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Rebuilding for Horsepower: .45 to Ten with Brownell’s

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Incessant arguments of caliber and  handgun vs. long gun aside, the best home defense weapon you can get is a Callahan full-bore auto-lock double cartridge thorough gauge — especially if you can get one with a customized trigger. It's the best gun made by man.

Failing that, a 10mm semi-automatic is a great option: just not for everybody. This is because the 10mm will ride roughshod over some shooters. If you can effectively drive this caliber — please forgive the mixed metaphors — then you'll be able to exploit the ballistic advantages it provides over the venerable but effective .45 and much younger .40.  Grain for grain, the 10mm is a substantially more powerful round. It's actually more akin to the old .41 Magnums used by cops in the 70s, though the two rounds are not as close as some would have you think.

That's why we chose a .45-to-10mm conversion as the second gun in our series that began with Searson's Piece Maker in Issue 25 (Brownell's Gunnery insert page 12). Not because conversions are a great way to get access to every bathroom in Target, but because having the option to shoot both the Ten and the Forty-Five is a great and wonderful thing.

Like, getting a massage from six hands worth of great and wonderful.

Rebuilding for horsepower - Glock 21 to Ten Mil - 4

Granted, such a conversion might not be as obvious or as intuitive as making one from .40 to 9mm but there are a number of reasons to do so—so long as you respect Newton's Third Law. With 700 foot pounds on tap, the greatest attribute of the round is also the one that puts most shooters off.

So why choose the 10mm?

Greater magazine capacity and improved terminal ballistics are the two most obvious. Throw the right Pearce Grip, Arredondo or other magazine extension on there and you can have as many as 20 rounds with which to greet uninvited guests in the middle of the night. 10mm ammo can be purchased in types ranging from 125gr solid copper all the way up to 220gr hardcast. This provides an incredible amount of diversity, for anyone who might have to smokecheck a pack of homicidal circus clowns to someone under siege by rampaging bears.

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It's also important thing to remember here is you’re not losing the .45. You’re just adding the versatility of the 10mm. Having the ability to shoot different ammunition from the same gun (with a barrel change) is never a bad thing, although if you have the same distractibility that I do you might consider using one of those adhesive label printers to keep your barrels and magazines straight.

Put a weapon light on it and you might just have one of the best bedside/nightstand guns around – though I personally would never carry one out and about, and I wouldn't carry one with a short barrel

That seems to be a contradiction, I know. Fact is, a G20, G21 or similar sized pistol is just too big and heavy for me to want to haul it around all the time. I might consider carrying it in a few specific instances, like if I was in some remote area of Wisconsin or in between Rosie O'Donnell and a buffet table, but otherwise I'll leave it in a nightstand safe at home where hopefully I won't every have to use it. Brownells Glock Upgrade 1Brownells Glock Upgrade 2

Brownells Glock Upgrade 3

Our conversion took less than 2 hours to accomplish. It would have been faster but we forgot some of our tools. Alterations were made to a used Glock 21 purchased online from J&G Sales. It took about 5 minutes to find what I wanted and order it, though contrary to what Amy Schumer and other idiots would have you believe, I still had to wait for it to arrive at an FFL and then do the background check before taking possession, just like any other Title 1 firearm.

Rebuilding for horsepower - Glock 21 to Ten Mil - 2

After that it was a simple matter of grabbing our parts from Brownell's and getting to it. Upgrades included a titanium safety plunger, Zev Ultimate Trigger Kit, Bar-sto barrel and a new extractor. Strictly speaking we didn’t need to change out the latter, but for $20 we figured we might as well be thorough. Here's a list of what we used while rebuilding for horsepower.

•Lightning Strike – Titanium Safety Plunger

•ZEV Technologies – Fulcrum Ultimate Trigger

•Bar-Sto Precision Machine – Semi-Fit Barrel

•XS Sight Systems – 24/7 Big Dot Tritium Express Set

•Glock Extractor w/ Loaded Chamber, New Style

•Glock Spring Loaded Bearing LCI

Rebuilding for horsepower - Glock 21 to Ten Mil - 5

We also threw a Surefire X300 Ultra on there, because a weapon built for defending hearth and home should have. a. light. on it.

