The World of Cartridges and Compromises........

[Boomer]

maybe there was some H4350/H100V stuck in your powder dispenser

I think I'd have noticed some other powder stuck to the Lee spoon. When I load a small number of rounds, such as when working up loads, I weigh each load on my balance beam scale, so there was no chance of contaminated powder. When working up loads, I check the capacity of each case to ensure uniformity, and my working load is never maximum, but reduced enough to account for variations in the uniformity of brass, bullet weight, and primer brisance. When I load a large number of rounds, I check the charge weight from my dispenser, digital for extruded, and thrower for ball, against my balance beam scale, that is zeroed to the exact charge weight with check weights. I don't leave much to chance; I've been in this game for a while.

 

[Boomer]

Well Mike, something very unusual happened, for sure. I know your point, we have talked about it before, but I just can't get my head wrapped around the compressed plug theory.
The major reason for me being skeptical, is the fact that millions of very similar conditions have regularly been loaded. That is, very high compression of slow burning powder in a great many different calibres and arrays of bullet weights. So, if that was the cause there would be Kabooms all over the place.
Jack O'Connor's load of 60 grains of war surplus 4831 powder in a 270, with a 130 grain bullet was typical. 60 grains filled the case right to the top. I used to tap the side of the case to lower the powder level a bit, so there was a tiny bit of room to start the bullet and the 130 grain Norma semi boat tail that I commonly used, is a pretty long bullet. When the bullet got seated full in, you held the press handle for a bit and eased it off, to see if the bullet was going to come out a bit, when the pressure was released.
Jack even wrote that 62 grains made a better load than 60, if you could figure out how to get all the powder in!
I used to force a flat base 100 grain bullet into an over flowing case of H4831 in a 243 case. That's a pretty heavy bullet in 243.
And still no Kabooms.
Could the problem have been Retumbo powder, as has been suggested?

Perhaps I got a pound of Retumbo that came from a lot that was on the fast side of the spec. But even if that was the case, it doesn't account for the difference between the 2350 fps load that showed normal pressure, and a Kaboom from a single grain increment, and a velocity increase of 200 fps. As Ackley stated with respect to problems associated with light loads of slow burning powder in large bottleneck cases, the phenomenon is difficult to replicate, even in a controlled environment. In fact for years he didn't believe it, and thought something else was responsible for the Kabooms; eventually he came around.

Clearly something happened here, and while I can only guess as the cause, it had nothing to do with either my components, (other than perhaps my choice of powder) or with my loading technique. The one element that stands out is the weight of my bullet; a .375/380 equates to a .243/160! I wonder how many calibers long that one would be??!!

 

[Boomer]

All Retumbo loads from Hodgdon.com :

243 Win 105 Amax, 49.0grs -- 109% load density

25-06 120gr Swift A-Frame, 60.0grs -- 109%

270WSM 140gr Swift AF, 71.0grs --106%

7mm SAUM 175gr Interlock,66.0grs -- 109%

7mm Rem Mag 150gr TTSX, 73.5grs -- 107%

300 Win Mag 208gr Amax, 81.0grs -- 110%

300 Win Mag 230gr Berger , 77,0grs -- 107%

338 RUM 300gr SMK, 90.5grs -- 107%

338 Lapua, 210gr Partition, 102grs -- 111%

338 Lapua, 300gr SMK, 94.0grs -- 112%

dozens of more examples on their list of pressure tested data -- http://www.hodgdonreloading.com/data/rifle

It seems to me that at the time I determined that my load density was 112%. Yes I know there are many published compressed loads, for many different propellants, but lets look at the 300 gr .338 Lapua load you refer to since that approximates the same degree of compression in an even larger capacity cartridge. The .375/380 equates to a .338/309, and while a 3% difference in bullet weight between 300 and 309 grs doesn't sound like very much, it remains a measurable difference.

 

[Dogleg]

Heavily compressed loads spook me. They never used to, but a couple of bad experiences with 7828 lead to an abrupt about face on that. In both instances the ammo was stored over the winter and fired in spring temperatures that wouldn't have been much different than the fall temps they had last been shot in. Losd was above max in one trustworthy source and below in another.

