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 Commercial Carbine Bolt Destruction
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americanboy
Advanced Member


USA
260 Posts

Posted - 03/21/2017 :  11:43:33 AM  Show Profile Send americanboy a Private Message  Reply with Quote
Anyone out there have any hard data on the life expectancy of a commercial carbine bolt, or discovered any method of mitigation....short of replacement with a USGI bolt?

I've ran a couple hundred-rounds thru my Iver Johnson and don't really know how many rounds it had fired B4 I came into possession, but I would guess only a few boxes from the looks of it when I cracked-it-open. I am starting to see some peening on the rear face as well as the bolt-lug. Maybe it's good for a thousand-or-so???

I'm wondering how reduction of the hammer-spring force may help? They are reasonably cheap enough to play with.

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Tuna
Moderator



3155 Posts

Posted - 03/21/2017 :  6:24:38 PM  Show Profile Send Tuna a Private Message  Reply with Quote
It won't help at all to reduce the hammer spring. Remember they increased the spring size and force during 1943 to insure that primers would fire. If I ever had a choice between a commercial and a USGI bolt the USGI bolt wins every time.
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americanboy
Advanced Member



USA
260 Posts

Posted - 03/21/2017 :  6:47:52 PM  Show Profile Send americanboy a Private Message  Reply with Quote
They for sure designed things on the safe side and not necessarily the comfort side, as-in trigger-pull. I understand there was a design change with the placement of the rod on the hammer along with the stronger spring. I've toyed with hammer springs in lots of guns and most of us know that reduced-power springs are routinely used to tune trigger-pull in hand guns. This particular weapon "almost" pierces the primers and the firing-pin nose foot-print has to be some 2X compared to firing those same primers in other weapons I reload for. I just see the possibility of some adjustment. I'd take off a coil at a time and read the primer. This would likely affect trigger-pull as well. Hey...it's not like I'm molesting a national treasure and the springs can be had for just a few dollars. I'm retired, nosey, like to break things and fix them to fight boredom. Think I may give it a try.
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americanboy
Advanced Member



USA
260 Posts

Posted - 04/04/2017 :  09:36:15 AM  Show Profile Send americanboy a Private Message  Reply with Quote
Us boys like to tinker-around....sometimes. Hammer springs can be had for around $6 and I'd never practice destruction of a USGI NOS spring. I decided to experiment with a $6 hammer spring. The carbine was designed to absolutely fire all the time, every time and under conditions of extreme duress. The hammer blow force was designed to ignite a primer under the worst conditions...and it does. I collapsed the ends of a hammer spring by 5-coils on each end resulting in a spring about 1/2-inch shorter than stock. I test fired the gun with 5-coils collapsed on one end and then collapsed 5-coils on the other end. The result was barely any difference in the depth and quality of the firing-pin footprint on the primer and it goes bang every time, even on known hard CCI primers. A surprising result was the reduction and feel of the trigger-pull. I never measured the pull B4 and after, but it feels much better. There is a law of diminishing returns when you fool with hammer or trigger springs. The hammer spring holds the sear engagement in place, so you can go so far as to create a dangerous trigger, a hair-trigger or one that will bounce out of engagement. I stopped it at the point where the sear engagement was still positive and the TP not too sensitive. For sure, the carbines are over-sprung for a good reason. I feel like I have reduced the punishment on the hammer and rear of the bolt. This should improve the longevity of a soft-bolted gun and will for sure improve trigger-pull.
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Tuna
Moderator



3155 Posts

Posted - 04/05/2017 :  09:46:32 AM  Show Profile Send Tuna a Private Message  Reply with Quote
The government found that the first hammer springs at 22 coils would work BUT not all the time and not under all conditions. That is why they became standard at 26 coils. What your trying to do is reinvent the wheel. Yes what you did reduced the feeling of the trigger pull but you have introduced a dangerous situation for possible accidental discharges. The US military didn't spend millions and millions of rounds just in experimenting with carbines to be sure they were safe in all situations. Best to leave well enough alone. Your IJ is what it is and it was not made to the standards of the US military for their carbines.
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americanboy
Advanced Member



USA
260 Posts

Posted - 04/05/2017 :  2:47:10 PM  Show Profile Send americanboy a Private Message  Reply with Quote
I certainly don't take issue with something that worked and worked very well. With all due respect, I also cede to the knowledge from people here on the forum that have been around this gun-design for a lot longer than I have. As I understand it, the longer spring was adopted along with a repositioning of the notch on the hammer where the plunger nested. This was done to both improve primer strikes and reduce trigger-pull as well. I also understand that these weapons went to war and had to perform in wet, muddy and sandy conditions. The main concern was that it fired and not so much how comfortable it was to shoot. I'd agree.....take any liberties with the design at your own risk. I've only pointed-out that this particular carbine will work just as well with a reduced hammer-blow, which likely equates to a well-worn spring in a USGI carbine. There is a point at which this can become dangerous, and I pointed that out as well. The advice given is well taken and should be well heeded by anyone desiring to tinker with this design.
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Satanta
Junior Member



