View Full Version : semi bcg
texasgunhand
10-17-13, 12:09
Ok iam gona get laughed at and ask..i keep seeing post were semi bcg are not as good as full auto bcg... I understand the difference and I also understand they removed the metal to keep people from converting to FA fire.
But this part of the gun has the recoil spring and buffer to take the shock away and i just dont see how it will fail in a semi auto gun even over thousands of rounds. If i were shooting FA fire i would want all the metal i could get back there,but most of us really only have or shoot semi auto rifles.
Even companys like LMT COLT etc, make semi and full auto bcgs why would these companys even bother if the only difference is a very small amount of metal removed from a part that is buffered against shock is gona fail.
Not entirely sure what you're asking, but I think it's "will modified carriers fail?" No. They won't fail. The benefit of using a standard carrier is more mass- they function better.
texasgunhand
10-17-13, 12:25
Sorry,yes thats what iam asking will they fail faster than a full auto bcg.
As far as mass it seems like having that extra mass then adding a bunch of spring and or buffer is going to make that not as effective. If using a carbine buffer and stock rate spring then i get the extra mass to help move a dirty bcg etc.
It just seems like a mute point once all the heavy springs and buffers are added.
steyrman13
10-17-13, 12:31
The spring, buffer, gas system, etc are all designed to work with the original design which is M16 carrier, not semi-carrier. It has nothing to do with how long one will last and how well it will hold up to "shock,' or a dirty weapon.
texasgunhand
10-17-13, 12:43
OK, then why did colt make them for their guns and they worked fine?? Iam not trying to be a smart butt here. I just dont see what they offer in semi auto gun.
Not trying to urgue with you, you all know more about this than i do...lol.. The bolt carrier not the bolt of course just doesnt seem like it would matter.
I just dont see the extra cost of that few grams of metal from the semi to FA bolt carrier.The FA carrier cost alot more almost every time.Just seems like another extra money outa your pocket thing, If theres no difference in the life of the product. And if your never gona convert to FA which most people arent gona do,unless you just want some jail time...
Theres no reason to put raceing connecting rods in a stock engine that will never turn over 6000 rpm, its a waste of money,but you cant put stock rods in a raceing engine and expect it to live long. somethings are cool but not effective..
Sorry,yes thats what iam asking will they fail faster than a full auto bcg.
As far as mass it seems like having that extra mass then adding a bunch of spring and or buffer is going to make that not as effective. If using a carbine buffer and stock rate spring then i get the extra mass to help move a dirty bcg etc.
It just seems like a mute point once all the heavy springs and buffers are added.
Visualize the action of the AR- gas flows into the carrier and expands against the bolt and carrier, taking pressure off the bolt lugs (pushed into the barrel extension by cartridge chamber pressure) and pushing the carrier rearward into the buffer, which begins compressing the action spring. This is where a lot of malfunctions can occur, and especially if the weapon is operating at a higher cycling rate. If the carrier has more mass, it will begin dissipating excess energy even before the buffer and spring come into play- a heavier carrier will take more energy to move into the buffer than a lighter one. By slowing down unlock time, chamber pressure is reduced, more energy is dissipated from the system, the weapon will cycle better overall.
Colt invented the modified carrier to kiss up to the ATF and put them in their "sport" line of rifles. I don't know if they make them anymore, but all of their duty grade guns have the standard carrier.
steyrman13
10-17-13, 12:55
OK, then why did colt make them for their guns and they worked fine?? Iam not trying to be a smart butt here. I just dont see what they offer in semi auto gun.
Not trying to urgue with you, you all know more about this than i do...lol The bolt carrier not the bolt of course just doesnt seem like it would matter.
I believe it was due to a ban or some other similar reason same as Colt making a web or block on the lower reciever, the SP1 bolt carrier, larger trigger pins, etc. To keep someone from easily converting one to full auto. The mass in the carrier is designed to work with the system as a whole, as well as trip the auto sear. The semi auto does not have the correct weight, nor is it capable of tripping an auto sear. Colt actually has 4 versions of carriers, M16, Semi, SP1, and half moon. the 3 latter mostly tp prevent full auto capability because of auto sears, RDIAS/DIAS, and Lightning links, etc.
