View Full Version : Chrome M16 Bolt...?
InfiniteGrim
07-27-15, 15:47
I will be replacing my SPR's barrel with a new LaRue one I got during their half off sale. The current bolt and barrel have 1000-1500 rounds through them. The rifle currently has a Young's Chrome BCG, I'm looking to replace just the bolt for use with the new barrel. Who makes a reasonably price Chrome Bolt? I was looking at Aimsurplus, but I'm a bit leery of their $58 NiB bolts, as I've heard people having issues, and I also do not want to handicap my new barrel.
Young Manufacturing's website is the only place I see their bolts sold by themselves, and they are charging $95 + $15 shipping, which in the current market doesn't seem very reasonable. (Or am I the one being unreasonable?)
Thanks in advance!
I'd use the bolt you have. I'd bet a good amount of money that it headspaces fine.
I wouldn't really want a chromed bolt. Hydrogen embrittlement really can happen. A chrome carrier would be fine.
Digital_Damage
07-27-15, 16:15
I will be replacing my SPR's barrel with a new LaRue one I got during their half off sale. The current bolt and barrel have 1000-1500 rounds through them. The rifle currently has a Young's Chrome BCG, I'm looking to replace just the bolt for use with the new barrel. Who makes a reasonably price Chrome Bolt? I was looking at Aimsurplus, but I'm a bit leery of their $58 NiB bolts, as I've heard people having issues, and I also do not want to handicap my new barrel.
Young Manufacturing's website is the only place I see their bolts sold by themselves, and they are charging $95 + $15 shipping, which in the current market doesn't seem very reasonable. (Or am I the one being unreasonable?)
Thanks in advance!
I think you need to worry more about the gas port on that barrel than the bolt. From some accounts they are stupid large.
InfiniteGrim
07-27-15, 16:53
I think you need to worry more about the gas port on that barrel than the bolt. From some accounts they are stupid large.
I believe the gas port issue is mainly the short barrels... 12" ?
InfiniteGrim
07-27-15, 16:53
I'd use the bolt you have. I'd bet a good amount of money that it headspaces fine.
I wouldn't really want a chromed bolt. Hydrogen embrittlement really can happen. A chrome carrier would be fine.
I've just fallen in love with the ease of cleaning...
Take a look at the SIONICS NP3 bolt. Carpenter 158, shot-peened, HP/MPI, etc.. with the addition of the NP3 coating.
http://sionicsweaponsystems.com/store/product.php?id_product=138
I've just fallen in love with the ease of cleaning...
Heavy Metal
07-27-15, 20:09
The NP3 Bolt will be the superior part.
Take a look at the SIONICS NP3 bolt. Carpenter 158, shot-peened, HP/MPI, etc.. with the addition of the NP3 coating.
http://sionicsweaponsystems.com/store/product.php?id_product=138
That bolt is legit....amazing quality.
NiB is not Chrome.
If you want a silver bolt, I'd go np3.
Afaik, the only two reputable manufactures of chrome BCGs are Young's MFG, and Daniel Defense.
Chrome is the only material that hasn't discolored from my suppressor use. Even NP3, while much better than NiB, has discolored to some extent (presumably that means that there is residual carbon left on it). This likely isn't a big deal though. I've picked up a SIONICS bcg and I'm very happy with it. I also have a young's bcg which I'm happy with, but ever so slightly weary of the 9310 bolt (that being said, I haven't ever been able to find a instance of a Young's Manufacturing Bolt that has broken).
Heavy Metal
07-27-15, 21:04
NiB is not Chrome.
No, it's better.
InfiniteGrim
07-27-15, 21:07
NiB is not Chrome.
If you want a silver bolt, I'd go np3.
Yes I am quite aware NiB is not chrome, but NiB bolts can be found easily and for under $55 shipped.
My friends have had issues with their NiB bolts ceasing when stored dirty and left alone for a few weeks, my chrome have never had that issue. All but one of my AR's have chrome BCG's (Two Youngs, One Spikes, the fourth AR is a parkerized bcg)
daddyusmaximus
07-27-15, 22:17
I've just fallen in love with the ease of cleaning...
