Loaded up some 460 Rowland for the Mechtech rifle using Power Pistol, load data from Realguns site. BIG mistake. ALWAYS check multiple sources. I should know better.

QL says 9.5 gr max, Realguns data is for a pistol at 12.5gr. Mechtech suggest using AA7 only.

The first shot cut the case in half right at the base of where the bullet would be seated.

Thank God the base of the case did not fail! I'm surprised the primer did not blow as well.
Glad your OK.
Always check load data on the web. There are just too many variables and mistakes made.

Yes Thank God. We checked the mechtech completely, no brass flow. The rear of the case ejected, the front had to be pulled out. No chamber scratches or ring or bulge.

Just have to pull a few reloads.

thanks

That's a close call! Glad you're able to tell us about it.

quote:

Originally posted by richj:
The first shot cut the case in half right at the base of where the bullet would be seated.

That sounds more like a defective case than a result of excess chamber pressure. However, I'm not familiar with this cartridge or the gun in which it was fired so my comment has to be taken as a generality.

This one may take the academy award for the perfect storm.

The weapon referenced isn't actually a complete firearm. It's a component that "converts" a semi automatic hand gun into a "rifle". The top of the hand gun is removed and replaced with a barrel, receiver and stock that provides for shoulder firing.

The Glock or 1911 pistol grip, trigger, is attached. The gun then is upgraded from a 5" barrel to a 16" barrel. The pressure is upgraded from as low as 5,000 psi to 40,000 psi.

There are several aspects of the accident that contribute. But the one outstanding is the powder. As the Quick Load manual explains in great detail there is a vast difference in powders today. There are several technical terms to describe it but one more easy to understand is relative burn rate. Of the 97 types listed, from fastest to slowest, Alliant Power Pistol ranks 27th fastest. Alliant Reloader 7 is 51st.

I spent some time running calculations on QL. The resulting differences are staggering. Further the published "Realguns" reloading data is so far off that it can't even be considered as for the same caliber and type seen in QL, i.e, the 460 Rowland. Some ran as high as 73,000 psi !!!! Even changing bullet types, leaving all else the same showed thousands of psi difference.

The 460 Rowland is essentially the old 45 ACP. The case is a tiny bit longer but the rest is so similar that the two can be interchanged in some chambers. Upon checking QL and comparing the two, again significant different results.

The semi auto receiver doesn't have locking lugs like bolt action rifles. When fired there is very little resistance from the receiver, only it's own weight and some small spring pressure. It begins to move back. The vast difference in the burn rate of the two different powders mentioned presumably caused the receiver to move at a far faster rate. It began to open exposing the case which blew.
I wouldn't call it out of battery firing.

Using the data available here, which is missing some essential information, and switching through the various combinations, the 16" barrel, some bullet types, and above all the powders showed several combinations far in excess of the 40,000 psi rating by the manufacturer.

Some other aspects were also ignored but I won't go into them all. Bottom line it is certainly disconcerting to see so much false and misleading loading data so hugely in disagreement.

I find it hard to believe that Mechtech didn't tell you to NOT fire 460 Rowland in their carbine conversion. 460 Rowland operates at nearly three times the pressure level of the 45 ACP - for it to safely operate in a blow-back action you would need a much heavier bolt and much stronger recoil spring to safely operate the action - if a blow-back action could even be safely operated at the pressures of the 460 Rowland cartridge. I am trying to think of any blow-back actions that function at 40,000+ psi, and can't remember any. All the semi-auto's I know of that use a cartridge even close to that pressure level use some form of mechanical locking. There have been a few 9x19 actions that used blow-back, but most use some form of mechanical locking and that is the most powerful cartridge I can think of that has successfully used a blow-back action. The 460 Rowland is much more powerful, and operates at a higher pressure level than the 9x19.

quote:

Originally posted by wetibbe:


I spent some time running calculations on QL. The resulting differences are staggering. Further the published "Realguns" reloading data is so far off that it can't even be considered as for the same caliber and type seen in QL, i.e, the 460 Rowland. Some ran as high as 73,000 psi !!!! Even changing bullet types, leaving all else the same showed thousands of psi difference.

The 460 Rowland is essentially the old 45 ACP. The case is a tiny bit longer but the rest is so similar that the two can be interchanged in some chambers. Upon checking QL and comparing the two, again significant different results.

The semi auto receiver doesn't have locking lugs like bolt action rifles. When fired there is very little resistance from the receiver, only it's own weight and some small spring pressure. It begins to move back. The vast difference in the burn rate of the two different powders mentioned presumably caused the receiver to move at a far faster rate. It began to open exposing the case which blew.
I wouldn't call it out of battery firing.

Using the data available here, which is missing some essential information, and switching through the various combinations, the 16" barrel, some bullet types, and above all the powders showed several combinations far in excess of the 40,000 psi rating by the manufacturer.

Some other aspects were also ignored but I won't go into them all. Bottom line it is certainly disconcerting to see so much false and misleading loading data so hugely in disagreement.

There is no SAAMI or CIP std for the cartridge. The round is for all intents a "wildcat" cartridge and very often data is whatever someone managed to shoot and still have a gun after, the same as it has always been with these cartridges.
Reliable data from a lab such as Hodgdon, offers is much preferred to a blog on the internet if it is available.