From: tcs@cbnewsb.cb.att.com (theodore.c.seed)
Newsgroups: rec.guns
Subject: Re: LUP vs psi
Date: 21 Jul 92 14:15:55 GMT
Organization: AT&T

On 17 Jul 92 02:02:46 GMT, james@csn.org (Jim Phillips) writes:
# 
# Does anyone know how to convert from LUP to psi in reloading data?

Jim:

I subscribe to a magazine called "Shotgun Sports", in which a
regular feature is "Shotshell Reloading". Each month, at the end
of this section is the following, which I reproduce here without
prior permission:

"Pressures are often listed as "p.s.i." or "l.u.p." values. You
may find different pressures listed for the same load in different
handloading manuals. They are not the same. In general, p.s.i.
values will be higher than l.u.p. values. As a rough rule of
thumb, p.s.i. readings tend to be about 1,000 units higher than
l.u.p. readings. Also remember there can be differences in how
loads act in various test guns and equipment that can also affect
these readings and the values published."

Ref: Don Zutz, "Shotshell Reloading", _Shotgun Sports_, July, 1992,
page 11.

# 
# For example the _Winchester Reloading Components Catalog_ sez
# "All pressure data listed as psi has been measured with the latest
# Piezo electric system showing actual pounds per square inch (psi)
# and CANNOT be compared directly to the old data which used the lead
# crusher method(LUP)."  Well okay, apples and oranges but is there
# a conversion?

As per the above, p.s.i. is roughly 1,000 units higher. Note the
word, "units", which means, as you point out, that we are comparing
apples and oranges. The thing to do is view all this as measures
of comparison, or a way to express the chamber pressure of one load
relative to another, within a comfortable margin of safety.

# 
# Specifically, I am considering moving to the following formula...
# 
# 	Winchester AA Hull
# 	Win 209 primer
# 	Win WSL 20 gr powder
# 	Win WAA12SL wad 	
# 	1 1/8 oz of #8
# 	Win Catalog lists this at 1,200 fps and 9,000 psi.

A 3 drams equivalent load.

# 
# I'm currently using...
# 
# 	Winchester AA Hull
# 	Win 209 primer
# 	PB 22 gr powder
# 	Win WAA12 wad 	
# 	1 1/8 oz of #8
# 	Shotshell Reloading (Couger) lists this at 1145 fps and 6600 LUP.

A 2-3/4 drams equivalent load.

# (much deleted for space, here) 

# 
# Okay, back to the point.  There is a considerable difference in felt
# recoil between the Super-Lite and the second formula using the PB
# powder.  The difference was also noticed by a fellow shooter who borrowed
# some of my reloads.  I wonder how 6,600 LUP compares to 9,000 psi.  
# (rest deleted) 

First, the two loads are not the same, as I indicated above. The
9,000 p.s.i. load is a 3 drams equivalent load, which is evident
by its 1200 fps velocity. The 6,600 l.u.p. load is a 2-3/4 drams
equivalent load, evident by its 1145 fps velocity. To put it in
better perspective, using the rough conversion, the 9,000 p.s.i.
converts to roughly 8,000 l.u.p. The 6,600 l.u.p. converts to
roughly 7,600 p.s.i. So, you can readily see we are not comparing
the same loads.

As for the felt recoil, you don't indicate which load you felt the
most, but I would guess it was the 9,000 p.s.i. load (the 3 drams
equivalent load). You might want to try the WSL in a 2-3/4 drams
equivalent load. That would get the chamber pressure down around
the 8,000+ p.s.i. range (7,000+ l.u.p.). Although the wads are the
WAA12SL or Rem. RXP12 or Fig-8. If you want to stick with the
readily available WAA12 wad, use the WST powder. 

The manual lists a 2-3/4 drams equivalent load, which should produce 
less felt recoil than the 9,000 p.s.i. load:


 	Winchester AA Hull
 	Win 209 primer
 	Win WST 18.5 gr powder
 	Win WAA12 wad 	
 	1-1/8 oz of lead shot

This load produces 1145 fps velocity and 8,600 p.s.i. pressure.
That's roughly 7,600 l.u.p., which is a little more lively than
the 6,600 l.u.p. produced by the IMR PB load above. It is listed
on page 18 of Winchester's Reloading Components Catalog, Eleventh
Edition. By the way, this one has a '*' by it, which means it 
duplicates the ballistics of their factory 2-3/4 drams equivalent
AA plus target load. 

This is what I have been loading since they discontinued the
452AA powder. For me, it is a nice, tolerable load as far as
recoil is concerned.

Welcome back to the reloading fraternity.

--Ted