2400 Implicated in Rifle Blow-up

[303Guy]

Yup, another blow-up report with 2400 in a rifle, this time a K31.



This is not the only K31 but the other one doesn't say what powder was involved. That brass wash indicates pretty high pressure. One wonders how a normal cast boolit load can produce such extreme pressure? If the powder were to truly detonate then maybe. More realistically, a double charge would raise the pressure appreciably, especially if the load is already getting up there to start with.

Anyway, we should all take note and watch our reloading practices!

Interesting how a K31 fails. Apparently they blow the top off the action just like this one, thus preventing injury to the shooter.

[swheeler]

Yup, another blow-up report with 2400 in a rifle, this time a K31.



This is not the only K31 but the other one doesn't say what powder was involved. That brass wash indicates pretty high pressure. One wonders how a normal cast boolit load can produce such extreme pressure? If the powder were to truly detonate then maybe. More realistically, a double charge would raise the pressure appreciably, especially if the load is already getting up there to start with.

Anyway, we should all take note and watch our reloading practices!

Interesting how a K31 fails. Apparently they blow the top off the action just like this one, thus preventing injury to the shooter.

I sure wouldn't want that going off infront of my face!

[1johnlb]

Good to know the lugs are good and strong, even after the receiver failed. 2400 has been my favorite in the Swiss. Might be a good sign to start looking for something a little slower.

[ThaDave]

that could have been a double charged case or even an internal flaw in the steel that over the years got worse and worse as the round count grew until KABOOM. I'm still pretty new at this reloading stuff but I would think that the best thing would be to pull all the left over rounds and measure the powder charge one at a time.

Hope no one got hurt

[1johnlb]

Obviously they have a weak spot in the receiver. In this thread on swiss rifle forums the op is complaining about a loose barrel on a rifle he just purchased from CFA. The rifle in the picture was another rifle posted by a member there showing the op where to look. He returned the gun. Stated by the SRF member that this rifle was probably used as a seat across the train bench seats. It's hard to tell from 303guy's post but if you look closely all the broken area around the receiver looks to be a clean break except that which is broke on the receiver below and it's black and gold from the powder and brass in that area. Possibly meaning that it had the same crack in the same area before the blow up. The bolt also has a chunk missing out of it and these are also known for stress cracks around the lug area. It also looks like the bolts serial number is electropenciled meaning that this unit fell in that 1944 range of rifles that had problems with the bolt and pull handle. Just to show and make the point to be sure to know your firearm and to regularly inspect it.

[Larry Gibson]

Would be interesting to know what the charge of 2400 was supposed to be, if a filler was used, what the bullet design is, the weight of the bullet, the sizing and alloy. Also how many rounds had been fired just prior to the blow up. To much left to conjecture otherwise.

Larry Gibson

[Geppetto]

Man I wish I could get my hands on that fracture surface to throw into the SEM (scanning electron microscope), just for kicks and giggles. Visually I doubt that there is any "flaw" or as I would term in a "prior discontinuity" that contributed to the failure. Looks pretty single cycle overload to me. (I'm a failure analysis metallurgist by trade, look at broken things all day and figure out why).

[Char-Gar]

Whatever caused that rifle to fail, it WAS NOT an appropriate charge of 2400 powder! That much is certain.

[Ricochet]

Looks like the case head failed first and dumped out lots of high pressure gas that the receiver ring couldn't contain. The lugs held and the barrel's intact. Hot gas torching out through the brass caused that brass wash. It is encouraging that no large parts came back toward the shooter, but as has already been said I'd hate to have that happen right in front of my face.

[JeffinNZ]

Waste of a damned fine rifle one which I would love to own.

[3006guns]

I'd like to see a LOT more information before blaming the load itself as it could have been a number of things. How many loadings did that particular case have? Was it 7.5 Swiss brass or formed from another "parent" case and, if so, how many firings had THAT case endured? Were the cases ever checked for incipient separation? Once those questions are answered, I'd look at other reasons.

Obviously, I'm looking at a case head failure which would let gas into the receiver where it has all sorts of surface area to push against. Even a "normal" charge of 2400 could wreck a rifle under those circumstances.