The end result? We went from a gently used G21 in .45 to a smooth-shooting pistol chambered what's prob'ly the most effective auto cartridge around, with the option to switch back to .45 in moments. Sure, it could use some body work but so could a lot of MILFs and they're still fun to play with.

Now, that would be the end of the story, but some of you are no doubt posing a very good question.

If the 10mm is such an effective round, why didn't it catch on? Why isn't it more widespread nowadays?

The short answer is, recoil management and evolution. Issues with recoil management led to a reversion to 9mm in some cases and the development-then-adoption of the .40 S&W round in others. Evolution, of both gun and bullet, have largely removed a need for such a bullet. This leaves it as the gun of choice for a much smaller group. In fact, 10mm handguns have been described as the “weapons of the cognoscenti.” There's a lot of truth to that.

The 10mm cartridge is rightfully described as a niche or “cult” round, and that's not likely to change. Not as long as modern ammunition delivers good performance even in smaller calibers.

Rebuilding for horsepower - Glock 21 to Ten Mil - 7

Few people consider evolution when they're talking guns or defensive rounds and frequently conflate the weapons and ammunition of a quarter century ago with those of today. The two are by no means the same. Just like cars, airplanes and breast implants, guns and bullets are constantly improved with technology. This has been true, albeit at varying rates, since long before Claude-Étienne Minié had his epiphany. Hell its been around since before anyone thought to call deflagration, well, deflagration. Couple this evolution with advancements in metallurgy, better CNC machining potential and other manufacturing improvements and you wind up with more effective weapons all around.

Consider just this one 3 year stretch. Interestingly it's around the time I first began carrying a firearm professionally.

“To examine the relative improvement in cartridges, the three best ammunition types per caliber were selected based on their wounding value. An average wounding value per caliber and test year was computed for each cartridge. The average wounding value of the three best .45 Auto cartridges increased by 63 percent over the 3- year test period. Accuracy indexes also rose slightly between 1989 and 1992. Wounding value and accuracy both improved in the 10mm Auto cartridges tested. ”  (Stone, FBI Law Enforcement Bulletin Vol. 64, Jan. 95)

The rate of bullet improvement might change, but improve they do. Getting 1350 fps out of a 9mm handgun these days is not a challenge. Twenty-five years ago many pistols couldn't have handled it.

With the ready availability of excellent 9mm, .40 and .45 semi-auto cartridges today, most to them substantially easier for the average shooter to control, why would you carry a 10mm?

Well — cuz you can, and cuz you want to. If you can and you want to.

Rebuilding for horsepower - Glock 21 to Ten Mil - 9

It isn’t new. The G20 came out over a decade and a half ago. I don’t claim to know its original history. I’ve heard its development ascribed to different people, so lacking any certainty I’ll go with the Bren Ten Birth of the 10mm Auto and the Whit Collins – Jeff Cooper connection as my origin story of choice.

According to the original ammunition manufacturer (Norma) the first food for a 10mm was a 200gr full-jacketed truncated cone bullet loaded to a mean pressure of 37,000psi, generating a muzzle velocity of 1200fps and energy at the muzzle of 635 ft-lbs. That’s getting close to some low end rifle loads. Newer bullets, with more recent bullet technologies, are substantially more effective now than they were then – and they were at the top of the scale when they first came out.

Rebuilding for horsepower - Glock 21 to Ten Mil - 8

The first “modern” production 10mm rounds first became available in the early 70s. Prototyped from .30 Remington Auto rifle shell cases cut off and straightwalled to accommodate a .38-40 Winchester bullet, it quickly proved to be a formidable cartridge. It did not rise to prominence, however, until after a 1986 gunfight in Dade County, Florida between 8 FBI agents and 2 bank robbers. The fight ended in the deaths of 2 agents and the wounding of five others. The death of the 2 suspects is noteworthy not because they deserved to live but because of how long it took to put them down. This led to a tremendous push for a more powerful round and a change from revolver to semi-auto. By 1989 repetitive testing showed the 10mm to be effective in 2 key areas — perhaps the 2 key areas (at least as I understand it): energy transfer and ballistic transfer. By the end of 1990 nearly 10,000 FBI agents were in the field with it.

