Ka-boooom and stumped

[alpine44]

After 20+ years of safe reloading I recently had a hair raising "event".

Loaded a 300 Whisper case formed from 5.56 Nato WCC brass, primed with CCI400, and charged with 14.4gr of H110 behind a 147gr FMJ mil surplus tracer seated to COL of 2.165". The AR15 DI action cycled OK but weakly, primer did not show any signs of pressure and the case was smoked about half way down. I concluded that more powder could not hurt and bumped the charge up to confirmed 15gr (the next cavity in the LEE powder measure) and got the results seen in the attached photos.
http://s557.photobucket.com/albums/ss13/alpine44m/300W_Kaboom/300W_KB1.jpg
http://s557.photobucket.com/albums/ss13/alpine44m/300W_Kaboom/300W_KB2.jpg
http://s557.photobucket.com/albums/ss13/alpine44m/300W_Kaboom/300W_KB3.jpg
http://s557.photobucket.com/albums/ss13/alpine44m/300W_Kaboom/300W_KB4.jpg
http://s557.photobucket.com/albums/ss13/alpine44m/300W_Kaboom/300W_KB5.jpg

Fortunately, I followed my habit of firing new loads with the the gun held away from face and body. The external damage was limited to the magazine being blown apart. I was able to open the action by carefully prying the bolt carrier backwards with a large screw driver resting against the upper receiver mag cut-out. There is no visible damage to the barrel extension and/or bolt other than the bent extractor. I will perform magnetic particle and dye-penetration testing on the bolt to see if any cracks have formed. For now, the bolt has been "quarantined".

http://s557.photobucket.com/albums/ss13/alpine44m/300W_Kaboom/300W_KB6.jpg
http://s557.photobucket.com/albums/ss13/alpine44m/300W_Kaboom/300W_KB7.jpg
http://s557.photobucket.com/albums/ss13/alpine44m/300W_Kaboom/300W_KB8.jpg

What happened here? Secondary Explosion?

I have worked up loads with 150gr FMJ to 17gr of H110 in the same cases and gun without ill effects. Granted, the bearing surface of the tracer bullet is larger, it will reduce the case volume due to its length, but that in itself should not cause one additional grain of powder more to have these devastating results.

We are not looking at a smoked or pierced primer here. This case has seen MAJOR overpressure befor it blew, judging by the severely expanded case head.

I have ruled out the following items to have caused the case blow out:

- Powder mix-up. I only keep one bottle on my bench at all times. (Have learned from dumping the powder hopper into the wrong bottle some 10 years ago).
- Double charge is impossible as the powder will overflow and the bullet will become impossible to seat.
- Obstructed barrel is ruled out as the previous bullet hit the target.
- Case neck diameter has been confirmed to be ok. Fired cases, including the blown one, will allow new bullet to be dropped in case.
- Bullet was confirmed to not sit against the lands. I wish I could get the mil bullets closer to the lands but in the barrel from Model 1 Sales you will run out of magazine space first.
- Soft case head. Unlikely, as this is once fired military brass that was not annealed after it left the factory. I have a hardness tester and could try to get a measurement on the mutilated case and on a comparable piece of another case from the same lot. However I am hesitant to destroy the "reloader's conversation starter". Also, if we look closely at the paper-thin and blown primer remnant we can point the finger at massive overpressure rather than weak case material.

[Alleycat]

I had an issue once where I dumped powder into a funnel and noticed something did not look right in the case. It had about 1.6 times the amount of powder that I had put in the funnel. The two cases before it had significantly less powder in them. The powder had gotten stuck in the funnel and finally dropped on that one case. I now check and see how many grains the loaded round is after it is loaded.

[alpine44]

Alleycat,

Powder bridging is a plausible explanation at this point. I was using a progressive loader and did not visually check (shame on me) the powder level in each and every case for small rifle ammo. I do this now, of course. Weighing the completed cartridge is a great idea.

I have to check how much H110 would fit into the case without the relatively long bullet bottoming out. When I seat bullets, I do not just yank the lever down but feel what is going on.

On a bright note. This event has given me more confidence in the safety of the AR platform, having "grown up" around Mauser K98 actions.