This is why I put chrome in two of mine a few years back. I want all my guns this easy to clean. Haven't tried a NP3 one yet, but I have heard great things about them. I'm thinking I'll try one of these next, but more research may be needed. In fact, the above post is the first thing bad I've read about the NP3. I can say I have failed to clean mine more than a few times, and even weeks later, my chrome BCG ARs function with absolute reliability. My SBR has a chrome BCG, is filthy right now from two trips to the range, and sits at my bedside. I have no doubt it will function.
Flankenstein
07-27-15, 22:19
I wouldn't. Would go NP3 if I wanted anything non standard/mil spec.
InfiniteGrim
07-27-15, 22:22
Ok in all honesty.....
Is NP3 the new NiB (aka flavor of the month)?
Flankenstein
07-27-15, 22:25
Ok in all honesty.....
Is NP3 the new NiB (aka flavor of the month)?
Guess only time will tell. All my BCGs are standard DD, Colt, or BCM....IF I was going to venture out today I'd go NP3. I have not plans on doing so.
Ok in all honesty.....
Is NP3 the new NiB (aka flavor of the month)?
No. People have been doing Np3 bolts and carriers for awhile. It's actually a good plating that has positive properties unlike Nib.
If you look at NP3, you will see it has been used for many years. I might say it was actually being used before NiB, although I would have dig to find exact dates.
Ok in all honesty.....
Is NP3 the new NiB (aka flavor of the month)?
No, it's better.
Please explain.
The original AR-15 had a chrome plated bolt and bolt carrier. The chrome plating on the bolt was dropped very early due to fatigue problems caused by the chrome plating process.
There will always be some hydrogen infusion from the chrome plating process (hydrogen embrittlement) which will always reduce the fatigue life between 22% and 55%. It is also possible that cracks in the plated surface form during the plating process and then propagate to the substrate during service.
EDIT:
Please explain.
The nickel boron application process reduces the potential of hydrogen embrittlement, it is not immune to it though.
Embrittlement would be minimized by proper application and post treatment. How much more risk there is with Cr vs NiB, I can't comment on.
The cracks your describing is what I believe to cause premature failure of NiB bolts.
Not a scientific poll at all, but I haven't read of many/any Cr plated bolts failing early. It seems much more common with NiB. That said it could be the plater, or even a bad base bolt.
I'd like to see 40 quality bolts, 10 each of Cr, NiB, np3, and phosphate, same firing schedule and see what happens.
I'd use the bolt you have. I'd bet a good amount of money that it headspaces fine.
I wouldn't really want a chromed bolt. Hydrogen embrittlement really can happen. A chrome carrier would be fine.
While true, I had a lengthy discussion with Chris Peters of Metaloy one day. I have sent them a number of bolts to have chromed and I mentioned the subject of hydrogen embrittlement. He explained that modern knowledge and processes have made HE something rather easily avoided, especially if you know what you're doing (his words). He then explained the steps taken to avoid HE (it's been a few years but it has to do with the cooling/reheating and doing it in the proper time window).
I feel confident with using them and the ease of cleaning speaks for itself.
While true, I had a lengthy discussion with Chris Peters of Metaloy one day. I have sent them a number of bolts to have chromed and I mentioned the subject of hydrogen embrittlement. He explained that modern knowledge and processes have made HE something rather easily avoided, especially if you know what you're doing (his words). He then explained the steps taken to avoid HE (it's been a few years but it has to do with the cooling/reheating and doing it in the proper time window).
I feel confident with using them and the ease of cleaning speaks for itself.
You really cannot avoid hydrogen absorption, The hydrogen is created during the plating process and is absorbed by the steel. What he was describing was baking the finished piece to drive out the entrapped hydrogen, baking will drive off most, but not all hydrogen. The usual method to avoid actual embrittlement is to bake and shot peen, these two processes will usually return steel to its "before" fatigue properties, as baking removes most of the hydrogen and shot peening introduces a compressive stress to the surface which will tend to reduce fatigue cracking. However, a phosphate bolt is also shot peened, so a chrome plated bolt is about the same fatigue strength as a non-shot peened bolt.