USA
63 Posts

Posted - 08/04/2017 :  4:08:05 PM  Show Profile Send Satanta a Private Message  Reply with Quote
Hello: I am interested in what americanboy was saying about the slight penning or dimple on the rear face of the bolt. I get it there only, nothing on the bolt lug. Mention was made about reducing the hammer spring tension. It's kind of hard to actually know when and where this actual contact is made. My hammer shows no obvious marks. It's a Universal, so I know the bolt is probably softer.
My question is this. Could the impact and dimple be made from the recoil cocking the hammer? Or are the contact points exactly the same?
I actually think it's probably due to the softer bolt, but not sure.
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americanboy
Advanced Member



USA
260 Posts

Posted - 08/04/2017 :  6:33:59 PM  Show Profile Send americanboy a Private Message  Reply with Quote
I've never seen many "good" answers as to when one can tell if the bolt has been damaged too-much at the rear skirt. I assume you have the late-model bolt...with the firing pin spring? No replacements were ever made for those as far as I know. They do turn-up on auction sites now-n-then. The rear of any carbine bolt will mushroom over time. GI bolts not so much. Commercial bolts, much faster. It may just be a judgement call as to when it needs to be replaced and surely so if chips, cracks or rub-marks are prevalent. Folks will not agree on this, but you can reduce hammer force by using a softer spring, but everything has it limits. You must have adequate spring force to firmly seat the hammer-notch to the sear. My gen-1 Universal has an aftermarket spring of 20-coils and it's never failed to shoot and delivers solid primer strikes every time. I just never have gotten around to changing it and maybe never will. I don't plan to storm Normandy with it anyway. Your Universal may have the aftermarket hammer spring? A softer hammer-spring will alter cocking force as well as hammer blow force. GI springs are not that expensive. I collapsed 4 coils on each end of one and am shooting it now in my Iver Johnson. Force is certainly applied to the face of the hammer and the rear of the bolt under cocking, but not nearly as much as the hammer-fall sequence.
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Satanta
Junior Member



USA
63 Posts

Posted - 08/04/2017 :  7:33:29 PM  Show Profile Send Satanta a Private Message  Reply with Quote
Thanks for the reply americanboy. My bolt does not have the firing pin spring, and doubt it's missing. Just no room for it.
I think the bolt is just soft. It does not really concern me, but it's there and the question did arrive with your earlier post. It's just a small dimple.
I mentioned the possible recoil compared to the hammer drop.
If I were to choose, I would prefer to have my finger between the hammer and bolt, than the recoil side for cocking the hammer.
Not picking, my thoughts only.
I like the idea of testing and trying a weaker hammer spring.
My primers are well struck and deep.
I do not do reloads. Not for a personal reason, just not cost effective because I own only 4 firearms, and all are different.
Going back to the possible soft bolt. Will a GI bolt fit?
I hear yes and no.
I have replaced all hardware in the bolt with good GI parts, it runs like a dream. But of course I feel I have the weak link of the softer bolt. Fulton Armory has the empty bolt at just over $100.
Then you should buy the head space tools at another $100.
Spinning wheels here. There are and never will be any true solutions to carbine problems. USGI or commercial.
I just enjoy getting in the dirt with you guys. I read, process, eliminate and file in the old brain box.
If you only even get 1%, then you are just that much more informed.
Clean, inspect, and oil on a regular time frame.
I just get upset hearing all the bad about the Universals.
I enjoy the heck out of mine, and yes... one day I will proudly own a tired Inland or another. Knowing well, it's gonna need some TLC.
Thanks........

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americanboy
Advanced Member



USA
260 Posts

Posted - 08/05/2017 :  05:45:25 AM  Show Profile Send americanboy a Private Message  Reply with Quote
USGI bolts are easy to identify. War era and post war USGI bolts should have a stamp somewhere around/on the left lug to ID the maker. Commercial bolts will not have a makers-mark. There will also be tracks from punch-marking the bolt to test for hardness, or to proof the bolt when the carbine it was in was test-fired. It sounds to me like you have a GI compatible bolt. Some light mushrooming can be normal, even on a well-fired GI bolt. Without some detailed pictures of what you have, it's just an assumption at this point. USGI bolts can be had from places like e-bay. There were some allowable tolerances during manufacture, but most bolts will interchange. I've swapped several around and never found one that wouldn't head-space, but the possibility exist.