[HUNTER2]

Agree with Alleycat - have had it to happen on more than one occasion, but only with stick powder. It is amazing an ar could take that kind of pressure!

[Colohunter]

Lookin at the enlarged portion of the brass just above the case head looks to me like it could be an out of battery discharge. It seems like the brass has enlarged more than the chamber should have allowed. Just my .02.

[cav_scout_tj]

H110 is so fine, I'd doubt suck funnel. It sure looks like you got 14.5g and then 15g more. I forget how much 14.5 grains fills the case, I been using VV110 and Lil'gun for a while, staying away from 296/H110.

I think 23grains is about all you could stuff into a case even if you were trying.

H110 and W296 are the only powders which I have seen with the warnings:


For those loads listed where a starting load is not shown, start 10% below the suggested maximum load and then approach maximums carefully, watching for any sign of pressure (difficult extraction, cratered and flattened or blown primers, and unusual recoil). H110 and Winchester 296 loads should not be reduced more than 3%.

Reduce H110 and Winchester 296 loads 3% and work up from there. H110 and Winchester 296 if reduced too much will cause inconsistent ignition. In some cases it will lodge a bullet in the barrel, causing a hazardous situation (Barrel Obstruction). This may cause severe personal injury or death to users or bystanders. DO NOT REDUCE H110 LOADS BY MORE THAN 3%.

Those warnings are one of the reasons I am using LilGun most of the time, the other big reason is 110/296 are almost too fine, clog up my meter.

Hodgdon page with warnings (http://data.hodgdon.com/main_menu.asp)

[mstarling]

Looks to me very much like an out of battery discharge ... end of the case is expanded larger than the body of the case, and the bowout occurred in a place that would be unsupported if the case were not fully into the chamber.

In fact ... look at the rear section of the case ... you can see a line that is likely to be the end of the chamber and the chamfer on it!

Bad business this one!

You were very lucky to be sure.

Mike

[Rikky Lee]

I'm with Mike due to the case shape and damage to the extractor. It went off before it should have.....?

[Alleycat]

I don't know. It's not as ez to fire an AR out of battery as say an AK or SKS. The bolt has to rotate almost completely for the firing pin can protrude through the bolt. The primer is flat and has a deep indention. It is also in the case. I think the pressure was too high when the bolt unlocked. If it was not an AR I would be on board with the out of battery idea. A high primer may cause it to fire prematurely, but It should not have the pin dimple.

[alpine44]

The bolt was 100% closed when the charge ignited. I let the BC slam home, pointed the gun away from me, and pulled the trigger. Also, I spent about 30 minutes to get the bolt open after the ka-boom. It needed a lot of lube to enable the bolt to turn together with the case. The bolt could not turn relative to the case because of the severe extrusion of brass into the ejector hole and into the extractor gap. The extrusion of brass into the ejector is another indication that the bolt was closed.

I agree with the posters that doubt real bridging on such a fine powder. But, I use the Lee universal powder die that has two brass bushings inside. These could cause trouble. Powder could get between them.

Putting 15gr on top of 14gr is impossible. Not enough space in case.

[mstarling]

The loading range given by Sierra for a 150 gr bullet is 13.8-17.0 gr of H110/W296. If you really had 14.4 in the case you should not have seen the secondary explosion effect.

I'd still like to know how you explain the expanded head which shows the radius of the barrel mouth well away from the extraction groove in the case.

[Rikky Lee]

That head expansion is my concern too. Not sure how you can get that much expansion inside the chamber, Feel like sectioning the brass to see if there is anything on that side?

The only thing I have seen similar results from old brass annealed on a BBQ to red hot and then used. Not the best idea - resulted in severe brass flow and a chipped bolt head ... and a new chamber ... and stock fixing ...

[pomofo]

I second the idea that the bolt unlocked while pressure was still high. What position is your gas port in? I have a carbine-length system and I was getting blown primers and enlarged primer pockets from loads that Quickload was estimating at 38000PSI, well within the loading parameters. I suspected that the H110 was too fast for the gas system and causing the bolt to unlock too early. I switched to Acc. 1680 and have had no problems since. Your loads with M80 ball would be generating around 35000PSI, I don't know how long the tracers are but I would guess pressure probably at around 40-42000PSI.

[alpine44]

Thanks for all the ideas and suggestions so far.

