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Would appreciate some help with lightweight AR build


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#1 OFFLINE   enduin

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Posted Jul. 02 2018 - 11:33 PM

Hi guys,

 

I'm not new to AR15s but I am new to building them. I decided I wanted to build a lightweight AR so I bought the components after doing extensive research, but I'm encountering some issues, and I would really appreciate if someone could enlighten me.

 

Here is the list of the main components:

 

Faxon 16" mid pencil barrel with A2 flash hider

Aero upper

Midwest lightweight handguard

Wojtek adjustable gas port and gas tube

Brownells lightweight nitride BCG (9oz)

Wolff RP spring

Polymer lower

 

The AR came out pretty lightweight so I was very happy with that. I know you can't cheat physics and that lighter weight = more perceived recoil, which is why I chose the lightweight BCG and adjustable gas port, so that I could tune the gas down. My preference was to avoid muzzle brakes..

 

When I went to the range to test the gun and tweak the gas port (single round in the mag, opening the gas bit by bit until the bolt locks open reliably) I was surprised to see how much perceived recoil it had. My range ammo is Wolf Gold 55gr btw. Now, perceived recoil is obviously subjective, but to give you an idea I have experience with a wide variety of guns from big bore revolvers to 12ga shotguns and Barrett M82A1. So when I say it had a lot more perceived recoil than expected, I mean for a .223. I expect .223 to be soft shooting. 

So, next I got a Wolff reduced power spring and removed the weights from the buffer, with the idea that I could then tune the gas down even more and see if that helped with the recoil. When I tested the gun and set the gas block so that the bolt would lock open, I noticed zero improvements in recoil and I started having FTE, with the spent case getting stuck in the chamber. Upon hammering it out with a rod, I noticed that the extractor ripped off the rim. I figured the bolt velocity increased too much and the extractor was trying to rip out the case too early in the cycle, so I added the weights back in the buffer and tested it again, just to experience the same problem. Cases were ejecting at 4 o’clock btw.

Eventually I put back the stock spring, tweaked the gas port again, and I stopped experiencing the problem (for the 100 or so rounds I fired after that).

 

I’m at this point a bit confused by 2 things:

 

  • it seems like making the reciprocating mass lighter and closing the gas port more is not having any effect whatsoever on the perceived recoil. Is this normal because the rifle is fairly light ( 4.9lbs) and I’m not using underpowered handloads like 3gunners, or is there something wrong?
 
  • It seems like using the lightweight BCG along with a reduced power spring (with or without reducing the buffer weight) results in excessive bolt speed and cases stuck in the chamber with ripped off rims. Is this normal? It was my understanding that tuning down the gas port balances out the reduction of reciprocating mass. 
 
Thank you for the help!

Edited by enduin, Jul. 03 2018 - 05:32 PM.



#2 ONLINE   hzhardy

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Posted Jul. 03 2018 - 12:41 AM

When you get to light the cyclic rate gets way to fast and the bolt starts to open before the case unseals from chamber. You also need the weights to stall the bcg in its rearward motion to slow it down enough so you dont override the next round.

So the gas tunning will slow the opening of bolt while buffer reciprocating weights slow the bolts return.

Edited by hzhardy, Jul. 03 2018 - 12:43 AM.



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#3 ONLINE   hzhardy

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Posted Jul. 03 2018 - 12:46 AM

I think what you are feeling is the bcg slamming to the back Of the reciever extension. I would look into a hydrolic buffer or a jp silent capture spring. I would also be curious of the effects of using a heavier buffer spring to help slow the action down even more prior to using the above mentioned systems.

Edited by hzhardy, Jul. 03 2018 - 12:48 AM.



#4 ONLINE   bamashooter

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Posted Jul. 03 2018 - 06:29 AM

OP, Is most of your post copy/pasted? If so, it needs editing.

 

Select edit.

 

Select / highlight all of that tiny text.

 

In upper left of edit window toolbar select "Remove Format". The tool symbol resembles an eraser.

 

If that's not what you did, select the txt and enlarge please.

 

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#5 OFFLINE   enduin

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Posted Jul. 03 2018 - 05:40 PM

Sorry about that @bamashooter, yes I usually write a post on the notepad and then copy and paste, I fixed it! And thanks for the welcome!

 

@hzhardy: if tuning the gas down slows down the opening of the bolt, then why even with the gas at the minimum for locking the bolt open does it still open too soon resulting in the FTE? 

