Buffer + Bolt Weight Combo + General Build Questions

[penguins]

Hi all - Been lurking this forum here and there for a few years. Am getting the rest of the parts together once things somewhat normalize and have a few questions:

Buffer + Bolt Weight Combo suggestion?
Am I going to see a functional difference between a heavy buffer and light bolt carrier vs a standard buffer and semi carrier? Is the recoil impulse and movement generally less w/ the lighter carrier due to less mass reciprocating the entire cycle (I realize mass in buffer still moves, but it moves less)? Will it actually make a significant difference with a brake or compensator on? Let's assume common factory ammo and not ragged edge of function super light or heavy handloads, etc.
Example: 1) LMOS buffer (which I am considering but isn't an absolute must for me) with the equivalent of an H2 buffer (~4.7oz) + a lightweight steel carrier (~6.7oz) for a total of 11.4oz. VERSUS 2) Standard carbine buffer (3oz) + semi carrier (8.8oz) = 11.8oz?


Planned build - would appreciate it if I'm missing something or making a blatant error, etc.
Upper:
18-20" barrel, 20" preferred, between 36-40oz - so far looking at Wilson Combat Recon 20" or Grendel Hunter 20" Fluted
Get matching bolt
Carrier depends on advice above
Area 419 Self Timing Brake or Lancer Nitrous - Like adjustability on Lancer but everything I've seen says the Area 419 works very well.
Handguard - Undecided
Gas Block - Undecided low profile clamp type adjustable block
Charging Handle - Geissele or Radian Ambi (last I checked most ambi handles were just OEM / rebranded Radian, not sure if this is still true)
Possible Stop or Jam for shooting against objects w/o bipod
Optic - Undecided, need to look through a few more, but will probably be ~4-16 or 5-20 w/ some sort of Horus or similar Christmas Tree type reticle
Mount - depends on optic
Other parts - "Standard", have a very well fitting upper/lower combo

Lower:
JP Trigger w/ Roller, Elft-SE, or Timney Calvin Elite - undecided, but leaning towards JP or Elft
Most likely the XLR AR Stock. Also looking at the MDT Carbine stock but it looks like that will not work with an actual AR due what looks like bolts running through the buffer tube. Magpul PRS doesn't fit me well.
Other parts - "Standard"

Lastly, is there anything drastically different about building a 6.5G vs a standard 223/556 or anything in particular I really need to watch out for that doesn't show up on other calibers? And I assume I don't need to run a go/no go gauge if the bolt and barrel come matched?

[KZero]

The only thing that's obviously missing are magazines. I'm just starting my first Grendel build myself, and as a 5.56 AR user up til now, I can say I've been spoiled into not thinking about magazines. There's not nearly as many options for the 6.5.
I have one ACS and one C Products Defense (CPD) magazine on order, as well as a couple from Amend 2 (something of a gamble at this point.)
So while I can't advise you which way to go, you'll need at least one of some kind to get started.

I'm also not well-versed enough to get that far into the reciprocating bits, but otherwise it appears you've thought it out pretty well. I'm looking forward to seeing what you come up with.

[A5BLASTER]

Having played with every combo of bcg and buffer/spring under the sun with gas lengths ranging from rifle length all the way down too carbine. Both with factory and handloads.

If your not intending on useing a adjustable gas block don't do any lowmass parts, if you go with a adjustable gas block it really doesn't matter what weight bcg/buffer/spring you go with because you can tune the gas too the parts.

Now I will say this, if your wanting the lightest recoil your going to have to go full lowmass meaning. Adjustable gas, lowmass bcg and lowmass buffer/spring system.

All my AR grendels use adjustable gas lowmass bcg and standard carbine buffer/spring, I can drop the standard carbine buffer/spring out for my taccom lowmass buffer/spring set up and the difference comes out too adjusting the gas exactly one click on the gas block.

As far as mags, my advice is buy the cpd/duramags they are the best of the metal grendel mags.

Hope this helps sir.

