Reducing recoil by using a lightweight bolt carrier group

[Steve in Allentown PA]

Currently there is a thread similar to this one but I didn't want to step on that one and make it veer off course.

 

I doubt there is anyone more familiar with ARs than you guys who shoot competitively which is why I'm turning to you

 

As background, I'm intimately familiar with the M-16 rifle courtesy of a long relationship with Uncle Sam. That experience was strictly as a user.

 

I'd like to put together a 16" AR with a mid-length gas system for someone who has a tough time dealing with the recoil of the 5.56 due to a shoulder injury. I'm already working on the back end of the rifle (butt pad) and am exploring the potential and practicality of using a lightweight bolt carrier to further reduce the recoil force.

 

There is a catch. The rifle needs to be dead-nuts reliable. Uncle Sugar's M-4s use a carbine length gas system which is way over gassed for civilian use but results in as reliable functioning as can be expected. I suspect the same is true for the full auto bolt carrier i.e. it's heavier than necessary to provide a wide margin of reliability.

 

I'm ignorant when it comes to lightweight bolt carriers, their long term durability, and their reliability when dirty. I'm looking to you folks for an education and recommendations. I may be barking up the wrong tree. If so, just say the word.

 

[Nathanb]

I run one in my match rifle.  Adjustable gas block, lightweight carrier and light buffer.  I don’t think it’s ever had a malfunction once it’s tuned in.  

[lefty o]

you definately want an adjustable gas block with the lightweight bcg.

[Boomstick303]

31 minutes ago, Nathanb said:

I run one in my match rifle.  Adjustable gas block, lightweight carrier and light buffer.  I don’t think it’s ever had a malfunction once it’s tuned in.

 

Same.  Once the system is tuned properly it has not malfunctioned due to the rifle.  Make sure you have fired 500-700 rounds through it and make final adjustable gas block adjustments once the system is dirty.  If you adjust it clean, once the system becomes gummed up it may not have enough gas adjusted to power through the muck.

[Steve in Allentown PA]

Thanks guys.  What I hear you saying is that an adjustable gas block is necessary to optimize the advantages of a lightweight carrier.

 

Am I correct in saying that the reduced mass of the lightweight carrier results in less impact force when the buffer contacts the back of the buffer tube?  The lightweight carrier allows for the use of a lighter buffer spring, right?  The lower mass coupled with the lighter spring therefore results in less felt recoil, right?

 

 

[Nathanb]

You’re correct. Less gas, less mass, less spring. 
 

you’re not that far from me and if it ever comes to it you can shoot mine.  A good brake goes a long way too

[MikeBurgess]

light weight bolt assy (bolt carrier and buffer) with adjustable gas and a decent comp can make for a very very light recoil gun.

But that is not free, while mine has been very reliable in competition I know the operating envelope is smaller than a factory system, one thing you may not immediately think of is the bolt speed is higher meaning that your magazines have less time to present the rounds. 

 

so the question is what do you call reliable? for end of days gun I would live with the recoil. for anything else I would consider Light weight adj gas.

[MikeBurgess]

40 minutes ago, Steve in Allentown PA said:

Thanks guys.  What I hear you saying is that an adjustable gas block is necessary to optimize the advantages of a lightweight carrier.

 

Am I correct in saying that the reduced mass of the lightweight carrier results in less impact force when the buffer contacts the back of the buffer tube?  The lightweight carrier allows for the use of a lighter buffer spring, right?  The lower mass coupled with the lighter spring therefore results in less felt recoil, right?

 

 

I will admit I thought it was all BS until I built one,  I did a cheep test gun with a drilled gas key with set screw for the adjustable gas portion and took all the weights out of a rifle buffer and a cheep comp, put it together and adjusted the gas till it locked back, and was totally amazed at how much the recoil was reduced, other than being loud it felt closer to a 22 than it did a regular AR

[Steve in Allentown PA]

1 hour ago, Nathanb said:

you’re not that far from me and if it ever comes to it you can shoot mine.  A good brake goes a long way too

A very kind offer.  In return you can shoot my Can Cannon.  There's not a lot that's more fun than launching cans of soda 100 yards down range.  It's like using an M203 40mm grenade launcher without the loud noise at the receiving end.

[Steve in Allentown PA]

54 minutes ago, MikeBurgess said:

I will admit I thought it was all BS until I built one.    . . .  it felt closer to a 22 than it did a regular AR

Okay, I'm hooked.

