Frequently Asked Questions: Buffer Weight

Aug 24th 2016

We’re thrilled that so many customers are pleased with their builds and using Faxon barrels as part of tuned weapon. Matching the components is critical to optimal functionality in an AR-15 and AR-10/LR-308.

We’re often asked “What buffer weight do you recommend?”. We'd like to say there is an easy response, but the specific answer to the question depends on many variables unique to each firearm including, but not limited to:

  • Gas seal on the gas block to the barrel
  • Gas seal on the bolt to the carrier group
  • Spring rate on the main buffer spring
  • Weight of the chosen bolt carrier
  • Coatings/Slickness of the bolt & carrier group
  • Machined finish on the inside of the receiver
  • Etc.

Each variable can effect the function of the weapon, either slowing it down or speeding it up. For example, using a slicker bolt carrier group such as nitride can make the weapon function easier, making one want to increase their buffer weight. Or, one may opt for a heavier buffer spring that reduces the weight needed for the buffer. There are a myriad of combinations to tune in an AR.

How Did You Determine Your Gas Port Diameters & Buffer?

Faxon created their gas port diameters by testing using a standard carbine. Specifically, we used a dry manganese phosphate carrier, an H2 buffer, and a military-specification spring. We then test-fired the weapon to ensure that it locked back with no lubrication and opened the port a bit further to account for adverse conditions.

So, What Do You Recommend?

if someone is building a rifle with quality components, H2 is generally good to go per our testing procedure.

For someone on a budget, it’s always best to default to a standard “Carbine” buffer and work their way up on the buffer weight with their chosen ammunition. Buffer inserts are easy to come by and inexpensive. A home builder can easily swap out components and tune the weapon to their build. 

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