View Full Version : Pros/cons: threaded bolt catch pins and receivers
DreadPirateMoyer
03-23-16, 09:40
NOTE: this thread is about lowers designed for this like the Battle Arms Development Gen 2 forged lowers. This thread is NOT about taking a standard mil-spec lower and doing some wonky conversion.
So, as the title says, does anyone have any insight, experience, or thoughts on these? I may purchase a lower designed for one as an experiment, but the inability to be cross compatible on parts with mil-spec lowers worries me.
As I see it:
PROS
Stronger than standard pin
Easier to install than standard pin
CONS
Not compatible with mil-spec pins if replacement parts are needed
May lead to stripped lower receiver threads, trashing the lower
Too strong, meaning bashes and drops on the bolt catch break it instead of the pin?
I'm inclined at this point to simply buy a well regarded mil-spec lower, but thought I'd check in with the hive. What do you guys think about these doodads?
I don't find a standard catch to be a difficult install with proper tools. So the "pro" is strength, which is immediately canceled out by not working with standard mil spec parts... Just my 2¢
The shear strength of the roll pin is what, 400lbs? It's a standard part that's easily obtained. What is the shear strength of a threaded solid pin?
I am against it. The ease of installation isn't worth the use of non-standard part to me, how often is the bolt catch installed and removed?
My new company (Forward Controls) makes bolt catches (ABC/R and ABC/R-F), I have not had to field any support calls for issues pertaining to the ABC/R installation. Yes there is a possibility the receiver may get scratched, my receivers are scratched from multiple install/remove cycles, but we make duty grade components for duty weapons, scratches are inevitable for a hard use tool, and therefore a non-issue to us and most of our customers.
I lost count of scratches on this thing, but who's counting :jester:
http://i75.photobucket.com/albums/i314/Duffypoo/abcrf_zpswqodlk5f.jpg (http://s75.photobucket.com/user/Duffypoo/media/abcrf_zpswqodlk5f.jpg.html)
Berserkr556
03-23-16, 15:23
I'd stick with the tried and true forged, mil-spec receiver. If you strip or cross thread the threaded bolt catch receiver it's done. The bolt catch pin is easy to install with the correct tools. If it would break or somehow work it's way free, which I've never heard of, it's easy to replace.
Pass. I don't find the standard setup problematic to install so that eliminates one of your pros. You also don't see many (any?) complaints about the standard roll pin failing so IMO that negates your other pro, which only leaves us with cons now.
Once you get the hang of installing the role pin it's not bad. Removing a bolt catch can be less fun. Both make it easy to mar the guns finish.
I have one lower with the thread in style. The other day I swapped bolt catches on it. It was amazingly simple and used a very basic tool. I had forgot the lower was a thread in, it was a pleasant surprise.
Being that bolts catches themselves are breakable items, it would be much easier to replace a broken bolt catch in the field or with limited tools with the thread in type.
I don't search out lowers with this feature but would certainly not avoid it.
SomeOtherGuy
03-23-16, 16:06
Same thoughts as TMS951. I think it's a trivial issue, as both the pluses and minuses are very small. I have one or two lowers with threaded holes but am indifferent to them when buying. I don't see any potential strength difference as significant.
Some have said that the lower is done if you damage the threads. I would think that you could simply drill or ream out the hole in the lower large enough to accept a rollpin in an available size (not necessarily the GI spec bolt catch size) and, if necessary, drill or ream out the corresponding hole in your replacement bolt catch to the same size. Not ideal but it would seem a simple and practical fix to keep the lower in use.
I don't see the appeal or the big hang up with the bolt catch pin. I've built one lower ever under the tutelage of a few different Youtube videos and got it together with no real aggravation and no scratches at all using nothing more special than the right sized roll pin punch, a small hammer and painter's tape.
I just installed a fwd controls bolt catch. Took under two minutes with the pin and I'm terrible and doing things. Not worth it to me to go non standard.
Once I started using a one handed bar clamp to squeeze it in instead of a tiny hammer, it got to be much less of an issue. No scratches. Minimal effort/concentration.
