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Cracked bolt replacement issues

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Em-one-car-bean View Drop Down
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    Posted: Jul 10 2017 at 5:52pm
I was at the range recently and my carbine started to jam up. I chalked it up to not enough lube and dirty ammo. Well after about 15 more rounds it completely jammed shut. Me nor anyone else at the range were able to get it open. I went home and took it apart to get the bolt out and to my surprise there was a hairline fracture on the right locking lug, barely noticeable on top and getting worse towards the bottom. The bolt was a type II, I will upload some pictures of the crack. Seeing the need for replacement I ordered a complete used saginaw bolt off ebay that looked to be in great shape

Fast forward to today. I got the bolt (which looked literally almost new) and prepared to install it. It had some cosmoline on it so I soaked it for a while in mineral spirits (I do not have a bolt tool at the moment). While it was soaking I noticed some substantial burrs on the left side of the receiver near the left lug lockup and after some research I concluded that this was probably at least partly responsible for my broken bolt. So I filed the burrs down and installed the new bolt, went to the range to test it, and first two rounds did not go off, I was using aguila ammo at the time. I also had a box of tulammo and armscor as well so I loaded up a mag of each and crossed my fingers. Sure enough both of them worked, I shot all 100 rounds from both boxes with no jams or problems. Then back to aguila which would not work, I tried 5 different bullets and all the primers were dented but not enough to set them off apparently. Before I cracked/replaced the bolt my gun preferred aguila and would not jam at all with it, but would occasionally jam with the armscor and tulammo. Now it doesn't work at all with aguila but likes the other stuff, go figure. As a result I have about 6 50rd boxes of aguila that I cannot use. 

Does aguila have hard primers? Should I replace the hammer spring or op rod spring or any of the components on the bolt? What are some common reasons for a cracked bolt other than burrs?

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blackfish View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote blackfish Quote  Post ReplyReply Direct Link To This Post Posted: Jul 10 2017 at 7:01pm
Sounds like a headspace issue to me. Did you check it when you swapped bolts?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote floydthecat Quote  Post ReplyReply Direct Link To This Post Posted: Jul 10 2017 at 7:27pm
I take it to mean that you have a complete replacement guts-n-all? Head-space could certainly be the issue, but it could be a firing pin. Since you had cosmoline on the replacement, the pin could be gooked-up a little. Certainly, you need to take it all to pieces and clean it up. Some ammo will have the primer set a tad deeper than others and I don't know if Aguila is in that family. I make sure I set mine no deeper than flush. You may need to "practice" getting the bolt disassembled by-hand, or just spring for a bolt tool....you will be glad you did sooner or later.

I know how even a small burr in the left bolt lug latch area can break a bolt.....been there and done that not too long ago. I tested a bolt by hand and it would slide-in-and-out and rotate, but there was a noticeable slight drag and I just chalked it off to..."it will wear-in". Well...it did not wear-in and I cracked a bolt. During all this, I had a few failure-to-fires and was chalking it off to ammo, but it wasn't. It was that small burr that was obviously "cocking" the bolt off line enough to cause the FTF issue. Once I extracted my head from a deep dark area...I seriously polished-out the burr and all that ammo that did not shoot, shot on the first strike. Make double-sure you have that restriction polished-out and that new bolt will practically fall into place on an empty chamber.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Em-one-car-bean Quote  Post ReplyReply Direct Link To This Post Posted: Jul 10 2017 at 9:15pm
Yes the bolt is a complete replacement (I will keep the cracked one for spare parts). No I did not check the headspace since I do not have the gauges (bad I know), but the gun was rebarreled recently and I was told by the gunsmith the headspacing was correct. I know changing out the bolt can change the headspace. I did measure the bolts and they were both the exact same length, inlcluding the depth of the face. The only discernible difference between them was the ejector plunger was a different shape. Other than spending $75 on a set of gauges I am pretty much out of ideas. I have given it a good looking over and I can see no other abnormalities. Maybe I just got a particularly hard or deep set batch of aguila primers. After hearing you say that I really think everyone should check for burrs on the receiver it seems like a fairly common problem but there is not too much information on the web about it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote blackfish Quote  Post ReplyReply Direct Link To This Post Posted: Jul 10 2017 at 10:01pm
Measuring overall length of the bolt and/or the depth of the face won't tell you anything.

The critical dimension is the distance between the plane of the bolt face and the plane at the rear surface of the right locking lug. That's where the difference in headspace enters when you change bolts.

Absent actual headspace gages, you could measure your Aguila cases to see if they are systematically different from the tulammo and armscor case lengths.

Too short for your chamber and you get light strikes and often no bang.

