Improve Your .45 Colt’s Accuracy

Chamber Reaming Tips And Tricks — It’s Easy!

By Roger Smith

Many moons ago in my callow youth, I fell in love with the .45 Colt cartridge while shooting a buddy’s 7½” Ruger Blackhawk. When I could finally afford one of my own, Lady Luck offered me a boxed 1981 7½” convertible, complete with the .45 ACP cylinder in the red bag, in the lobby at the entrance to a gun show. Quick action rescued it from the others reaching for it, and it proved to be a delightful gun. Years later, a 4-5/8″ .45 Blackhawk also built in 1981 turned out to be a disappointing shooter. I just chalked it up to my sadly lacking shooting skills coupled with the shorter barrel. It languished, neglected. The long one shot like it had eyes of its own.

One evening, however, while perusing the Brownells catalog for edification and entertainment, I ran across the Manson Precision Revolver Cylinder Throating Reamer which opens undersized .45 chamber mouths to .4525″. As I was reading the description, the cartoon light bulb above my head began to glow dimly. A dial caliper revealed the chamber mouths of the good shooter were .453″ and .454″ diameter. The mouths of the disappointing gun were less than .450″.


A firm grasp on the cylinder and maintaining control
of the reamer makes for success.


Loads: Left, Lee 452-252-SWC over 8.0 grains of Unique. Right,
RCBS 45-270-SAA over 19.0 grains H4227. Both bullets cast from
wheelweights and lubricated with White Label Lube’s Liquid X-Lox,
fired un-sized. Primers used were Winchester large Pistol. Un-reamed
cylinder targets show poor accuracy. Better accuracy after chamber
reaming. Even at 8 yards, I’d say it was worth the effort to enlarge
the cylinder mouths from .451″ to .4525″.

Some Facts

Blowing a larger cast bullet through a .4480″ chamber mouth so it can sort of find its own way down a .451-.452″ barrel isn’t conducive to satisfying target results to start with. Now add in the fact most .45 chambers are rather generously sized, so the cartridge just sort of lies there in the bottom of that oversized hole. The bullet isn’t even close to being centered when it hits the undersized chamber mouth and then that undersized lopsided bullet gets tipped as it goes through the forcing cone at who-knows-what angle before it enters the barrel. High velocity gasses blow past that misshapen undersized bullet and deposit vaporized lead in the barrel ahead of it. The cartoon light bulb began to shine much brighter. Small wonder 10 yard target results were disappointing, and I couldn’t hit squat at 50.

I promptly ordered the reamer and the companion Chamber Throat Reamer Pilot Pak for 45 from Brownells. Yes, internet research turned up alternative ways of wrapping various things around various things and using various abrasive compounds with an electric drill to do the job, checking your work with a caliper as you go. Instead of jackassing around with the Bubba methods, I chose to do it right.

Current price of the .45 reamer is up to $80 and the Pilot Pak is $60 nowadays, but what is the cost of a replacement cylinder if you screw up? Buy the right tools, and the job is quick, simple, easy and safe. Besides, why do we take on new projects, if it isn’t to buy more tools? While you’re ordering the reamer and pilots, also buy a can of Brownells Do-Drill cutting and reaming oil, as recommended in the directions.

I followed the instructions, and the results were downright thrilling! It made the gun well worth upgrading with a Power Custom free-spin pawl. I also installed the Bisley-style half-cock hammer and trigger, so it can also be loaded just like a Colt single-action army, but both of those upgrades are subjects for future stories.


A jacketed .452″ bullet makes a quick way to determine whether
your chamber mouths are too small. The bullet should easily
slide in, not stop part way.


Ruger single action chamber throats are easily checked on the
spot with a .452″ jacketed bullet from your pocket before the
negotiations begin.

More Adventures

A couple of years after reaming the Blackhawk’s cylinder, I found a leaded-up 2004 bird’s head Vaquero in .45. Dismal targets, even after cleaning the lead out of the barrel. Same undersized chamber throat problem. Same solution. Same improved results.

I’ve always had difficulty getting a consistent hold on that bird’s head grip, even with nice aftermarket “gunfighter”-style grips, so I put a Lightning-style grip frame from NC Ordnance on it and took it to the range. What an improvement! From an inexpensive plastic MTM pistol rest I shot six rounds each of two distinctly different loads. Different style and weight bullets (255 and 283 grains) with different powders. I flinched on the first shot, and put the next eleven into one ragged hole at 8 yards. Now we’re talking! But that’s also an upgrade for yet another story.