Here is some more info:

The rifle has a carbine length gas tube.
The bolt was closed (lugs locked behind extension) after the event.
The BC was pushed slighly backwards but not enough to unlock the bolt.
There is actually enough space available between barrel and bolt for the "homemade Weatherby belt" due to the generous radius on the barrel end (see picture).

http://s557.photobucket.com/albums/ss13/alpine44m/300W_Kaboom/Chamber.jpg

Blown primer, belt on case head, and extrusion of case into ejector hole are clear signs of EXCESSIVE pressure (much more than "blue pill" proof loads).

Where did this pressure come from?

[cav_scout_tj]

Clearly too much pressure.

The usual suspects:
Too much powder-- maybe, powder is so fine, it could have flowed alittle around the measure? Try the measure, messing with it while throwing charges, weight what you get, see if you can get more weight. The case only holds so much, so double charge not possible.

Wrong type of powder-- would not be the first guy.

Bullet setback-- When hitting the feed ramp, the bullet can get pushed all the way into the case. Depends on case neck tension, brass and bullets.

Secondary Explosive effect-- not well known, but the H110 powder has ominous warnings attached to it. Temperature appears to be a factor, what was the outside temp, and temp of the rounds? Cold==bad.

Over on THR I found this (http://www.thehighroad.org/showthread.php?t=282078)

Slow single-base powders or heavily retarded double base ball powders need pressure, not just ignition heat, to burn well. They generally burn well in a full case with no air space (other than inter-powder space). In cold conditions, with weak primers, and/or low pressures (light loads) it is quite possible to get a "bad burn" (large percentage of propellant never ignites.) This manifests itself in erratic velocites, hangfires and so-called "bloopers".

Occasional detonations of light loads of slow powders was well debated in the 50's and 60's and is now an accepted fact of interior ballistics. They are easier to understand given the facts above, and the fact that most energetic materials have two burn rates, a deflagration rate and a detonation rate. Propellants are distinguished from explosives (by the knowledgable, anyway) as energetic material being consumed at its deflagration rate. Explosives are self-consuming at their detonation rate.

Most energetic materials can be consumed at either rate, given certain circumstances. Dynamite lit with a match will produce a blazing bonfire, but no explosion. Expose it to the concussion of a blasting cap and it will detonate. Light it with a match in an small, unvented closed chamber (called a "bomb") and it will transition from deflagration to detonation once the pressures get high enough (assuming it is not already completely consumed.)

Detonations of small charges of slow powder work the same way. They deflagrate (relatively) slowly. Often pressure waves move the powder around and pack it against the base of the bullet. Single base extruded grains often break and are crushed by the slowly rising pressure. Now propellant is burning front-to-back, where it was burning top-to-bottom and/or back-to-front.

Pressure waves then bounce back and forth along the case, sometimes meeting each other in opposing directions and producing peak pressures nearly twice the expected, given the volume of gas. This impact or concussion sometimes pushes the burn rate of the propellant into its detonation rate.

Modern reloading manuals warn against reducing loads of W296 and H110 in magnum pistol, and H4350/IRM4350 and slower in magnum rifle, for this reason.

[DonT]

I would agree with other posters. With the bulge all the way around the base of the cartridge one of two things my have happened... Please note that I am not questioning but just making an observation.

One the gun was not in battery when discharged. As one poster stated it is not easy to fire an AR out of battery but it can happen.

Second, the gun came out of battery before that pressure dropped significantly in the barrel (a timing issue). This "could" happen if too light a buffer was used or a lighter than normal buffer spring was used. Also hammer springs delay the bolt unlocking, if this is lighter than stock it could contribute to the problem... What happens is the lighter springs fail to delay the bolt movement until the pressure subsides to a safe level. The bolt starts to move prematurely and starts to extract the round before the pressure has adequately dropped in the barrel, as this happens a portion of the case is left unsupported while pressures are still near peak levels, the extractor is working the brass abnormally hard since the case has not fully retracted from the chamber walls so it is putting undo stress on the case, all this comes together in a catastophic case failure. When this happens it has all the signs of the bolt not being fully closed when the round was fired.

Since you seem pretty confident the gun was in battery when fired I would opt for door #2.

