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I am looking to work up a load for a "between the wars" English BLE 12ga. It is recommended to keep working pressure less than 10,000 PSI. I have Lyman's 4th edition and checked the Hodgdon's website for recipes. I found the identical recipe (shells, powder, wad, primer) in both sources. I was puzzled by the difference in pressure although the velocities for both sources are almost identical. Lyman shows 10,000 PSI and Hodgdon's website shows 9,200 LUP. I then noticed on the same page of both the Lyman manual and the Hodgdon webpage, they showed loads in either PSI or LUP depending on the loading.

Looking closer at the Lyman manual, it has a section on PSI vs LUP. LUP being Lead Units of Pressure which was an older method of testing pressures versus newer electronic piezo methods. LUP pressure reading for a given load is always lower than the PSI reading for the same load. BUT there is no standardized conversion.

The take-away here is when working up loads for older pressure sensitive guns, pay close attention to the pressure units. I did not want to exceed 10,000 PSI but just using Hodgdon webpage, I would have been on the bleeding edge.

Be careful out there!

Hc

You are correct; there is no conversion of LUP or CUP to PSI.

Glue on a strain gage, hook it up to your Oehler 43PBL and find the pressure in PSI for your own gun.

Member Joined: 26 Apr 2005 Posts: 743

You won't see pressures listed in LUP any more. That's strictly stuff you find in old reloading manuals. And while there is no direct conversion, you can "ballpark" it with this very simple formula: PSI-1,000=LUP. (Or, if you prefer to go the other way, LUP+1,000=psi.) You'll find, if you pressure test enough reloads, that they will vary a few hundred psi. (So will factory loads, for that matter.) So apply the above ballpark formula, build in a bit more "margin for error", and you'll be OK.

Member Joined: 08 Nov 2005 Posts: 3438 Location: Illinois

LUP and Dram equivalant need to be dropped from our vocabulary

Joined: 17 Jan 2007 Posts: 76 Location: north Texas

Amen, hoashooter!

I'll bet at least 75% of the folks who buy shotshells couldn't tell you what dram equivalency really is!

And LUP......just a buncha numbers that ballistic engineers spout off for relative comparison to each other, and otherwise can't be reliably converted to a widely-recognized standard measurement.

xtm

Member Joined: 26 Apr 2005 Posts: 743

I stand corrected, HC. I've got the latest Hodgdon manual, and they do list some pressures in LUP. Shame on them! My Alliant manual is a couple years older, and all their listings are in psi.

Actually, the history behind "LUP" is kind of interesting. LUP is nothing more than psi as measured by the lead crusher method, which was standard prior to WWII--not quite sure when the piezo-electric measurement system took over. Anyhow, when the conversion was made to the modern system, it was discovered that what had always been listed as "psi" were, in fact, incorrect readings. (If you go back to the 20's and 30's, you'll find pressures listed as psi, but they were using the lead crusher system back then.) So to differentiate, the powder companies started using "LUP" to designate those old readings. Not sure why they would be continued today, because I don't think the lead crusher measurement system has been used in this country for quite some time.

I emailed Hodgdon last week, asking when they intend to update their out-of-date 16ga load data. No reply to date.

Joined: 16 Nov 2006 Posts: 367

The LUP is an avaerage reading of force. You are measuring the deformation of an pre-measured lead cylinder, knowning the after firing results you can calculate the average force to cause the deformation, then dived that force by the original surface area to get the force per area (LUP)
CUP are the same just using a known cylinder of copper.
Today's measurements of pressure should be ID as: PSIA, the "A" being for absolute. The reading is taken against time giving the pressure-time curve .

Howdy Guys,
When dealing with the powder companies its best to call, ask for the ballistician and direct question to them. I've talked with Hodgdon's several times and they have been very helpful and given me recipes for the 16 that are not on the web page or in the manual. Go Figure Wink

Have a good day Smile

Charlie

Joined: 01 Dec 2006 Posts: 21 Location: Michigan

Alliant is probably the most consciencious of all the companies about modernizing its data. However, none of them update 16 ga stuff very often. Hodgdon has been posting some data exactly as printed for 30 years or more. Its still good data if the powder being called for is canister grade.

Older data can be valuable. I've kept a log of the relative capacity of the various 16 gauge shells I've used over the years. If a newer type shell has the same type construction as the older one, and the internal capacity is determined accurately to be within 1-2 percent, you can use one shell for the other without any problems.

I've posted how to do this already a couple of times. You must accurately cut both shells to a standard height of 2-1/2 inches, make sure each is perfectly round, and fill with water. Weighing the water will give you a comparitve analysis of the volume of each.

Cheddite, New Winchester, Fiocchi cases with the same height base wad, and some others based on a Cheddite type hull all will work for the same moderate loads up to 9500 PSI without problems. Older Federal paper based hulls are the same as the newest Federal and Estate paper based cases. All Reminton plastic wad based polyformed hulls are interchangable. there are others too.

Keeoping a log is the answer. I can use 40 year old data without a problem if I can find a very similar modern shell and the same wad and powder.

One more point. If a shell is both similarly constructed and has a bigger capacity, then any load for a shell with a bit less capacity will be safe. You might have to add a grain or so of powder to get the same ballistics, but it will work.

A shotgun shell is nothing but a gas proof combustion chamber liner or seal. If the seal is made of the same materials and has the same capacity and basic internal shape, then an identical load using the same internal componants will develop the same pressures within a safe range and with only minor differences.