[penguins]

Oops, yeah, forgot magazines.

Plan was to get C-products 10 round magazines due to these being the most reliable. From what I understand and heard - right when the Grendel came out, Magpul and another poly mag mfg took a lot of interest, but no matter what they did and tried, they couldn't make a reliable 6.5grendel mag over 10ish that either 1) didn't bulge over time or 2) was completely reliable and hence neither company went through with it. Not much research has been done by anyone else afterwards.

Having played with every combo of bcg and buffer/spring under the sun with gas lengths ranging from rifle length all the way down too carbine. Both with factory and handloads.

If your not intending on useing a adjustable gas block don't do any lowmass parts, if you go with a adjustable gas block it really doesn't matter what weight bcg/buffer/spring you go with because you can tune the gas too the parts.

Now I will say this, if your wanting the lightest recoil your going to have to go full lowmass meaning. Adjustable gas, lowmass bcg and lowmass buffer/spring system.

All my AR grendels use adjustable gas lowmass bcg and standard carbine buffer/spring, I can drop the standard carbine buffer/spring out for my taccom lowmass buffer/spring set up and the difference comes out too adjusting the gas exactly one click on the gas block.

As far as mags, my advice is buy the cpd/duramags they are the best of the metal grendel mags.

Hope this helps sir.

Thank you much. Yes, I'm going with an adjustable gas block. Clamp style for more even distribution of force on barrel.

Was leaning towards light bcg + doing all the tuning in buffer + springs (easier and cheaper to tune where-as BCG is more or less fixed w/o buying a new one) but just wanted to see if it just ends up being moot (in which case I get standard parts and save a few hundred $). Leaning towards JP Enterprises LMOS with standard springs and standard weights first + an extra H2 weight + low mass bolt carrier (leaning towards JP as well as these seem to work pretty consistently, but may try Faxon or Odin Works as well). I imagined with an adjustable gas block this should give me a big enough window to get it figured out.

[montana]

It depends on how gas efficient your rifle is. The adjustable or non adjustable gas block seal between the barrel and gas tube, the size of the barrel's gas port, the gas tube-bolt carrier key "chamber size" seal, the size of the 3 bolt carrier chambers, muzzle break or none, the bolt's support shoulder's size, the OD of the bolt's firing pin barrel, the friction between the bolt carrier and the upper's BCG channel, the recoil spring type, the friction between the trigger, magazine and bolt carrier, the weight of the BCG. Then the ammunition you are planning to use, will determine the best buffer, bolt carrier combination" if recoil mitigation or reliability is your goal. Every rifle build should be head spaced, and the throat size checked..

[Klem]

I would go easy on gluing the gas block, and maybe even the barrel unless it is a loose fit. If you build AR's then at some stage you will be thinking of pulling them apart. Once glued, joins are not impossible to break but it becomes a pain and might dissuade you from tinkering.

You only need to add glue to the gas block to seal it from leaking gas. The design accommodates the joins in the gas system leaking like a sieve. You only need to keep this from happening if you don't have enough gas to cycle the action reliably. I recommend building the gun and then taking to to the Range to check with the mildest loads you are likely to use. Open the AGB right up and if you still need more gas you can pull that section apart and reassemble using glue. Otherwise you don't need to seal it. That said, you are very unlikely to need it.

Making the cycling system lighter in the hope of mitigating felt recoil does not make sense to me. I would think the opposite will do this. The heaviest full-mass carrier you can find to absorb as much of the rearward momentum that would otherwise be transferred to the shoulder.

If however your goal is to save weight in the gun, with an adjustable gas block you decide how much gas pushes that combined system of BCG /spring/buffer. Why not go a light MILSPEC buffer, normal spring and light BCG and just dial down the gas so this combined mass only travels rearward as far as is reliable.

There are two competing scenarios here so what you want to achieve?

[Growler]

There is a handguard fit “gotcha” I’d recommend you look closely at, since it sounds like you are going down the adjustable gas block path.