Glad you were not hurt and the gun did not suffer more severe damage.

Just one old guys take on the issue......

DonT

[mstarling]

I have heard of folks (but not seen it) having case head problems in rifles set up for subsonic ammo when they shoot supersonic ammo. Usually this involves a three position gas block left set at the wrong port size.

(I have shot some ammunition built with 14.5 and 15.5 gr of W296 (supposedly the same as H110), 147 gr FMJBT projectiles using LC 97 brass as a start. Was fireforming cases with the gas port CLOSED). My barrel is a 16.5" tp555 Douglas SS unit.

No problem with 14.5 gr. 15.5 gr was getting a "little" warm and required that the brass be very gently tapped out with a rod.

If you are ABSOLUTELY certain (that is you actually checked and clearly remember doing it) that the bolt was fully closed before the trigger was pullet, I wonder is your gas port is just too big for use with this load ... and the pressure started opening the chamber before the bullet left the barrel.

[alpine44]

The most important thing to keep in mind is that the bolt was closed after the event.

The BC was pushed back to the point where the cam pin would start rotating the bolt, but the bolt could not rotate because of the brass wedged between barrel and bolt. The bulge (belt) on the case will fit between the barrel and the bolt due to the chamfer radius at the breach end of the barrel.

Also, an out of battery discharge will not force brass into the ejector hole the way this event did.

All signs point to the fact that the powder charge developed A WHOLE LOT more pressure than desired. The question is: Why?

I agree with the assumptions that the powder measure is a suspect. It could have trown less powder (some got stuck in the funnel) or more (powder that got stuck on the previous shell came loose).

My gut feeling is that filling the case until the long tracer bullet bottoms out would not yield these drastic results. I may verify this in 2 weeks with the tree and string method.

I lean towards explaining the dramatic results with a low charge and a subsequent detonation or Secondary Explosion Effect. An indication of a SSE may be the smoking of the front to the cartridge seen in pic#4. A simply overcharged cartridge would have sealed well at the neck and would not show any smoking.

The outside temp was 54 degrees F and the cartridge was probably around 60 deg F.

[HUNTER2]

Sometimes it is small things that make us remember what we are dealing with. I'll bet there has been more than one to double check their loads after reading this. Sounds like you are on the right track. Thanks for sharing....

[alpine44]

There are a lot of dumb things we all have done that are not worth sharing.

This however was one of those "gotchas" that simply leave you scratching your head. When I started loading the .300 Whisper/Fireball I thought that it can be relatively safely loaded in a progressive press whithout checking each case individually.

I also have been using W296/H110 extensively in my S&W629 .44Magnum with excellent results and through that I am well aware of the low charge issue with these powders.

I guess we all have to make sure, by checking each charge, that we do not unintentionally enter the danger zone with these powders. Using magnum primers (e.g. CCI450) and a factory crimp would probably not hurt either to guard against ill effects with low charges.

In about 2 week I will be back home with my toys and will report how much H110 could fit in a case behind a properly seated M25 tracer, without this overcharge becoming noticeable during bullet seating. If the amount is not too outrageous I may prove, using tree and string, that an overcharge may blow a primer but not cause the brass mutilation seen in the photos. This would be the proof of my assumption that the event discussed in this thread was caused by an unintended undercharge.

If a whole lot more than 15-16gr of H110 will fit in the case without becoming noticeable, then we are unfortunately left with flipping a coin to decide whether overcharge or undercharge caused the Ka-boom.

[Mike-Sid]

My first guess would be out of battery detonation, but you rule that out. My only other guess would be excessive...real excessive head spacing.

How does this sound?

[DonT]

If it is not too much trouble can you measure the distance from the base to the sharp angle of the cartridge where the neck meets the body of shell and then measure this on one of your loaded unfired rounds (one that has not been fire formed) and then one that has been fired at least once in the rifle.

It would be interesting to see if the distance changed in any of the cartridges.

Also I pulled the bolt out of my AR to look at the chamber area and mine appears to have a slight angle to guide the nose of the bullet into the chamber with a very small radius where this breaks into the chamber. As near as I can tell everything in front of the extractor groove on the round is support by chamber, it is hard to see as I don't want to pull my barrel. maybe if someone has a barrel that is not installed they can try it with a factory round. In the photo of your chamber, and maybe it is just the photo, your chamber appears to have quite a substantial radius. If this is the case is it leaving the portion of the cartridge right ahead of the extractor groove unsupported??? Just curious.

