I’m piecing together a carbine, and wanted to try a pencil barrel vs. an HBAR on this one. Got a lightly used BM 16" pencil for 40 bucks. Question is, should I put my new YM bolt in the carrier while I try out the BM barrel, or run an old bolt in the used barrel, then put the new bolt in whatever new barrel I buy? Will the carrier bore break into the bolt, or being chrome lined and with the gas rings, will it be ok to swap em out? I’m a car/bike guy, and the modular nature of the AR is a little foreign to me, thanks all.
It is my understanding that a USED bolt should not be paired with a USED barrel, unless they wore together, or have been properly headspaced for safety.
You can swap a NEW bolt into a used barrel with almost %100 certainty it will be gtg.
“Will the carrier bore break into…” Safety criteria in this platform has nothing to do with the carrier bore or gas ring fitment. Its how the face of the bolt mates up with the barrel extension.
ETA: If I’m wrong, someone please correct me & I’ll stay in my lane.
The TM says to check headspace after every barrel or bolt change. Tolerance stacking could get you to a unsafe headspace condition.
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Definately, a good idea and I plan to take it by my local armorer (sp?) to get that checked out like I did when I built my SPR wanna be. I guess my concern would be lateral movement of the bolt in the carrier, like piston slap in an engine. Does that happen or even matter? The bolt has rings like a piston, but no lands in between
i can’t imagine that headspace would do anything but grow with wear. so i doubt that having things “wear together” would matter.
I’d wager that any in spec bolt and barrel should be fine together. operative word here being “in spec” so your advice to headspace it is good.
My other option would be to buy a new cheapo (DPMS) bolt, run it in the BM barrel, then match my YM bolt to the new (?? Unsure) barrel that I choose. Of course if running the YM bolt in the BM barrel for a little while, then just swapping barrels won’t hurt anything, I could do that. I’m not looking for match accuracy here, but as precision is low on the priority list for this build, I’d like to avoid anythign that will further degrade it if I can.
A few questions.
Why are you going to buy shit parts from DPMS, BM, etc… Get a bolt from BCM, LMT or Colt.
Do you understand that the inside of the barrier is hard chromed and your gas rings are not. The gas rings will wear out which is why they need to be replaced. You need to be more concerned about whether the BCG is made properly and was gauged per the TDP.
Also your local armorer/ gunsmith may not even have the correct gages and may not realize that BM barrels often times have out of spec chambers.
I’m using cheapo parts for the time being to experiment with a couple different configurations while I decide which route I go with the build, then the cheapo parts will end up back in the cheapo box and I’ll re-build with proven stuff. My local (hour drive) AR guy seems pretty sharp, and is onboard with most of the stuff I hear from the experts here, I think he also has training or a cert from Colt on this platform.
So the bolt rings are some sort of softer metal than the carrier lining? How about the locking lugs, do they wear to the barrel extension, or just pretty much wear the same?
I think they should wear about the same. But when you’re playing with cheap stuff like DPMS/Bushmaster… there is NO telling if they’ve used properly hardended barrel extensions.
Judging by the other corners these jokers cut, I’d bet they aren’t.
The lugs on the bolt and barrel extension probably do mate together slightly.
They are both case hardened, so I wouldn’t expect a significant headspace growth until a very high number of rounds.
As I understand it, most high count barrels fail throat erosion check before headspace.
The more likely concern for you assembling parts would be initial tolerance stacking.
Commercial parts may be made to the high or low end of the range.
They may also be spot on.
You can’t know, hence the recomendation to do a quick headspace check on whatever combination of parts you have.
If it passes you should be GTG.
A bolt carrier never changes- thus the argument doesn’t hold water. Things like different barrel lengths, profile, etc… and furniture makes sense. Skimping on critical parts doesn’t.
Do whatever makes you happy. I am not going to force you to re-examine your position.
Where the hell did you get that price? That’s awesome.
The magic of Gunbroker, saw a 14.5 no name go right after that for $57, but I was already covered on that front, so I let it ride. I’m leaning towards a DD when I put this puppy together for real.
So bolt carriers don’t wear at the same rate as barrels and bolts? When you get a shot out rifle in for repair, you’d swap out the bolt + barrel, check everything to make sure it’s in spec, and call it good? Is my understanding that good bolts last longer than good barrels correct as well?
There is a trend here of saying if it isn’t xyz brand it isn’t worth having.