I got burned by an older drawing of a gas block that did not include clearance for the adjustment screw. Except for that, my handguard would have fit nicely. So a few hundred later I had a new handguard and a slimmer adjustable gas block. The Odin works adjustable seems like the lowest profile I could find. Even with it, many handguards I’d like to use wouldn’t clear.

If you can shoot a rental or loaner before you commit to a specific trigger, I’d recommend it. The roller trigger is a competition optimized design. For target and hunting, it might disappoint, or you might dig it more after the comparison. Either way, playing the field first is a win.

ETA - there are many happy LaRue MBT customers here. Myself, I can’t give an opinion, since I drank the ALG/Geissele Kool-Aid.

[penguins]

It depends on how gas efficient your rifle is. The adjustable or non adjustable gas block seal between the barrel and gas tube, the size of the barrel's gas port, the gas tube-bolt carrier key "chamber size" seal, the size of the 3 bolt carrier chambers, muzzle break or none, the bolt's support shoulder's size, the OD of the bolt's firing pin barrel, the friction between the bolt carrier and the upper's BCG channel, the recoil spring type, the friction between the trigger, magazine and bolt carrier, the weight of the BCG. Then the ammunition you are planning to use, will determine the best buffer, bolt carrier combination" if recoil mitigation or reliability is your goal. Every rifle build should be head spaced, and the throat size checked..

Yes, considered many of the above already, but still wasn't sure if I could get away with not experimenting on buffer/bcg or if there is 1 generally known answer as there often is for the less standard AR calibers. As you can probably guess from my build notes, I'm leaning more towards recoil mitigation instead of reliability, but am not trying to win any competitions or other controlled environment shoots with this either where one generally does have to sacrifice some kind of reliability or robustness outside of ideal conditions.

I would go easy on gluing the gas block, and maybe even the barrel unless it is a loose fit. If you build AR's then at some stage you will be thinking of pulling them apart. Once glued, joins are not impossible to break but it becomes a pain and might dissuade you from tinkering.

You only need to add glue to the gas block to seal it from leaking gas. The design accommodates the joins in the gas system leaking like a sieve. You only need to keep this from happening if you don't have enough gas to cycle the action reliably. I recommend building the gun and then taking to to the Range to check with the mildest loads you are likely to use. Open the AGB right up and if you still need more gas you can pull that section apart and reassemble using glue. Otherwise you don't need to seal it. That said, you are very unlikely to need it.

Making the cycling system lighter in the hope of mitigating felt recoil does not make sense to me. I would think the opposite will do this. .......

Heh, I have been there with the stuck on parts before (not by me). Completely agree. I did use a high temp but low bond strength thread locker between the gas block and barrel once and didn't feel it offered any benefit over just turning gas up/down depending on how much bleed off there was.

Regarding mass, I thought the same in the past that more mass = more inertia to stay still = less recoil in all situations. However, in experimenting (YMMV), if I had the same gun with the total mass and same ammo/load (let's assume it's appropriate and reliable per individual goals), I have found that using low reciprocating mass + easier to move parts (such as lighter buffer, springs, etc.) resulted in a different kind of felt recoil and muzzle movement than the same gun with more reciprocating mass. Based on the characteristics / differences, I am leaning towards lighter reciprocating parts for this build. Again, YMMV per so many different factors and I could easily see that for some people they would prefer extra mass in everything.

... The Odin works adjustable seems like the lowest profile I could find. Even with it, many handguards I’d like to use wouldn’t clear.

If you can shoot a rental or loaner before you commit to a specific trigger, I’d recommend it. The roller trigger is a competition optimized design. For target and hunting, it might disappoint, or you might dig it more after the comparison. Either way, playing the field first is a win.

ETA - there are many happy LaRue MBT customers here. Myself, I can’t give an opinion, since I drank the ALG/Geissele Kool-Aid.