How does all of this effect you, you might ask? You would need some very specialized and expensive equipment, and the knowledge to use them safely, to measure the difference. But what collective experience has shown is that standard carriers do actually seem to work better overall. Mildly malfunctioning guns have been "fixed" by nothing more than installing a standard carrier. There's even a thread running on this board right now that demonstrates the difference it makes.
https://www.m4carbine.net/showthread.php?t=139476
Read post #32.
texasgunhand
10-17-13, 13:08
Oh ok i see, i think,, there using the mass to slow the bcg BEFORE it makes contact with the buffer...So by adding a FA bcg to a gun that came stock with a SA bcg could you get it outa of time? And couse problems?
steyrman13
10-17-13, 13:16
Oh ok i see, i think,, there using the mass to slow the bcg BEFORE it makes contact with the buffer...So by adding a FA bcg to a gun that came stock with a SA bcg could you get it outa of time? And couse problems?
98% of the time, no because the gun is designed with an M16 carrier in mind and then a semi auto carrier thrown in as an afterthought. This is of course speaking of quality manufacturers like Colt, LMT, BCM, DD, etc.
Oh ok i see, i think,, there using the mass to slow the bcg BEFORE it makes contact with the buffer...So by adding a FA bcg to a gun that came stock with a SA bcg could you get it outa of time? And couse problems?
The AR15 family of weapons were designed with use of a full mass carrier, and that design was not altered when some companies experimented with modified carriers. Which is why guns with the modified carriers are slightly more likely to have cycle-rate related problems. Slightly.
Using a modified carrier is not likely to cause problems. It's one aspect among many that can be considered when trying to put together the most reliable gun possible.
Gas port size, carrier weight, buffer weight, spring tension, chambering, cartridge load, dwell time, correct machining of all parts etc., all play into it. No one component is going to greatly change the reliability of the gun (unless grossly out of spec), but put them all together, and your odds go up.
I am pretty sure that if you use the search feature you will find a lot of information that has been discussed before.
halfmoonclip
10-17-13, 18:19
Okay, let's get clear on a couple of things.
First, the bolt carrier is in contact with the buffer as soon as the upper is pivoted down against the lower; there is no 'gap' between the two parts, and as soon as the BC moves, so does the buffer.
Secondly, advantages of the 'full auto' or 'full circle' carrier are likely more theoretical than actual; tho' it may impart some larger degree of forgiveness if some other parts or loads are out of spec.
Now, all that said, I've converted some ARs that started with semi-auto carriers to full circle carriers in the past, but it appears current production, from Colt and others, now utilizes the full circle carrier. Colt has of course done away with some of the other 'belt and suspenders' things they did in this regard, including the block in the lower, the odd-sized action pins, and the non-standard takedown screw.
What all this means is fairly simple; if you'll feel better about it, swap out the part circle carrier for its full circle cousin.
Moon
as soon as the BC moves, so does the buffer.
Ever notice how your buffer rattles?
steyrman13
10-17-13, 18:32
Ever notice how your buffer rattles?
That is the weights inside of it rattling, not space between BCG and buffer.
OP. The price difference is due to supply and Demand. There isn't really any "demand" for the semi carrier aftermarket. Only demand for m16 carrier
That is the weights inside of it rattling, not space between BCG and buffer.
I asked why the buffer rattles, not why the space between the carrier and buffer rattles.
My point is that the reason the buffer rattles is because its full of reciprocating weights, which cause the buffering effect of the "buffer," and this mass is loose- it does not start moving the moment the carrier moves, unless all the weights just happen to be fully compressed against the front of the buffer.
halfmoonclip
10-17-13, 18:48
Okay, point taken.
That is not how I had read some of the previous posts, and I had wanted to clear up any possible confusion.
Thanks,
Moon
steyrman13
10-17-13, 19:08
I asked why the buffer rattles, not why the space between the carrier and buffer rattles.
My point is that the reason the buffer rattles is because its full of reciprocating weights, which cause the buffering effect of the "buffer," and this mass is loose- it does not start moving the moment the carrier moves, unless all the weights just happen to be fully compressed against the front of the buffer.
Gotcha, just misread....
texasgunhand
10-21-13, 15:58
OK, thanks, i see what your saying .. and IG i did a lot of searching before i asked but thanks for your input? It was a lot of help? Everything has been asked before ,but if i dont understand the concept it does no good! You seem to take a great deal of pleasure in talking down to people. IF i knew i wouldnt ask!
I didnt understand that they were using the mass to help slow the unlock time instead of a heavy buffer or heavy spring. I will look into buying one as a spare. I just didnt want to spend $189 from BCM if there was no need to, you can buy the semi for like $130. But i dont mind spending $50 bucks more for a tougher product .THANKS to all who took the time to answer. I hope i can help you out some time.
https://www.m4carbine.net/showthread.php?t=442
https://www.m4carbine.net/showthread.php?t=14534
https://www.m4carbine.net/archive/index.php/t-25765.html
https://www.m4carbine.net/archive/index.php/t-126812.html
https://www.m4carbine.net/showthread.php?t=8583
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