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  #1  
Old 09-21-2011, 08:07 PM
Bradd D Bradd D is offline
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Bolt over base malfunction




I have experienced several bolt over base malfunctions with my relatively new Springfield Milspec. Each occurrence has been on the last round of the mag. The mags are CMC Power Mags and they haven't seen much use yet. The pistol has 84 rounds of FMJ and 92 rounds of Winchester Ranger through it. All the malfunctions occurred with the Ranger. One thing that is interesting to note is that all the FMJ and 42 rounds of the Ranger were fired with a buffer and only one malfunction occurred. I removed the buffer and fired 50 more rounds of Ranger and had 3 or 4 malfunctions.

Suggestions?
  #2  
Old 09-21-2011, 08:36 PM
Lord_of_1911 Lord_of_1911 is offline
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way too soon to say on a new gun and could be any litany of things from ammo to mags to the gun itself. Most standard advice is a few hundred rounds of ball/FMJ ammo before as a break-in for the gun. Are these 8 rd mags or 7? if they're 8 rounders, try loading just 7 and see how that goes.

what is a "bolt over face" malfunction...haven't heard that in the 1911 world...can you elaborate...I assume it's nose-diving on the feedramp.

Last edited by Lord_of_1911; 09-21-2011 at 08:38 PM.
  #3  
Old 09-21-2011, 08:47 PM
Bradd D Bradd D is offline
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Here is a photo from Hilton Yam illustrating the malfunction.



Would this mark have anything to do with the problem or is it just from the brass getting dinged on the way out of the gun?

  #4  
Old 09-21-2011, 10:33 PM
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10ring 10ring is offline
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I had a problem like this several years ago and the problem had to do with the slide binding during recoil. This basically would prevent the slide from moving back far enough to get behind the base of the next cartridge. The bottom of the breachface would catch the rim of the case like yours is doing.
  #5  
Old 09-22-2011, 02:07 AM
oldandslower oldandslower is offline
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brad, 9/22/11

I have had a number of similar type malfunctions over the years but none with my Milspec (more than 5000 trouble free rounds so far). I think it is called a breach over base malfunction. One time it was with underpowered reloads which did not cycle the slide fully to the rear which prevented the magazine from lifting up the round in time for the breach to contact the cartridge base. I would think that if you were using factory ammo this is less likely.

Another time it was with a too strong recoil spring which prevented the slide from fully cycling as above. And yet again it has occurred when my magazine springs get weak and are unable to cycle that last round up quick enough to get picked up by the breach. I am sure others with more knowledge will chime in soon. Good luck.

best wishes- oldandslower
  #6  
Old 09-22-2011, 12:03 PM
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Weak magazine spring?

Have you installed a different recoil spring lately?

It may be a combination of a weak mag spring and shorter than full slide travel due to a strong recoil spring because it happens on the last round only.

If shockbuffs are used, this will make the problem worse due to shortening the slide travel, thus reducing the time available for the top round in the mag to pop up fully before the slide returns.
  #7  
Old 09-22-2011, 12:19 PM
rex rex is offline
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Sould have nothing to do with the mag,if the slide cycles enough the next round will pop up in front of the breachface.Your slide is shortstroking.Where's your brass landing and any chance you relaxed your grip?

There is a chance the last round isn't popping up quick enough but on a new mag I would doubt it,trying another mag will tell.The dent in the brass looks too high for that malf,the slide hits at the web and the barrel ramp would be higher,the frame ramp is a mile away.If that's on alot of the brass it's hitting on the way out.You'll see brass marks where it hits after a few rounds.