Sent from my iPhone using Tapatalk
My DPMS 308 lower has a screw in pin which was Loctited and had to be smithed out to install a phase 5 EBR latch. If it was a roll pin I could have done it myself. It isn't worth it for me, all my regular lowers use roll pins.
To me, the threaded bolt catch pin is no different than the rear detent mod many do to use a set screw to retain it. It is an evolution of the design to ease assembly and prevent those new to the platform from buggering up the pin or receiver when installing it. To many, it's unneeded and merely a solution to a nonexistent problem, to others...it's a godsend. I've put together both and neither were more difficult than the other. I do think that those new to the AR, if faced with the choice between receivers, would opt for the pin less choice. Just like the BAD enhanced pivot/takedown pin set...accomplishes the same goal, just easier to do.
Some just can't help making things "better" by making them worse :nono:
Re: BAD-EPS, they are direct replacements for factory takedown and pivot pins, and don't require anything different to work on a receiver, the same can't be said of the threaded bolt catch holes, unless a standard roll pin can be used when the threaded pin can't be found.
When designing a part that is meant to be better than the original, it's often a balance act. What do we gain, and what do we lose in obtaining this gain. Using the same balancing formula on the subject at hand, my conclusions has always been that for the little benefit it brings to the table, namely, ease of installation, too many shortcomings have tagged along: non-standard part, the need to use thread locker on the threaded pin (and the need to undo the thread locker should you need to remove the threaded pin).
Not debilitating drawbacks, but just not justified ones.
When designing a part that is meant to be better than the original, it's often a balance act. What do we gain, and what do we lose in obtaining this gain. Using the same balancing formula on the subject at hand, my conclusions has always been that for the little benefit it brings to the table, namely, ease of installation, too many shortcomings have tagged along: non-standard part, the need to use thread locker on the threaded pin (and the need to undo the thread locker should you need to remove the threaded pin).
Not debilitating drawbacks, but just not justified ones.
I'm glad you brought that up Duffy - unretained threaded fasteners.
Part of the genious of the AR and many combat grade small arms is how interlocking parts, roll pins, staking and rivets are used to create an assembly that will not rattle loose under extreme heat cycling and impact, yet can be easily disassembled for cleaning.
The standard design has no unretained threaded fasteners because they are a liability.
Roll pins don't come out by themselves; neither does staking.
Threaded fasteners can and do spontaneously loosen.
This threaded bolt catch adds one unnecessarily.
I have both, don't mind both, depending. A lot of 308 receivers will have a threaded BCP. It's a real easy thing with some blue loctite to handle. I've never had issues with them backing out or getting stuck. I've always been able to easily back them out because I wasn't a sloppy monkey putting on the loctite. A little goes a long way. Don't drip blue loctite directly on the threads of the pin in a big messy glob. Put a drop on a qtip, then apply to threads with a qtip. This will create a bond plenty strong to hold the pin, but not completely saturate the threads through and through.
I prefer a standard roll pin, but gladly go without depending on the receiver set.
I'd never give up my MATEN 308s because they have a threaded BCP, for instance. I also have spare threaded pins should I lose one and if availability could be an issue in the future.
I recently had to back out a pin that I loctited in on a 3yr+ old MATEN that had seen some pretty good field use, hundreds of rounds, with plenty of dirt and oil after many uses/cleanings/lubings. The BCP unscrewed perfectly with minimal issue, yet with proper resistance. The threads were gummed up enough to hold the pin with strength, yet not create an epoxy-like bond.
Flip-side, I prefer a standard pin and would probably never Form 1 a lower with a threaded pin.
DreadPirateMoyer
03-24-16, 07:50
Thanks everyone. This pretty much confirms what I came into this thinking.
Going to go with a mil-spec lower, likely a Noveske Gen 1 since they're the only reputable manufacturer I trust (Colt, BCM, DD, LMT, etc.) that still offers a stripped lower without crazy doodads like this or the nylon tension screws. Receivers with threaded bolt catch pins officially off the list.
