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Why light weight bolt carriers?

4.9K views 26 replies 14 participants last post by  mcl  
#1 ·
I see they use them in 3 gun rifles a lot. I just dont see why somone would use one and then run a h2 buffer. I understand using a heavier carrier to slow cycle rate and smooth cycling out but a light carrier would force you cut back on the adjustable GB right?

Please I need some edumacatin.

AL
 
#2 ·
Lighter buffer, lighter BCG, choked back gas block/carrier key (tuned)... softer recoil pulse, less muzzle movement, faster target reacquisition
 
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#12 ·
Yep. If anybody (I know the older vets have) has held an M16A1, a real one, they are noticeably not heavy. It's amazing. I see the appeal.
 
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#3 · (Edited)
Some people have also made the point that a light carrier with a heavier buffer.... While retaining the same operating mass as before weight changes... Can slightly improve reliability and reduce bolt bounce.

Now within that statement, people will disagree about all kinds of stuff. I am not knowledgeable enough to know if that's true or not, I'm simply suggesting a possible reason.

Edit: phone spelling/grammar
 
#11 · (Edited)
OK so it reduces the cycling mass and reduces recoil. Why are we all not doing this? Seems like a home run? Draw backs?
Durability. A proper functioning discharge is an extremely violent action and puts stress on the weapon. Every single time you fire.
 
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#5 ·
only real drawback, is that when proper maintenance and cleaning are not adhered to it can cause cycling issues (or in "full auto combat mode", you want the extra gas pressure and reciprocating weight for 100% reliable cycling---pull trigger, go boom)
 
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#6 ·
Right I could see a dirty rifle screwing up not having much inertia with a light Buf and bcg on the return stroke of a cycle. But for a hunting rifle that doesnt see hundreds of rounds at a time it could be a good thing. Maybe my next experiment for a new designated coyote rifle.

Thanks guys
AL
 
#8 ·
RD pretty much nailed it down but the only benefit I am not seeing mentioned is a much cleaner/cooling running rifle.
An adjustable gas block should be considered a must have in my opinion to maximize the benefits.
In my 20" ARP barreled rifle I am running a JP low mass carrier and low mass buffer in concert with a Syrak adjustable gas block.
After a range session of say 90-120 rounds the carrier and bolt really don't have enough build up to even bother with cleaning using 30.4 grains of AR-COMP powder running 115 match kings at 2670 fps .
 
#10 ·
My hunting 6.8 has a Syrac adjustable gas block and voodoo one piece carrier and just silent capture spring. I installed each item one at a time starting with the gas block. The lightweight carrier made the most difference in felt recoil and the silent capture spring made the least. There is much less fouling after shooting and if needed I can always give it more gas. The silent capture takes the sproing sound out of the buffer tube so I would say it has a purpose but not really worth the price. I will be making these upgrades to almost all my rifles. It has really tamed the recoil but you can't do the lightweight carrier without the adjustable gas block.
 
#13 ·
I have already switched to adjustable GB on all my uppers. Maybe I'll try out a low mass carrier on a 5.56. Just to play around. I may even try and make my own.
 
#15 ·
Keeping it basic is not a big deal at all. Most carbines in order to remain reliable for the majority of configurations come over gassed. When you hear about problems they are normally pertaining to high round count training or from poor configurations. If this is a duty rife then prudence would be advised but for target or hunting this may be ideal. If you want a set it and forget it rifle standard is just great. If you want a racer they you will need proper tuning. Either will result in good results as long as it is properly done.
 
#16 ·
My shtf rifle is pure bone stock m4orgery, but my hunting rifle is tricked out to get a soft recoil impulse.

The M4orgery runs any ammo it is fed while the hunting AR(30 Herrett AR) prefers to run just a few similar loads because of the tuned set-up, LMOS carrier, SCS(with green spring) and a Syrac GenII adjustable gasblock(what a slick super soft shooting rifle). Two entirely different rifles with 2 different goals in mind.
 
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#17 ·
I would really like to see some empirical measurements to see if these changes actually reduce recoil. I am very skeptical. I can see how it would lessen the secondary recoil impulse (the BCG cycling) and how it would help you stay on target. Which is why the three gunners do it. However, I just can't see how it would change the initial recoil impulse. In fact when you turn down your gas you are bleeding less energy off the initial movement and it should increase recoil. This why felt recoil is usually more on equivalent bolt guns compared to gas guns.
 
#18 · (Edited)
That is correct, it is all about reducing the secondary recoil impulse, AKA action cycling. And as you mentioned it is sending more pressure down the barrel, but more pressure exiting the muzzle is more to act upon the muzzle device as well. More pressure also means you could run less powder and get the same FPS. What you are doing is limiting, narrowing the performance envelope, focusing upon a narrow selection of loadings. For my plinking and hunting rifles I only develop a single load, so why not tune the action to function optimally with that load. I also prefer to play with wildcats so having the ability to adjust how the action reacts during cycling is needed.
 
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#19 ·
Believe it

mcl, believe it. The combination of a good muzzle brake and lighter action weights (BCG and Buffer) can make nearly 50% reduction in recoil.

I have had a bad shoulder since 1989, Dr's wanted to operate on it. Everyone I knew who had the shoulder surgery said don't let them. To get to sleep at night I take 2 Naproxen so the shoulder pain won't wake me up. I still wake up sometimes and can't lift my right arm because of the pain..