Go to "Maintenance & Troubleshooting" and find the thread "A Sane Head Space Discussion" to read some details about how you can check your head-space without gauges.

Edited by - americanboy on 08/05/2017 05:49:21 AM
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Satanta
Junior Member



USA
63 Posts

Posted - 08/05/2017 :  3:18:07 PM  Show Profile Send Satanta a Private Message  Reply with Quote
Thanks, what a great thread. Appreciate input from all of you.
It was a big help doing the scotch tape thing. Saves the coin for a gauge.
I was not to concerned, but the not knowing was always tossing in my mind.
Case length was 1.287 I took it to 1.290 with the tape and with the striped bolt. Passed, Went one more at 1.291 and it would close with just a little finger pressure.
Obvious it passes, and I would consider this good per say it has a good life span in front of it. But does concern me a little with ammo purchase. I think I would actually prefer a little more slop. Ha - never happy.
Just gonna have to put my trust in a good name brand and shoot away.
I have trust in Hornady but expensive. Armscor, good price but the cases have dents sometimes.
Anyway, thanks to all, my mind is more at rest. Unless you might think the 1.290 -91 is pushing it?
Once again it's a Universal and I purchased it from a know gunsmith. We all know that sometimes does not pan out either.
But I love it. Comes a time that if all is well. Leave it alone and enjoy it.
My next purchase will be a Inland or ??? So need to own a true piece of history.
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americanboy
Advanced Member



USA
260 Posts

Posted - 08/05/2017 :  4:47:44 PM  Show Profile Send americanboy a Private Message  Reply with Quote
My gen-1 is no-go at 1.291 as well. With fitment this tight, it pays to monitor ammo case-length...both commercial and reloads and keep the chamber and ammo clean. My Iver Johnson is not quite as tight. The head-space is closer to .002. I routinely check commercial ammo, since these particular guns are so tight. My Underwood shooter no-goes at 1.297 and nobody knows the round-count, surely in the thousands like most. I don't shoot it as much, but it has a lot of life left in it....that's why I have other shooters.
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Satanta
Junior Member



USA
63 Posts

Posted - 08/05/2017 :  5:23:52 PM  Show Profile Send Satanta a Private Message  Reply with Quote
I guess now I'm concerned again. How can a Gen 1 be a no go at 1.291?
Bolt vs receiver I guess?
Yes I agree I will have to keep a close eye on case length. That's why I said I wish it had more give room.
Who would of ever guessed, if you pass, you would prefer to pass with a tad more sloppy mark.

2132
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Satanta
Junior Member



USA
63 Posts

Posted - 08/05/2017 :  6:55:19 PM  Show Profile Send Satanta a Private Message  Reply with Quote
My bad! I'm left handed so the brain sometimes does not function in the right handed world. Yes a 1.291 would be a no go. I get it now.
Like I said I'm good on the 1.290 but the 1.291 took just a little tiny push. Might of been the tape? but it would still close easy.
With that said, yes -- I wish I had a little more clearance. It's a snug fit.
Thanks again.

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americanboy
Advanced Member



USA
260 Posts

Posted - 08/06/2017 :  07:40:52 AM  Show Profile Send americanboy a Private Message  Reply with Quote
Head-spaces of .001 and even close to zero are desirable in accurized bolt-guns. These guns are surely built to work with a specific controlled case length and that can be determined by the builder. The M1 carbine was obviously designed to shoot reliably in not-so-perfect conditions with not-so-perfect ammo. In reality, the head-space at any given moment depends on the case-length of the round you chamber. If the gun head-spaces at .001 on a case of 1.29 in length, it will head-space at .006 with a round of 1.285 in length. Obviously, all commercial ammo (at least what I have found) measures shorter than 1.29. One will not be in any danger as long as he/she pays attention to what they feed it. I would never chamber a round longer than 1.290 in a carbine with a head-space of .001. I don't think you have an issue, but the only way you can adjust tight head-space is to finish ream the chamber, or swap bolts until you find one that delivers the desired results.

I am pleased to know that the commercial carbines I have are tight. All other issues aside, like reputation, quality and longevity, it means they have a lot of life in them like the USGI carbine did right off the assembly line. I am in no way suggesting the commercial carbine family ever turned-out a gun that matches USGI quality and endurance, but somebody did pay attention to some parts that mattered, at least in the ones I own.

Edited by - americanboy on 08/06/2017 09:49:49 AM
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