Ballistics by the inch

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



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.

October 21, 2015 - Posted by | .45 ACP, .45 Super, .450 SMC, .460 Rowland, Anecdotes, Data, Discussion., General Procedures | , , , , , , , , , , , , , , , , , ,


  1. If the discrepancy is a function of barrel length, why is the highest discrepancy apparently in the mid-range of barrel length tested for the two larger loads? It seems to be a non-linear relationship.

    Comment by Tim Weitzel | October 21, 2015 | Reply

    • I seem to be missing what you’re seeing, Tim. If you compare the Super/SMC numbers for each weight and barrel length, the pattern of difference is:

      40 50 50
      40 35 0
      20 30 0

      As quick & dirty as these numbers are, I wouldn’t over-emphasis 5 or 10 fps. And the barrel length difference between the G30S and G21 is just 1.4″ (approx). As the weight of the bullet increases substantially (15 gr and then 30gr) that probably has as big or bigger effect than the difference between the two pistols.

      I just think that the lighter bullet has a chance to clear the barrel before all the powder full combusts in the SMC loads. Does that make sense?

      Comment by James Downey | October 21, 2015 | Reply

      • Okay, well, my calculations are within your error factor but different from what you posted. At any rate 50 fps is not exactly 0, which is why I was looking at the higher two loads.

        Here are my calculations.

        1185 1250 1550
        1125 1200 1500
        60 50 50

        1130 1225 1420
        1090 1180 1420
        40 45 0

        1080 1160 1310
        1060 1130 1310
        20 30 0

        Comment by Tim Weitzel | October 21, 2015

      • D’Oh!! Of course, you’re right, Tim. See, that’s what happens when I try and dash off a comment reply when I am doing a couple of other things. Sorry about that!

        The middle set of numbers out of the carbine (1420, 1420) is a little surprising, I agree. That’s the set that I would expect to see change if I were to be more rigorous about testing. Or perhaps the first set (1550,1500) would change.

        But I think overall my interpretation is still probably true — that there is a differential between the two types of cases which changes how completely the powder charge burns before the bullet exits the barrel.

        Comment by James Downey | October 21, 2015

      • It seems to be a reasonable hypothesis.

        Comment by Tim Weitzel | October 21, 2015

      • Your “discrepancy data sets” also occurred in the broken in barrel. You said the
        other two were both Brand New, (G30S and Beretta Cx4) and I would postulate that the increased drag of a new barrel would have dampened out differences. Just a Guess!
        (he said _postulate_!!! lmao)

        Great catch, Tim Weitzel! I “saw that” but it did not register until I read your comment.

        Comment by underground12x8 | December 25, 2015

  2. JIM: Only one comment, and I see my initial misgiving was unfounded, but I would have suggested using small standard pistol primers vs. large standard pistol primers, to avoid having a difference that was too small to measure. Apparently that was unfounded!

    Your analysis seems to hold water as well, great work! If you re-do these tests with the usual BBTI regimen, you may consider the small pistol primer versus the large pistol primer, no magnums 😀 One might expect an even greater spread of measurements? Or did you use the Magnum primers because that is standard practice for the SMC rounds? Great Info!


    Comment by underground12x8 | October 21, 2015 | Reply

    • Honestly, I couldn’t find hardly anything from a reputable source about SMC loads. So I went with the Magnum primers simply because the SMC stands for “Small Magnum Cartridge”, and I figured might as well give it the benefit of the doubt.

      I think that it’s largely a moot point, because the SMC cartridges are pretty rare, and it is unlikely most people would ever have a reason to use them. And even if you do, the difference between the two isn’t *that* large (and may well disappear with a different type of powder).

      Comment by James Downey | October 21, 2015 | Reply

      • That is entirely logical. I believe your sample size proved sufficient, due to your vast experience and the spread in the data set. In fact, the data generated seems to fit an entirely logical explanation and rationale. If I ever get a chrony, I may test some things relating to primers, but that device is much lower on my list. But I am sure I will want one, once I obtain the other equipment.

        Comment by underground12x8 | December 25, 2015

  3. Between the 45 Super and 450 SMC are the case wall thicknesses identical as well? I know next to nothing about these two cartridges. But I assume that could impact the results between the two.

    Awesome test. Thank you for conducting and posting the results.

    Comment by Stephen | October 22, 2015 | Reply

    • To the best of my knowledge, yes they are identical in every regard except the size of the primer pocket.

      It’s a very interesting cartridge in several ways, not the least of which is that the case is noticeably more robust (both heavier and a denser/stronger metal formulation) than either the .45 ACP or the .460 Rowland — meaning that it helps give more support even in pistols which don’t have a completely supported chamber.

      Comment by James Downey | October 22, 2015 | Reply

  4. …another late PS:
    Federal makes a small primer 45 ACP, not sure if it is a totally separate cartridge, but my friend has to sort these out when he reloads 45 ACP. I was hopeful that this brass is a suitable substitute for the SMC brass, or at least a good candidate for loading 45 Super.
    I would imagine it fulfills some of the “advantages” that the SMC architecture has over the
    common Large Primer 45 ACP. Input, Jim?

    Comment by underground12x8 | January 23, 2016 | Reply

    • Sorry for the delay in responding … I had missed the notice on this new comment.

      To the best of my knowledge, the brass you’re talking about does NOT have the same specs as .45 Super/.450 SMC brass, which has a different & stronger metal formulation. Personally, I would be reluctant to push it much past usual .45 +P loadings.

      Comment by James Downey | January 28, 2016 | Reply

      • Still a very timely response 😉 I am a patient man!

        I will do some cutting, but I would imagine the metallurgy is very similar to the standard Federal Brass in 45 ACP. Limited to +P, makes sense. Thanks Again!
        I have been working on a Hi Point (groan) 4595 extended capacity carbine, 28 round 1911 Korean Sourced Drum magazine, the conversion magazine catch supplier has beat me to the punch on running this drum because I told him my intentions, and he found it VERY Reliable!
        Hi Points are all +P rated, and one of our fellows at the forums has ran 4 Super with good results. I’m thinking a Stout +P loading, in the 185 or 200 grain range, which will have a good trajectory. A Carbine Specific loading (relatively slow burn powder) matched to the 17.5″ barrel would be a really sweet shooter 😀
        There are also some great new products for rails from LongShot MFG that revolutionize the optics and sights arrangements, making them ON PAR with AR offerings!
        I am also excited to try some Underwood +P rounds, I know the G20 loves the hotter loads like Buffalo Bore and Underwood 😀 (I Do Too!)

        Comment by underground12x8 | January 28, 2016

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