Full Auto vs. Semi Auto Bolts

crashcollins said:
My Colt semi auto carrier chewed up the buffer pretty good before it broke in. I have heard but can't confirm that a full round carrier is easier on the buffer, It does make sense though as it has more contact area.
Click to expand...
Meh... that's what the buffer is for. If it gets too chewed up just buy a new one.

Like others have said, if you're not shooting select-fire buy either type. S/A carrier will result in a (slightly) lighter rifle...
 
My Stag 4R buffer after 5000 rnds, no wear, no damage, just how it should be.
th_DSCN3427.jpg
 
There is a touch more metal in left on the FA carrier after manufacture i.e. about the mass difference between a CAR weight and an H weight buffer.

If you are concerned with the lighter buffer and BCG group, just go up a weight in buffer.
The BCG will otherwise function IDENTICALLY in an S/A gun.

Most S/A carriers are just F/A carriers with another mill pass.

Also, LMT run smaller gas ports and ship many rifles with CAR Buffer/SA BCG configs, so probably not an issue. Then again, doesn't really hurt to go a touch heavier especially if firing full power 5.56.

To summarise: d:h:
 
Jobbass, look at the picture of the full-auto versus semi-auto bolts. You will notice the full-auto bolt has more metal on the underside. In full-auto mode in a full-auto AR, this metal part trips the full-auto sear when the bolts closes and if the finger is still holding the trigger, it will fire the weapon. Every time the bolt closes with the trigger still depressed, the rifle will fire.

If you install a semi-auto bolt in a full-auto AR and select the full-auto mode, the bolt will not be able to trip the full-auto mechanism so you will only get semi-auto operation.

A full-auto bolt in a semi-auto AR will not change anything as there are no full-auto sear to trip. You will only get semi-auto operation. SInce the full-auto bolt has more metal, it is heavier. More mass is sometimes desirable in some AR configurations, mainly with short barrels, telescoping stocks, etc... Mainly, a Full-auto bolt will change nothing in a semi-auto rifle.

Is it more clear???
 
crashcollins said:
My Colt semi auto carrier chewed up the buffer pretty good before it broke in. I have heard but can't confirm that a full round carrier is easier on the buffer, It does make sense though as it has more contact area.
Click to expand...

It is not your bolt carrier - you have other issues, the receiver is out of spec. most likely.
 
I shot the notoriously under powered PMC 55gr 223 out of my 10.5 LMT with FA carrier and H-buffer.

I don't know where you get a "lighter" buffer spring - There is only one type of buffer spring for all carbines.

Every upper that I have ever bought or built, with quality components from reputatable vendors, do not need all the BS tinkering.

I haved use SA carrier with H-buffer with a Bushmaster M4 for years, that thing is super reliable even without the feedramp cut. Before I discovered H buffer, it ran on a carbine buffer without any issues.

I have even used 2H by mis-stake on a 16" - I don't know know the difference.

If you rifle is doing all the funky things, most likely your gas port is wrong to start with, or you have a gas leak somewhere.

chopper 1 said:
S/A might be more reliable in a shorty with 55gr. commercial ammo.

My shorty with an S/A bolt and a Heavy buffer ran fine with 69 gr. milspec but short stroked with the lightweight stuff. - To much mass not enough gas.

A lighter buffer didnt work either - (not enough mass in the buffer for reliable chambering).

A lighter buffer spring with the H buffer cured it for 55's.

When I can afford SS109's I just put the normal spring back.
swingerlh.gif
Click to expand...
 
It is not your bolt carrier - you have other issues, the receiver is out of spec. most likely.
Click to expand...

Nothing wrong with the receiver. There is no real 'issue'. Other than having a hardened metal carrier 'smacking' against an anodized piece of aluminum. I've heard that if you polish the rear face of the carrier this helps eliminate the 'chewing' but more likely it's just the buffer rotating as it's cycling.
If you wear through a buffer, it's likely that you've put enough rounds down the pipe that it's time to change some other parts too ;)

Also, there's no (good) reason that a F/A carrier should cost more than a S/A carrier seeing as it actually requires (slightly) more work to machine off the extra material on a S/A carrier. There's more material at the rear of a F/A carrier to trip the auto-sear (as seen/explained in the above posts/pictures) and the F/A carrier also shrouds the firing pin although more recently they've made S/A carriers that shroud the firing pin as well.
 
greentips said:
I shot the notoriously under powered PMC 55gr 223 out of my 10.5 LMT with FA carrier and H-buffer.