[rollmyown]

I'd hazard a guess and say the vast majority of blow ups we see talked about are reloader error or in the case of antiques (read pre 1900's with soft steel or cast iron construction) using loads with pressures they were never intended for.

[Gtek]

What about maybe no 2400 in the round right before the one with correct amount of 2400?

[Old Coot]

I'd hazard a guess and say the vast majority of blow ups we see talked about are reloader error or in the case of antiques (read pre 1900's with soft steel or cast iron construction) using loads with pressures they were never intended for.

Sir; I agree with you completely. Brodie

[Outpost75]

Would be interesting to know what the charge of 2400 was supposed to be, if a filler was used, what the bullet design is, the weight of the bullet, the sizing and alloy. Also how many rounds had been fired just prior to the blow up. To much left to conjecture otherwise. Larry Gibson

FWIW, I once double-charged a Remington 03A3 .30-'06 Springfield with 32 grains of Alliant #2400 and a 160-grain cast bullet. While the primer pocket of the TW54 case expanded dropped the primer, I felt no gas in my face, and was only alerted to anything wrong by the additional recoil and flier on my record match target and a thoroughly leaded barrel! The bolt lifted hard and required assistance from a lead dead-blow hammer to open the bolt, but upon inspection headspace still aged OK normal and the rifle was undamaged. I still have and shoot the rifle.

IMPORTANT SAFETY TIP: I do not reload at the range anymore where people might try to carry on a conversation and interrupt your attention@!

[ReloaderEd]

Looks like a preexisting crack to me. Awfully thin metal around the barrel thread. If I owned a K31 I would magnifux it asap. It is good to be aware of the problem! Be safe!

[BruceB]

It was many years ago, but I remember like it was yesterday.

In a "stacking of my personal tolerances", I managed to load FIFTY-NINE grains of 2400 under a 200-grain Partition for my M700 .30'06.

The "how" makes a rather involved story; suffice it to say that my normal loading routine caught the error before I finished the loading session.

That particular "load" was better named "grenade". I usually remember it every time I sit down to the bench..... after almost thirty years!

[geargnasher]

I mis-set my beam scale by ten grains once and used it to set my measure. After throwing 20 charges in the cases in the tray, the flashlight test caught my attention. Gee, never seen Unique come up that high in an '06 case before, hmmm. Now I double-check the measure after setting by throwing a charge and checking it on a digital scale. It's good to get both analog and digital input to the central computer, as decoding requires two different thought processes and if one of them is fatigued the other will likely catch the error.

Gear

[303Guy]

What about maybe no 2400 in the round right before the one with correct amount of 2400?

That thought crossed my mind too (I have first hand experience with that one). Would a double charge be any different to a double boolit? Ok, a double boolit could also involve less case capacity if the second boolit got pushed back into the case. But then the first boolit could be driven just far enough forward to accept the second round. But under the circumstances the shooter might notice a shot not 'going off' (one would hope).

The examining gunsmith did say there appeared to have been a pre-existing crack, possibly like the crack shown by 1johnlb? That action appears to be well sealed which would put extreme forces on the action around a ruptured case head. Why would there be no vents? Was it the C Mauser action that would blow up if a case head ruptured due to the sealing effect of the blown out brass, allowing the pressure to act on a large area?

What scares me is the fact that a double charge is so easy to do and I am kinda fond of using H4227 in my Brit. And a Brit doesn't blow off the action top, it buckles the bolt rearward and can allow bits to fly into the shooters face! If only the powder manufacturers would make a bulky powder in the 2400/4227 range.

[ReloaderEd]

There are so many ways to mess up when reloading. Especially when one gets older and do a lot of things automatically.
When loading rifle cartriges I have always used a loading block and when all the cases are powdered, I put the block under a good light and can spot any cases that are empty or double charged.
The scale is checked with a good light to assure the proper charge weight is set. My eyes aren't the best anymore.
I use the RCBS powder checker in rhe progressive Piggyback press.
Shooting glasses and ear protection is a must. Be safe!