Walmart winchester AA

[Big Friend Ten (BFT)]

Originally Posted by wayne goerres

Lower velocity means lower preasure.

Lower velocity does NOT mean lower pressure! That is a logical assumption but unless you have measured the pressure you cannot be certain of this. Luckily Sherman Bell conducted a test on the subject ammunition and provided the results in writing, albeit that was 14 years ago.

[Gary]

How do we find out the pressures of box ammo?
I have been on the Winchester site and it does not state the pressure of most of there shells.

[wayne goerres]

Send 40.00 and five shells to precision reloading and they will put them through a preasure barrel for you. Lower preasure dose equate to lower velocity It just dosn't always work on a fixed ratio(such as one FPS equals one PSI) And if you read the original statement you will see that nthese are not the same shell sherman bell tested.Winchester did not make these shells back then.

[Big Friend Ten (BFT)]

Originally Posted by wayne goerres

Lower preasure dose equate to lower velocity It just dosn't always work on a fixed ratio(such as one FPS equals one PSI)

Once again a logical assumption but only if all else is equal. There are no guarantees except that the ammunition will not exceed the SAAMI maximum (peak) mean working pressure.

How could this be so? Is the manufacturer using the same primers, powder, and wads? They may have even changed the design of the case! Changing any of the components (or amount of powder) can and will vary the pressures.

Perhaps what you are thinking of is total pressure during the time the load is moving through the barrel. If so then you are correct. Total pressure "under the curve" is what is doing the work of accelerating the ejecta. The ejecta includes all things moving don the barrel including weight of powder, wad, and shot. If however you were referring to the "peak" pressure which is what 99.99% of persons are referring when they refer to high pressure, then you would be wrong. Peak pressure is what will blow up a barrel if it is too high.

For example one could load a shotshell that would only develop 900 fps in a certain gun but have a peak pressure of 18000 psi. How could this be possible? If a small amount of very fast burning powder is ignited and burns developing a very high pressure but then the pressure curve drops almost immediately (because the powder is almost completely burnt) to less than 1000 psi the load will likely develop only a low velocity. No, a manufacturer won't sell something like this due the the risk of a secondary implosion. If different powder is used a lower velocity may be developed at a higher maximum "peak" pressure.

The bottom line is that unless you test or pay to have shotshells tested, all you will know is that they do not exceed the SAAMI maximum mean working pressure.

[Bill Murphy]

All we have to do to prove Mark's point is to read a loading manual. Loads of certain shot weight and velocity have pressure figures all over the map.

[Paul Harm]

About the only time lower pressure means lower velocity is if you hand loaded a shell then kept everything the same but next time you used a little less powder. You'd then have less pressure and less velocity. Looking in my IMR handbook there's a 1100fps load at 7800psi and just down from it there's a 1200fps load at 5400psi. Different powder and primers. So you could have high pressure with low velocity. If you don't know, get it tested.

[charlie cleveland]

i ve seen loads that were tested the loads were identical in all areas but there wasover 2000 lbs pressure differace in the two loads...i guess its like buying two new chevy sboth coming off assembly line both being exact twins...you put them on the drag strip with the same driver and one will out perform the other in speed acceleration etc...most are pretty close in performance but then comes along a shell or car that blows the hole thing apart... charlie

[Big Friend Ten (BFT)]

A good analogy Charlie!

A couple years ago I measured the pressure on promotional Federal and Winchester 12 gauge cartridges. From the same box the pressures varied more than 1000 psi between individual shells.

The figure below shows pressure traces from two handloads in which I varied only the type of shot.

Traces 1-5 were with lead shot where a spread of almost 1500 psi and mean of 6658 psi. Of these T5 was 700 PSI above the highest of the other four traces (shells fired). There could have been something very minor which caused this 10% pressure increase such as a stronger crimp.

Traces 6-10 (T8 didn't register) were with ITX shot (which is harder than lead) where a spread of only 627 psi and mean of 9771 psi.

What I learned from this was that with the hulls, wads, primers, and certain amount a specific powder, an equal weight of ITX would cause a 32% pressure increase. Had I thrown out trace T5 the pressure increase would have been even higher! Also notice that there is only a range of 600 psi difference in the IXT loads. Perhaps the higher pressure caused a more efficient burning of powder?

[J.B. Books]

Originally Posted by Mark Ouellette

A good analogy Charlie!

A couple years ago I measured the pressure on promotional Federal and Winchester 12 gauge cartridges. From the same box the pressures varied more than 1000 psi between individual shells.

Mark, how and what did you use to measure these pressures? Do you have the same ability to measure pressure in the 10 gauge?

[Big Friend Ten (BFT)]

Pete,

These loads were in measured using a 10 gauge and a Pressure Trace II.

The PTII works as long as one has a standard (reference load) to calibrate it to. Also, precise measurements must be taken of chamber thickness. The process is a pain in the butt but given a day to dabble with it good results can be obtained. I like it for starting with a good loading data such as that from a Lyman manual or Sherman Bell's research. Those are my standards (actually approximate references and certain not a "Standard"!) from which I experiment with a change of primer, shot, wad or so on...

Last year I used a single barrel American Arms as my test gun. I recently obtained a Marlin Super Goose 10. The gun is like new and it will be a shame to glue the strain gage (sensor) to the chamber. I also bought a simple return to battery cradle to save my shoulder! Now all I have to do it to build a bench strong enough to mount the rig to!!!

As you might guess this part of my hobby is getting expensive but it's at about $20k less than a real test barrel, universal breach, and Ohler pressure measuring equipment.