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Pressure Testing Homemade .45 Colt Shotshells
by Roy Seifert

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Disclaimer:  This article is for entertainment only and is not to be used in lieu of a qualified gunsmith.  Please defer all firearms work to a qualified gunsmith.  Any loads mentioned in this article are my loads for my guns and have been carefully worked up using established guidelines and special tools.  The author assumes no responsibility or liability for use of these loads, or use or misuse of this article.  Please note that I am not a professional gunsmith, just a shooting enthusiast and hobbyist, as well as a tinkerer.  This article explains work that I performed to my guns without the assistance of a qualified gunsmith.  Some procedures described in this article require special tools and cannot/should not be performed without them.

Warning:  Disassembling and tinkering with your firearm may void the warranty.  I claim no responsibility for use or misuse of this article.  Again, this article is for entertainment purposes only!

Tools and firearms are the trademark/service mark or registered trademark of their respective manufacturers.


I was surfing the Internet one day and found a YouTube video by MannyCA on how to make .45 Colt shotshells using tools and materials I already had on hand; the link to the video is below. 

Making .45 Colt Shotshells by MannyCA  WARNING:  These loads are over-pressure loads and should only be used in Ruger or Contender handguns!

He also has a video on shooting these homemade shotshells showing their effectiveness.  Handgun caliber shotshells can be very effective against rats, snakes and other small varmints if you get close enough.  Often times you are right on top of a snake before ever seeing it, which makes it close enough for these shotshells to be effective.  That’s why they are sometimes called snake shot.  When I hike through the woods I carry a .45 Colt Ruger Blackhawk revolver and usually my first two rounds are shotshell loads. 


Assembling the Loads
Following MannyCA’s video I made my own .45 Colt shotshell loads using the following materials:

  • Stiff Cardboard – Any source of stiff cardboard will work; I used a 12-gauge shotshell box, but cereal boxes and canned beverage boxes work great as well.

  • Wad Cutter – This is made from a resized and sharpened .45 Colt shell casing.  I resized a case, then sharpened the mouth with my chamfering tool and wrapped some blue painter’s tape around it so I wouldn’t mistake it for a reloadable case.  I was surprised just how tightly my cardboard wads fit in the case!

  • Standard .45 Colt Reloading Dies

  • Reloading Press

  • Powder – For my test loads I used Unique, Red Dot and Green Dot.

  • #8 shot – 160 grains

  • Dippers

  • Powder funnel

  • Scale – beam or digital to weigh powder and shot

  • Gas Checks (optional) – The gas check is used to cap the shot, but you can use a cardboard wad as well.

I had all these materials at home already so I didn’t have to go out and buy anything.  MannyCA used 9.5 grains of Unique, but I wondered why he used this amount and if this load generated excessive pressure.  He was shooting them out of a Ruger Blackhawk, the new mid-size model, so even if the pressure was beyond the SAAMI maximum, it might not be a problem for the Blackhawk.  The online Alliant Powder reloading manual gives 8.5 grains of Unique for a 230 grain cast lead bullet as maximum at 850 feet per second, but did not provide any pressure data.  Since the shotshell uses only 160 grains of shot, 9.5 grains of Unique might be alright; but how would I know without any data?  And what about other powders; would there be pressure issues using other powders?  I had 8-pound kegs of both Red Dot and Green Dot so I decided to test some shotshell loads using these other powders.  My theory was that there would be a pressure spike to get the shot column moving out of the case, but would drop off quickly once the shot spread out.  I also thought that the pressure spike would be lower for shot than for a solid bullet because gas would escape around the shot once it left the case.  (Wow was I wrong on that theory; read on!)  The only way to know was to perform pressure testing.

Powder Volume
I started with MannyCA’s recipe of 9.5 grains of Unique.  I discovered that Lee powder dipper 1.3cc threw about that amount of powder.  I wanted to keep the volume of powder the same because I wanted it to take up the same amount of space in the case, or less.  Different powders have a different load density; in other words, the same weight of different powders will take up a different amount of space (have a different volume).  Looking at it the other way; the same volume of different powders will have different weights.

I used the 1.3cc Lee dipper because that left me enough space in the case to load 160 grains of #8 shot and cap it with a .45 gas check.  Using the 1.3cc Lee dipper gave me the following powder weights:


Weight (grs)



Red Dot


Green Dot


I backed-off the Unique weight to 9.5 grains to match MannyCA’s load and used a powder scale to accurately measure the powder.  These were the starting weights of powder with which I performed my pressure measurements.