 

I was thinking a 16" heavy barrel (~32 ounces) would also help reduce recoil.  This rifle is pretty much a blank canvas at this point.  Now all I need are recommendations on the other components (adjustable gas block, buffer, buffer spring, lightweight bolt carrier, bolt).  Any and all recommendations are most welcome.

[Ming the Merciless]

The most reliable lightweight bolt carrier I've found is the JP Low Mass Steel BCG with enhanced bolt.  I have one that has outlasted 2 barrels, but I did replace the bolt last year and kept the original as a spare.  I can count the number of malfunctions I've had with this setup in 5 years of competition on one hand and have 2 digits left over and I think one of them was a sandy magazine.

 

https://jprifles.com/buy.php?item=JPBC-3 BCG if you don't want to know how dirty your BCG is.

https://jprifles.com/buy.php?item=JPBC-3SP BCG if you clean your gear often.

 

I use the JP Silent Captured Spring system in all of my AR's small and large.  I just run the standard spring and it has worked with every thing I've run through the gun from light hoser loads to hot 77 grain loads.

 

https://jprifles.com/buy.php?item=JPSCS2-15

 

For gas blocks I run SLR Sentry 7 adjustable gas blocks, but I did have an early model one that spit out the adjusting screw.  They replaced it with the later model upgraded gas block and I haven't had any problems with it since and have about twice as many rounds through it as the failed one.

 

https://slrrifleworks.com/sentry-7-set-screw-adjustable-gas-block/

 

 

[gerritm]

12 hours ago, Steve in Allentown PA said:

Okay, I'm hooked.

 

I was thinking a 16" heavy barrel (~32 ounces) would also help reduce recoil.  This rifle is pretty much a blank canvas at this point.  Now all I need are recommendations on the other components (adjustable gas block, buffer, buffer spring, lightweight bolt carrier, bolt).  Any and all recommendations are most welcome.

If you go with the lightened bolt (JP & JP SCS buffer system and adjustable gas system and a 16" rifle length or Stretch 16 barrel you will not need or want a heavy barrel. Your recoil will be minimal if set up properly. The heavy barrel will slow you down way too much in transitions. 

 

gerritm

[Steve in Allentown PA]

17 minutes ago, gerritm said:

If you go with the lightened bolt (JP & JP SCS buffer system and adjustable gas system and a 16" rifle length or Stretch 16 barrel you will not need or want a heavy barrel.  The heavy barrel will slow you down way too much in transitions. 

A key piece of information.  16" it is then.

 

Let me demonstrate my ignorance yet again.  What's a Stretch 16" barrel?  I'm assuming it's a gas length somewhere between mid-length and rifle-length.  If it's longer than mid but shorter than rifle, what advantages does it offer?

[gerritm]

Stretch Precision has there own proprietary designed barrels that come with there custom length gas system and gas tube. Criterion, Spec Ops and others have standard 16" rifle length gas systems. All great and very soft shooting when set up with BCG & buffer. Even a mid length JP barrel set up with their SCS buffer & low mass BCG can be tuned to be very soft. 

 

gerritm

[Steve in Allentown PA]

The wealth of experience and knowledge you folks have is impressive.  You're helping me jump the learning curve and I really appreciate it.  You've given me lots to consider.  Don't be surprised if I continue to ask more newbie questions as I navigate my way toward a final decision.

[Old3GNR]

I've been shooting ARs in competition for 25 years, primarily 3 Gun where fast double taps can be required.  I used lightweight bolt carriers but now, shooting PRS type matches, use a standard weight carrier.  If you're looking for parts you might check out EGW in Quakertown https://www.egwguns.com/  I have also have a lightly used JP lightweight carrier if your interested in going that route.

[Steve in Allentown PA]

38 minutes ago, Old3GNR said:

If you're looking for parts you might check out EGW in Quakertown https://www.egwguns.com/

EGW is a 20 minute drive from me and prior to the Wuhan Flu I frequently visited them to pick up 1911 parts for my builds.  George gave me two guided tours of the manufacturing floor and is one of the funniest guys I know.  I've known him since his days in Pipersville. Top quality parts and a great bunch of folks.

[inertia]

On 2/26/2021 at 1:14 PM, Steve in Allentown PA said:

The wealth of experience and knowledge you folks have is impressive.  You're helping me jump the learning curve and I really appreciate it.  You've given me lots to consider.  Don't be surprised if I continue to ask more newbie questions as I navigate my way toward a final decision.