Last edited by rex; 09-22-2011 at 12:28 PM.
  #8  
Old 09-22-2011, 12:40 PM
Bradd D Bradd D is offline
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The mags don't have alot of mileage on them yet so I don't think it's a problem with the mag springs. I took the buffer out so it isn't that. The recoil spring is the one that came in the gun new. It is possible that I am relaxing my grip due to fatigue.
  #9  
Old 09-25-2011, 01:03 AM
Bradd D Bradd D is offline
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Any other thoughts on this? Bad feedramp geometry maybe?
  #10  
Old 09-25-2011, 07:56 AM
Lord_of_1911 Lord_of_1911 is offline
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if its smooth and free of machining marks and such even if the geometry is off it should be serviceable. I said smooth not polished, it only need be smooth but many polish it. Google it, it's easy to do and easy to F up, too. Bad feed ramps from being too shallow, to off angle (31.5 degrees) seem to be fairly common. EGW makes a mag catch that hold the mag .020 higher than standard to try and counter a bad feed ramp.
  #11  
Old 09-25-2011, 08:36 AM
timcalhoun timcalhoun is offline
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The fact that it is happening with the presumed hotter "ranger" load, and constantly on the last round, points to a weak mag spring or weak recoil spring. When the recoil spring is too light it allows the slide to outrun the mag, not giving the mag time enough to get the round up fully.

Also, as said, It could come from short stroking too. Short stroking can come from a bad grip/limp wristing, too heavy a recoil spring, too light of a load, possibly a problem with the gun itself too. But again, I doubt this because the consistent pattern with the ammo and the last round.
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  #12  
Old 09-25-2011, 08:48 AM
bjg-1911 bjg-1911 is offline
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Check your extractor for clocking and tension first.
Second check the barrel for being out of time.
  #13  
Old 09-25-2011, 08:59 AM
superdude superdude is offline
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Quote:
Originally Posted by bjg-1911 View Post
Check your extractor for clocking and tension first.
Second check the barrel for being out of time.
the extractor is not involved in this malfunction.
  #14  
Old 09-25-2011, 04:53 PM
bjg-1911 bjg-1911 is offline
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I respectfully disagree...

The extractor can cause the slide to slow down if tensioned too high and clocking can let a spent shell slip down and force it back into the mag lips....usually not a problem if another round is coming up to keep it up under the extractor but always good to know when evaluating reliability. All reliability tuning starts with measuring the pistol first and then checking the extractor whether "You" think it needs it or not.
In this case it is not a spent shell and the complete bullet could not fire because it never could come up to make the transition into the chamber which could be from tolerance stacking, such as the mag catch being too low along with a weak mag spring, mag feed lips that are too wide and essentially adding to releasing the round late (due to a weak mag spring) and the slide and disconnector rail getting ahead not being able to push the cartridge forward properly, and possibly improper frame ramp and barrel mouth angles forcing the bullet up in front as well. In addition, the the barrel not swinging down far enough and/or the barrel going up too far into the slide would add to the tolerance stacking and exacerbate the problem. I have repaired many pistols which started off just fine and in short order were jamming due to the barrel moving up into the slide from a standard .045" lockup to .055-.060" depending on the slide lug cuts. This does happen and is caused by the slide lugs and barrel lugs having dissimilar radii letting the barrel stops wear and go "up."
If you are going to reliability tune the pistol ,imho,you might as well take care of all of it and enjoy the pistol instead of making it a lifetime project....YMMV.

Barry

Last edited by bjg-1911; 09-25-2011 at 05:02 PM.
  #15  
Old 09-25-2011, 05:14 PM
bjg-1911 bjg-1911 is offline
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I respectfully disagree...

deleted....double post

Last edited by bjg-1911; 09-25-2011 at 05:17 PM. Reason: double post
  #16  
Old 09-25-2011, 08:13 PM
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Unlikely since it happened both before and after the buffer removal but check for spring bind. Easy check. I see that it is a milspec so it is a full sized pistol again reducing the chances but itis a quick and easy check that positively eliminates one cause of short stroking.
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  #17  
Old 09-25-2011, 10:48 PM
skylerbone skylerbone is offline
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Best to start with the magazines and work from there. Start by marking the mags to keep track of which are problematic and if available rotate the originals back in to see if they fair any better.

If the Chips are newer it isn't likely the springs but not every pistol likes every follower and it is possible the magazine bodies are out of spec in some way.

Next would be feed ramp but that would best be determined by Springfield.

Best of luck getting it running again.
  #18  
Old 09-26-2011, 11:09 AM
bjg-1911 bjg-1911 is offline
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Magazines...