I can't stand receivers with threaded bolt catch pin holes and tension screws.
A year and a half ago I wanted to buy the Battle Arms Development forged lower, I ended up waiting a little to long to get it and then the Gen 2 came out and messed up my plans. Now I'm going to have to buy a stripped Colt lower from Specialized Armament. :sad:
I spent not insignificant amount of time trying to assure folks that the use of a screw isn't necessarily a bad thing, an AR has lots of parts held together by screws, some are retained by thread locker, most by friction alone. As you recall, when Battle Arms first brought forth the BAD-ASS that uses screws on both sides, many expressed concerns. Fast forward to 2016, many ambidextrous AR and SCAR selectors have two screws (HK and FN come to mind) in order to make levers on both sides configurable. Selectors that go out of their way to not use screws (Troy and AXTS) have doubled their parts counts, it's always something I keep an eye out for.
That said, it's a balancing act. What you gain by adding, or replacing a part with something different, should outweigh the shortcomings it might introduce which the standard part did not have.
Sometimes, the intention is good, but the unintended consequences are not.
Press Check
03-24-16, 12:54
Reading this thread reminds me of the old saying, you can't teach an old dog new tricks. Speculative insight about what could happen, but nothing tangible regarding what has happened. There are more than enough MATEN's in circulation to have heard about issues from end-users, and to date, I have not heard anything.
At the end of the day, it's simply one of a few distinct features associated with billet receiver sets, which have been around for a good minute now.
Forged and a roll pin? Awesome! Billet and a threaded BCP? No tangible reason not to.
Duffy,
Screws? On an AR15 safety? Oh heavens. What will we do during an Apocalypse and there's NO Torx wrenches around? How will we change our safety levers? Not a suitable product for a working gun!
Nothing like tiny, threaded fasteners in a dissimilar metal situation.
Which is significantly different than Stoner's use of threaded fasteners, say, the screws holding a gas key in place.
Sent from my PRC-104 using phonetics
Press Check
03-24-16, 14:06
Nothing like tiny, threaded fasteners in a dissimilar metal situation.
Which is significantly different than Stoner's use of threaded fasteners, say, the screws holding a gas key in place.
Sent from my PRC-104 using phonetics
What are we talking about, galvanic corrosion between active and inactive metals? Doesn't really apply in this case.
I have experience with both lowers that utilize roll pins and set screws. I personally prefer the set screw method - and I could care less if it's weaker, more prone to breaking, or possible cross threading issues.
If someone is worried about potential cross threading something so simple, they will definitely **** up a traditional roll pin install on the bolt catch.
It's a seemless install that takes maybe 20 seconds. Oh, and you don't have to worry about the detent/spring going flying when installing the buffer tube.
What are we talking about, galvanic corrosion between active and inactive metals? Doesn't really apply in this case.
How so? Granted, phosphates roll pins and andonized/hardcoat receivers may be enough of an insulator to stave off the issue, as we don't see much corrosion in ARs. But we also largely keep them away from electrolytes.
But I wince when people talk about tapping holes. And especially, then using big box set screws. Break the andonizing/hardcoat, then use a mild steel uncoated
Press Check
03-24-16, 19:25
How so? Granted, phosphates roll pins and andonized/hardcoat receivers may be enough of an insulator to stave off the issue, as we don't see much corrosion in ARs. But we also largely keep them away from electrolytes.
But I wince when people talk about tapping holes. And especially, then using big box set screws. Break the andonizing/hardcoat, then use a mild steel uncoated
It does not apply based on what you already said. 1, we are not dealing with bare metals. 2, phosphates, anodizing and most coatings insulate active / inactive dissimilar metals. 3, while our weapons may be exposed to corrosive environments, they are not exposed to conductive environments. 4, the list goes on...
Besides that, even if the dissimilar metals were bare, the rule of thumb would be to avoid using small / active metal with large / inactive metal. For the most part, you can almost always get away with it.
I am against it. The ease of installation isn't worth the use of non-standard part to me, how often is the bolt catch installed and removed?