I know certain companies use mil spec parts and some do not. The problem with saying all other brands are junk is Microbest makes apx 20,000 bolts and 30,000 carriers a month. Their products are mil spec and sold to everybody and their brother including Colt and FN and probably BCM and Noveske. Anyone that can order 1000 pieces can buy these mil-spec Carpenter alloy 158 bolts and mil spec M16 carriers. CMT and LMT also produce mil spec parts and sell to everyone. 4150 CMV barrels are made by several companies that also sell to anyone. Those 3 parts are the heart of the rifle. It’s just too tough to tell which companies use real mil specs parts and who doesn’t. For the consumer that doesn’t deal with this stuff all the time it can be very confusing. This is a big forum, there’s a lot of shooters here that aren’t professionals, they don’t take tac courses every time they come to town, they don’t use their rifles on duty. They don’t need a professional grade rifle but I understand the need to relay accurate information and say these “xyz” brands use true mil spec parts without a doubt.
What makes things worse is for the public walking into a local gun shop the stuff they see on the wall that is the most well known in their world is usually the cheap stuff that isn’t mil spec but they think they are the best brands. Try telling someone who thinks the big 3 are the best that they are really just the cheapest. Many companies are only interested in the most profit, others are interested producing a professional grade rifle. The big 3 (commercial) will work just fine for most people that go out once a month and blast a few mags or stick them under the bed just in case.
The professionals that use ARs should know enough to dig deeper. Some don’t because I know of a federal agency that purchased rifles that did not have 1 part that was mil spec. It’s a shame that people that have the power to order rifles for a large group of officers that will without a doubt use their rifles to protect themselves and others do not know more or research better before they buy for those in harms way.
Maybe I shouldn’t have posted, maybe I’m getting softer as i get older I just think guys that want to shoot and have fun don’t need to be beat over the head if they know that a mid grade rifle will work fine for their uses.
Your point is valid. But in most instances, folks will spend the SAME money on so-so guns, when they could have bought a Basic BCM or something.
constructor,
You are missing the point. And your observation about Microbest and Toolcraft is partially correct. The problem is that they have also turned out bad stuff and unless you have a good QA/QC system in place with people who know what they are doing those parts can end up in your weapons.
You should see the stuff I have found already in just 2 armorer courses I have done. Airsoft buffers of dubious manufacture, an extractor pin that was broken in 3 places, crush washer that was like cream cheese, etc… I have no doubt that it will continue as I conduct more classes and see more weapons.
If you want a plinking gun then get a S&W MP-15/22 or something else. I am not in LE nor am I in the military anymore. But, I use my AR’s for personal defense and I do not want shit parts in it, nor do I want it to fail when I need it the most.
I also recently saw a CMT carrier that had a gas key which had not been drilled all the way through and the weapon wouldn’t function. So my question is how did they HP/MPI test or even test fire it without catching that? They couldn’t have.
I know mistakes are made without a doubt, when I buy parts in 1000 piece batches I do have to check and that is where the assembly company comes in. It’s up to the company to test rifles before they go out, Even then stuff happens, I get my share of call backs. It seems like every batch of extractors are different, ejectors between manufacturers are different lengths. I think I have seen just about everything. I’ve had people send other brands of uppers in so i could check them out. I’ve found uppers with the wrong length gas tubes like a carbine on a mid length…how was that tested for function?
I understand what this forum is about and can see why this place is growing and that other place is just spreading internet wisdom.
At one time I built high end custom builds for highpower and long range use. I didn’t think anything about dropping $4-5000 get a rig set up with a trigger and scope. Now I know there are guys out there who have young families and it takes saving for months before they can buy a $600 to hunt with. All I am saying is the professional should get professional grade rifles but some guys can probably get by with a mid grade rifle until they can afford something better, help them understand the difference. On the other hand there are some rifles out there that are very expensive and not as good as the XYZ brands you recommend. $10,000 for a semi auto 308?!!!
Consumers should do their research, God help those that just walk in to the local gun shop. Didn’t mean to interrupt carry on.
Not sure where you get this assumption. All critical mil-spec parts (BCGs, barrels and extensions, FCGs), for military use, are produced in govt. approved facilities with govt. inspections. Has this changed? Anything else would be commercial grade, made by Microbest.
The last part I would consider buying from DPMS is the Bolt. DPMS Bolts are notorious for their high failure rate.
The whole DPMS is crap and only blah, blah, and blah are any good argument is getting a bit tired. I didn’t ask if DPMS was any good. I didn’t ask if I should get the fanboy brand. Let me re-state my question, and somebody give me an answer, and give me a reason for the answer. I am temporarily running a used barrel in an AR-15, and at a later date, plan to install a brand new barrel along with a brand new bolt, both of fanboy quality. Would I be better off simply running the brand new bolt I have in the used barrel with the carrier I own, or picking up a cheap or used bolt to run with the used barrel, and putting the new bolt into the new barrel. Thanks.