Ruger Forum banner

1 - 10 of 10 Posts

·
Registered
Joined
·
1,876 Posts
Discussion Starter #1
This was posted over at Brian Enos Revolver Forum relative to trigger pull on tweaked 625s. As the thread evolved not certain it is for small pistol primers but AZShooter stated:

"Federal primers will go off with 32 oz of force. Winchester takes 44 and CCI takes 56 oz. These are out of my guns but have been very consistent numbers."

The thread is at:

625 spring balance - Brian Enos's Forums... Maku mozo!

wonder where Remingtons would fit in on the above. Some concrete info compared to just pure ranking.
 

·
Registered
Joined
·
477 Posts
Primers used to be tested with a dropped weight at a known distance. They use a different method now a days, but the concept is the same.

So my question would be, 32 oz at what drop? Like 32 inch oz., 44 inch oz.

I would think that the numbers are very subjective. Maybe I've missed something.
 

·
Retired Moderator & Gunsmith
Joined
·
16,083 Posts
Rover, One of my good friends used to hit the gun shows and sell all sorts of reloading supplies and equipment. He finally got tired of the drill and sold out his existing stock of materials. I bought a bunch of powder, bullets and more than 40 bricks of primers in various brands .... rifle, pistol, magnum, and standard. This was before the Obama induced shortages.

Being retired, I had a lot of time to spend on projects so I decided to do kind of like a "Myth Busters" for primers. According to what I had read, there was quite a controversy on what primers were the most sensitive, which ones produced the most "ignition power", and which ones were the most uniform. I gave it a lot of thought and came up with what I considered to be fair tests .... trying not to be biased on any one brand.

I started by first trying to determine order of sensitivity. To keep tests as controlled as possible, I used a S&W Mod 10-6 revolver (4" barrel) with a hammer nose firing pin for all tests. I used Starline 38 Special brass for small pistol primers and Speer 38 Spec target plastic cases for large pistol primers. The strain screw on a S&W can be adjusted for hammer spring tension so that's how I controlled how much tension was required to detonate primers.

I started by loading up a bunch of Federal 100 primers in brass cases (no powder or bullet). As I increased the tension on the revolver's strain screw, I noticed the primers would go "pffft" with light spring tension, then go to a "pop" with increased tension and finally a full "bang" with even more tension. Once I found the minimum tension for a reliable "bang", I then tried Winchesters (two types), Remington, and CCI standard primers. None of them would ignite reliably when hammer spring tension was too light ... some would go pffft and a few went pop. I then increased spring tension a little at a time and repeated the tests using fresh primers each time. So the order was ... Federal 100 were the most sensitive, followed by the new brass colored Winchester WSPs, Remington 1 1/2s came in third. The older Winchester WSPs with nickle plated cups came in fourth and finally CCI 500s, fifth. As I tested the various primers, I noted the depth of the dents. They followed the same order as sensitivity. When the proper hammer spring tension was applied for a good "bang", the primer dents were pretty much the same. This tells me the thickness or softness of the primer cups is related to their sensitivity. I repeated the tests using Small Pistol Magnum primers and the results were different. CCI Magnum Primers were definitely the hardest but the other brands of mag primers seemed to be about the same. I didn't have any Winchester WSM primers with the brass colored cups. Next I tried Large Pistol Standard and Magnum Primers. Again the results were the same as standard small primers except the Winchester WLPs are made for either Standard or Magnum loads so they were used in both large primer tests. The first observation of the pffft, pop, and bang told me there was a threshold for "full power" that I had to explore.

My next series of tests used .357" CCI plastic bullets. They weigh a very uniform 15 grains, look like a HBWC, and are intended for indoor target practice using just the primer .... no powder. I loaded up a batch of each of the 5 small standard pistol primers in Starline cases, keeping seating depth uniform. This time I set up my chronograph in the basement using an artificial light source with the Chrony placed exactly 12" from the muzzle. There's no muzzle flash to spoof the chrony so this worked exceptionally well. With the S&W's strain screw set for reliable ignition with all primers, I chronographed 6 shots with each brand of primer. The velocities were quite uniform for all brands ... ranging from 350~375 fps. This tells me there is very little difference in "ignition power" from brand to brand and with the variance in each brand, none were consistently higher or lower than other brands. When the same tests were conducted with Small Pistol Magnum Primers, the velocity increased to about 425 fps +or- 20 fps. Again, the different brands were very consistent and no one brand was faster or slower than the others.

Standard Large Pistol Primers also produced very consistent results between the four brands and were in the same velocity range as Small Magnum primers ... the exception being Winchester WLPs, which ran about 15% faster than the other three brands (435 fps for Federal, CCI, and Remington vs 475 fps for WLPs). When I tested Large Magnum Pistol primers, (Remington doesn't make one), CCI 350s and Federal 155s produced near identical results at about 500 fps. Of course Winchester WLPs were a bit slower (475 fps).

