Big iron: building the longslide .45 auto.
From "BIG IRON" by Marty Robbins
OK, so Mr. Robbins was most likely not referring to a 1911 pistol when he referenced the big iron in his classic song. I get it. But, every time I start thinking about longslide 1911s that song pops into my head.
Properly constructed, a 1911 can deliver phenomenal accuracy. Bred for combat and refined by custom gunsmiths for more than a half century, you won't find many pistol competitions that aren't dominated by old slab-sides. So, if you're a 1911aholic like me and you already have a bushel basket of Government models in various flavors what do you add to the collection next? How about a long slide target model?
But, you say, those are hideously expensive custom guns. Out of the price range of blue collar dudes. Heinie, Nighthawk and Wilson big irons run $3,000 to $5,000. What to do? Build your own, of course. You'll need some parts and tools (or someone with tools who will loan them to you) and probably some expert assistance along the way but it's not that difficult.
Generally, customers I deal with who desire a long slide pistol already have a 5-inch 1911 and we build a 6-inch slide assembly for their existing frame. The gun I used as a demo for this article is a customer-supplied G.I.style Rock Island Armory 5-inch model produced by The Arms Corporation of the Philipines (Armscor). Lou, my customer, desired a long slide target pistol and he had a spare RIA gun on hand we could use as a chassis.
The first step in a project like this is gathering parts. I purchased the long carbon steel slide from Caspian Arms (www.caspianarms.com) in Wolcott, Vt. Machined from barstock and hardened to RC40, it arrived in the white with a Novak front sight dovetail and classic Colt style vertical serrations at the rear. I ordered it with no 1 rear sight cut because I prefer to machine my own ^ a bit higher than the standard low mount. However, for the hobbyist who doesn't have access to a milling machine Caspian slides can be purchased with the rear (Bo-Mar) sight cut already machined for an extra $60. That's a deal.
The barrel I selected is a 6-inch Kart gunsmith fit model I purchased from Brownell's (472-021-045). Kart barrels are machined from forgings with a highly polished bore that is great for the lead bullets many bullseye competitors employ in their handloads. The gunsmith-fit models are supplied with an oversized hood (width and length) and oversized bottom lug. The fit of the bottom lug to the slide stop is critical for best accuracy and special tools are required for best results. If you lack machine tools, a hand-driven Brownell's lug cutter (080-000-068) will work. I used one for years before I owned a mill. You might be able to find a drop-in style 6-inch barrel, but be advised it is unlikely a barrel that is pre-fitted to generic tolerances will provide the best accuracy obtainable from your pistol.
We purchased a .225" high Novak plain black front sight from Brownell's (662-000-013). I chose Novak because they offer a wide variety of front sights that fit the same .330" x 65 degree dovetail so if Lou gets bored with plain black we have the option of swapping it out for a gold bead, white dot; tritium dot or a fiber optic model. Most serious target shooters prefer the plain black post. This one might be a bit high but if it is we'll just mill it down until we get the zero we want.
The rear sight will be Ed Brown's copy of the original Bo-Mar adjustable sight. Bo-Mar sights graced the slides of 191 Is for many years but the company closed its doors leaving pistolsmiths temporarily without quality adjustable rear sights. Into the breech stepped Ed Brown. His copy of the Bo-Mar is probably better than the original, made in USA and reasonably priced. Beware of cheap, imported copies. Trust me on this.
The first step is to test fit the Caspian slide to the stripped RIA frame. Caspian slide rails are on the large side of the tolerance range and often require lapping, but I was pleasantly surprised this one slid right in place with virtually no horizontal or vertical play. Nice!
Normally, you'd think fitting the barrel would be the next step, but you would be wrong. Experience dictates that machining the slide for sights should be done next. The reason for this is the slim possibility of a mishap on the milling machine. Let's say you've fitted your barrel and you are machining the dovetails for the sights as a last step before final assembly. Whoops! The slide moves in the vise while a cutter is engaged and puts a nice gouge in it or the dovetail is diagonal because the head on your mill/drill isn't tightened down sufficiently. You've bought a slide. If you've already fitted the barrel you may own it also. Replacing a slide is in the $200-$300 range. Add another $200 for a barrel. Stuff happens. Thinking things through ahead of time and will save you dough in the long run.