Thanks,
DonT

[alpine44]

Yes, the "entrance" radius on my barrel is quite generous. But that turned out to be a good thing as it allowed the case to blow through the extractor cut-out and vent the pressure. Otherwise, the bolt would have failed. Keep in mind that the pressure was WAY over the design limit as indicated by the massive flow of brass.

I have added one picture to show how the barrel geometry will allow the bulged case head to fit between the barrel and a closed bolt.

http://s557.photobucket.com/albums/ss13/alpine44m/300W_Kaboom/300W_KB9.jpg

Around Christmas, I will post more photos with actual case dimensions compared to a unfired and a "normally" fired case from the same gun.

Thanks to all for the input and suggestions.

[mstarling]

WOW ... I find that much unsupported case to be unsatisfying to say the least.

How did you measure the charge put into the cases? Lee dippers?

If so, have you measured the actual weights of say 10 to 20 charges using the same dipper? Would be very interested in knowing what kinds of charge weights you were actually getting (extremes and average).

As I said before I have used weighted 15.5 gr charges of W296 behind 147 gr FMJBTs ... and they were stiff in my 16.5" bbl. I backed down some for fireforming with the gas port closed.

[amafrank]

A couple possiblities not mentioned.....
the tracer bullet is much much longer than the standard ball bullet of the same weight. That creates much more drag and would indeed raise the pressure. If you had a little extra powder it probably wouldn't create much trouble with a normal bullet but a little extra and the long tracer might just do the trick. Another possibility is that H110 is too fast for that bullet and the combo of fast and hot could be just enough to create the blowout. I agree with some of the others that the chamfer/radius is more than generous and is in fact excessive. There is a lot of unsupported case that could contribute to a blowout. I do agree with your position that this is not the problem in the current case in question. There is a lot of excess with the primer and case head in that condition. The ejector formed a nice dimple as well with the case head flowing into the bolt face. I've seen some of this when using powders that are too fast even though the charge weight should be ok. 2400 seems to go that way with just a .1gr increase past what was working ok. I haven't blown any out to the extent you've shown but I have had some definite pressure signs with flowed case heads and primers. Another thing I've noted is that what works good in the bolt gun may blow the semi. I keep brass fired in the SIG separate from anything fired in a bolt gun due to differences in the case support which change how much stretching there is. Probably no simple answer to your case so use caution when using tracers or other large light bullets.


Frank

[Expatriot]

One thing nobody has mentioned is the possibilty of the neck being too long (case OAL too long) which would cause the bullet to be pinched into the neck when chambered. That would def cause an overpressure condition.

What are the chances that round had a magnum primer rather than a normal primer? That could also cause an overpressure condition.

Excess headspace does not cause excess pressure but it can cause the case to rupture. This issue was clearly caused by a massive overpressure.

[amafrank]

Expat is correct that a long case neck could create a pressure problem though it appears that the overpressure is pretty extreme and excess powder is still the most likely culprit.

One other suggestion is that you reduce your picture sizes. When you post the huge pics the screen can't contain it all and the posting has to be scrolled back and forth on a lot of our computers. If you crop them down to size that will help and not reduce the clarity.

Frank

[travelingman]

No more pics?

[miker557]

When I saw your pictures and read your description, I was reminded of something that happened to me. Many years ago I bought a Plainfield Enforcer M-1 Carbine Pistol. I shot a lot of ammo through it, but would frequently have problems with cases bulging at the base. I even had a few rupture, as yours did, at the base (and even blow out the bottom of the magazine, dumping spring and rounds all over my feet). I originally thought I had gotten some bad ammo, but after using different brands and having the same thing happen, I realized it was the gun. I invested in tooling to check my suspicions, and when I got it, they were confirmed.

It had excessive headspace.

I put a new barrel on the pistol, confirmed proper headspace, and it shot fine after that.

So, here's the $64,000 question - have you checked the headspace of your chamber? I have read that chamber dimensions vary slightly between JDJ's Whisper and the 30-221 that others make. Fortunately, I believe headspace gauges should be easy to find - I think that 221 Fireball gauges work for the 300 as well.

