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proof testing article from Pedersoli


Professor Marvel:
Waaay back in 2010 I found this article I can't remember from where and I think from Sep 2004, but do not hold me to it...
Whilst cleaning up this hard drive I came across it again and thought I wouldshare this little tidbit.

edit: AHA - It was on the Black Powder Cartridge Rifle site:

prof marvel

Pedersoli Proof Test Rules and Allowable Limits


Many BPCR owners are concerned about the safety of original and replica
rifles. Of course an original should be examined by a gunsmith who is
familiar with such arms and who is competent to pronounce the arm safe
or unsafe. There is always the temptation to try and shoot an old gun
which may have been in your family a long time or which you recently
obtained. In most cases it is safe to fire such an old gun using the
correct black powder and bullet weight but the following advice should
be considered first.

Certain types of steel alloy used in original guns of the BP era may
have changed over the 100+ years of time. Once safe guns may now have
internal cracks or molecular flaws which have developed over such long
time periods. Age alone may have made the steel become "brittle" and
unable to withstand ignition pressure safely.

Therefore, even though the exterior of a gun may look normal, there
could be serious problems within the barrel and action which might cause
a failure when even a "normal" powder charge is fired.

As a basic guideline.........when loading "full case" charges of the
correct grade of BP behind a bullet of normal weight for that caliber,
you will not exceed a pressure of around 22,000 to 26000 psi (or CUP)
and modern made replica guns can handle such pressures safely. Use of a
heavier than normal bullet or a black powder grain size which is too
small in size, will cause higher than expected ignition pressures.

Original BP guns with internal flaws or replica guns which may have been
repeatedly fired with excessive pressures in the past, may fail even
with a so called "normal" load.

Original antique firearms have the best steel available at that time but
today we understand more clearly that the old time steel contains
various impurities and inclusions which after more than 100 years, can
cause internal weakness and flaws which could cause the gun to be unable
to safely handle it's normal chamber pressure. To avoid damage to the
old gun as well as preventing injuries to the shooter or bystanders, it
is suggested that original antique guns be fired only with reduced or
mild charges……. after having been inspected by a qualified gunsmith.

The situation is quite different when smokeless powders or a "duplex
load" having both smokeless and BP is being used.

Really dangerous and destructive pressures are easily produced which can
result in damage to the gun as well as injury to both shooter and

Because of the dangers mentioned above, and the fact that no one outside
of a testing laboratory or proof house has the proper equipment to
measure the pressure and strain produced by any ammunition, the
Pedersoli company states that their cartridge rifles are to be fired
only with "commercially produced" smokeless powder ammunition or, with
black powder ammunition which meets the pressure limits set forth by the
European C.I.P or American SAAMI organizations for each caliber or
cartridge name.

Pedersoli & Co. like all Italian firearms manufacturers, is required by
law, to have every firearm proof tested at the Italian National Proof
House in Gardone Italy.

Many other European gun makers also send their complete gun or barreled
actions to this same proof house when there is no similar proof house in
their home country. Buyers look for proof marks as an assurance of
safety and quality so manufacturers pay the extra price to have guns
proofed by a recognized govt. controlled proof house.

Below is a copy of the standard letter Pedersoli provides to customers
who ask about the proof test pressures for their Black Powder Ctg. Rifles.

It should be noted that in the USA, Federal or State Law does not
require the proof testing of civilian firearms and there is no national
proof house in the USA for such testing.

Only military contract firearms receive high pressure proof testing
under strictly controlled conditions. All other firearms may or may not
be proof tested by the manufacturer in some manner and if proof testing
is performed, there is no government supervision or control so the
customer must rely upon the manufacturers’ reputation in regards to the
firearm strength. Fortunately, even though commercial firearms made in
the USA do not have proof testing marks they are found to be strong
enough for commercial ammunition made according to recognized SAAMI
pressure ratings and the customer relies upon the reputation of both the
gun and ammo manufacturer.


All Pedersoli rifles are proof tested at the (Italian government)
National Firing Proof House with smokeless powder cartridges with a
pressure exceeding that of the ‘commercial’ factory made ammunition by 30 %.

For the .45-70 caliber we normally recommend the use of commercially
made ammunition because of it being easily available on the world
market. We show here some warnings about C.I.P. rules:


Our guns are proof tested according to the rules imposed by C.I.P.
(International Proof Commission). Proof test pressure is 30% stronger
than the maximum pressure of a commercial cartridge (Pmax.) Pmax
pressures are measured in BAR units.

The below mentioned data are compared to the Crusher (CUP) and PSI method.

The equivalent maximum pressure value of the commercial cartridges
measured according to the English/American P.S.I. and C.U.P. system is
obtained by multiplying the BAR value x 14.5037.

The list below represents the maximum pressure to be developed by a
commercial cartridge to be used with our guns, in the various calibers
shown .In no case should the cartridges exceed such pressure values.


