Does primer size make a difference?

Following the success of our .45 Super/.450 SMC tests this summer, I sat down to work up some reloads which would mimic the factory ammo we had tested.

Since both of these cartridges are fairly unknown, there isn’t a whole lot of good information out there to draw upon. But there is some, at least for the .45 Super, and late last year/earlier this year I had worked up some preliminary loads, starting with .45 ACP +P (overpressure) published load data. But that was done using .460 Rowland cases and shot through my converted Glock G21, which I knew could handle the extra power. When reloading, it pays to be careful and conservative.

After I had seen the results from the extensive .45 Super/.450 SMC tests (some of which has already been published), I had a pretty good idea of where the power band for these loads was, and how different guns could handle it. Since I had previously worked up loads for .460 Rowland as well as done a lot of .45 ACP reloading over the years, I figured that I could come up with some pretty reasonable load levels to match what we had seen in the factory ammo.

So I sat down, looked through all my results and what was available elsewhere, and came up with loads* for three different bullet weights I had on hand: 185gr XTP, and 200gr & 230gr FP. I chose to use Longshot powder, which I have used successfully for both .45 ACP and .460 Rowland loads. (This is not an endorsement of any of these products, and I have not been compensated from these manufacturers in any way. This is just stuff I have on hand and know has worked previously.) I loaded 50 rounds each in .45 Super cases, using standard Large Pistol Primers.

But as I was doing so, I also realized that I had a bunch of .450 SMC cases left from the tests. And I figured that it might be an interesting experiment to load those cases to the exact same specs, other than the difference in primer size. To give the cartridge the benefit of better ignition, I used Small Magnum Pistol primers.  Again, I loaded 50 rounds of each bullet weight.

Again, other than the difference in primers, the reloads I worked up were identical.

 

OK, before I go any further, I want to toss in some caveats and explanations:

1. This was an informal test, using only one chronograph and under less rigorous conditions than the formal BBTI tests. It was just me shooting a string of five shots, keeping mental track of what the numbers were for each, and then writing down a ballpark figure which seemed to best represent the overall performance. Also, I wasn’t using the BBTI light-frame which gives us more consistent chrono results.
2. I was using my personal firearms, two of which (the Cx4 and Glock G30S) were brand new — this was their very first trip to the range. Yeah, I got them after seeing how similar guns performed in the .45 Super/.450 SMC tests earlier.

 

Now, about the guns used:

• Glock G30S with a Lone Wolf 23lb recoil spring and steel guide rod package. 3.77″ barrel
• Glock 21 converted to .460 Rowland (heavier recoil spring, compensator, and Lone Wolf .460 R barrel). 5.2″ barrel
• Beretta Cx4 carbine, standard right out of the case. But I am going to install a steel guide rod and heavy buffer in it. 16.6″ barrel

 

Results:

Ammo                                     G30S                                    G21                                             Cx4

.45 Super 185gr                 1185 fps / 577 ft-lbs                1250 fps/ 642  ft-lbs             1550 fps / 987 ft-lbs

.450 SMC 185gr                 1125 fps / 520 ft-lbs                1200 fps / 592 ft-lbs             1500 fps / 925 ft-lbs

 

.45 Super 200gr                1130 fps / 567 ft-lbs                1225 fps / 667 ft-lbs              1420 fps / 896 ft-lbs

.450 SMC 200gr                1090 fps  / 528 ft-lbs               1180 fps / 619 ft-lbs              1420 fps / 896 ft-lbs

 

.45 Super 230gr                1080 fps / 596 ft-lbs                 1160 fps / 687 ft-lbs              1310 fps / 877 ft-lbs

.450 SMC 230gr                1060 fps  / 676 ft-lbs                1130 fps / 652 ft-lbs              1310 fps / 877 ft-lbs

 

Interesting, eh? What seems to be happening is that full ignition of the powder takes longer with the .450 SMC loads. That would explain why there’s more of a discrepancy with the lighter bullets and shorter barrels, so the bullet clears the barrel faster — some of the powder hasn’t yet ignited with the Small Magnum Primer. But with the heavier bullets and longer barrel of the Cx4, there more time for more of the powder to ignite, reducing or eliminating the difference in performance.

That’s my take on it. If you have another one, please comment.

Also, I want to note just how well I managed to emulate the performance of the factory ammo. Compare the numbers above with what I have already published for the Glock 21 and Cx4 used in the tests earlier. And it isn’t published yet, but the G30S numbers are also right on-the-money for how the G36 used in the tests earlier performed (the two guns have the same barrel length). In all instances, my reloads* performed within 10-15 fps of the factory loads.

 

Jim Downey

*So, what exactly were those loads specs? OK, here’s the data, but provided with the understanding that you should WORK UP YOUR OWN LOADS starting below these amounts, and accepting that you do so on your own responsibility. Also note that any changes in bullet weight, bullet brand, or powder type may/will alter the results you can expect. AGAIN: you use this data on your own responsibility. Be safe.

All bullet weights had a 1.250″ O.A.L.

All were given a slight taper crimp.

185gr XTP rounds had 11.0gr of Longshot powder.

200gr FP rounds had 10.5gr of Longshot powder.

230gr FP rounds had 10.0gr of Longshot powder.

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