Give it a try. If nothing else, you'll eliminate that as a possible source of your problems.


Miker

[A62Rambler]

I think we have several factors working together. One we have a bullet with more bearing surface. Two we have clear indications of excessive pressure. Since the AR gas system works by gas pushing the carrier back and pushing the bolt forward and since the carrier was found to be partially back, I think we can conclude that there was still too high pressure when the gas began the process.

I think you should check the following: Were you using brass that had previously been fired with other loadings in this chamber? When you resized these cases did you check the case length?

The reason I ask is that if these cases had stretched or were too long plus the bullet with a greater bearing surface with even a slightly high powder charge you could have this result. I would take a close look at the bolt lugs to see if they show any damage. Pressure of powders when graphed is not a single line growing at a constant rate. At some point they jump at a much sharper incline. With the three factors above (long case, longer bullet, slightly higher charge) you could have hit the point in the pressure curve where you jump greatly in pressure for a small increase.

I hope that makes sense.

[Jerryr98]

I too had similar issues with H110 in my Remington 700 300/221. Not to the extremes seen here but I sure did get an eye opener and after 25 years of handloading....I am lost. I followed Sierra's loading data of 10.7grs of H110 behind a 200gr SMK. This is a low end starting load. Had 50 rounds loaded. Had fired forty of them over the course of a week and then BOOM. Why have the others worked out so good and then the mishap? I weigh each load to the 1/10 of one grain. Did I screw up and over/under charge a case? No, I pulled the bullets on the remaing rounds and weighed each charge only to find that each charge was exactly 10.7grs of H110. Was temp an issue? Don't think that was an issues as daily temps were 65 to 70 degrees. What gives? If this is symptoms of SEE then I will not use this powder again for I intend on a lower charge in an attempt to get in the 1000 -1050fops range for subsonic use. I also have AA # 9, AA1680, AA 2015 and VV N110 to play with also. The H110 has me gun shy to say the least.

Jerryr98

[alpine44]

Hi Jerryr98, I am glad to see your post. I thought I was loosing it on the reloading bench.

I would not worry with a Remington 700. That action was designed for much (!) higher loads. The AR15 'mouse gun' is a different story.

For 300/221 supersonics I switched to WC297 surplus powder that is supposed to be slower that H110/W296. My initial results were slightly more speed, better cycling, and more consistency. I am going to clock a larger batch soon and will post the results.

For subsonic loads, faster powders (like 2400) would be better.

[HUNTER2]

Have been using H-110 in the 300-221 in bolt and single shot rifles for a few years now. Never had a problem with any loads. Have came close to short charging a couple of times - that could be a problem.

[Scalce]

H110 may be the cause but couldn't it also be a cooincidence since it is such a common powder used in 300 Whisper-300/221 and you are more likely to have a major issue like a blowout due to a slight reloading error or variation that may not be the case like in a standard SAAMI load?

I mean this is a Wildcat, using heavy bullets, fast powder, and chambers which can differ based on alot of factors.

I am not saying the reloaders who have had kabooms are not experienced or that it is even their fault, as it may be the powder, but everyone makes mistakes and it seems like this catridge has some challenges.

I'm sorry but weighing the charges in the cases that you have left over does not prove anything about the charge that was in the catridge that blew up.

[FrankL]

I know this is an old thread, but I am new to the forum, and I am trying to catch up on some reading and learn a lot. I did not see any reference to the brass thickness at the neck. I don't know the history of the brass, but would it be possible to have excessive thickness cause a very tight release of the bullet, resulting in excessive pressure?

Thanks for the consideration.

Frank

[Tokarev]

Hi Jerryr98, I am glad to see your post. I thought I was loosing it on the reloading bench.

I would not worry with a Remington 700. That action was designed for much (!) higher loads. The AR15 'mouse gun' is a different story.

For 300/221 supersonics I switched to WC297 surplus powder that is supposed to be slower that H110/W296. My initial results were slightly more speed, better cycling, and more consistency. I am going to clock a larger batch soon and will post the results.

For subsonic loads, faster powders (like 2400) would be better.


Can you share some supersonic WC297 data, please?