Recently I succumbed to a couple more Ruger .45’s, an ex-cowboy action shooter’s stainless 2005 New Vaquero and a lower mileage blued 1998 Blackhawk, and they both had that same old problem. Manson’s instructions are good enough, but as I was about to go to work on them, it occurred to me American Handgunner readers with no previous experience might appreciate a well-illustrated detailed step-by-step guide to doing it themselves. There are always details which don’t make into the printed instructions coming with whatever. Editor Roy agreed, so, here goes. We’ll use the stainless gun for this article.


You’ll need the Manson .45 Cal Throat Reamer and
the .45 Cal Throat Pilot Pak.


You’ll need cutting oil, mineral spirits and compressed air.
A tuna can to hold a small amount of oil is spill-proof, but a
capable plastic film can in a block of wood with a 1¼” hole and
a plywood bottom doesn’t waste oil, although it does drp off the
brush. A plastic drip bottle (not shown) also works well, but
can be pretty messy to fill in the first place. Brownells
Do-Drill is the cutting oil recommended in the instructions.
Thanks, Michael, for the loan! I didn’t have any and it
was on back order.

Easy How-To

Start by using a soft enough work surface so your pilots don’t go rolling off into Never-Never Land when you dump them out of the plastic bag. Be careful to not lose the extra c-clips that come in the bag. They’re very easy to lose when you remove them from the reamer to change pilots and that’s why Manson includes extras. Don’t lose any of them before you even get started.

Remove the empty cylinder from the gun, thoroughly clean all of the chambers, and test-fit the various pilots to see what size is the tightest fit in your chambers. Check each and every chamber. You may actually need two or even three different sizes.

The most difficult part of this whole job is removing and replacing those *@*#! little c-clips to change the pilot bushings on the front end of the reamer. I’m no longer 17 and burdened with excess testosterone, so these days it seems I only have two hands. However, it seems to require several more to remove the c-clips without a special tool. Doing the Mechanic’s Vocabulary Exercises makes me feel a little better, but doesn’t make the job any easier.

So, let’s take a little side trip, and remove them the easy way. Yep, with another new tool, except we have to make this one ourselves. I’ve never been able to find a ready-made. Cheat, and look ahead to the photo of the two screwdriver blades. We want to file one down to that round notch in the end of the blade, so we can easily push the c-clip off.

Don’t grab one of your extra ¼” hex drive screwdriver bits and try to notch it with your bargain-bin file set. Doesn’t work. Trust me. Screwdriver bits are hard, meant for long life when power driven. File sets are made to sell cheaply, and to be used for softer stuff. Not a good combination.

Go buy an inexpensive, hopefully softer steel screwdriver. I bought two of the Doit number 322423’s for show and tell for $1.79 each. I spent the bigger money on two good files. One was a USA-made (maybe it was new old stock) Nicholson Slim Taper triangular file 7″ long, not including the tang. The other was a blister-packed Nicholson #01765 8″x3/16″ Special Purpose Chain Saw file, made in Brazil. While you’re there, buy a file card and a file handle or two. Jamming a file tang into the palm or heel of your hand is kinda ugly.


Removing and replacing the little snap ring to change
reamer pilots can be pretty frustrating.


Use an inexpensive screwdriver and a couple of good sharp files.
After you have a good V-groove started, switch to a 3/16″ round file.

Getting To Work

Clamp the screwdriver in a vise, and use the triangular file to cut a nice, deep v-gouge into the screwdriver blade, centered as best you can. Check your work with a 3/16″ drill bit, because that’s the size groove in the reamer shaft the c-clip pops into. Clean the file frequently with the file card. When you have a good v-groove started, switch to the round file, and keep going until you’re a just little past the halfway point as measured with your drill bit. It’ll probably work as-is, but my screwdriver blade was just a trifle thick for full-depth engagement. If you don’t already own a hollow-grinding stone from Brownells for correctly grinding custom-sized screwdriver bits for your guns, blow the extra $6 and get one when you order your Manson reamer and pilots. I used mine to hollow grind a little of the tapered blade of my cheap screwdriver so it could fully engage in that little c-clip slot.