Measure the width...factory specs are approximately, give or take a couple of thousandths,.538". If your mags are above .548"+ you might have failures to drop properly and feed lip swelling, etc. The magwell width is approx. .550" - .560". You have to have room for "dirt." If the mags are swelling , and Chip McCormicks tend to do that along with early Wilson 47D's, you can squeeze them in a vise to re-establish the correct width, however , if they do it more than once get rid of them. The length of a mag is 1.380" front to back.
Now you have the info you need without guessing.

Last edited by bjg-1911; 09-26-2011 at 11:16 AM.
  #19  
Old 09-26-2011, 11:23 AM
OnTarget1911 OnTarget1911 is offline
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Why re-engineer?

Try hand cycling the rounds through with no recoil spring and all mags and only one round in the mags. Should allow you to eliminate or point to timing problems or just roughness on the breechface, feedramp, barrel throat or mag or follower snags and problems. Just cycle them very slowly with no recoil spring in the gun and it should be easy to see if it hangs up and if it does where.

Jess
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Last edited by OnTarget1911; 09-26-2011 at 11:26 AM.
  #20  
Old 09-26-2011, 02:23 PM
Bradd D Bradd D is offline
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Quote:
Originally Posted by OnTarget1911 View Post
Try hand cycling the rounds through with no recoil spring and all mags and only one round in the mags. Should allow you to eliminate or point to timing problems or just roughness on the breechface, feedramp, barrel throat or mag or follower snags and problems. Just cycle them very slowly with no recoil spring in the gun and it should be easy to see if it hangs up and if it does where.

Jess
I just did this with 7 Power Mags and 2 Springfield factory mags. 4 of the Power Mags released the round in front of the extractor. The remainder of the mags fed fine with the round snapping up under the extractor after it entered the chamber.
  #21  
Old 09-26-2011, 02:54 PM
OnTarget1911 OnTarget1911 is offline
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Mag difference?

When you look at the ones that work vs. the ones that don't, can you see or measure any difference in the shape of the mag lips, or the distance between them? Do the rounds sit in the mag at a different angle on the ones that work vs. the ones that don't? Do they release from the mag too soon? If so are the lips on the ones that don't work too far apart? I know it seems like a lot of questions. Also, when you were at the range did you track which mags seemed to fail and which ones did not?

Jess
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  #22  
Old 09-26-2011, 03:11 PM
jerm1812 jerm1812 is offline
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Hand cycling a gun tells us very little about how it actually functions in real time. If a round is jumping in front of the ejector is happens as the slide slams back which causes the round to jump up into the chamber ahead of the extractor. A round cannot jump in front of the extractor after the slide has come forward and stripped the round from the magazine.
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  #23  
Old 09-26-2011, 03:15 PM
OnTarget1911 OnTarget1911 is offline
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Stripping

Did you not say that the gun would feed rounds ahead of the extractor when hand cycling? If that is the case then the gun would not need the "shock" of firing a round and the slide "slamming" to the rear to cause the round to pop loose. If it won't function hand cycling then there is not much chance of it working in live fire. IMHO and as always, YMMV.

Jess
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  #24  
Old 09-29-2011, 05:26 AM
banjoboyjohn banjoboyjohn is offline
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BOB malfunction

in every 1911 i've owned, CMC mags have cause the same problem. the hotter loaded ranger ammunition cycles the action faster and the mag spring isn't pushing the rounds up fast enough. personally if i had to use an8 8 rounder, i'd use ACT mags. they're cheaper too. you can get them from advancedtactical.com
  #25  
Old 09-29-2011, 05:20 PM
CWarner CWarner is offline
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The biggest clue is that you added a buffer to a working gun.The very first thing to check is that you put the recoil spring in correctly.

I would start there.

A reversed recoil spring can be very erratic in its affect on the operation.
No problem one moment, and slide will hardly move the next.

Sometimes the SITUATION is the biggest clue to a problem.



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Last edited by CWarner; 09-29-2011 at 05:31 PM.
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