“After the shooting of a number of FBI agents by two felons in Miami on April 11, 1986, the 9mm round lost favor with the FBI. After a battery of tests in which the operative criterion was how deeply a round penetrated, the new 10mm standard was adopted for use in a Smith and Wesson Model 1076 Third Generation pistol. The FBI Academy's Firearms Training Unit conducted eight tests. The tests revealed that an FBI-specified loading by Federal Cartridge Company, using a 180-grain Sierra hollowpoint traveling at 1,035 feet per second out of a 6-inch test barrel, was second only to the Norma 170-grain JHP in its penetration. The Norma round, however, was deemed too unmanageable in the shorter barreled pistol favored by the Firearms Unit. As of November 1, 1990, the first groups of 9,500 agents were going into the field with the new gun and cartridge. At the time of the writing of this article, there had been no firings in the line of duty. Law enforcement agencies will be watching the FBI's shooting reports to determine if they justify switching to the 10mm cartridge also.” Lydecker, Law Enforcement Technology Jan 1991

More agents carrying 10m followed, but none of them kept them for very long, for reasons articulated above. The 10mm Auto was an extremely effective bullet; it was just too difficult to manage for the typical agent (or LEO — it was also adopted by such agencies as the Kentucky and Virginia State Police). This led to the evolution of the .40, which is a story for another day.

Another fair question is, why didn't you get something in ten before now? Well, 2 reasons. First, for pragmatic home defense. I eschewed the 10mm for years because no one else in my house would have been able to effectively run it. That has now changed, and other members of my family now have the background, training (and are old enough) to have their own preferred tools. Another was my first experience with it, which was shooting an S&W 1076. In retrospect I probably let my dissatisfaction with the weapon (that's a polite way of saying I thought it sucked sweaty dog balls) color my perception of the round. The greatest reason, however, was without a doubt finances — I've never been the guy who had large numbers of handguns. A pistol is a tool and I've owned a couple to use as tools, but it has only been recently that I've been in a position to buy one for no more compelling reason than I just wanted it.

Thankfully that has changed, which is why I now have a Browning Hi-Power and a newly upgraded Glock 21 converted to shoot 10mm.

Life is good and so are guns.

Rebuilding for horsepower - Glock 21 to Ten Mil - 6

Stepping it Down: Forty to Nine

If you aren't looking for something with the horses of a 10mm and cannot find a Callahan Full-Bore Thorough-Gage, you could also consider a .40 cal to 9mm conversion — note, that's forty caliber, not forty millimeter. If you've got the stones to handle a 40 mike-mike semi-auto handgun you clearly need no advice from someone like me. That, or your name is Wun Weg Wun Dar Wun.

We did that very thing with another Glock while working on that G-Ten. The .40 is a fairly hot round, certainly more difficult for some people to manage than a 9mm, and while many people are perfectly capable of driving a .40 with great accuracy the ammunition is more expensive. So why not have the option of a second caliber?

There's no reason not to. Here's what was added to the G23 while converting it to 9mm:

Apex Tactical Specialties Inc – Ultimate Safety Plunger

Trijicon – HD Tritium Night Sight Set

Lone Wolf Dist – Conversion barrel

Apex Tactical Specialties Inc – Action Enhancement Trigger w/Gen 3 Trigger Bar

Almost forgot —  you will also need magazines for it — a gun's gotta eat. The ones we used for the 40-to-9 can be found here; for the .45-to-10, right here.

Now, keep in mind that none of this is going to make you a better shooter. It may improve your performance, but it won't make you any less of a soup sandwich behind the trigger if you haven't mastered the fundamentals. So, definitely fine-tune your blaster, absolutely — but if you're spending money on equipment to fix problems instead of ammo and training you're wrong.

Skills first. Gun improvements after. Aesthetic improvements last.

Rebuilding for horsepower - Forty to Nine 3Rebuilding for horsepower - Forty to Nine 2

Should you consider a conversion? That's a question only you can answer. If you can drive it effectively and afford to feed it during training, sure. Don't buy one without trying it, and like any defensive weapon you might have to stake your life on, don't take any single person's opinion as gospel, no matter what their background is. Get multiple perspectives and get one on the range. You wouldn't buy a vehicle sight unseen without driving it, and that's not a machine built for the purpose of killing someone.

Rebuilding for horsepower - Forty to Nine 1


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That's it for now. Go forth and conquer.

Rebuilding for horsepower - Glock 21 to Ten Mil - 1

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