I decided to play with the strain screw and see what (if any) effect a lighter primer hit would do. This is where the tests got very interesting. With each of the 5 standard primers, I reduced the hammer spring tension below the optimum threshold and all 5 gave erratic velocities over the chronograph. I found by reducing the spring tension just a tad, the velocities of the tested plastic bullet loads would drop by as much as 100 fps. Armed with this data, I loaded up several batches of 158 gr LSWC bullets with 5.8 gr of AA#5 powder. This is one of my benchmark loads that produces a very consistent 850 fps from my 4" Mod 10. At the range, I chronographed a 6 round string with the strain screw tightened to optimum for each brand of primer. My average velocities were very close with all primers and the max velocity spreads were all about 25 fps. When I backed the strain screw out (which reduces hammer spring tension), the velocities started getting erratic. The harder primers were the first to show radical max velocity spreads .... on the order of 200 fps. As the strain screw was backed out even further, the more sensitive primers also stated getting erratic.

Here's what I learned .... different brands of primers will produce near identical velocity results assuming you are comparing Standard to Standard or Magnum to Magnum and there is enough hammer spring tension. Winchester WLPs do not track with other brands of Standard or Magnum primers.

Hammer spring tension can radically change the velocity spreads, which is important for accuracy. Using Federal or the brass colored Winchester small standard primers will give the most reliable ignition with lighter hammer spring tension. The affects will be less noticeable with faster burning powders and way more noticeable with slower burning powders.

With the loads I used for the tests, the dents in the softer primers pushed out ... making them appear to be over pressure. The harder primers maintained good dents. This tells me primers are a very poor way to judge chamber pressure.

If you plan to shoot magnum primers in any revolver, don't reduce your hammer spring tension unless you thoroughly test the gun with mag primers.
 

·
Registered
Joined
·
143 Posts
Iowegan,
That is an interesting test you conducted. Thanks for sharing that. I'm surprised at the variation in primer performance with the variation in firing pin striking force. I would have thought as volatile as a primer is that it would either go bang or not. It shows that some who have installed lighter springs in their guns may be injecting another problem.
Cary
 

·
Registered
Joined
·
5,560 Posts
Iowegan,

Interesting test. Thanks! Hope you don't mind that I copied your post, printed, and will file in my 'Gun folder' at home with other tidbits of interesting information :) .
 

·
Registered
Joined
·
1,876 Posts
Discussion Starter #6
Iowegan, thanks for the information as it is quite interesting. I gather the original thread was concerned with competition 625 .45 ACP revolvers and related to trigger pull but somehow got into small vs. large primer .45 ACP loadings and sensitivity.
 

·
Retired Moderator & Gunsmith
Joined
·
16,083 Posts
Tork, I was under the same assumption until I conducted the above tests. Afterwards, I took my 4" GP-100 (with a reduced power hammer spring) to the range and fired the same AA#5 loads over a chronograph. I found my max velocity spreads were pretty wild ... over 100 fps variation. I installed the factory hammer spring and the spreads dropped to 25 fps ... which is quite good.

Because Ruger revolvers use an "in frame" firing pin and a transfer bar vs a S&W hammer nose firing pin with no transfer bar, there's quite a difference in the amount of energy applied to the primer. With Rugers, much of the hammer's energy is dissipated when the hammer's top step contacts the frame. I found a solution for this and included the details in my DA Gun Guide. By removing .020" from the hammer's top step, you can get about the same firing pin energy with a reduced power spring as you do with a factory spring and a factory hammer, yet have a much lighter trigger pull in both SA & DA.

In theory, the same ammo fired in different revolvers with the same barrel length should perform nearly identical .... but we all know that doesn't always happen. Yes, there are some minor variations with the B/C gap, throat diameters, and bore but that will only changes muzzle velocity and should not affect max velocity spreads. I'm convinced the primer strike pressure (hammer spring tension) is one of the main reasons why ammo can shoot fine in one gun yet have wild velocity spreads in another revolver.
 

·
Registered
Joined
·
8 Posts
thats some good usable information. i'm a new reloading hobbist. your testing feed alot of answers to my many questons on primers.
 

·
Registered
Joined
·
321 Posts
Fascinating. I have a light(er) hammer spring in my 6" GP-100 and thought I was getting away with it because I've never had a misfire, even with small rifle magnum primers. I have noticed some pretty wide spreads on velocity though. I think I'll try the .020" off the hammer before I revert back to the factory spring. The trigger is light and crisp and shoots like a dream
 
1 - 10 of 10 Posts
Top