doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Pressure vs. Velocity

What if Skeettx had said Velocity and true peek pressure rather than just velocity and pressure.

Given the context of Tom's question (appropriate shells for a particular gun and application) and without going into a long dissertation, it would seem Skeettx's response is a good short answer. Worked for me anyway.

Ithaca1

I shoot promo 12 G Shells in my modern O/U. Work fine, sharp recoil and loud, probably due to light weight charges of fast powder. They have to save on component cost to sell them cheap. SxS's for high volume shooting I don't want to use them.

Not a question of pressure, the guns barrels are strong enough, like something easier on my shoulder. Thin comb light weight guns, and have seen old doubles crack with recoil.

B&P's Competition one 7/8 oz is a good choice. 1 oz load if you want more shot. B&P's High Pheasant 1 oz # 6 is good one too. Use RST's too just bought some # 6 10 G, but for volume couple of us group order B&P's

Opinion based on no data is pellet size and density does the job and no shotgun load needs over 1200 fps. Tight choked SxS guns get density with chokes and don't need heavy shot charges for most targets.



Boats

Pressure curves for the aforementioned Alliant loads. Green Dot and Unique curves are indistinguishable.
More infro - http://www.shotgunworld.com/bbs/viewtopic.php?f=13&t=405370



Possibly Hodgdon Clays.
Courtesy of http://www.arizonaammunition.net/

Thanks for the info. I think Skeetx summed it up in his first sentence with the operable wording being "direct". "Velocity and pressure do NOT have a direct correlation." I believe there is a correlation between pressure and velocity. However there may not be a exact correlation. If I was to take two shells and load them exactly the same except for powder charge and shot them through the exact same barrel the one with the higher pressure would have a higher velocity. Correct? Generally if I am looking for a 12 gauge shell and want a lower pressure but the pressure is not listed on the box, I can look for the lower velocity shells and this will give me a good idea that they are lower pressure. I typically shoot shells with a velocity of less than 1150 fps in my 12s which are all fluid steel barrels in good condition with good wood on the stock. Please correct me if I am wrong. I am always open to learning new things.

If you're using the same brand of powder and you change nothing else--same hull, same primer, same wad, same shot weight--but only increase the powder charge, you're correct. More powder = more velocity and more pressure, assuming nothing else changes. However, you can get more velocity with less pressure, or less velocity with more pressure, if everything remains the same BUT you switch brands of powder even if you keep the powder charge weight the same. That's because of faster vs slower burning powders.

Something to keep in mind is the powder a company is using in its shell.

While the bulk of my reloading expereince is with handguns, I know it is possible to use identical compenents, get similiar velocities and a different powder and seen a C.U.P. difference in pressure of a couple thousand C.U.P. in a handgun

My view is that I will pay the extra money for the RST shells or maybe the Winchester Feather Lites rather then take a chance with a really nice, expensive shotgun that might be hard or impossible to replace using ammo that may or may not be too much for the gun.

I would NOT make that assumption!
IMO, I would not use any currently mfg'ed ammo in an old shotgun unless the gun were checked out, and the ammo mfg'er states that it is for vintage guns. I know some guys shoot the lite and low noise/low recoil Winchesters, and have had a specific lot pressure tested, but it makes me uneasy. The reason is, if the mfg'er changes powder, the pressure info may go out the window.
This is an opinion and its worth what you paid for it.

Ithaca1

Thanks for all the info. I am ordering a couple flats of RST shells today and I may pull out the old MEC Sizemaster and look at reloading again. Where can I find the best info on reloading low pressure shells. It's been about 20 years since I reloaded.

Any of the powder co. web sites will give you loads. Claybuster wads has a web site with info. They're also a lot cheaper than factory wads. All my hand loads are low pressure, and there are many, many of them out there. As stated earlier, you can have the same FPS with either a high or low pressure. The velocity is not a good indicator of pressure. Paul

Tom,
One last comment and I'll leave it alone. Loading shotgun for low pressure is very different then loading rifle. Do not deviate from the listed load. Don't change the primer, don't change the wad, don't change the hull and don't change the powder. Substituting one component can make a significant difference in the pressure.

As you know with a rifle, if you are out of CCI BR2's you can use Rem 9-1/2's or Fed LR without a big change. You may change POI a little but you still won't overpressure, and could short range hunt with it in a pinch. Not so when loading shotgun. Don't make assumptions.

Be safe and I hope this helps.
Ithaca1