Building a 12 inch Grendel that is going to be suppressed

[Tog7125]

I just picked up a bolt and 12 inch barrel from the monster group buy and I'm looking to do build. I will run it suppressed, but it won't be suppressed right away. I will likely start with a spare noveske kx5 I have laying around until I get around to buying the suppressor. The upper and lower will be noveske Gen 3s, monster 12 inch barrel, sba3 brace, and an 11 inch NSR handguard. What do I need in order for this to function optimally? I need to know if I need an adjustable gasblock, what kind of buffer I need, and really anything to make it function optimally. I believe the barrel has a .750 gas port and the gas system is carbine length. Thanks

[VASCAR2]

If your using an adjustable gas block you can use the supplied buffer and spring. Just adjust the gas where the bolt locks back via bolt catch on an empty mag. If you have a heavier buffer you can tune the gas to compensate for the heavier buffer. The 6.5 Grendel has mild recoil and I’m using the carbine buffer and spring. Brass lands at 3:30 to 4 O Clock and has functioned 100%. I have not used a suppressor on my 12” 6.5 Grendel but having an adjustable gas block it is easy enough to tune the gas to be reliable with a suppressor. Some people prefer to use a T-2 or H-2 buffer as it can change how the recoil feels. Really boils down to personal choice.

[LRRPF52]

I did the same as you while I was waiting for my TBAC Ultra 5 to clear NFA's terrible system.

I used the Maxim PDW brace with tiny buffer and their really stout, short spring, and it runs like a raped ape with 120-123gr Federal OTM and Hornady AG ammo.

I have a Group Buy barrel with a .068" port.

I shoot it now suppressed with the Bootleg ABC carrier turned all the way to suppressed setting, with my TBAC can.

[Drillboss]

I did the same as you while I was waiting for my TBAC Ultra 5 to clear NFA's terrible system.

I used the Maxim PDW brace with tiny buffer and their really stout, short spring, and it runs like a raped ape with 120-123gr Federal OTM and Hornady AG ammo.

I have a Group Buy barrel with a .068" port.

I shoot it now suppressed with the Bootleg ABC carrier turned all the way to suppressed setting, with my TBAC can.

Ditto, kinda.

Ultra 5 is in ATF limbo, Bootleg carrier was under the Christmas tree. Does anyone know if the ATF is included in the shutdown. I had a Form 3 approved on December 28th, which makes me think they're still working.

[Tog7125]

I was hoping you'd reply. Your posts on arfcom are the reason I decided to build one. Is the ABC carrier the 4 position adjustable here?

https://lanbosarmory.com/index.php?main_page=product_info&cPath=114&products_id=43308

Also, I plan on using an SBA3 for the moment. What spring and buffer would be optimal? What gas block should I use if I use this carrier?

[Tog7125]

I don't have a buffer at all as of yet. I have heard of breaking bolts even with an adjustable. Is that true?

[Tog7125]

Sorry, still figuring out how to quote.

[VASCAR2]

With the current quality manufactured bolts from Manson, AA, Millennium (Monster), ToolCraft and JP you don’t hear much about broken bolts. Most broken bolts are attributed to excessive gas caused by oversized gas ports. Suppressors on 18” midlength gas system are the hardest on bolts even with an adjustable gas block. This is probably the reason your seeing more rifle length gas system 18” 6.5 Grendel barrels today.

My 18” Faxon Group Buy midlength gas runs great but I don’t use suppressors. The other culprit which contributes to broken bolts is if the barrel and bolt are not square. Uneven pressure on an AR-15 bolt regardless of caliber is not good. Many people are lapping their receivers before assembling so bolt breakage is not very common with the 6.5 Grendel.

If you get over the 52,000 PSI SAAMI spec pressure you’ll shorten the life of your bolt. Be careful with IMR8208XBR powder as pressures spike quickly. One advantage with high BC bullets in 6.5 Grendel is you don’t have to squeeze every foot per second out of the gun to get good results.

I good way to gauge bolt breakage is to check out the trouble shooting questions on this forum. With the internet if someone has a problem with their car they hit the internet to figure out what is wrong. Same with the 6.5 Grendel. Usually if there is a continual problem with poor design or poorly manfufactured parts you see the same questions on a regular basis. Check the trouble shooting forum on this site then you decide.

[LRRPF52]

I was hoping you'd reply. Your posts on arfcom are the reason I decided to build one. Is the ABC carrier the 4 position adjustable here?

https://lanbosarmory.com/index.php?main_page=product_info&cPath=114&products_id=43308

Also, I plan on using an SBA3 for the moment. What spring and buffer would be optimal? What gas block should I use if I use this carrier?

I'm actually going to test an SBA3 brace, which uses a normal carbine RET.

Instead of trying to deal with it using a heavier buffer, I'm going to try a stronger spring.

[Tog7125]

I'm actually going to test an SBA3 brace, which uses a normal carbine RET.

Instead of trying to deal with it using a heavier buffer, I'm going to try a stronger spring.

Was that the correct BCG? I'll order a stronger spring on mine.

[Tog7125]

With the current quality manufactured bolts from Manson, AA, Millennium (Monster), ToolCraft and JP you don’t hear much about broken bolts. Most broken bolts are attributed to excessive gas caused by oversized gas ports. Suppressors on 18” midlength gas system are the hardest on bolts even with an adjustable gas block. This is probably the reason your seeing more rifle length gas system 18” 6.5 Grendel barrels today.

My 18” Faxon Group Buy midlength gas runs great but I don’t use suppressors. The other culprit which contributes to broken bolts is if the barrel and bolt are not square. Uneven pressure on an AR-15 bolt regardless of caliber is not good. Many people are lapping their receivers before assembling so bolt breakage is not very common with the 6.5 Grendel.

If you get over the 52,000 PSI SAAMI spec pressure you’ll shorten the life of your bolt. Be careful with IMR8208XBR powder as pressures spike quickly. One advantage with high BC bullets in 6.5 Grendel is you don’t have to squeeze every foot per second out of the gun to get good results.

I good way to gauge bolt breakage is to check out the trouble shooting questions on this forum. With the internet if someone has a problem with their car they hit the internet to figure out what is wrong. Same with the 6.5 Grendel. Usually if there is a continual problem with poor design or poorly manfufactured parts you see the same questions on a regular basis. Check the trouble shooting forum on this site then you decide.

Great info. Thank you for the help.

[LRRPF52]

Was that the correct BCG? I'll order a stronger spring on mine.

Any AR15 BCG made to Mil-Spec dimensions will work. I'm using a BCG with an Adjustable Gas Carrier from Bootleg.

There are no springs in the carrier. I'm talking about using the action/recoil spring in the Receiver Extension Tube (RET-commonly called the "buffer tube").

[Tog7125]

Any AR15 BCG made to Mil-Spec dimensions will work. I'm using a BCG with an Adjustable Gas Carrier from Bootleg.

There are no springs in the carrier. I'm talking about using the action/recoil spring in the Receiver Extension Tube (RET-commonly called the "buffer tube").

Yeah that's the BCG I linked. I was talking about the buffer spring, yes.