If you bought your Caspian slide with the sight cuts you can skip this section. The Bo-mar cut for the Ed Brown adjustable sight is done in four steps. First, we begin our primary cut one inch back from the breech face and mill down the rear of the slide to create a flat for the sight base. Traditionally, the depth for this cut is around .100" because most factory slides already have a dovetail for a fixed rear sight and material is removed down to the bottom of the existing sight cut. Our Caspian slide was ordered without a rear dovetail so we could position the sight a little higher with a corresponding higher front sight. Target pistols should have sights that are highly visible. My final cut was .088" hoping that a front sight height over .200" would give us a good zero. We'll see how it works out later. The second step is cutting the dovetail using a .359 x 60 degree dovetail cutter (Brownell's 080-621-060). The cutter is slightly undersized so some hand fitting wiH be required for a good press fit. When fitting the sight base remove material from the sight itself rather than the slide. The golden rule of gunsmithing is ALWAYS REMOVE MATERIAL FROM THE CHEAPEST PART, If you screw it up the sight only costs $60 compared to over $250 for the slide. Get my point?
The last rear sight milling operation is the pocket at the very rear of the slide for the blade. You can use a square cutter for this operation but I had a 3/16" radius ground on a 1/2" carbide end mill specifically for this job so the radius at the front of the pocket matches the front bottom corner of the sight.
With the rear sight mounted and centered, we drill the elevation screw hole. When milling the cuts for the sight base, the slide was level in the mill vise but for drilling the elevation screw hole it should be slightly muzzle high so the sight leaf is level and the elevation screw won't bind. Center a #21 short screw machine drill in the hole where the elevation screw normally lives and spot the slide through that hole. Now chuck up a #31 drill and run it down all the way through the top of the firing pin tunnel. Tap this hole with a high quality 6-48 gun tap (carefully). Blow all the chips out of the tapped hole and deburr the firing pin tunnel as necessary before you install the screw.
The Novak front sight cut only required final fitting to install the front sight. Novak sights are pinned with a roll pin through the slide but we won't pin this one until after the pistol is zeroed.
We now move on to the heart of the matter: barrel fitting. We'll need the stripped frame, the barrel, a working barrel bushing that fits loose enough we can install/ remove it without a wrench and the slide stop.
The first barrel fitting step is the hood. Our Kart barrel hood will be oversized in both width and length so it can be fitted precisely to any slide. First, the width. The slot in our Caspian slide above the breech face measures .439" and the width of the Kart hood is .453". Add .003" clearance to each side and we will need to remove .020" total material from the barrel. This is easily done with a safe-sided pillar file. Take a few strokes off each side keeping the cut square and test fit the barrel. Repeat until the barrel drops into the slide so the end of the hood contacts the breech face. I use .003" as a tolerance for side clearance but this number isn't critical. The sides of the hood shouldn't contact the slide when the pistol is assembled. Use a loose bushing and a barrel alignment block (Brownell's 080-000-041) that keeps the bottom lug vertical while test fitting the barrel. When you can insert a .003" feeler gage between the hood and slide on both sides with the barrel alignment block in place you're done.
Now we must shorten the hood so the barrel can lock up fully into the slide. Clamp the barrel vertically in your bench vise, take a stroke or two with a file and test fit. The result we are looking for is a barrel that can be fully locked up with a light tap on the bottom lugs from a plastic hammer. The hood should be kept square to the breech face. When you get close, ditch the file and use a stone. Final fitting is done with lapping compound so the hood just kisses the breech face when the barrel is in firing position. I fitted hoods with files and stones for many years but once I aquired a lathe I used it to shorten the hood length. It's much easier to keep it square than free-handing it with a file. Keep in mind that some older breech faces aren't square so adjusting the hood to fit them is necessary.
Cutting the bottom lugs to fit the slide stop is the most critical operation where accuracy is concerned. Back in the dark ages when I built bullseye pistols as a young sergeant, we used a special hand-driven lug cutter. The barrel, slide and frame were assembled, the cutter was inserted through the slide stop hole and rotated by hand while forward pressure was applied to the rear of the slide. With care, this will work. Brownell's sells a basic lug cutter (080-000-068) that is a simplified version of the tool we used.
However, having used both manual and machine tools to cut lugs I have to say a mill or mill drill with the proper fixture and a digital readout is the way to go. It's simply more accurate and allows the gunsmith to adjust lug contact with the slide stop during the cutting operation. I use a Weigand barrel fitting fixture which presents the barrel to the cutter at the proper lockup angle and allows the operator to remove the barrel and test fit it at any time without losing zero.
