A Bit About Shotshells
First, lets discuss hull length. This can be very confusing to a lot of folks and its easy to understand why. In the world of cartridge fire arms such as the 45-70 the case length is always 2-1/10th inches. It’s been that length since the 1870’s when it was first introduced. However, in the world of the shotgun it’s not uncommon to find 12 gauge chambers for 2-3/4, 2-1/2 and 2-5/8 inches while 2-7/8 inches was very common for 10 gauge. What’s up with that! It’s the same reason why the 45-70 was stretched to make the 45-90, 45-100 and 45-110; more powder more power. In some cases it was to allow for a modern star crimp which requires more material then a classic roll crimp.
The first thing a newbie must understand is that the hull length is the overall length before it is crimped or folded. Thus a brand new un-loaded 12 gauge 2-3/4 inch hull will measure 2-3/4 inches. Loaded it can measure anything less then 2-3/4inches. The loaded length of the shell is not as critical as the unloaded length. I know, I know I will explain a bit further. When the shell is fired all that hull length (a ¼ inch or more) taken-up by the crimp or fold has to go somewhere. It cannot obstruct the forcing cone of the barrel so it must lay open and provide a smooth transition between the hull and the forcing cone. If the end of the fired hull obstructs the forcing cone and creates a bottle neck effect it can cause problems when the wads and shot try to squeeze through.
Now if you fire a shell that’s shorter then the chamber length no bad stuff happens. The end of the hull has plenty of room to open out into. Thus the loaded length is not as critical. Just for kicks measure a star crimped shell and a roll crimped shell and you will see a difference in length even though they are both 2-3/4 inch hulls. Yes, if you’re a dedicated hand loader of rifle or pistol cartridges were the overall loaded length (OAL) is precisely measured this will drive you nuts. Get over it.
So what bad things happen if I shoot a 2-3/4 inch hull in a 2-1/2 inch chamber? I will defer to W.W. Greener who probably forgot more about shotguns then most modern gun writing wags will ever hope to know. "Shooting long cases, as 2 3/4" case in 2 5/8" chamber, increases the pressures enormously; with 47 grains of nitro the pressures registered were DOUBLE those registered with cases of the proper length."
The Gun and its Development - Ninth Edition 1910
Another problem is what this bottle neck at the forcing cone does to the pellets and the pattern. Its estimated that nearly 20%-30% of the pellets can be deformed which of course means they aren’t going where you’re aiming! Remember, the object is to protect the pellets during their journey up the bore so they stay nice and round and fly straight and true. In some cases the part of the hull obstructing the forcing cone can tear-off and be carried up the bore. If it exits the bore that’s good but if it stops somewhere along the way now you have the potential for a big problem when the next load starts its journey. Granted there are those who shoot over length hulls in short chambers and shoot them often and still walk and talk as normal. Yes we are talking about black powder which generates much lower pressures then nitro but do you really want to risk it with that very, very expensive Parker with its high grade
It’s easy and simple to measure your chamber. Chamber gauges are available from brownell’s www.brownells.com or you can make your own: http://www.tbullock.com/images/BPSG/ChamberGauge.jpg
Use proper length hulls. We all have enough worries. Why add more?
Republic Metallic Cartridge Company
is not liable for injury and or damage resulting from the use of its products in firearms
equipped with damascus, twist steel or laminated barrels.