About once a month a new thread appears concerning the use of cast boolits in a 1911. IMHO the majority of the problems with failure to go fully into battery, or leading in the first inch of the barrel, when folks first try cast in their 1911 result from the lack of throating in many newer production line models. As I recently needed to throat a barrel for a commander build I was completing for my wife, I decided to take a few pictures and post this thread explaining this simple process. Maybe it would make a suitable "sticky"
These are the boolits that I use in all of my 1911s. My goal is always that they function reliably without any leading. The lineup is a H&G #68 style SWC, the BDacp and a group buy HP version of the BDacp
Here is the BDacp sized .451 and dropped into a very tight 1911 chamber (bore is .449) easy to see that it is not going to allow the pistol to go completely into battery. In this barrel the HP BDacp and the #68 did better, but still did not fully seat.
This pick is the BDacp after throating. This is what I want to see, the head of the case just slightly below the barrel hood
Here is what is required: A 1911 throating reamer and handle, and a little cutting oil.
This is a closeup of the end of the chamber prior to throating it. Note the abrupt sharp edge at the end of the chamber, and the abrupt square start of the lands. In most barrels all that is needed is to slope the start of the lands just a bit. As this chamber is very tight, and the bore only .449, the reamer will also put a bevel on the end of the chamber. The real issue with most leading in the first inch of the barrel is that you simply can't shove a .452 object through a .450 hole, when both have square edges, without shaving off some lead. Rifles have "ball throats", revolvers have "forcing cones" and before the advent of CNC mass produced 1911s, nearly all nonmilitary 1911s had someone spend the 20 seconds needed to throat the barrel before it left the factory.
This is a closeup of the end of the chamber after throating. If you click on this pic it will get big enough to really see what's going on. Note the taper on the end of the lands and the bevel at the end of the chamber. In a barrel that slugged .4505 - .451, (the more common dimension I see in modern 1911s), you would barely be able to discern the bevel at the end of the chamber. In a .452 bore, the reamer would only touch the lands. It's about 30 seconds work to get to this point. This particular reamer has been used between 30 and 40 times, and I've lent it out 7 or 8 times, so it is not as sharp, and does not cut as clean as it once did. It is also apparent that it was back turned at some point, (rotated counterclockwise while in contact with the lands, a definite no-no), so it's probably ready for retirement.
Bore slug for this barrel.
Throat slug. I do this by starting a soft lead ball into the throat, then I stand the barrel up with a 3/8" brass rod in the barrel against the ball while I tap the ball a few times with another brass rod from the chamber end. This embosses the end of the chamber on the ball so when I tap it back out I have a definite point at which to measure the throat. .452 is all the reamer will do, if you over do the reaming, you just get a little longer section at .452 I prefer just enough throat to allow my boolits to enter the very start of the barrel so they are centered up before they get the big kick in the rear sending them on their way.
I am going to try and embed a link to a short 20 second vid that junkyard was kind enough to put on U-tube for me. I don't know if it will work or not. If not, maybe junk could put it in a response to this thread.
https://www.youtube.com/watch?v=f6FX...ature=youtu.be
Ok, the link seems to work! My wife is demanding film credits for shooting the short clip, "Thanks Claudine!". In any event, this is a very quick and easy process. The key being to use plenty of cutting oil, and take your time to feel for the very start of the lands before you try and turn the reamer. NEVER turn the reamer backwards against the lands as this will turn down the very fine, sharp leading edges of the reamer.
BD