Too long and you could, IF YOU ARE ONE LUCKY SOB, get the same "light strikes" if the hammer is prevented from fully impacting the firing pin in a bolt not fully locked into battery! If unlucky, I hope you have insurance.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote floydthecat Quote  Post ReplyReply Direct Link To This Post Posted: Jul 11 2017 at 7:06am
Originally posted by blackfish blackfish wrote:


Too long and you could, IF YOU ARE ONE LUCKY SOB, get the same "light strikes" if the hammer is prevented from fully impacting the firing pin in a bolt not fully locked into battery! If unlucky, I hope you have insurance.



Amen on that. The bolt may "look" like it's rotated and locked, but light-strikes on known good ammo can be a huge warning-light that it has not fully rotated. Strip the gun and slide the bolt thru the action with your fingers on an empty chamber. It should fall right into place into the lugs and slip right back up and out under finger pressure only. If you detect any bumps or resistance, find out what's causing it. The safety feature in the gun is doing it's job by not allowing the hammer to fall on the firing-pin. Like mentioned above, if the cases are too long....same thing happens. Bolt won't rotate and lock. If the bolt runs free and you're satisfied there are no mechanical issues, it just about has to be head-space or out-of-spec. ammo.

Find another gun, or a buddy that has one and test fire that ammo in a known good carbine. If it shoots in his, it should shoot in yours. I've heard things about it, but it mostly concerns it being dirty. You can get a decent set of calipers fairly cheap from places like Lowe's, Home Depot or Harbor Freight to measure those cases. If the are over 1.29....don't shoot 'em.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sling00 Quote  Post ReplyReply Direct Link To This Post Posted: Jul 11 2017 at 7:18am
As a minimum I would at least invest in a FIELD GAUGE to check headspace.   Also good to have during the "inspection period" when buying a rifle, especially from an individual..."trust but verify"  On a quick Googlin' I saw a Forster on ebay $29.95 + $2.99 shipping, or the GO and NO-GO for $59.95 + $2.99 shipping. 

Here's a quick FYI:
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bonnie Quote  Post ReplyReply Direct Link To This Post Posted: Jul 11 2017 at 2:52pm
Buy just a go gauge. It measures 1.290.

Cut a .005 piece of feeler gauge, add to end of go gauge/bolt face. This is the 1.295 no go gauge measurement.

Cut a piece of .012 feeler gauge, add to end of go gauge/bolt face. This is the 1.302 field gauge measurement.



The head space needs to be checked when replacing a bolt.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Em-one-car-bean Quote  Post ReplyReply Direct Link To This Post Posted: Jul 11 2017 at 6:48pm
Thank you bonnie for the economical alternative to buying all the gauges, I know I have a feeler gauge laying around here somewhere and $25 or $35 is much more doable than buying all three. As for the ammo, without having any empty brass with me I can say this: The cases are all the same height, from an ocular inspection on a level surface (3 groups of 3). The aguila ammo does however have the bullet seated deeper making it about ~1 mm shorter than the armscor or tulammo. One other noticeable difference is the extractor groove on the aguila is much thinner than the other two, not sure if that would effect anything but ejection though.

Since everyone is telling me I need to check my headspace or risk blowing my gun up I think I will order the gauge and check it out.

I am under the impression that since the barrel is new, and the replacement bolt also appears new then it is possible I have too short of a chamber since the gunsmith checked the headspace with the old and much more worn bolt when installing the new barrel, thus making it too short for the new bolt with tighter tolerances. I think it is unlikely that the headspace in the chamber is too long (shot out) since I have only fired a few hundred rounds through it so far.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote blackfish Quote  Post ReplyReply Direct Link To This Post Posted: Jul 11 2017 at 7:35pm
An "ocular inspection"? You're talking thousandths of an inch difference here. Without at least a caliper to take a measurment you will not be able to "see" any significant difference.

And you would need to measure the UNFIRED cases from your Aguila collection. The fired cases would be shorter than they were before firing.

Beware of trying to augment a gage with feeler stock. When you cut it, unless a laser or waterjet is used, the edge created by your snips is NOT "flat". So you must add "that" to your new gage's extent, or NOT.

You will NOT go wrong buying a GO gage and a FIELD gage. Those are the gages relevent to assessing a USED firearm. You can always sell them for not much less, and maybe even a bit more, than you paid for them if you decide the carbine is really not "your thing". Otherwise they are a once-in-a-lifetime purchase.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bonnie Quote  Post ReplyReply Direct Link To This Post Posted: Jul 11 2017 at 8:18pm
Using feeler gauges to measure headspace with a Go gauge.
Not my brilliant idea. Learned this from some genuine firearms experts above my pay grade. Never have had an issue. If you want to take the time, you can find out the exact headspace of a particular gun using this method.