If its an AP 308 then the answer is quite often. :snicker: :rolleyes:
But I agree that a roll pin is better in a standard mil spec lower.
AP = Aero Precision? We're coming out with 308 spec ABC/R-F that should address the breaking issue. Predictably, it appears to break around the weakest point of the bolt catch (pivot pin area) that has the least amount of material.
308 spec ABC/R-F has more material (that's machined off on the AR15 ABC/R-F), it also will do without the lightening cuts.
Note the reinforced pivot pin area on the AR15 spec ABC/R.
http://i75.photobucket.com/albums/i314/Duffypoo/reinforcement_zpszzkf0xzf.jpg (http://s75.photobucket.com/user/Duffypoo/media/reinforcement_zpszzkf0xzf.jpg.html)
Your assertion is pretty laughable. I have people come to my classes and learn how to correctly install both in a matter of minutes. Most people that mess it up do not take the time to get the correct punches and then learn how to use them.
I have experience with both lowers that utilize roll pins and set screws. I personally prefer the set screw method - and I could care less if it's weaker, more prone to breaking, or possible cross threading issues.
If someone is worried about potential cross threading something so simple, they will definitely **** up a traditional roll pin install on the bolt catch.
It's a seemless install that takes maybe 20 seconds. Oh, and you don't have to worry about the detent/spring going flying when installing the buffer tube.
titsonritz
03-26-16, 02:26
Your assertion is pretty laughable. I have people come to my classes and learn how to correctly install both in a matter of minutes. Most people that mess it up do not take the time to get the correct punches and then learn how to use them.
It is funny you say that, I actually did laugh when I read that post.
38567They both have their pros and cons. The threaded ones are very easy to install but harder to find. Like every mechanical thing in this world, you can mess it up. The roll pin ones are easy with the correct tools ( three tools used). And yes, you can mess this up also. I am currently using the threaded screw but it wasn't by choice. I do like this style over the roll pin and I won't argue over the points. Our AR's have progressed towards more custom and proprietary these days that it really doesn't matter from a civilian's point of use.
How many documented failures of this part; roll pin or cap screw, are there? I have both and noticed screws are more commonly used in billet stock than forged. I really don't see the need to paint this as the devil on earth, other than from a purist aspect. I have several receivers that also use set screws to capture the Forward assist and breakdown springs and none of them have failed. IMO, a static pin with miniscule load has the easiest job on the whole rifle. I would think the Stoner team would applaud improvements like this, where a design evolves logically. I think they make life just a little easier.
556BlackRifle
03-26-16, 09:51
How many documented failures of this part; roll pin or cap screw, are there? I have both and noticed screws are more commonly used in billet stock than forged. I really don't see the need to paint this as the devil on earth, other than from a purist aspect. I have several receivers that also use set screws to capture the Forward assist and breakdown springs and none of them have failed. IMO, a static pin with miniscule load has the easiest job on the whole rifle. I would think the Stoner team would applaud improvements like this, where a design evolves logically. I think they make life just a little easier.
You have to remember that the AR15 design is of combat rifle lineage. Every component has been designed or selected with that in mind. IMO if Stoner and team were considering the threaded bolt catch pin for use in their design, they’d want to be sure that under harsh use it wouldn’t fail. Most threaded parts on the AR (gas key screws – castle nut) are staked to prevent them from backing out under harsh use. [Exception: grip screw locked in place with a star washer.]
What would happen if the BC screw came loose in the middle of a firefight? I could see it becoming a huge problem. In combat situations where you are running, jumping, diving for cover, rolling onto your side to take a shot, it could pop up and block bolt travel at the worst possible moment.
Additionally, roll pins are proven to be effective and the cost is minimal both in the cost of the part as well as in the cost to machine the lower receiver. If the lower receiver became stripped at the BC screw, it would be very difficult if not impossible to make a field repair. Sure you could pop the upper and take the bolt catch out and run without one knowing that when you pull the trigger and it goes click, it’s time to reload and pull the charging handle. What a PITA. Is Loctite a solution? Maybe but it makes things more complicated.