Things happen, and that they never happened to one individual or happen very rarely doesn't change that. For instance I've never been bitten by a shark or hit by lightening either.

 

[hoytcanon]

Heavily compressed loads spook me. They never used to, but a couple of bad experiences with 7828 lead to an abrupt about face on that. In both instances the ammo was stored over the winter and fired in spring temperatures that wouldn't have been much different than the fall temps they had last been shot in. Losd was above max in one trustworthy source and below in another.

Things happen, and that they never happened to one individual or happen very rarely doesn't change that. For instance I've never been bitten by a shark or hit by lightening either.

I am not a fan of "heavily" compressed loads either, but quite a few of my more accurate loads in various calibers are "snug."

 

[MiG25]

I've never been a fan of apply much compression, if I want more powder in the case, I'll get a bigger case. I'm not saying I know what happened, but look at newspaper, crumple it up and it burns quickly, compress it into a bale and it doesn't really burn at all. Or when you walk in the snow, the compression in your footprint isn't even all the way down to the ground, a crust is formed.

So what happens to the pressure if the top of the powder column is harder to ignite due to being compressed? Say the top 20 grains, would this not be a 400 grain projectile, powered by XX grains of powder in effectively a smaller case?

What happens to compressed powder over time? Do the grains deform into a mass?

 

[kamlooky]

Curious to know if humidity had an effect on Boomer's kah-boom?
Meaning, humid powder packing more than it would normally?

 

[Dogleg]

What happens to compressed powder over time? Do the grains deform into a mass?

Some of it does.Its not like they store some for 10 years before they print the manual either.

African game departments tended to buy .458 Win Mag in volume and only use it as needed. Its a safe bet that .458 factory loads are compressed, and much of it didnt take to long term storage well. Squibs and bullets pushing back out were the most common failures, but I would imagine there is a big difference between a hardened mass in a straight case and the same thing in a bottle-neck.

 

[todbartell]

Some of it does.Its not like they store some for 10 years before they print the manual either.

African game departments tended to buy .458 Win Mag in volume and only use it as needed. Its a safe bet that .458 factory loads are compressed, and much of it didnt take to long term storage well. Squibs and bullets pushing back out were the most common failures, but I would imagine there is a big difference between a hardened mass in a straight case and the same thing in a bottle-neck.

I wonder if powder quality has improved since the 1950's?

 

[Dogleg]

I wonder if powder quality has improved since the 1950's?

Likely, but the way to tell would be to store a huge pile of compressed ammo for decades and see the results. By the time you know the answer the information isn't worth much.

 

[Gatehouse]

I'm starting to wonder if the bullet didn't get pushed in too deep one way or another, or if there wasn't something stuck in the bore somehow. I'm having a hard time wrapping my head around the powder charge being the culprit when it goes from no pressure signs to kaboom with one extra grain, especially in a large volume case.

 

[Boomer]

I'm starting to wonder if the bullet didn't get pushed in too deep one way or another, or if there wasn't something stuck in the bore somehow. I'm having a hard time wrapping my head around the powder charge being the culprit when it goes from no pressure signs to kaboom with one extra grain, especially in a large volume case.

The brass was all to spec, each bullet was crimped, and there was only enough time between shots to look at the chronograph display, so I think we can rule out those kinds of problems.

 

[MiG25]

The photos I see online for the Rhino bullet show a solid shank bullet without relief grooves similar to the original Barnes X.

 

[BCBRAD]

Quickload (QL) and an accurate chronograph are two items for successful load development.

I only purchased QL when I received my LabRadar (claimed accuracy to 0.1%), the two are inseparable for producing consistent accurate handloads.

QL is a program that requires a lot of background knowledge in physics and thermodynamics to get the most out of it. Fear is replaced by knowledge in this case. (refer post #87).

As with any computer program, accurate inputs yield accurate outputs.....then you must have the ability to understand the information produced.

So, in a few easy steps and in depth knowledge of the program and the subject, here is how I develop a load.

Assemble the various components to be tested, case, powder, primer, and bullet.

Decide if bullet will be jumped or jammed and by how much.