I am not opposed to have a set of go, no go, field gauges myself.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote blackfish Quote  Post ReplyReply Direct Link To This Post Posted: Jul 11 2017 at 9:06pm
Brownells sells a chamber length gage for about $6 which will tell you what your EXACT headspace is. No need to buy a GO gage or to try cutting hardened spring steel feeler gage stock. It is essentially a variable length headspace gage. To use it, you need some basic reloading equipment as well as the ability to lookup SAAMI chamber length specs yourself (or ask somebody else on the internet what they are) though.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sling00 Quote  Post ReplyReply Direct Link To This Post Posted: Jul 12 2017 at 6:40am
Originally posted by blackfish blackfish wrote:

Brownells sells a chamber length gage for about $6 which will tell you what your EXACT headspace is.
I had not seen those.  Pretty neat!  Why do you think they say,"Should not be used in handguns, semi automatic rifles, lever actions rifles and pump action rifles."?  Lack of force control for loading and ejecting the cartridge?

It is interesting the various means for checking headspace.  I may be a little too cautious but for something like this I prefer the right tool made for the job.  I had forgotten that you also need the GO gauge for installing a new barrel or bolt replacements.  For a "new" installation you might want a No Go although the Field Gauge will work, just doesn't use the "new" installation tolerances.  Like blackfish said, "You will NOT go wrong buying a GO gauge and a FIELD gage. Those are the gauges relevant to assessing a USED firearm."
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Post Options Post Options   Thanks (0) Thanks(0)   Quote floydthecat Quote  Post ReplyReply Direct Link To This Post Posted: Jul 12 2017 at 7:51am
If one does this a lot, then surely having the gauges is a necessity. In light of the possibly blowing-up a gun in your face, having the gauges seems appropriate at any price. You can make some determination though just using what you have. Gut the bolt and insert a round (make sure it's spec.) in the chamber. Using finger pressure, close and rotate the bolt on the round. You have no firing-pin in the bolt, so setting it off is practically an impossibility. It gets somewhat subjective at this point, but the bolt should easily rotate and close on a spec. round. You're looking for tight head-space here and if it doesn't close smoothly....it's too tight, or something is binding.

I have found an extractor making contact with the chamber. The extractor should never overhang the front skirt and kiss the breech-face.

I did find a post in another forum concerning Aguila which indicated they may be known for case inconsistencies. I don't know, but your gun apparently doesn't like it. If they are inconsistent and long....maybe they work in a looser gun, but not a tight gun.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote blackfish Quote  Post ReplyReply Direct Link To This Post Posted: Jul 12 2017 at 12:02pm
Originally posted by sling00 sling00 wrote:

Why do you think they say,"Should not be used in handguns, semi automatic rifles, lever actions rifles and pump action rifles."? Lack of force control for loading and ejecting the cartridge?


That I don't know, never noticed that warning before. Maybe it's because they also have headspace gages they'd rather sell you for 5X the price. As to force control, just remove the springs as you would when using a standard headspace gage (i.e. don't load the gage into the chamber like a cartridge) and I don't see, nor have I encountered, any problem in actual use, for semi-automatic rifles at least. YMMV
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SWANEEDMB Quote  Post ReplyReply Direct Link To This Post Posted: Jul 12 2017 at 1:50pm
How many carbines if anyone knows blew up due to a bad bolt? Sure, have heard a failure due to some ones reloading but never a bad bolt. Really have enjoyed this thread.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote W5USMC Quote  Post ReplyReply Direct Link To This Post Posted: Jul 12 2017 at 1:55pm
Chamber length gauges are not headspace gauges. Chamber length guages are machined to a lesser diameter then the chambers specs to allow them to always reach the point where the chamber ends and the rifling begins in order to get perfection when trimming cases while reloading.  Headspace gauges are machined to near exacting specs of what a chamber should be.  I did recently read a thread about headspace on an old CMP forum where someone said that you could make a no-go guage by wrapping scotch tape over a casing (so many wraps were equal to how ever many thousands of an inch) sounded kinda crazy to me.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote floydthecat Quote  Post ReplyReply Direct Link To This Post Posted: Jul 12 2017 at 2:54pm
May depend on the brand, but Scotch tape is between .001 and .002 thick. I've seen it done on the web on bolt-guns and it's really not all that silly if you think about it. If you're good with a pen-knife...stick a layer on and trim it to fit on the base of the rim. One doesn't usually ram the bolt home on a gauge, it's a matter of "feel".  I'm sure the tape is strong enough for that. Next time I have one torn-down, I may try it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote blackfish Quote  Post ReplyReply Direct Link To This Post Posted: Jul 12 2017 at 7:12pm
I don't believe this is correct, but I'll measure the 0.336" diameter dimension for this gage myself (it looks the same as the case neck diameter for this caliber - yes, 30 caliber does have a "neck"!)



and the diameter for the associated headspace gages the next time I have access to all my stuff.



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Post Options Post Options   Thanks (0) Thanks(0)   Quote bonnie Quote  Post ReplyReply Direct Link To This Post Posted: Jul 12 2017 at 7:24pm
Scotch tape is an interesting exercise but I will go with an actual, measurable piece of feeler gauge that I cut with a sharp pair of scissors in lieu of head space gauges.
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