 

The JP SCS is a bit out of the budget, so that's not an option. I can always abandon the lightweight BCG idea and go back to a normal BCG with normal carbine buffer and spring, but before doing that I would like to know if it's normal. 

 

Also as far as the BCG slamming into the receiver, I'm sure sure that's the case, as the perceived recoil was pretty much the same even when the gas was still tuned too low to keep the bolt open on the last round. If the BCG doesn't go back enough to lock open, how can it slam into the receiver? Or am I missing something?


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#6 ONLINE   bamashooter

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Posted Jul. 03 2018 - 07:24 PM

Thanks buddy. Now lets get this resolved. :)




#7 ONLINE   bamashooter

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Posted Jul. 03 2018 - 07:33 PM

Of course the 5.56 isn't a mule kicker but I think the "perceived" recoil is greater than what many folks expect. Even more so with your set up. Under 5 pounds is pretty cool though for a carbine.




#8 OFFLINE   enduin

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Posted Jul. 03 2018 - 09:42 PM

That's one of the things I'm trying to figure out. The other AR I have (Armalite Eagle15) has a heavy profile barrel and is quite a bit heavier but definitely softer shooting. I wonder if all the reports I read of 3gun ARs that "shoot like a 22r" because of lightweight BCG and adjustable gas ports have more to do with the weight of the ARs (and underpowered handholds). 

 

Thing is, for the recoil, if I can establish that it's normal, I'm gonna slap a muzzle break on it and call it a day. But the FTE is a deal-breaker. 


Edited by enduin, Jul. 03 2018 - 09:43 PM.



#9 ONLINE   hzhardy

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Posted Jul. 04 2018 - 03:38 PM

Sorry about that @bamashooter, yes I usually write a post on the notepad and then copy and paste, I fixed it! And thanks for the welcome!
 
@hzhardy: if tuning the gas down slows down the opening of the bolt, then why even with the gas at the minimum for locking the bolt open does it still open too soon resulting in the FTE? 
 
The JP SCS is a bit out of the budget, so that's not an option. I can always abandon the lightweight BCG idea and go back to a normal BCG with normal carbine buffer and spring, but before doing that I would like to know if it's normal. 
 
Also as far as the BCG slamming into the receiver, I'm sure sure that's the case, as the perceived recoil was pretty much the same even when the gas was still tuned too low to keep the bolt open on the last round. If the BCG doesn't go back enough to lock open, how can it slam into the receiver? Or am I missing something?

the carrier could be running so fast the catch dkes not react fast enough the engage before the bolt goes back to battery. When you tooknthe weights out of the buffer you lost the slap weight inertia that stalls the bolt in its rear ward motion.


#10 ONLINE   TackleberryMCS

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Posted Jul. 04 2018 - 05:33 PM

Personally, I have never had the need for an adjustable gas block or lightweight BCG for recoil compensation. I use a M16 BCG and a standard carbine buffer and spring in this lightweight build (less than 6 lbs. with optic). I have no issues with, what someone would call, excessive recoil. It is pretty mild shooting. The barrel is a LaRue Tactical PredatAR 16" mid-length and is gassed perfectly.

JPXREKW.jpg

To me, what is important is to get a good quality barrel that is designed correctly. The Faxon barrel may be a bit over-gassed to begin with and the Wolf is not the best ammo to work with. Additionally, I do not recommend using a polymer lower in a full-powered 5.56/.223 AR.


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#11 OFFLINE   enduin

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Posted Jul. 04 2018 - 10:34 PM

the carrier could be running so fast the catch dkes not react fast enough the engage before the bolt goes back to battery. When you tooknthe weights out of the buffer you lost the slap weight inertia that stalls the bolt in its rear ward motion.

 

I think I get what you are saying, but when the FTEs happened, I was loading the rounds one at a time in the mag to see if it would lock back, so I believe what you said doesn't apply to this situation.

 

 

Also @TackleberryMCS: in your picture I'm seeing a good 2 chamber muzzle break, and that alone I'm sure does a good job at taming the perceived recoil. Plus if your AR is around 1 pound heavier (almost 6lbs vs almost 5lbs) it's definitely a soft shooter. My goal was to see if I could build a soft shooting AR without using a brake, hence experimenting with the lightweight BCG, etc. 

 

Right now I'm thinking that the benefits from the low BCG, buffer, RP spring and adjustable gas block are noticeable either :

 

- when using underpowered handloads (which have less recoil because they are loaded mild and would normally not cycle in a regular AR) 

 

- when someone replaces the parts on a normal weight AR that was previously overgassed

 

Can anybody confirm or deny these hypotheses?

