About a month ago my wife purachased an STI Ranger .45.  If you are not familiar with the pistol, it is a short grip (6rounds) 4" barrel 1911.  Anyway, I expected some jamming, etc during the break in.  So far we have put about 700 rounds through it and it still has a problem with the slide not locking all of the way forward (only lacks about 1/8") about every 4 or five rounds.  It will usually shoot through one mag before the problem starts, whether the gun is clean or not.  If you take a long break it will usually not have any problems for one mag or so.  I have polished the feed ramp and extractor, which cured its other problems, but this one still remains.  I polished the chamber a little bit, but it hasn't helped.  It sounds to me like it is a chamber -related problem.  I think that the chamber is too tight.  What do you think?  The ammo I have been using is PMC FMJ.  While it isn't the cleanest ammo on the market, I have always found it to be good practice ammo.  It has always worked in my Ruger (yuck!) and my Glock without a hitch.  Anyway I hope someone has some suggestions as to how I could fix the problem.  I am new to 1911s so I figure there are a few tricks that I am unaware of.  Thanks        

Here's something to check, rather than assume chamber is outta spec...

Take an empty mag and run a majic marker or similar over the mags feed lips, top-most edges. Insert the mag with slide locked back and then press the slide release and let slide slam shut. Eject mag and take a close look at the feed lips of your mag. Is the marker on the feed lips still just the way ya marked it.... or did the slide rub off any portion of marker on the lips ya marked?

If it contacted the feed lips, rubbed off the marker, the slide is dragging on the mag lips and this is impeding function. I had this happen on a very early Detonics Combat Master and it did exactly as you describe... on occasion ya had to whack the rear of the slide to get it to go into full-battery, this was defect in early Detonics pistols, and not something I have run into w/ Colts, Auto-Ordinance, Kimbers or later model Detonics pistols, but your description reminded me of it.

If this is the case, suggest ya return the pistol to STI for repair as the mag dragging ruined a few mags, making the feed-lips crack and causing them to be unreliable.

If I'm out in left field, worse that you'll have to do is wipe the mag off.....

Mike

mr_wilson,
Thanks for the reply.  I tried what you said and it doesn't look like there is any contact with the top of the mag.  

A little bit ago I manually cycled a box of ammo through it and about 1/4 of the cartriges failed to go into battery.  I took the ones that didn't have the problem, fired them, and they all worked fine.  I took the ones that didn't cycle, loaded them in my Glock and never had a problem.  Also, the 1911 shoots groups half the size of what my Glock does.  That is part of the reason why I think the 1911 has a tight chamber.  Any suggestions?

By the way, I am NOT trying to turn this into a Glock vs 1911 debate.  

Something else to check is to field strip the pistol and take a close look at the breech face on the slide. I had a 45 once that did what yours is doing and the probem turned out to be a rough breech face. During chambering the base of the round needs to slide against the breech and if its too rough then it may not feed.

I polished mine up just a little and problem solved...don't go over board though with this.

I have had same prob with my 5"gov model, since fitting a new oversized bar bushing. Turns out that it being fitted to match tolerances was fine with good ammo but with cheaper ammo dirter powder, after a few shots did the very same thing.I don't know if your 4" has a bushing, but it still could be simmular prob, very tight fit on lock up.  

Could also be the slide hanging up on the disconnector.

is this factory ammo or reloads? either way, did you notice the headstamp on the ammo that doesn't feed properly? i've had problems with remington/umc brass; i think the rim is thicker on the remington/umc ammo, and has trouble fitting under the extractor. your glock has a hinged extractor, so it tisn't as big a problem there.

Clearly the first thing you need to do is try different ammo. Next, how much lube are you using? Are all of the rails on the slide & frame nicely lubed?

I may be different than most folks but I feel there's no such thing as too much lube on a firearm, specifically a 1911.

There's also the possibility that the recoil spring may not be quite what it should be & is leaving the slide short.

Sounds like the slide is hanging up on the disconector to me.

Check your chamber by removing the barrel from the gun and being certain the chamber is clean and dry. Hold the barrel so the muzzle end is pointed directly down and the chamber up. Drop your loaded round(s) into the chamber and see where they stop from gravity only. The base of the cartridge should be slightly below the top edge of the barrel hood, and should fall out from gravity if you turn the muzzle up. Rounds that do not go far enough into the chamber would have to be pushed in deeper by the slide momentum when firing...which could cause your problem.

If you are shooting PMC, try some premium-grade rounds from another manufacturer. PMC .45 ain't Wolf, but it also is not the equal of something like Federal Match ball. If the chamber is the problem, send it back to the folks at STI. A "fix" may be temporarily effected by using a loading press and a taper crimp die to tightly taper crimp your new ammo before shooting, but you certainly should not have to do this for ths pistol to work reliably.

My WAG is that you will find it to be something other than the chamber. Let a more experienced 1911 shooter fire it and see if they have the same problems...the short slide stroke and reduced weight / increased recoil of some of the small .45's makes them a bit more influenced by shooter technique than others.

I had that happen on a Springfield 1911.

It turned out to be the spring plug/ guide rod.  The rod had a burr on it, and the spring plug wouldn't let it slide all the way into battery.  Quick fix:  Remove the guide rod.  Long fix: Replace the rod and spring plug.