For a bench rest / weekend range gun, I see no problem going with the threaded BC screw. Combat, I don’t think it would make the cut.
Agreed ^^ which is why I prefer Std roll pins.
I don't think anybody (hopefully not anyway) is suggesting Colt adopt this on the M4, lol.
If I need to do 'Combat' with one of my loc-tited threaded BCP guns (the two I own), I would trust my life with it.
That's not the same thing as deploying loc-tited threaded BCP guns by the millions to World Super-Power armed forces. :)
Press Check
03-26-16, 12:54
What would happen if the BC screw came loose in the middle of a firefight? I could see it becoming a huge problem. In combat situations where you are running, jumping, diving for cover, rolling onto your side to take a shot, it could pop up and block bolt travel at the worst possible moment.
The same thing that would happen if the bolt catch itself broke in the field.
I have seen countless pictures of broken bolt catches, in addition to numerous pictures of the support bosses on the receiver being broken or sheared off whilst driving a BCP into the support bosses. Careless installation, improper tools, correct tools and an out of spec pin? Who knows, but the point is, the BCP has never been a weak point in this particular system, be it rolled or threaded.
If history tells us anything, the bolt catch itself will break before anything else in that 4-part system fails, but I know everyone has that covered during a firefight because everyone includes a roll pin punch and brass hammer in their kit, and can install a new one in under a minute.
What if, what if, what if. If anything, we should be talking about BC's, not BCP's.
titsonritz
03-26-16, 13:21
The same thing that would happen if the bolt catch itself broke in the field.
I have seen countless pictures of broken bolt catches, in addition to numerous pictures of the support bosses on the receiver being broken or sheared off whilst driving a BCP into the support bosses. Careless installation, improper tools, correct tools and an out of spec pin? Who knows, but the point is, the BCP has never been a weak point in this particular system, be it rolled or threaded.
If history tells us anything, the bolt catch itself will break before anything else in that 4-part system fails, but I know everyone has that covered during a firefight because everyone includes a roll pin punch and brass hammer in their kit, and can install a new one in under a minute.
What if, what if, what if. If anything, we should be talking about BC's, not BCP's.
That is why I replace all mine with a ABC/R-F.
My experience with threaded screws for the bolt catch pin has been nothing but positive. I did have an issue with the threaded pin that retains the detent and spring for the rear takedown. It was a brand new Seekins lower and I was in the process of installing the takedown pins. The rear takedown detent and spring on this lower are held in place by a threaded pin on the underside of the lower, near where the safety selector spring sits.
This small threaded pin wouldn't budge and the head was stripped. My local gun shop couldn't remove it either. Seekins customer service was exceptional. They paid for shipping both ways and had the problem resolved quickly. In the end they had sent me a brand new lower.
While I am very satisfied with how this issue was resolved, and very happy with the lower, it shows that these small threaded pins can present difficulties that otherwise may not arise.
Press Check
03-26-16, 13:51
That is why I replace all mine with a ABC/R-F.
Well played, Sir. Well played.
mkmckinley
03-26-16, 16:41
I prefer threaded. They're theoretically stronger (a solid steel screw vs a rolled tube), easier to install, less likely to cause the receiver to be marred, and don't need to be replaced if I feel like changing out my bolt catch for any reason. Loctite is a simple insurance policy that I wouldn't consider overly complicated. The original design probably used roll pins because they're cheap and didn't require threading.
It does not apply based on what you already said. 1, we are not dealing with bare metals. 2, phosphates, anodizing and most coatings insulate active / inactive dissimilar metals. 3, while our weapons may be exposed to corrosive environments, they are not exposed to conductive environments. 4, the list goes on...
Besides that, even if the dissimilar metals were bare, the rule of thumb would be to avoid using small / active metal with large / inactive metal. For the most part, you can almost always get away with it.
I think the bare metal aspect is absolutely at play unless it's a receiver that came threaded before hardcoat. (Many people are tapping the receivers or just running screws in)
Hopefully people are using phosphated screws is they are doing this.
