16ga.com ~ View topic

Joined: 08 Feb 2009 Posts: 1310 Location: Western WA

Hi All (again),

I am preparing to begin reloading for my 16 ga SxS, and was wondering if there were shotshell pressure warning indicators analogous to centerfire rifle cartridges (hard extraction, cratered primers, stretched cases, etc.), but for lower pressures? Realizing that shotshell pressures are much lower than centerfire rifles, are there any things to look out for, other than bulged barrels and loose ribs?

V/R,

Brewster11

Joined: 17 Sep 2008 Posts: 31 Location: Eastern Washington

I have loaded federal hulls with 1 1/8 oz shot hot enough to where the brass visibly bulged out quite a bit. It was so bad that i couldn't resize them in my reloader and had to throw them all away.

Guest

There are no reliable methods of predicting pressures in a shotshell load, except to actually have them tested. Stories of flattened primers, brass measurements etc. are only stories and are not indicators of pressure.

Use published data from a good source, like the powder and component manufacturers. The Low Pressure Group has some loads tested by Tom Armbrust, they should also fill the bill.

Member Joined: 16 Aug 2004 Posts: 317

The only given in 16 ga. shells retailed in the US is that they comply with SAAMI. So average service pressure of 11,500 psi.

Member Joined: 27 Jun 2005 Posts: 1545 Location: Michigan

This is a sure sign or warning of excessive pressure in a shotshell. Wink

Brewster,
As stated above, there are no true pressure signs with shotshells as there are with rifle brass. Don't tread down this road unless you've updated your life insurance policy to make mama really happy and you don't care about the loss of fingers or limbs. Shotguns unlike rifles are working at 11,000psi
and do not tolerate excess abuse well. I can't overstate the importance to not tamper on unproven soil, it's much like a land mine. Send loads in to Tom Armburst for testing first, or follow the manual to the T.
Good Luck,
Charlie

Joined: 08 Feb 2009 Posts: 1310 Location: Western WA

Folks,

Rest assured that I have absolutely no intention of using anything but well-tested, modest pressure loads exactly as directed. But rifle reloading experience taught me that one must approach any published load with reduced powder charges and look for pressure indicators while gradually increasing the charge to the prescribed level, because pressure levels are highly dependent on the individual firearm being used. A load producing nominal pressures in a test gun could produce much higher pressures in another gun.

Is this the case with shotguns as it is with centerfire rifles, and if so, what indicators should be monitored as one tests new loads, even those that are considered low to medium pressure?

Thanks

Brewster11

Guest

Hi Brewster,

No, shotguns are a bit different than rifles. There is no rifling, short throats, short chambers, or tight chambers or the like to produce substantially different pressures. If anything, and I can only speak for firearms manufactured to SAAMI reccomendations, the pressure test barrels will produce MARGINALLY higher pressures than those produced in production shotguns, as the chambers TEND to be cut a little tighter in the test barrels. That is a rule of thumb, not an absolute.

The one rule that you don't violate is, NEVER substitute components. That includes backing off powder charges. There is really no perfect way to predict what will happen with pressure, velocity or extreme variation snd standard deviation of both, except to properly test the component change. A lot of reloaders including those that write about topics here speak of switching components in a rather casual manner. They can speculate all they want, but they really have no idea what happens to pressure and velocity and the EV and SD of both. Primer switching is the favorite and probably the one switch the screws stuff up more than any other. For the most part there is a window where the powder charge, primer and shot charge marry up pretty well, start messing around with it and you will lose the nice consistent round that is was intended to be.

Tom Armbrust has written a great article on it.

http://www.armbrust.acf2.org/

Again, there are NO reliable indicators of chamber pressure that can be read by visual inspection or measuring fired shotshells.

Guest

I agree on the standard of using only published loads from reputable sources.

That said, I loaded a load from a manual, "Reloading for Shotgunners, 4th Ed." a few years ago and I followed the recipe to a T. I always check the powder with a certified scale, etc. The one ounce load was supposed to clock at 1220 fps, and I noticed that the recoil was way more than I expected. I then chronographed the loads and found they were at 1310 fps and I'm pretty sure the pressure was significantly higher than the published data.

Nothing is more conclusive than sending loads to a lab like Tom Armbrust's (done that), but you can make some commen sense determinations with a chronograph as I did above. I'm now leary of that manual and any data put out by Ballistic Products. (same guys that put out the manual mentioned above)

Guest

Dave,

Many people have the same issue with BPI loading data. I never have been able to find out what lab does their testing. There aren't very many ballistic testing facilities and at one time I knew most all of them.

Before buying a reloading manual, ask the folks that published it who / how the data was tested. If they are evasive or if it wasn't done with Piezo equipment and by a source that you can get information on, stop right there. Get your data somewhere else.