Assemble a dummy round.

Measure , weigh, calculate free-bore in grains of water all components with accurate measuring tools, scales and methodology.
Input values to the program, with a mid range powder charge.

Shoot 5 rounds across the LabRadar.

See if the average velocity is vs. what QL predicted.

Say the load is 30 ft/sec faster than predicted.

There are some things you can do within the program to get it spot on, adjust burn rate of the powder, bullet weight and the weighting factor these are suggested in the program. What I do is adjust the case volume in water, it is the most difficult weigh accurately and doesn't mess with the generic defaults.

Now I am ready to manipulate the program to my purposes as I have the base line covered. And , there are things in there that I will leave you to discover.

A few weeks ago I went to a 1000 yard shooting match, there are several categories as this is a fun club event.

Unlimited, 10 rounds, anything goes
Heavy barrel 5 rounds, limited to 17 Lbs
Sporting rifles 5 rounds, max 0.750" at the muzzle
Hunting rifles 3 rounds, max 0.750" at the muzzle and scope limited to 9X

All my loads, I used three rifles , were developed as described. They had good ES, mid range optics, and Tikka actions, in 300 WM and 6 Dasher and I used a Sako M-85 in 30-06 for sporter and hunter.

The 30-06 with a fixed 6X scope produced a best group of 7 5/8ths", the Dasher was in the 9's". The 300WM was 18" for 10 shots (this is an off the shelf Tikka Tactical.

It was not the loads that kept me out of the prizes this year, but rather not been able to read changing conditions and ...well I suck at shooting.

The theory works in practice, 7 5/8ths" group at 1040 yards with a stock Sako in 30-06 with a 6X scope and a 'computer 'load.

There was another guy who posts here that had similar results using the same methodology, maybe he will chime in.

 

[BCBRAD]

The brass was all to spec, each bullet was crimped, and there was only enough time between shots to look at the chronograph display, so I think we can rule out those kinds of problems.

Send the rifle to a metallurgist to see if it was fatigue cracking or a one time event, time to stop guessing.

 

[Boomer]

Send the rifle to a metallurgist to see if it was fatigue cracking or a one time event, time to stop guessing.

I sent the bolt to a very knowledgeable gunsmith I trust, and he said it had been exposed to an extremely high pressure event, as one might expect when velocity jumps 200 fps instead of 20-40. He said the locking lugs had deformed, and that "the action is toast."

With respect to Quickload, if staying within the normal range of bullet weights and within the usual powder burn rate for a particular cartridge, its a useful tool, just like a loading manual is. By the way, I've caught enough errors in loading manuals that I don't have blind faith in them either, and I'm tempted to believe that those errors come from computer generated predictions rather than from data collected from pressure barrels. There is no way pressure barrel data could have led to some of that published data. When I use published load data today, it has to be corroborated in another source before I accept it at face value. If you're an experienced handloader, and you are working outside the normal parameters for a given cartridge, you are far better off relying on your experience than you are on a computer program that lacks the ability to consider the nuances in the relationship between heavy bullets, extremely slow burning powder, compressed loads, and case volume. The answer to my problem lives in there somewhere. You don't really need a computer program to work up a .308 load of 4895 under a 150; that data can be found in every loading manual that's been printed since the late 1950s, and is easily corroborated. I purchased Quickload to help me work up loads with combinations of components that are not easily found in published material. Live 'n learn.

 

[BCBRAD]

^^^ Do you manipulate the parameters in the program to coincide with the velocity you are getting?

Are you using an 'optical' chronograph?

Do you charge a case then seat the bullet or do you charge all the cases then seat the bullets?

Do you pay attention to bullet seating pressure?

Is your extreme spread low for the combination of components your using?

Has the piece of brass that was used first time or loaded at least once before?

Has the rifle in question been in your possession since new?

Did or were you distracted while reloading the cartridges?


Basically take a long hard look in the mirror as you consider these questions.