The object is to end up with a screwdriver with a
round notch in the end of the blade like this.


With the right tool, removing the c-clips becomes easy.

Doing The Job Itself

Now, install the correct size pilot. One word of caution: when removing the c-clip to change the pilot, hold the reamer in a cloth in one hand while you push the c-clip out of the slot with the other hand. That little humdinger will fly! If you don’t catch it in the cloth, you may never see it again.

Reaming the cylinder is a hand job. Don’t even think of clamping your cylinder in a vise or of chucking the reamer in a drill press and turning it by hand. You’re going to remove very little metal, and the reamer must go through straight. Any sort of rigid setup must either be absolutely perfect, or the reamer won’t go through straight. Don’t do it. To repeat, this is a hand job. Relax. This really is going to be easy, even for a first timer. If you can pick grapes without crushing them, you can do this.

I think the screw-pressure tap handle coming with those cheap tap sets from you-know-where is much easier to use for this job than a good quality collet-type tap handle.

You’re going to hold the cylinder in one hand, and the reamer in a handle in the other hand. If you pay attention to what you’re doing, you’ll easily be able to tell by feel if you’re tilting the reamer as you turn and push it through the cylinder hole. You need to be able to feel both the side-to-side and forward pressures as you turn the reamer. Don’t force anything. Yes, it does take firm pressure, but just let the piloted reamer align itself.

You did make sure the chambers are all good and clean, didn’t you? Good. Using a soldering flux brush, swab a little bit of Do-Drill on the pilot and on the leading edges and in the flute grooves of the reamer. A small drip-type bottle works well, too, but can be messy to fill in the first place. No need to juice up the whole reamer. All the cutting is done by the leading edges of the flutes.

From the rear of the cylinder, carefully insert the reamer with a slight clockwise twisting motion so the pilot glides smoothly out the front. Tilt the front of the cylinder slightly downhill so the oil keeps the front edges of the reamer well lubed, and keep pushing and turning gently. You’ll soon feel it make contact, and here’s where the action begins. Now begin turning the reamer clockwise while applying forward pressure. Pay attention to the feel, and keep the reamer straight. Push and twist. Push and twist.


Just opening the chamber mouths from .451″ to .4525″ removes an impressive-looking
amount of metal. No, that bottom reamer flute isn’t all chipped and chewed up. That
is a reflection from the lights on the oil and chips along the edge of the reamer flute.


After reaming, all the oil and chips must be carefully cleaned from the reamer.
Mineral spirits from a squeeze bottle and canned air make the job easy. I’m
using an old plastic Paterson photo print tray leftover from my darkroom days
to catch the runoff.


Never turn a reamer counter-clockwise, like you do with a tap to clear the tapping chips. Reamers are different. Turning them counterclockwise will cause the metal chips you have cut out to dull and even chip the cutting edges of the reamer when you drag the cutting edges back over those previously cut chips. Don’t do it!

Just keep firmly but gently pushing and twisting the reamer until it clears the front of the chamber. Stop. Do not withdraw the reamer yet. It must be completely clean of all that steel you have scraped out of the chamber mouths. The reason I like the cheap tap handle so much is I can easily remove the reamer from the handle while it’s still inside the chamber, then push it on forward and out the front. No need to fumble around risking turning the reamer backwards cleaning it while it’s still in the cylinder before you can withdraw it from the rear.

Use canned air to blow the oil and chips off the reamer. Next I use mineral spirits in a condiment bottle to thoroughly hose off all remaining oil and chips from the reamer, then blow it some more, until I’m sure it’s completely clean.

Repeat five times, and you’re done. Make sure the reamer is really clean, lightly oil it with your favorite, and put it away in the storage tube it came in.

Make sure all six holes in the cylinder are completely clean of metal chips, oil the base pin and lightly grease the ratchet teeth as usual, put it back in the gun, and go try it out. If you’re doing a blued gun, you might want to thoroughly degrease the chamber mouths and cold blue them before lubing and reassembling.

Ruger .45’s may be notorious for undersized chamber mouths, but that’s not the only make where you can find the problem, nor is the problem limited to .45’s. Manson Chamber Mouth Reamers and Pilot Paks are also available for .38/.357’s and .44’s. Check your own smokepoles and you may be able to easily make a mediocre one into an excellent shooter like I have done — four times now.

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