 

BTW one more detail, the BCG fits kind of tight and is making the charging handle rub against the top of the upper receiver. I feel more friction compared to a mil-spec BCG even when well lubed, and I wonder if that has any impact. 




#12 ONLINE   TackleberryMCS

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Posted Jul. 05 2018 - 05:18 AM

I think I get what you are saying, but when the FTEs happened, I was loading the rounds one at a time in the mag to see if it would lock back, so I believe what you said doesn't apply to this situation.
 
 
Also @TackleberryMCS: in your picture I'm seeing a good 2 chamber muzzle break, and that alone I'm sure does a good job at taming the perceived recoil. Plus if your AR is around 1 pound heavier (almost 6lbs vs almost 5lbs) it's definitely a soft shooter. My goal was to see if I could build a soft shooting AR without using a brake, hence experimenting with the lightweight BCG, etc. 
 
Right now I'm thinking that the benefits from the low BCG, buffer, RP spring and adjustable gas block are noticeable either :
 
- when using underpowered handloads (which have less recoil because they are loaded mild and would normally not cycle in a regular AR) 
 
- when someone replaces the parts on a normal weight AR that was previously overgassed
 
Can anybody confirm or deny these hypotheses?
 
BTW one more detail, the BCG fits kind of tight and is making the charging handle rub against the top of the upper receiver. I feel more friction compared to a mil-spec BCG even when well lubed, and I wonder if that has any impact.


The muzzle device is actually a brake/compensator/flash hider. It helps, but it is not the main factor in controlling recoil. It does help to control muzzle rise somewhat. Gas flow/system, gas port size, cyclic rate, and reciprocating mass are the main factors in how much recoil an AR will have. When building a lightweight AR-15, you will find that you will be giving up something in order to keep the weight down. When it comes to recoil reduction, weight is your friend as well as an appropriately gassed barrel and appropriate muzzle device.

Edited by TackleberryMCS, Jul. 05 2018 - 11:35 AM.



#13 OFFLINE   porterdavid98

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Posted Jul. 05 2018 - 09:48 AM

I hesitate to comment on this one.

First why the firm stance against a muzzle brake/flash hider? Weight saving?

Second: have you ever shot a 38 special snub nose air weight pistol? Kicks like a mule. Compared to a 357 Magnum full frame. Much more power in the Magnum but not as much kick compared to the light weight 38.

From my side of your situation you are too concerned about carry weight and can’t have it both ways. Perceived recoil kick will always be greater in a super light weight build...period! The muzzle brake/flash hider will have almost no noticeable effect in your hands for actual shooting feel.


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#14 OFFLINE   enduin

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Posted Jul. 05 2018 - 02:22 PM

I hesitate to comment on this one.

First why the firm stance against a muzzle brake/flash hider? Weight saving?

Second: have you ever shot a 38 special snub nose air weight pistol? Kicks like a mule. Compared to a 357 Magnum full frame. Much more power in the Magnum but not as much kick compared to the light weight 38.

From my side of your situation you are too concerned about carry weight and can’t have it both ways. Perceived recoil kick will always be greater in a super light weight build...period! The muzzle brake/flash hider will have almost no noticeable effect in your hands for actual shooting feel.


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I'm not firm at all about the muzzle brake. My PREFERENCE is to avoid it not only for the extra weight at the end of the barrel where it matters the most, but also because I don't want to be that guy at the range next to you blasting you to hell with his brake. With that said, if the gas tweaking/lightweight BCG/RP spring are not helping, I'm definitely ready to consider a brake. I found some lightweight ones, and I could always avoid shooting if the firing lane is too crowded.  

 

Also, I most certainly have experience with a snub 38. I actually owned a 38spl LCR that with good defensive 38spl loads would kick way more than my 44mag Redhawk. I'm very aware that you can't cheat physics when it comes to recoil and weight is the biggest factor. But a revolver doesn't have a gas system nor reciprocating parts, and it was my understanding that tweaking the reciprocating mass and gas system the perceived recoil could be reduced regardless of the weight of the rifle. 

 

My two questions remain the same:

 

- is it normal to have excessive bolt speed in spite of tuning down the gas port?

 

- does a lightweight BCG/RP spring/adjustable gas port/lightweight buffer have any impact on perceived recoil on a LIGHTWEIGHT rifle shooting regular factory ammo?

