I've got a pistol where the headspace is larger than desired for accuracy, but not actually excessive to the point of being unsafe. This extra headspace is the result of over ambitious removal of machining marks from the slide breech face. I am trying to figure out if the barrel can be adjusted to compensate for this material removal. And if it is too late for the original barrel, can an aftermarket gunsmith fit barrel be fitted to compensate for this?
<<< I am trying to figure out if the barrel can be adjusted to compensate for this material removal. >>>
In a word no, if your gun displays excessive headspace it can not be fixed by modifying or welding on your barrel. What relegates your headspace is the gap or distance between the end of your round and the breechface. Where the round stops in your barrel can not be changed by you unless you want your round to go further in the barrel then reaming is in order. The only thing you could do to your barrel is weld on the barrel hood or lower lugs but this will not change your headspace dilemma.
Personally I doubt that you have a headspace problem even if you filed on your breechface, as you would have to file a SHITE load of steel to get you excessive headspace. The best way to check excessive headspace is to purchase a no-go gauge from Brownells and put it in your barrel and see if it links up in your slide. Or you could drop in a good brand name round and after slide removed and barrel linked up into slide start slipping in feeler gauges and see what the biggest one you can get between the end of the round and the breechface and if its less than I beleive a .022 then your fine.
I dont beleive headspace is your accuracy problem more like loose barrel bushing or overcut lower lugs. Both very common in most box stock 1911's.
I've got a few more questions on the topic if you don't mind. I actually replaced the barrel bushing with a Match bushing very shortly after purchasing it, and it did improve accuracy. As for the amount of material removed, it was probably about 10 thou. As I said, I don't consider it to have unsafe headspace, just more than I think it should have. :) The pistol is fairly accurate, though I have come accross several references which state that accuracy will suffer some amount due to variable primer ignition due to headspace. Hence the reason for the question. Also, when firing factory ammo, I get some primer flattening, which was my first clue that I had increased the headspace. More importantly, I have a BarSto match barrel that I originally purchased to go into this pistol. After realizing my mistake many years ago with the breechface, it seemed like I could be shorting myself by fitting the BarSto into this slide. However, I recall in one of your write ups regarding barrel fitting,that as long as the hood is overly long to begin with (prior to fitting) that you like to smooth out the breechface. This lead me to believe that perhaps the fitting process would compensate for the breechface work. So the question would be, am I doing myself a disservice by installing the BarSto into this slide? Also, what would be the best method to determine if the barrel lugs are overcut on the original barrel?
That's right the first step I usually do when fitting a barrel is measure the slide from the first locking lug to the breech face then measure the barrel. If it is a match oversize barrel and the slide is in spec then I find I must usually remove material from the end of the barrels barrel hood. Once I confirm this I start to polish and remove all scratches from the slides breechface. Once that is done I remeasure slide and start to fit the length of the barrel hood.
Ok your second question is will you be doing a disservice fitting the bar-sto to this slide. Probably not, if fit properly it should greatly improve your groups. But ensure you have all the proper tools to fit it and if its short chambered ensure you have a 45 ACP finish reamer as some match barrels are short chambered.
OK the test to see if the barrels lower lugs are overcut well thats easy rack the slide real fast and then with the thumb of one hand push down on the top of the barrels hood and see if you can see it go down at all. You can also remove barrel and see if large end of the barrel link is standing taller than the barrels lower lugs it should not be so tall that if does not permit the slide stop to bear evenly on both barrels lower lugs.
PS Bear in mind most 1911's coming across my bench display the symptom of overcut lower lugs and it does not make for a unsafe firearm just a not so accurate one as the barrel after every shot will return to a different place when it links up.
Seems to me a short-chambered barrel would fix the headspace problem. You could finish ream it to gain the proper headspace.
Of course the extractor would still stick out farther than usual, but it oughta work anyway.
Do not forget to look on Chris' site, http://www.blindhogg.com/gunsmithing.html for the info he was giving. He goes into good detail on what to do and what tools to use. We are privileged to have him here! I say the same for GrahamCracker, http://www.geocities.com/kemays/ as his home page offers valuable information. His info considers building the 80% and 1911 gun smithing.
Thanks again Chris. I did the check for the overcut lugs; if I press real hard, the barrel moves down about 3-5 thou.
Yep, it sounds like a short chambered barrel is the only way to actually eliminate the headspace. I actually read all of the articles over on Blindhogg's site a couple of years ago (as well as Frank's.) I'm looking forward to the "Reliability" installment over at BlindHogg's site, when it is added.
I have also machined my own 40% and 80% 1911's, but the barrel geometry on the 1911 is quite complex, and not always easy to visualize. I had actually worked the breachface over about 11 years ago, when I first bought the pistol. I have since fired about 75,000 rounds through it. :) In that time I have fit a match bushing, an ambi safety, a beavertail grip safety, milled and serrated the top of the slide, and milled front and rear dovetails for Heine straight eight pro night sights.
Part of my dilemma is whether to install the BarSto in this pistol or fit it to one of my self made stainless jobs, including one with an unfinished stainless slide that has no sight cuts whatsoever. It looks like BarSto may not offer a short chambered 1911 barrel, so I guess I will have to check Kart and the others to see if they do.
How can you tell if you have so much headspace in a 1911 that it's unsafe?
Easy get a no-go 45 gauge from Brownells and see if your barrel links up properly with it in your barrel. If so you have a headspace problem and I would not shoot that pistol.