Yep, was leaning towards an Odin block already, have had good luck with those, and luckily I also generally prefer a slightly larger hand guard around 1.7 or 1.8" OD (think roughly ALG size handguard). At the same time I didn't know if people here have found quirks with certain gas blocks not working well with this caliber or certain barrels, etc.

I've tried a lot of triggers out there, but so far my favorite for anything that may be "duty" (which I am not "duty" so maybe I actually have no clue) is the Wilson TTU Single Stage, standard weight, not the heavy one. For stuff where I want to go fast or just want something that really fits me it's the Hiperfire Reflex or Competition. Precision is Elft triggers. I have not tried the JP roller trigger or Timney AR trigger though so thought I'd ask. If the Timney feels like their bolt action triggers, then I'd actually lean more towards the Elft (Timney stuff is good IMO, but based on a conjecture/approximate triangulation it's just not 100% ideal for my preferences when shooting semi-auto).

[just_john]

Penguins, a few years ago, I built a Grendel for a nephew with a broken back and mostly severed spinal column. He had hunted since very young and mre recently did so with a 300 WinMag. Until he fell out of a tree stand. I built this with the intent of absolute recoil mitigation but could not sacrifice reliability. It had a 20" barrel and an adjustable stock. The keys were the longest possible gas length ( RLGS ), significant porting on a muzle break and the strongest buffer spring that would still work. On completion, I could hold the rifle out to my side at full length and fire it with no discomfort at all. Recoil was hardly noticible. The Grendel is, by design, one of the most recoil friendly cartridges there is. Don;t go nuts trying to reduce an almost non-existant recoil. Especially at the expense of reliability. An unreliable rifle ends up in the back of a safe, soon forgotten. The Grendel has too much to offer.

[Mad Charlie]

Penguins, a few years ago, I built a Grendel for a nephew with a broken back and mostly severed spinal column. He had hunted since very young and mre recently did so with a 300 WinMag. Until he fell out of a tree stand. I built this with the intent of absolute recoil mitigation but could not sacrifice reliability. It had a 20" barrel and an adjustable stock. The keys were the longest possible gas length ( RLGS ), significant porting on a muzle break and the strongest buffer spring that would still work. On completion, I could hold the rifle out to my side at full length and fire it with no discomfort at all. Recoil was hardly noticible. The Grendel is, by design, one of the most recoil friendly cartridges there is. Don;t go nuts trying to reduce an almost non-existant recoil. Especially at the expense of reliability. An unreliable rifle ends up in the back of a safe, soon forgotten. The Grendel has too much to offer.

I would listen to this man.
I want accuracy and low recoil as much as anyone, but reliability is king.

[montana]

I would listen to this man.
I want accuracy and low recoil as much as anyone, but reliability is king.

Setting a rifle up, "to find the sweet spot for recoil" can be very reliable. If a rifle is set to fire the lowest end of the spectrum ammunition, then it will be over gassed for the higher end of the spectrum or vise versa.. When comparing mil spec in 5.56, the rifle is set to that ammunition. Most shooters use lower pressure ammunition in their mil spec AR rifles and are actually under gassed.. As a result, many AR manufacturers over size their gas ports, "so the rifle will reliably function across a larger spectrum of ammunition" resulting in a rifle that is over gassed. Having the ability to adjust the rifle to the ammunition is an option I use without sacrificing reliability.. Not knowing how to adjust the rifle, "to the ammunition and field conditions" is where reliability problems can occur...

[penguins]

Thanks for all the feedback everyone.

Have decided to go with JP captured system with extra springs/weights... even if I don't end up needing them here, I'm sure I'll be able to use them again later down the line. Will also go with a low mass carrier - if it doesn't work, I have another rifle I was thinking of using the low mass carrier in anyways.

Regarding reliability and an overall robust system, I figured adjustable gas + spring + buffer/carrier mass + proper building/fitting would more or less take care of it (with factory ammo at least). I understand that reliability of a system overall is a lot of different things, but so many people encounter problems here there or elsewhere when building "non-standard" so may as well ask here first.