Although I used the same size dipper for each load, I discovered that 9.5 grains of Green Dot filled the case too much so I had trouble seating the gas-check on top.  If I was to use this load I would probably back this off to 8.5 grains.  As you can see in the above photo, each load is labeled; U for Unique, R for Red Dot, and G for Green Dot.

Installing a Strain Gauge


I found a used Thompson/Center Contender® with a .45 Colt/410 barrel on Gunbroker for a very reasonable price.  Not only will the Contender allow me to attach a strain gauge over the chamber, I can purchase additional barrels to test other calibers, not to mention it’s a fun gun to shoot.

When I performed the pressure measurements for my .45 Colt hog loads I attached a strain gauge to the barrel of my Marlin 1894 Cowboy rifle.  Because the .45 Colt case is so short most of the chamber was under the receiver threads so I could only measure pressure at the mouth of the case, not over the center of the case as recommended. 


I fabricated a strain gauge assembly by attaching 30-gauge wires and a connecter to a strain gauge.  Rather than using the 28-gauge stranded wire which had a tendency to break (refer to my article Strain Gauges for Chamber Pressure Measurements) I used 30-gauge solid wire-wrap wire available from Radio Shack.  I placed a dab of Armstrong A-12 epoxy on the soldered ends of the strain gauge and on the back of the connector to act as strain relief so the wires wouldn’t break during handling.


I removed the rear sight blade assembly and attached the gauge to the Contender barrel over the chamber using JB Weld epoxy.  I couldn’t get it over the center of the chamber because of the rear sight base.  Even though I had covered the soldered connections on the strain gauge with A-12 epoxy, I was careful not to get any JB Weld on those connections because JB Weld has iron in it so it is not electrically insulated.  The A-12 epoxy didn’t seem to harden; it stayed tacky which is why I decided to use the JB Weld.  The blob of epoxy on the side of the barrel in the above photo acts as strain relief so I’m not moving the wires on the strain gauge connections.

Measuring Pressure


The strain gauge is connected to the excellent PressureTrace™ device available from Recreational Software, Inc., which in turn is connected to my laptop via the serial RS232 port.  I have the older RS232 version; the newer version connects to a computer via a wireless Bluetooth connection.  The Pressure Trace device measures and amplifies the slight voltage change in the strain gauge caused by the barrel expanding when a round is fired.  The software running in the laptop converts that reading into pressure in PSI and graphs it on the display.

The SAAMI maximum pressure for .45 Colt is 14,000 PSI so I wanted my shotshell loads to be at or below this figure.  That would make them safe in both the heavier Rugers and Contenders, and lighter Colts and Colt clones.

I first calibrated the Pressure Trace device by firing a verification load of 5.4-grains of Titegroup powder under a 230-grain cast lead round nose bullet.  This is my normal cowboy load that chronographs at 740 feet per second.  All of my reloading manuals show .45 Colt loads in copper units of pressure (CUP) so I made an assumption.  Since the SAAMI maximum pressure for .45 Colt is 14,000 PSI my cowboy load should be below that since it is far from the maximum load of 6.5-grains of Titegroup.  I did a rough ratio and proportion calculation and assumed that if 6.5-grains of Titegroup equaled 14,000 PSI (just a guess on my part since no pressure data was available), then 5.4-grains would equal in the neighborhood of 11,600 PSI.


My cowboy loads averaged 5,719 PSI.  This makes sense since test barrels have a very tight chamber which generates higher pressure readings.  My Contender has a commercial chamber so the readings would be lower.  Once the device was calibrated I began testing my shotshell loads.




I fired three loads of each different powder to get an average pressure reading.  I eliminated the highest of the three readings; the results are in the following table.


Weight (grs)

Pressure (PSI)




Red Dot



Green Dot



To my surprise all three loads were over the SAAMI maximum pressure of 14,000 PSI!  This is probably safe in Ruger single-actions and Contenders, but not for an original Colt that was designed to shoot only black powder, low-pressure loads.  I would even question using these loads in modern Colt clones!  I would probably reduce each load by at least 1.0 full grain to get them within the SAAMI maximum pressure specification.

I have a personal philosophy to never shoot someone else’s reloads, nor use someone else’s handload recipe.  I have had problems in the past with other people’s reloads; I damaged my son’s M1 Garand barrel because we were shooting gun show reloads (refer to my article Rebarreling Two M1 Garands).  Reloading manuals contain safe handload formulas that have been thoroughly tested and should be followed; not someone’s personal pet load.  Pet loads should be verified against published reloading data.  Someone’s personal recipe may just be a recipe for disaster!


   © Copyright 2015 Roy Seifert.