 

I actually tried swapping the lightweight BCG with a mil-spec one from my other AR and I noticed ZERO difference in perceived recoil (and it locked open in spite of not increasing the gas which I didn't expect), so now I'm leaning towards the lightweight BCG and the other stuff being 100% irrelevant in a lightweight AR with factory ammo. I would just like someone with more knowledge than me to confirm/debunk what I'm thinking. 




#15 ONLINE   towtruck

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Posted Jul. 05 2018 - 02:43 PM

Two things happen when you pull that trigger that are of concern as to recoil. If you block off the gas port and fire the weapon you are getting 100% of the recoil to your body from the cartridge. If you open the gas port up and siphon away as much of the gasses as you can from the barrel the recoil impulse changes from the cartridge to the BCG, and that timing changes with different gas system and barrel  lengths. Too much gas and the BCG slams back hard against the buffer tube and you feel that. 

 

The best of both worlds is to have heavy enough reciprocating mass to catch as much of that gas as you can and stop the reward movement of those parts with just a kiss of the buffer on the rear of the tube. That will spread the recoil out giving you some directly from the cartridge and a soft push from the mass of the BCG and buffer going back. The lighter the parts the harder it will be to tune it....the heavy the parts the easier it will be to tune it....and don't forget heavy wins with recoil management almost every time. 




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#16 OFFLINE   porterdavid98

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Posted Jul. 05 2018 - 04:00 PM

Well I think you have answered your own question. In my opinion you are correct in that a lightweight bcg even when paired with a tuned gas block will have very little to do with perceived recoil kick.

Your question number one can be fielded by someone else.

Regarding your compassion to shield someone along side from your muzzle brake blast that is mighty nice of you. I have several different muzzle brakes that each direct that blast differently. Most direct the strongest part of the blast upward in an attempt to hold the barrel tip down, limiting barrel rise. But you are right, I have felt the blast when standing to the side of someone else. You might want to avoid the more common “bird cage” styles. The designs that deal with the visual flash won’t help with perceived recoil. Yes your comment about the leverage from any weight mounted on the end of a barrel will be noticeable but again not very helpful either way with perceived recoil forces.

Good luck to you, under 5 pounds is really unusual congrats.


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#17 OFFLINE   porterdavid98

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Posted Jul. 05 2018 - 04:57 PM

One more curiosity for me.

If in fact you wound up building without a muzzle brake, how were you going to finish the end of the barrel? Leave the threads showing, cut those off or what?


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#18 ONLINE   TackleberryMCS

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Posted Jul. 05 2018 - 05:03 PM

One more curiosity for me.

If in fact you wound up building without a muzzle brake, how were you going to finish the end of the barrel? Leave the threads showing, cut those off or what?


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It already has an A2 FH on it. In my opinion, he might as well leave it there unless he decides to use some sort of combination muzzle device (brake/compensator/FH) like I mentioned previously.


#19 OFFLINE   enduin

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Posted Jul. 06 2018 - 10:33 AM

One more curiosity for me.

If in fact you wound up building without a muzzle brake, how were you going to finish the end of the barrel? Leave the threads showing, cut those off or what?


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My original plan was to use a thread protector or a titanium A2 flash hider. Right now I have a normal A2 from my other AR to protect the threads while I decide what to do. The VG6 Gamma (brake/comp) looks promising and it's not too heavy. 


Edited by enduin, Jul. 06 2018 - 10:34 AM.



#20 OFFLINE   Joel74

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Posted Jul. 06 2018 - 10:55 AM

Lots of interesting info here.

 

To the OP I have a question. What do you see the benefits of having a sub 5lb gun vs a gun set up like Tackleberry's. 

 

I'b be interested in knowing how that polymer lower stands up over the long haul. 

 

Personally, I have never had the need for an adjustable gas block or lightweight BCG for recoil compensation. I use a M16 BCG and a standard carbine buffer and spring in this lightweight build (less than 6 lbs. with optic). I have no issues with, what someone would call, excessive recoil. It is pretty mild shooting. The barrel is a LaRue Tactical PredatAR 16" mid-length and is gassed perfectly.

JPXREKW.jpg

To me, what is important is to get a good quality barrel that is designed correctly. The Faxon barrel may be a bit over-gassed to begin with and the Wolf is not the best ammo to work with. Additionally, I do not recommend using a polymer lower in a full-powered 5.56/.223 AR.

What does that optic and riser weigh? Curious to see how close your rifle weighs compared to the one built by enduin. 


Edited by Joel74, Jul. 06 2018 - 10:57 AM.



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