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Discussion Starter · #1 ·
working on getting parts together for a AR 6.5 Grendel build.
planning on a 20" barrel and BCG kit from Odin.

I ordered my LPK and grip this morning for the lower.
going to go with a ALG ACT trigger

next up that im a little unsure on is the buffer setup.
little confused on what to look for. can someone help explain a little for me.

Thanks
 

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Maybe this will help? As far as what to use with that particular setup I'm not sure but this at least explains the difference.
 

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luked, I don't know if I can help or not. You buffer weight is going to be dependent on gas port size, to a point. Considering it is a 20" barrel, the port "should' be sized to work with a conventional weight rifle buffer, and spring. The stock rifle buffer should weigh about 5.2 ounces, and use a standard rifle buffer spring. I found this reference, and suggest you check it out:

6.5 Grendel Buffer Change?

If you are using a collapsible stock, then buffer weights will vary from 3.0 ounces for a standard carbine buffer, 3.6 ounces for an "H" buffer, 4.6 ounces for a "H2" buffer, and 5.4 ounces for a "H3" buffer. These difference in weights, and their uses will be dependent on length of the barrel, and port diameter, using a standard carbine buffer spring. The heavier the weight of the buffer "delays" longer, the opening of the bolt from the receiver extension. If it opens too soon before the pressure curve of the burning powder reaches it's optimum, it may cause stove pipes, and jam the action.

Basically the bolt and carrier need to operate at the correct "velocity", to feed from the magazine, and eject the fired cases. When using exchangeable parts between rifles and carbines with different barrel lengths, bolts and carriers should be standard, and springs also between fixed and collapsible. By varying buffer weights the other parts can function in a variety of weapons.

I know this is a little "wordy", but it isn't an easy question to answer simply!
 

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Discussion Starter · #4 ·
Thanks for the info fellas.

Willard as far as the gas port. would this be something that possibly the barrel manufacture would be able to recommend a buffer weight?

the Stock I am looking at is a Fixed stock from Luth AR Skullaton.
it is aprox 10.50 long stock so I assume a rifle length spring and heavier buffer might be my best bet due to the recoil of the 6.5 vs the lighter buffer for a 223/5.56 buffer

is that a correct assumption?
 

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You will probably have to experiment and "tune" both buffer and spring unless you can get your hands on an already-built 6.5 Grendel w/ a 20" barrel.

I recently finished a carbine 6.5 Grendel AR build with a 16" barrel and bolt from Barrier Defense. I had an Adams Arms piston kit laying around (originally for 5.56/.223) so I put that on to save money on the bolt carrier and related parts (also used the ACT trigger which is great for the money).

I ended up with a standard-weight carbine buffer and an extra-power spring from Wolff Gunsprings.

I use the same lower with a 7.62 x 39 upper (also 16"), but for that I have to change out the buffer to an H3.

I would start with a standard weight rifle buffer and spring and go from there ...
 

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Be sure to keep them between the AQ and AS ones. Sorry, couldn't resist.
 

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Thanks for the info fellas.

Willard as far as the gas port. would this be something that possibly the barrel manufacture would be able to recommend a buffer weight?

the Stock I am looking at is a Fixed stock from Luth AR Skullaton.
it is aprox 10.50 long stock so I assume a rifle length spring and heavier buffer might be my best bet due to the recoil of the 6.5 vs the lighter buffer for a 223/5.56 buffer

is that a correct assumption?
Yes, the barrel manufacture could be a good start, as far as their intent, on using that size. Just as reiney has stated, you may have to do some "tuning" to get it right. One way to accomplish that, is with an adjustable gas block. I would suggest getting one made with a steel body, instead of one made of aluminum. Adjusting gas flow will allow "finer tuning" than adjusting buffer weight, as with the buffer, they would be "courser", by exchanging steel discs for tungsten discs, and/or steel bodies for aluminum.

As far as your buttstock choice, a standard rifle buffer tube/receiver extension is 10-1/8" long, where as the carbine buffer tube/receiver extension can run from 7-1/4" to 7-3/4" long.

If your barrel manufacturer cannot be of any help, I would suggest you measure your gas port diameter (use of # drill bits will help). You may try to contact Alexander Arms, as I believe they are the folks that developed the cartridge, to see if they could/would help you out with any recommendations,
 

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What I am running on my 6.5 is a standard weight carbine buffer, extra power recoil spring, collapsible stock, 18" mid length barrel and a adustable gas block.

As you are planning on using a fixed stock, I would start with the standard rifle buffer and spring. Regardless of what buffer/spring you use, I highly recommend a adjustable gas block.

John K
 
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