From the information you have provided, you must consider the cause for a one time pressure event. This can include an extremely heavy piece of brass (small volume compared to others in the batch), a bullet that is extremely heavy in comparison, bullet of slightly larger caliber (eg: a 358 bore with a 366 bullet), misread scale or one that was 'hung up'. Running the risk of faster burning powders that do not have adequate case fill ( less grief 'no secondary uncontrolled explosion' and better performance with powders that fill case from ~95% to 100+%).

Again , a metallurgist can tell you if the metal is sub-standard to the application, has seen repeated high pressure and if underlying fatigue was a factor in seemingly a one time event.

The QL program is quite safe , especially if you leave the human element out.

 

[Boomer]

^^^ Do you manipulate the parameters in the program to coincide with the velocity you are getting? I checked the program's prediction against my known loads

Are you using an 'optical' chronograph? Ohler 35P

Do you charge a case then seat the bullet or do you charge all the cases then seat the bullets? I seat the bullet as I charge each case

Do you pay attention to bullet seating pressure? yes

Is your extreme spread low for the combination of components your using? within 15 fps

Has the piece of brass that was used first time or loaded at least once before? second loading

Has the rifle in question been in your possession since new? yes

Did or were you distracted while reloading the cartridges? no, when distracted the process stops, and isn't resumed until I can give it my full attention.

Basically take a long hard look in the mirror as you consider these questions.

From the information you have provided, you must consider the cause for a one time pressure event. This can include an extremely heavy piece of brass (small volume compared to others in the batch), a bullet that is extremely heavy in comparison, bullet of slightly larger caliber (eg: a 358 bore with a 366 bullet), misread scale or one that was 'hung up'. Running the risk of faster burning powders that do not have adequate case fill ( less grief 'no secondary uncontrolled explosion' and better performance with powders that fill case from ~95% to 100+%).

Again , a metallurgist can tell you if the metal is sub-standard to the application, has seen repeated high pressure and if underlying fatigue was a factor in seemingly a one time event.

The QL program is quite safe , especially if you leave the human element out.

Additionally I never rush the loading process. I zero my scale to the charge weight with check weights, and the charge weight must weigh correctly twice consecutively. When I use a digital scale I check the charges against a balance beam scale zeroed to the exact charge weight. When there is a discrepancy I go with the balance beam scale once its provided two equal consecutive reading. Cases were trimmed to a uniform length on a Giraud case trimmer. I have an individual cutter for each caliber size. Primer pockets and flash holes are uniformed with a Sinclair tool. Cases are lightly lubed with Imperial Sizing Wax, then wiped dry, and case necks are dipped into Imperial Dry Neck Lube. Primers were seated with a bench mounted tool. Sizing and seating dies are set up for minimum run-out, and the lock rings are snugged with a wrench to ensure nothing moves throughout the loading process once the dies are set up. I use a rubber O ring to secure the shell holder so it can float and find its own center, rather than the retaining spring that can hold the shell holder canted or misaligned. Bullet crimping is done as a separate step from seating, and the crimping is accomplished through turning in the die with finger pressure to refusal, with the ram already at the top of its stroke. When working up loads I take pains to ensure that the brass and bullets are equal in volume and weight, and once the maximum load is determined, my working load is reduced from maximum to allow for variations is case volume and bullet weight.

I agree that QL is safe without the human element. Humans should use loading manuals, adhere to rules of thumb, and pay heed to Always and Nevers.

 

[BCBRAD]

What do you think happened?

 

[Boomer]

What do you think happened?

I think the compression of the powder in the neck and shoulder area, changed the structure of that powder from loose extruded granules to a compressed solid mass. I believe this change of structure resulted in a change to the burn rate of the powder within that solid mass, and perhaps the high degree of compression, combined with the pressure of the expanding propellant gases, exceeded the powder's critical density, making it inert, a phenomenon that occurs in some high explosives. Either way, this solid mass of powder formed a plug in the shoulder/neck area of the cartridge, for the fraction of a millisecond that was required for the pressure to build beyond the strength of the rifle. I believe this is the process that occurred, and is the only explanation I'm left with after discounting the other possibilities. If someone wants to say that it was a million to one chance, and couldn't be repeated, then clearly I should have bought lottery tickets that day instead of going shooting, but its not an experiment I wish to repeat.