----------Smokeless Powder Cartridges------------------

*Calibers*      *BAR*      *CUP – PSI*
30-30 Win.      2800      40611
30-40 Krag      2850      41335
38-55 Win.      2150      31182
357 Mag.        3200      46411
45 Colt         1100      15945
45-70 Govt.     2000      29007(*)
8x57 JRS        2900      42060
9,3x74R         3000      43511

--------Black Powder Cartridges------------------------

*Caliber*         *BAR*      *CUP – PSI*
38-55 B.P.         2000      29007
40-65 B.P.         1723      25000
45-70 B.P.         1723      25000
45-90 B.P.         1723      25000
45-100,110 BP      1723      25000
45-120 B.P.        1723      25000
45-70 Light BP     1241      18000 (**)
50-70  Light BP    1241      18000 (**)
50-90 Light BP     1241      18000 (**)
50-70,50-90 BP     1723      25000 (*)

These calibers with B.P. indicate the use of commercial cartridges cases
reloaded with BLACK POWDER only.

(*) This pressure is allowable for modern made Pedersoli rifles in
38-55, 40-65, 45-70, -90, -100, -110, -120, 50-70, and 50-90. It may not
be safe with other brands of replica arms and those mfrs. must be
consulted for their data.

(**) This pressure is generally considered to be near the safe limit for
original antique Trapdoor model rifles which have been examined by a
qualified gunsmith and found to be in good condition. Modern made
Pedersoli Trapdoor 45-70 rifles are safe to the higher 29007 PSI/CUP
pressure. Other brands of modern made Trapdoor rifles may not be safe at
this high pressure and the mfr. must be consulted for their data.

The modern replica Sharps, Rolling Block and Trapdoor models we produce
are stronger than their original versions due in part to improved steels
as well as minor changes made to strengthen original design weakness and
add some discrete safety features. Although it is unpleasant to shoot
maximum pressure loadings, we do permit the use of ammunition which does
not exceed 29007 psi or CUP in these BP Ctg Rifles, regardless of their
caliber. This allowable maximum pressure may be obtained using either
black powder or smokeless powder loadings.

When using smokeless powder it is the responsibility of the reloader to
use only the correct type of powder as well as the correct weight of
powder in conjunction with the type and weight of bullet being reloaded.

Use ONLY the printed reloading charges listed by the powder manufacturer
and which show the chamber pressure for each such reloading combination.

We recommend the Accurate Arms reloading book #2 (phone 800 416 3006 )
as meeting all our requirements for bullet types, pressure readings and
powder charge selections.

Other powder and bullet manufacturers books are equally recommended if
they list all the required data.

The Pedersoli company assumes no responsibility for injury or damage
caused by firing ammunition loaded wrongly or to excessive pressures.

We are aware that there is smokeless powder 45-70 cal. commercial
ammunition being sold which advertises pressures of 40,000 psi and we
advise against use of this type ammunition. The large capacity thinwall
brass cases are not designed to handle such excessive pressures and will
have a very short reloadable life and may burst when fired at such high
psi. For "ALL" large case black powder calibers, the best accuracy is
obtained by the use of carefully developed loads using blackpowder and
cast lead bullets in a bullet length suitable for the barrel twist of
your rifle.

For Davide Pedersoli & Co.

Dick Trenk
Competition Events Coordinator

rev 9-04

Kent Shootwell:
Finding and sharing info like this must be how you earned your name! Thanks

To the best of knowledge, there is still a lack of available proof testing for Citizen Kane, should he wish to have his firearm tested.  I also feel in some instances, Proof Testing will provide a false sense of security.  A successful proof test only truly indicates a specific firearm survived that single proof round .... ONCE.  In the future ................................................


Professor Marvel:

--- Quote from: Coffinmaker on September 25, 2017, 01:42:31 PM ---To the best of knowledge, there is still a lack of available proof testing for Citizen Kane, should he wish to have his firearm tested.  I also feel in some instances, Proof Testing will provide a false sense of security.  A successful proof test only truly indicates a specific firearm survived that single proof round .... ONCE.  In the future ................................................

--- End quote ---

Therein is the conundrum behind proofing!
Does the proofing "prove" anything? or does it actually "pre-stress" the gun and make it MORE susceptible to future failure?

I personally feel that with modern manufacture tehniques, non-destructive testing of each unit, with "test-to destruction" of a small sample, such as 1 out of 500 , is more useful...

prof marvel

I'm not too sure that every gun is tested. I visited the Italian proof house in 2005. We watched them do a shotgun and before the gun was fired the pressure bearing parts were measured and noted. After proof firing the gun was measured again and if anything had stretched that is a fail. If everything is OK then the proof marks are stamped on the gun.

I don't know for sure how many test chambers there were - we only saw one - but there cannot have been too many. Given that all of the guns from Uberti, Pietta, Pedersoli. Chiappa, Beretta and the myriad of small gun makers in the valley all go through the one proof house, it seems unlikely that time would permit testing every individual gun. More likely a batch is sent down and guns tested randomly.

The two photographs are from part of the Uberti despatch room. The other big manufacturers will be very much the same.



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