I certainly like and use BCM. I also find PSA premium BCG to be reliable. I have one PSA premium (toolcraft carrier) that has the Diamond Like Coating (DLC). The coating has held up great (no flaking or damage) after 3,000 rounds. JP Enterprises makes great BCG’s as well, but spendy.
Forging pretty much helps everything. Of course the heat treat is equally important.
Well, I guess it comes down to if you want a coating on your bolt/carrier and if it really helps. I can see the potential benefits of lubricity and easier clean, but always the question is durability. I will say, if true as some advertise, easier clean is a major plus for me.
The problem is easier clean often means lube doesn’t stay put. The only finish I’ve tried that BOTH seems easier to clean, AND keep lube where you put it is NP3. And keeping lube where it’s supposed to be is WAY more important than clean up ease.
There are lots of good BCGs, particularly those mentioned.
If I had to settle for 1 for all future builds, it would be a Sionics NP3.
Not really.
The improvements gained from forging are due to the grain distribution and grain flow. For something shaped like an AR bolt, any improvements would come from upsetting the head. But, due to the size of the bolt, the allowable radii and other forging considerations, machining the bolt from the resulting forging will reduce the grain flow to pretty much the same as in bar stock.
Second, you don’t get something for nothing. In forging you gain in one direction, but loose in the direction perpendicular. In an AR bolt if forge so you gain the fore-and-aft direction, you will loose in the transverse, or twisting. Bolt lugs are subject to considerable twisting loads.
I do not see any benefit from forging that would justify the increased cost.
Having raced cars and boats for years, there is a reason crankshafts, connecting rods, pistons, etc. are forged. The stresses induced, particularly in high rpm engines, are profound, thus forging.
While you point is taken, is forging necessary? Of course not, otherwise it would have been the standard, but I am suspect to your analysis of the machining of the bolt post forging would reduce it to bar stock composition. Throwing a flag on that one. As you probably know, forging generally and vastly reduces the amount of machining necessary to get to the final result as say for example machining from bar stock.
The forging benefits aside, if that almost doubles the cost of a BCG, you gotta ask yourself what are the benefits. Geissele claims 5 times the life expectancy versus a mil-spec bolt. Why is that? Is it because of the C158+ steel? The forged bolt? Both? Which I suspect. I find the claim interesting.
Speaking of BCGs… this just came out in Bravo’s email blast
While pretty damned expensive, the Cryptic Coatings “Mystic Black” BCG is hard to beat for cleaning. It also checks all the boxes for “The List”. Member here VIP3R 237 had one he ran with 20K+ rounds before he retired it. Cleaning is really easy, even the infamous bolt tail. Again, it ain’t cheap but is definitely a good product.
You can also buy components from Cryptic Coatings, like a bolt only. One of those Mystic Black bolts coupled with an LMT-E carrier would be sweet for a carbine.
No such thing.
An AR bolt is not a crankshaft, a connecting rod, or a piston. Different applications, different loads, different geometries, yield different optimal designs.
Second, The cycle time for a nine-axis machining center to make one AR bolt, ready for deburring and heat treating is nine minutes, with no human intervention.
https://www.youtube.com/watch?v=Nkn3P2Z5m5U
To forge, you would have to cut the stock into billets, load the billets into the oven, then someone would have to remove the heated billet from the oven, put in a die, twice, (with another person to handle the steam spray), and then someone to load the forging into a machine center, where it still has to make almost all the same cuts. All that is not going to add up to less than nine minutes. Yes, there will be more chips, but they can be recycled and the cost of the extra material, minus recycling, is far less than the cost of one or two people’s labor. (Don’t forget “labor” includes health benefits, pension, taxes, vacation, sick leave, and hourly wage.)
As stated before, nothing in nature is free, if you gain in one place you loose in another. Forging is no different. Some properties improve in the longitudinal direction, but drop in the transverse
Geissele claims 5 times the life expectancy versus a mil-spec bolt.
As to what Geissele claims, they can claim anything they want, but I will take a skeptical eye on their claims until I see one of their bolts last 50,000 to 75,000 rounds. As the standard MIL-SPEC bolt has a expected life of 10,000 to 15,000 rounds, as far as the Army is concerned.
I totally agree.
Historically I’ve used BCM because after ‘04 that’s what they built their rep on and was born out by Pat and others. It seems like that angle has been taken over by SOLGW these days and I think it’s interesting that they haven’t come up in this thread. That being said, I sprung for the Geissele REBCG and we’ll see how the NANO does on it. I believe SOLGW is saying these coatings promote wear as they don’t absorb lube like phosphate does but I’ve yet to test that personally.
Why didn’t Geissele forged the gas key in with the body to eliminate a weak link?
I use the Geissele REBCG in all my AR’s.
A properly installed gas key is not a weak link and can be easily replaced if damaged. With a forged key, if a soldier drops the carrier while cleaning and damages/dents the key the entire carrier would have be replaced at a much higher cost.
It is also not a very heavily stressed part.
I’m not sure the gas channel through the key could be machined if it was integral with the carrier.
I have found this thread very interesting since I’m always trying to maintain a high lever of quality and reliability in my AR’s. I’ve looked into the Surefire, Giesselle, LMT and Young Manufacturing BCGs. All very expensive and IMO not so much better than the BCM and Colt BCG’s I have and yet to break.
BCM bolts have been great to me as well, quality and pricepoint.
The only reason I prefer Colt over BCM is the billboard “BCM” on the outside of the bolt, big and in bold gold lettering. Colt barely puts a “C” somewhere hidden on the bolt…