As to environment, I have seen enough steel allen screws corroded into alloy parts that I would never want to setup that condition. Yes, many were in marine environments, but small allen screws are a problem with even mild corrosion. Where a roll pin, even if corroded, can usually be tapped out.
I'll just say it, I don't want to have to worry about this, not enough advantage to using threaded for this application.
556BlackRifle
03-26-16, 17:42
The same thing that would happen if the bolt catch itself broke in the field.
I have seen countless pictures of broken bolt catches, in addition to numerous pictures of the support bosses on the receiver being broken or sheared off whilst driving a BCP into the support bosses. Careless installation, improper tools, correct tools and an out of spec pin? Who knows, but the point is, the BCP has never been a weak point in this particular system, be it rolled or threaded.
If history tells us anything, the bolt catch itself will break before anything else in that 4-part system fails, but I know everyone has that covered during a firefight because everyone includes a roll pin punch and brass hammer in their kit, and can install a new one in under a minute.
What if, what if, what if. If anything, we should be talking about BC's, not BCP's.
I pretty much agree with everything you stated here PC. I favor the roll pin over the screw in a combat weapon because I feel confident that it's in there to stay. I've never had one break when I was in the service but I suppose anything's possible. As far as bolt catches breaking, yeah, that can happen. Mechanical stuff breaking is part of life. Minimizing breakage is what makes for a good design. Kind of like the roll pin. ;)
You can throw blood and guts at this all day and yet, lots of other parts will fail well before a screw. As for cross-threading, the back lug lines the thing up. If you're talented enough to cross thread that, you should put all your tools and guns on craigslist.
elephantrider
03-26-16, 19:50
AP = Aero Precision? We're coming out with 308 spec ABC/R-F that should address the breaking issue.
AWESOME!!! Can't wait.
I don't think the strength of the solid pin is necessary, or that of the roll pin is in doubt here. Some us had done so earlier, as wigbones had done from personal experience, the threaded pin should have thread locker applied, which then needs to be undone when the user wants to remove the bolt catch.
I remember in the days before Battle Arms came along and started using Torx screws for its ambi selectors, other AR ambi selectors used (and many still do) Allen screws, which are easily stripped, all due to tiny Allen screw head, and exacerbated by the thread locker applied (as it should be).
How much thread locker, and what kind? Is this information disclosed in the manual? I'm not sure if receiver manufacturers adhere to such a standard. The threaded pin being non-standard to begin with, I doubt if manufacturers agree to a set amount and type among themselves. If the manufacturer does not use thread locker, it's then up to the user to do it, then it's the same question again: how much, and what kind? This isn't an issue for roll pins.
To me, it makes as little sense as manufacturers that use red locktite to secure the castle nut on a carbine receiver extension. They should not assume the end users will not remove it, and their capability to remove it.
It's a minor issue for most users, unless of course you're like wigbones and have to send your receiver back to the manufacturer for them to remove the thread locked pin, then it doesn't justify whatever convenience you might have gained.
As mentioned previously, after weighing the pros and cons, the cons are not insufferable, they're just unjustified.
Never had a problem with either one. They both have worked just fine for me. The threaded one has proven to be much faster for install/removal for changing out parts. (I never do this anyhow personally) "What if you get into a firefight." Threaded vs Pinned won't be going through my head at that point, but I try my best on a day to day basis to not get into firefights.
Ryan
rcoodyar15
03-27-16, 18:23
I like it. Put a lower together yesterday that had one. Hate roll pins.
the only argument against them is this violates the mil spec, battle ready, soldier proof design of the m16/M4
truth is I don't believe many on this forum will be taking their AR15 into battle.
the only argument against them is this violates the mil spec, battle ready, soldier proof design of the m16/M4
Actually numerous legitimate arguments against them were made on the last four pages of posts, "mil spec" being very low on the list.
Press Check
03-27-16, 23:09
Actually numerous legitimate arguments against them were made...
I was still waiting to hear one...
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