Got my first AR in 2012, a Stag 5H in 6.8. All 556/223 were sold out. I did all the recommended stuff. A heavier carrier, heavier buffer and a Mako recoil reduction stock with a Limbsaver pad added. Maybe 10% recoil reduction total, but enough that I could shoot any 6.8 ammo 40-50 rounds per range trip.

Then I discovered adjustable gas blocks, and lighter BCG and Buffers go right along. Now I can shoot 308s all day, as long as I have a good muzzle break and light weight action components. I had the first AR308 titanium carrier, the 308 went from 22-24 ounces action weight down to led than 14 ounces.

I can shoot my 5 pound AR308 all day, as in 40-60 rounds with no ill affect. I tried shooting with out a 2 chamber muzzle brake and my shoulder hurt after 30 rounds, not bad but not great. I shot one day with the adjustable carrier key starting at nearly wide open. Wham Bam, now that HURT.

Quickly adjusted gas block and recoil of the 308 is just a little bit more than a 6.8. That is a 50% actual reduction in recoil!

Reduced recoil and the lighter action weights do three things. Longer component life. Much less recoil, and the kicker, GREATER ACCURACY.
 
#20 · (Edited)
mcl, believe it. The combination of a good muzzle brake and lighter action weights (BCG and Buffer) can make nearly 50% reduction in recoil.I have had a bad shoulder since 1989, Dr's wanted to operate on it. Everyone I knew who had the shoulder surgery said don't let them. To get to sleep at night I take 2 Naproxen so the shoulder pain won't wake me up. I still wake up sometimes and can't lift my right arm because of the pain..
shoulder still buggin ya? if so, i wouldnt hesitate to go under and get it done
there are all kinds of diff. things that can go wrong in there, which could equal all different types of surgical procedures/end results- so by taking others word over it doesnt count much unless same issues/operation. plus the fact, the final outcome is based on PThereapy aft., a lot of guys dont do what they are supposed to and loose range of motion, ect.
I had 2 surgeries in same shoulder (2 diff. issues) all is fine now, but plenty of people and Docs warned me to do all my therapy after. 1 was 6-12 month commitment, 2nd not as critical, 3 mo.
Also with scopes, surgeries have come a long way, instead of being cut all the way open, both times I got 4 little holes they went into, cuts down on recovery time too.
I even got a cool little DVD video of the whole operation (from inside) boy is that freaky watchin just cuz i knew it was me and i could still feel it due to still recovering, now i could watch it again no squirms.
 
#21 ·
The brake will certainly lessen recoil and it is easy to see why. Again I am not saying the low mass bgc and tuning the gas to match has no value. I feel it does and run adj gb's on all my builds. I am saying it won't reduce the total recoil. Like I said a properly tuned gun will shoot "smoother". I would like to see some tests to confirm or deny these claims of reduced recoil. Similar to the test of different muzzle devices.
 
#22 ·
A muzzle brake is more effect the more gas it has to work with.
 
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#23 ·
I can see that. However all the gas that goes through the GB is being redirected backward. This is why gas guns have less recoil than equally configured bolt guns(same load, same weight)
 
#24 ·
Simple physics!

Lighter weight with less force (gas) means less reciprocating weight, equals less recoil.

There are sound reasons 3 Gun shooters have used lower weights for years, better accuracy through lesser recoil. Leave it up to Americans and the almighty dollar to drive innovation.
 
#25 ·
I guess I will bow out. Simple physics is the side I am arguing. Or thought I was. Equal and opposite and all that. The more gas through the GB system the more your opposite force. Additionally the higher the total weight the more inertia that has to be overcome for recoil. I will just have to wait for those "tests" which will probably never come. Also I have acknowledged the professionals run these setups for a reason.

As an aside, I enjoy reading you lightweight build threads. You take them much farther than I ever will but it is interesting seeing the possibilities.
 
#26 · (Edited)
However all the gas that goes through the GB is being redirected backward
The gas stream in the gas tube is not what causes recoil, it is the BCG and buffer weights being pushed by the gas stream. The gas pressure on some barrels is about 900 PSI, but an adjustable gas system can be as low as 300 PSI.

That is exactly why adjustable gas block works so well, less gas pressure. With less weight to push there is a lot less recoil.

Ever fire an AR308/AR10? Much higher pressure against an almost double action parts. Like a sledge hammer going into battery and like a mule kick in recoil. But cut the gas pressure and reduce weight by 45% and the recoil is almost 50% less.

But you are also missing the recoil difference between a straight stock and a bolt rifle stock. Felt recoil is changed by stock angle.

Equal and opposite and all that
Nothing to do with it. 99% of the gas follows out behind the bullet, which is why a well designed muzzle brake works so well. And Inertia really doesn't come into play with an oiled BCG of 11 ounces being pushed by 300 to 900 PSIA. The area is pretty constant, the inner chamber where the gas expands against the bolt.

Hope you are enjoying this forum, I am getting into reloading again and these guys are the best.
 
#27 ·
We will never come to an agreement on this. You are equating the movement of the bcg and how violent it is as recoil, I don't. I consider that a secondary impulse(when the bcg slams at the end of the buffer tube). Recoil is simply the total reward force. In very simple terms any gas that is redirected rearward reduces total recoil (again this is what muzzle brakes do) because it is acting opposite of the recoil direction. Now tuning the gun correct and smoothing out the secondary impulse makes the gun run much smoother.
 
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