I don't know where you get a "lighter" buffer spring - There is only one type of buffer spring for all carbines.

Every upper that I have ever bought or built, with quality components from reputatable vendors, do not need all the BS tinkering.

I haved use SA carrier with H-buffer with a Bushmaster M4 for years, that thing is super reliable even without the feedramp cut. Before I discovered H buffer, it ran on a carbine buffer without any issues.

I have even used 2H by mis-stake on a 16" - I don't know know the difference.

If you rifle is doing all the funky things, most likely your gas port is wrong to start with, or you have a gas leak somewhere.
Click to expand...

Lighter buffer springs come from cutting a coil or two off a standard spring, which I did after determining the gas hole was the proper size, and lined up correctly with the gas block, and properly sealed .

EVERY possibility was examined - { proper bolt staking, different buffers, insufficient gas dwell etc. } and no explanation was found for short stroking with low powered commercial 55 grainers. SO I took the not recommended drastic step of cutting a couple of coils - and presto - problem solved without any failures to go into battery.

Its a quality all Stag 10" shorty of a batch that went to private security contractors in the sand box. ALL those functioned perfectly with milspec 69 grainers .

Having said all that - A couple of range buddies with the same guns had the same problems of intermittent short stroking with civvie ammo BUT- after a few hundred rounds - problem went away.

I think it was just that they were super tight { a good thing } when new and wore in,
or that the gas hole tube and block had normal leakage when new and as a result not enough gas was available for civvie ammo. After a few hundred rds. the carbon sealed everything tighter making more gas available.
swingerlh.gif
 
When he said chewing - I take that he means the buffer retain pin is battering the buffer.
Click to expand...

If that's what he's talking about then, yes, it's the lower out of spec, however, I think he was referring to the circular ring that appears on the face of some buffers. :)
 
Shrapnel said:
Jobbass, look at the picture of the full-auto versus semi-auto bolts. You will notice the full-auto bolt has more metal on the underside. In full-auto mode in a full-auto AR, this metal part trips the full-auto sear when the bolts closes and if the finger is still holding the trigger, it will fire the weapon. Every time the bolt closes with the trigger still depressed, the rifle will fire.

If you install a semi-auto bolt in a full-auto AR and select the full-auto mode, the bolt will not be able to trip the full-auto mechanism so you will only get semi-auto operation.

A full-auto bolt in a semi-auto AR will not change anything as there are no full-auto sear to trip. You will only get semi-auto operation. SInce the full-auto bolt has more metal, it is heavier. More mass is sometimes desirable in some AR configurations, mainly with short barrels, telescoping stocks, etc... Mainly, a Full-auto bolt will change nothing in a semi-auto rifle.

Is it more clear???
Click to expand...

Thank you SHRAPNEL.
 
chopper 1 said:
I thought the F/A had more metal - yes ? no ?

Sure looks it -
swingerlh.gif
Click to expand...

Here is the exact weight of complete bolts

F/A = 326g OR 11.5 oz

VS

S/A= 313g OR 11 oz

Hope that clears up the HEAVIER issue.

If anyone wants to put the weight difference in perspective its the weight of 3 Canadian quarters.
 
Last edited:
The only difference i can see... is the uncutt carrier(engages an auto sear and allows the bolt to become fully closed before releasing the hammer in order to safely fire in battery)
Pointless to civilians with a semi trigger group, except for bragging rights.
Otherwize they are 50 bucks more than a chopped one. The finnish(rough phosphating or chroming) on a carrier is more of a factor in the operation of your AR If everything has been fitted right. (I've seen carriers hung up on the buffer tube retaining pin because the stock was loose and unthreaded the pin.)

I'm not sure about the added weight being a significant factor...it may be in a shorty.

Funny thought... Years ago on a range i saw Someone who couldn't fire thier weapon on auto because some one had did a "switch a roo" and pinched a FA bcg off a C7 and replaced it with a chopped one. It must of happened after it was drawn from the arsenal.(i doulbt the weapons techs would've caught it anyway)

....anyways f**k NOOOOOOO to your question. I've been using semi carriers for 30 years in configurations i forgot about.
 
You must log in or register to reply here.
Back
Top Bottom