that instance. Are those 40 grain charged cases needing trimming after sizing? __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

April 27, 2013, 05:54 AM	#30
WESHOOT2 Senior Member Join Date: February 20, 1999 Location: home on the range; Vermont (Caspian country) Posts: 14,324	seen it during chrono-mapping I have observed similar signs testing handgun ammo. As the charge increased, there may be charge weights that show distinct pressure signs, but as one moves upward in charge weight those signs disappear, and the load 'acts' normally. Sometimes along the charge weighnt curve one will find lowered velocity with a charge increase, or a disproportinal increase in velocity. And as we move past, velocity becomes progressive in gain with its charge increase. What I think the OP saw was exactly that: An increase in charge weight gave proper results, once past that wackadoo charge. __________________ . "all my ammo is mostly retired factory ammo"

April 29, 2013, 10:08 AM	#33
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	Hodgdon's data is all by copper crusher, unfortunately. 39-42 grain load range is their recommendation. And old transducer data may not help, either, as the 1992 standard for conformal Piezo transducers just calls for a peak value detector, offering no way to view spiky behavior. You'd need someone with not only a transducer but specifically one with a more modern graphical output display to discern that, and I don't know who is using which instrument setups? Also note that the kind of event Brian showed will only appear on strain gage measurements, since the transducers are tied to and move with the barrel, and so can only spot pressure at the transducer, but not a transverse wave in the steel that echoes an event local to the bore further down, as those seem to be. Reynolds357, Can you report the case water capacity of one of your fired cases taken just before it needs FL resizing? That is, weigh the case with the fired primer still in it, fill it level to the mouth with water (no meniscus, no air bubbles, no water drops on the outside) and weigh it again. Report the weight of the empty, primed case and the weight filled with water. Preferably, use a case that is of average weight and length. Additionally, before filling with water, fill the same case level to the mouth with 760 from your lot and report that weight, too. (Then get all that powder back out before filling with water.) What I noticed in the Hodgdon data is the difference between the top and bottom load is less than the usual 10%. It's about 7%. It makes me wonder if that powder is sensitive to ignition conditions with less than some certain percent of case fill. One possible indicator for this would be to see whether a 40 grain load produces the same pressure signs in a full length resized case (or, better yet, in a new case) than it does in the neck-sized-only cases, in which the % case fill would be smaller. Despite conventional wisdom on the Winchester Ball powders, I would also try a mild primer if you can find one. A Tulammo KVB7, for example, or a Federal 210. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

April 26, 2013, 03:38 PM	#27
243winxb Senior Member Join Date: July 26, 2011 Location: USA Posts: 1,730	That would rule out the "coated bullets" if not like moly.

April 26, 2013, 08:51 PM	#28
reynolds357 Senior Member Join Date: December 10, 2012 Posts: 6,165	lubrilox might not be moly, but it definitely reduces pressure. I did extensive work with the lubrilox coated vs non coated bullet in my 7WSM. With same powder charge, coated bullet much slower.

April 27, 2013, 07:10 PM	#31
reynolds357 Senior Member Join Date: December 10, 2012 Posts: 6,165	unclenick, I am neck sizing with a Lee Collet die. I only shot the brass one time each piece with the 40 grain charge, but it did not need trimming. It actually got a slight bit shorter the first time it was fired and neck sized. I have shot the brass I am load developing with six times. After the sixth firing it had grown to the max length. I full length sized it, which put it well over the full size length and then trimmed it. I will probably start playing with the rifle again Monday. I am going to get the chronograph out and try to figure out what is going on with the rifle. Its favorite load is H 1000 compressed to the point the bullet gets pushed back out and being jammed so hard into the rifling that the bolt is very hard to close. That load is not practical, so I will keep looking for a reasonable load it likes. I guess I could try crimping, but I have never had any luck in the past crimping a Nosler ballistic tip.

April 28, 2013, 10:10 AM	#32
SL1 Senior Member Join Date: November 8, 2007 Posts: 2,001	It sounds like you are quite possibly getting "secondary explosion effect" with the 40 grain load. If so, then it might not be a vry consistent effect. ONE round might gie you much higher pressures in the future than you have seen in the past. So, I would urge caution. Working DOWN with the chronograph might be a better idea than working up, since you have already worked the load up and know that the higher charges are safe in your gun. Working down would allow you to spot the differences early on when you get to the 40 grain loads, so you can stop if things look really bad, before shooting enough loads to get a decent average. But, before shooting them at all, I suggest that you talk to the folks who produced the load data that you are using. If it is new data shot with a transducer, they should be able to give you some good advice. If it is old data shot with a crusher, that would be good to know. But, I seriously doubt that the pressure-testing folks would knowingly publish a load that looked "spikey" to them while testing. SL1

April 29, 2013, 08:32 PM	#34
reynolds357 Senior Member Join Date: December 10, 2012 Posts: 6,165	I will have to fire form some more brass because I full length sized it all. I will get you the water capacity of full length sized and fire formed. I am confident it will be a significant difference based on what I saw when loading compressed loads with H 1000 and based on how rediculously hard the brass was to full length size. I am sure Ruger has cut a chamber on the high side of SAAMI spec.