Higher strength steels are more susceptible to hydrogen embrittlement.
Most people probably don't shoot enough to worry about it though.
The process to hard chrome components can be very involving. That does not automatically make hard chrome inferior, hard chrome can have many benefits. In the balance of the desired results, hard chroming can be a benefit, it can be a negative.
The unfortunate reality is that most will not invest in the component that costs more. The consumer that is not informed unfortunately normally makes decisions on dollars rather than possible results.
You really cannot avoid hydrogen absorption, The hydrogen is created during the plating process and is absorbed by the steel. What he was describing was baking the finished piece to drive out the entrapped hydrogen, baking will drive off most, but not all hydrogen. The usual method to avoid actual embrittlement is to bake and shot peen, these two processes will usually return steel to its "before" fatigue properties, as baking removes most of the hydrogen and shot peening introduces a compressive stress to the surface which will tend to reduce fatigue cracking. However, a phosphate bolt is also shot peened, so a chrome plated bolt is about the same fatigue strength as a non-shot peened bolt.
Higher strength steels are more susceptible to hydrogen embrittlement.
Most people probably don't shoot enough to worry about it though.
Any of the bolts I've sent Metaloy have been mil-spec C158/HPT/MPI/shot-peened (the whole nine yards). So chroming would negate the original shot peening process and it would have to be done over again after plating?
If you look at NP3, you will see it has been used for many years. I might say it was actually being used before NiB, although I would have dig to find exact dates.
To the best of my knowledge it was, but it may be that it was simply more well known. I had a Melonite QPQ M4 barrel back in 99 or 01, far before anyone else was trying anything like that on M4 barrels that I'm aware of. What is new is usually old, it just failed to catch on the first time.
Any of the bolts I've sent Metaloy have been mil-spec C158/HPT/MPI/shot-peened (the whole nine yards). So chroming would negate the original shot peening process and it would have to be done over again after plating?
Shot peening introduces compressive stresses on the surface of the base metal. This reduces the propensity of the base metal's surface to crack and thus increases fatigue life.
Shot peening can be done either before or after the plating process, doing twice (before and after) does not increase its effectiveness. You have a bolt that has about the same life (90%-95%) as an un-shot peened parkerized bolt.
Another thing not addressed yet is the final grinding of the bolt lugs. Is it done before or after the plating process? And, how it is done? These factors make a big difference in the fatigue life.
To me, chrome plating a bolt introduces more problems than it solves.
Shot peening introduces compressive stresses on the surface of the base metal. This reduces the propensity of the base metal's surface to crack and thus increases fatigue life.
Shot peening can be done either before or after the plating process, doing twice (before and after) does not increase its effectiveness. You have a bolt that has about the same life (90%-95%) as an un-shot peened parkerized bolt.
Another thing not addressed yet is the final grinding of the bolt lugs. Is it done before or after the plating process? And, how it is done? These factors make a big difference in the fatigue life.
To me, chrome plating a bolt introduces more problems than it solves.
Thanks for the input.
To pick your brain, how else could a hard-chromed bolt be put out? Manufactured with the plating taking place at just the right point in the process? Parkerizing can't be the only alternative to a coating on an AR bolt (not saying you think it is).
Why would chrome plating cause embrittlement and phosphate not?
Does shot peening not effect the chrome surface in a positive way, as far as micro cracking?
Does the bake to reduce hydrogen embrittlement really effect properties to a meaningful extent?
Shot peening introduces compressive stresses on the surface of the base metal. This reduces the propensity of the base metal's surface to crack and thus increases fatigue life.
Shot peening can be done either before or after the plating process, doing twice (before and after) does not increase its effectiveness. You have a bolt that has about the same life (90%-95%) as an un-shot peened parkerized bolt.
Another thing not addressed yet is the final grinding of the bolt lugs. Is it done before or after the plating process? And, how it is done? These factors make a big difference in the fatigue life.
To me, chrome plating a bolt introduces more problems than it solves.
How would plating a shot peened bolt reduce fatigue life to less than a non shot peened bolt?
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