I had a 1911 that I had the same problem with, ran a chamber reamer through it and never again had that happen.

Wow, this thread really took off while I was gone!

ECS,
I did polish the breech face earlier to no avail.  I had the same line of thinking as you did.

IceMan_1,
This one doesn't have a bushing, but I think that the tight lockup might be a problem with this gun, especially since the frequency of malfunction slichtly increases with heat.  Any suggestions on how to alleviate this without hurting accuracy too bad?  Maybe lightly polish the barrel / slide interface?

QCMGR and schapman43,
The disconnector doesn't seem to be the problem from what I can see.

WV_mntn_man,
I was shooting PMC ammo earlier in the process, but the other day I ran a few boxes of Fiocci (sp?) through it.  The stuff worked in my Glock, but everything always works in it.

BobCole,
I have the gun well-lubed and I was very careful about my form while shooting the pistol, as I had the same thought.  As to ammo, I am going to try some of the better stuff out there and see what happens.

ikor,
I did the gravity test and didn't have any problems, even with the crappy - looking Fiocci.  I have also watched my form and I don't think that it is form related.  I am starting to doubt that it is a chamber problem, though.

Matthew_Q,
I polished and checked the guide rod and it seems to be OK.  It has some kind of dual-spring setup - you know, one of those things that makes you say "WTF is this crap?".  Anyway, it does seem to provide consistent pressure and is pretty strong, but I am considering getting a differnt spring to try, just to make sure it isn't the problem.

e-geo,
My original thought exactly.  However, cartridges that I drop in seem to not fit too tight, so I am starting to thik that there is another problem.

Thanks for all of the replies.  While looking at it today, I noticed something.  between the small and large springs on the guide rod, there is a collar.  That collar looks like it has had the hell beaten out of it on its outside edge.  However, I can't find any corresponding marks on the rest of the pistol.  Do you think it would be wise to take a little off of the outside edge of this collar or not?  Just for clarification, it is NOT the collar that goes between the frame and the spring.  It is a collar BETWEEN the collar that contacts the frame and the spring cap.  At any rate, I'll try some better ammo (I didn't think that PMC was all THAT bad!) and get back to you.  Thanks for all of the help.

Sounds like a tightly fitted gun and when it heats up, too tightly fitted.
Drop a line to STI for their advice before tinkering and possibly voiding any warranty.
After all, it's only a month old.

Damn! I went to the STI website to see if they had a FAQ section (they did) and looked at the prices on these things.  This Ranger's MSRP is $1,029.00!  I bought it NIB for $650!  The dealer said they were a reputable brand and that he had received it (the only one) from his distributor for cheap because of some problems the distributor had with STI.  Cheap is an understatement!  Anyway, I am afraid to touch the damn thing now...OK, maybe not, but I can't believe how much these things cost!  No wonder the thing is so tight.  I think I will give it a couplehundred rounds of quality ammo before I call STI though - just to make sure it isn't a break-in issue.  STI recommends at least 500 rounds of hot-loaded ammo for break-in.  Somehow I doubt that my 500 or so rounds of cheap crap (Fiocci) and a couple hundred rounds of PMC is what they had in mind (I usually run lower-powered, cheaper stuff for break-in and work up to hotter stuff, like when re-loading).  I just figured it needed some work because my friends who have bought 1911 pistols had a shorter break-in of 200-300 rounds...I know, stupid me - don't ASS-U-ME anything!  Anyway, thanks for the help.  I have learned a lot about troubleshooting 1911s.  I'll keep you posted.

Have you allowed a different shooter to try the gun & did they experience the same problem?

Mine would work fine for the couple mags when it was clean and then as it started to get a little dirty, thats when the problem ocurred.

BobCole,
Everyone who has shot it has had the same malfunction.  One of my friends has a Colt Commander, which is somewhat similar, and he had the same problem with the Ranger as I had.  It jams on everyone.

e-geo,
That sounds similar to what this pistol is doing.  What is the round count on yours?  I am going to run some hotter ammo through this one for a while an see if that helps.

when the slide hangs up, try and bump/bang the slife forward with the edge of your hand and see if the gun locks up correctly. if it does then its prolly a tight chamber, or the barrels needs to be ramped/throated (if its not already).

i would suspect the dual spring thing might be the problem as well, you could get a full length spring guide or an original standard 1911 short guide system and see if that cures it.

the gun prolly has a very tight chamber which might be reamed a hair bigger.

High_Plains_Drifter, my gun was brand new. Try this, clean the chamber, while the barrel is out of the gun, drop about 50 rds into the chamber to make sure they all go in (case heads should not extend above the barrel hood). Take these 50 rds out and fire them until the gun  malfunctions. Take the rounds that cause the malfunction and set them off to the side. Now, disassemble the gun and drop the rounds that cause the problem into the chamber to insure they don't fully go into the chamber. After doing this clean the chamber. Now drop in the  problem rounds again and see if they go all the way into the chamber.    

Garand1911,
That is what I did when the slide hung up.  That is why I thought it was a tight chamber in the beginning.  I tried what e-geo suggested in the post below yours, and the rounds dropped in just fine.  I am starting to think that it is just an ammo and break-in issue.  I didn't break it in with hot ammo like they suggest and I think it might make a difference.  I am going to try some Winchester FMJ (when I get some more money) and see if it is any better.  The thing sure didn't like Fiocci!