The last step of barrel fitting is finishing the chamber so headspace is correct. When we shortened the barrel hood we also shortened the headspace. This operation requires a chamber reamer and headspace gages. Take a cut, assemble the barrel to the slide, drop a headspace gage into the chamber and try to push the barrel up into full lockup. Repeat as necessary until the barrel can be locked with the "GO" gage in the chamber.
One unexpected problem we ran into when fitting the barrel was the frame feed ramp location. It was a bit farther forward than say a Colt or Springfield Armory gun. This caused the barrel ramp to slightly overhang the frame and surely would result in feeding issues. The rear of the Kart barrel was machined forward and the barrel feed ramp re-cut to create the proper jump between the frame and barrel. This is not a ding on RIA because their factory barrel fit fine and they can manufacture guns to whatever spec they desire but it's something to be aware of if you use an Armscor pistol as a base gun.
Fitting barrels requires specialized tools and knowledge. It may be best to farm out this job to an experienced professional.
With the barrel fitted, we can replace the loose "working" bushing with a precisely fitted one. For best accuracy the barrel bushing inside diameter must be a close fit to the barrel and the outside diameter should be a light press fit in the slide. Back in the day the bushings we used to build National Match pistols for the military teams had undersized bores and were hand reamed to fit the individual barrel. The outside diameters were expanded with plugs in a hydraulic press to fit the slides. Today, there are other options. Evolution Gun Works (www. egwguns.com) in Quakertown, Penn., can supply bushings in custom sizes. Our Kart barrel measured .580" at the muzzle and the Caspian slide bore was .699" so we simply ordered a bushing to fit.
The Caspian slide was supplied in the white (bare steel) and required finishing. The RIA frame has a parkerized finish and we attempted to match it rather than refinish the whole pistol. The stripped slide was degreased, bead blasted, warmed up under hot water and submerged in a hot tank of Brownell's Manganese Phosphate solution (082-200-128) where it proceeded to fizz like the proverbial Alka Seltzer tablet for a few minutes. The resulting color was dark, almost black, and matched the original RIA parts pretty well.
The sights are now installed on the finished slide along with the barrel, barrel bushing, firing pin, firing pin stop and extractor. Caspian slides utilize a small-diameter 9mm firing pin regardless of caliber so keep that in mind when ordering parts. The firing pin stop was milled down to provide clearance for the rear sight and a Caspian extractor was polished, installed and checked for tension.
Another consideration when assembling longslide 1911s is the recoil spring and spring plug. Ideally, we would prefer to use readily available standard-length recoil springs. If we run a standard spring plug a conventional spring will be an inch too short. We can remedy this situation in two ways: a combination of a standard plug and a shorter Commander-length plug stacked end to end or a special long plug with an internal shoulder that shortens spring travel by an inch. I usually go with the long plug sourced from EGW. Due to the extra slide mass spring rates will be slightly less than a standard Government Model. Subtract 2 pounds from the spring rate you would normally use for a given load in a 5-inch gun. The pistol we built for this article functioned fine with a 14 pound spring and 200-grain lead semi-wadcutters.
With the slide assembly finished we moved to the frame. The only frame modifications requested by the customer were a long aluminum trigger, tuned trigger pull and arched, checkered mainspring housing.
A Cylinder & Slide long aluminum trigger (209-000033) dropped right into the frame. The original RIA sear and hammer were prepped on a Power Custom series 1 stoning fixture (713-070-002), the factory sear spring was replaced with a (properly adjusted) Wolff spring and the hammer pin was replaced with a slightly larger one from Cylinder and Slide. The final trigger pull weight was set at a crisp 3 1/2 pounds with minimum overtravel.
Trigger work is an acquired skill. Incorrect adjustment of the fire control parts can cause a dangerous situation. If you are not experienced in this type of work I would suggest hiring a professional for best (and safest) results.
The finished pistol was test fired primarily with lead 200-grain semi-wadcutters over a moderate charge of Bullseye or WST. My personal accuracy standards are 1" 5-shot groups at 25 yards firing hand-held or 2" 10-shot groups at 50 yards from the machine rest. As I write this we are in the grip of a Maine winter and the machine rest has been put up until Spring but hand-held test groups look good so far and I'm sure our new Big Iron will not disappoint.
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|Date:||Feb 20, 2016|
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