There is some good advice here but don't rush. If you want to keep this simple buy everything from JP, barrel, carrier, captured spring, a jp comp is also effective but not as much as some more modern designs with angled baffles. If your on a budget there are some totally acceptable light carriers & adjustable gas blocks from places like brownells and midway house brands. Also keep in mind making the barrel (or the whole gun) heavier doest help as much as you may think, if you have a very light reciprocating mass with a very agressive comp and gas tuned carefully reward recoil is almost non existent. Also like it or not the lighter the carrier gets the lighter the recoil gets if you can tune for it. So for example an aluminum JP carrier produces noticeably less recoil than a lightened (but not as light) steel JP carrier. Some of us spend absurd $ getting race rifles down to the least recoil possible and there is always a price in money or reliability or both so its really just how hard you want to go.

[Snausages32]

I went with the Brownells light weight BCG (nickel boron coat), SLR 7 adjustable gas block, and the JP Silent Capture Spring (using the white spring from the kit), and it works great.  If I were to do it again, I'd go with the 18" rifle length fluted BA 223 wylde instead of the 16" mid-length , but it puts a hole in a hole at 100 yards, so I can't really complain here.  It's an amazing combo, and you'll be happy with whatever you go with.  It's a HUGE improvement over anything mil-spec.  Add a good muzzle brake and you'll be done.

Edited March 8, 2021 by Snausages32

[Steve in Allentown PA]

Snausages, thanks for the info.  The Brownells LW BCG is certainly easier on the wallet.  I wonder who makes their BCGs - RBC (Rubber City Armory)? 

Edited March 8, 2021 by Steve in Allentown PA

[Kokeman]

My son did a lot of research to build a light gun with light recoil. He used the Brownells BCG, an adjustable mid length gas block, light spring and buffer and a good size comp. The gun is very light with half the recoil of any of my guns. But it is loud as hell. Once adjusted it runs flawless. I don't know the exact build specs but could get them if you want them. 

[Steve in Allentown PA]

11 minutes ago, Kokeman said:

I don't know the exact build specs but could get them if you want them. 

If it wouldn't be a bother.  No such thing as too much information.

[Kokeman]

1 minute ago, Steve in Allentown PA said:

If it wouldn't be a bother.  No such thing as too much information.

I will ask him. Might be a day or so. Our work schedules are different and chasing girls are more important than dad now days. 

[Snausages32]

I'll add this about an adjustable gas block:

 

When everything is fully assembled, and you take it to the range for the first time - make sure you bring the allen key that comes with that gas block.  You'll want to load your fist couple magazines with only 2 rounds.  The first, to make sure it has enough gas to cycle the next round, and the second round to make sure there's enough gas to lock the bolt back on an empty mag.  You'll need to adjust it (adjustable gas block) and increase or decrease the gas depending on what's going on.  

Everything works perfectly?  Reduce the gas until it doesn't.  

Doesn't cycle?  Increase the gas until it does.

 

To add to "reliability" once you find that sweet spot - turn it 1 more click to give it a tiny bit more gas, and you're done.  Then just run some rounds to make sure it's all set and there's no gas issues.

 

About the lightweight AR thing above:  mine weighs in just under 6.5 pounds with an optic (not loaded), and it's fun to shoot.  Don't get caught up in those "fancy" uppers and lowers with the cutouts - they actually weigh more than standard ones (I used Aero).  They're thicker to compensate the lack of strength from the cutouts.  If this is for competition, I'd absolutely recommend at 15" handguard and a great trigger.  Handguards are largely cosmetic, and triggers are 100% personal preference (although I love my Timney 3 pound single stage).  A great muzzle brake will make a HUGE difference - https://www.thetruthaboutguns.com/ar-15-muzzle-brake-shootout-3/

[gerritm]

Just an add to this. Some ammo is temperature sensitive. Depending on where you live and what ammo you use, especially if you switch ammo to whatever is available make sure you have enough gas to run based on ammo & temp.

 

When I set up ours it was a bright sunny 80 degree day using Federal XM193. Ran out of that, and shot a night match with temps in the high 30's-low 40's and the other brand ammo would not run consistently, fortunately it was in the old days and had another hotter brand with and it ran fine. Side note is this ammo was remanufactured and from a well known company.

 

Or make sure you can get to the adjustment on the gas block and be able to open it up if this happens. 

 

gerritm