Sunday, March 4, 2012

M14 Expert, Lee Emerson, Sends Email About our M14 Piston

We got this email from Lee Emerson who is from the TACOM EBR shop.  He has nothing but nice things to say about our M14 Gas Piston (PN 2075) we make:

Hi, Ron

I looked at the print for the USGI gas piston.  Wow, that is a huge difference taking the tolerance on the interior holes down to 0.001", sweet!  I have posted information on the new SEI M14 gas piston at these Internet sites: - -

FaceBook -!/groups/m14research/

Here is what I posted, let me know if it needs some clean up:

I spoke with Ron Smith, Smith Enterprise, Inc., today about the new SEI radiused groove M14 gas piston. Here's what I learned.
The USGI M14 gas piston major diameter is 0.4975 " - 0.0005 ". The new radiused groove SEI M14 gas piston major diameter is 0.4975 " + 0.0005 ". Thus, there is less area for gas to blow by between the gas cylinder wall and the gas piston. The SEI radiused groove gas piston is made from 420 stainless steel that is heat treated to 58 HRC. The piston is then plated with thin dense chromium and baked to prevent hydrogen embrittlement cracking corrosion. The chromium plating is given a highly polished surface finish, 9 microinches as measured by profilometer, through several operations on an OD surface grinder. The surface finish requirement for a USGI gas piston is not as smooth, 16 microinches.
The circumferential grooves are fully radiused instead of being flat bottomed. This feature will make it easier to remove carbon when cleaning. The large interior hole is drilled, reamed and bored. The small interior hole is drilled and reamed. Both holes are held to 0.001 " tolerance. This is significant as the USGI tolerance is 0.004 " for the two internal cavities.
FYI, dealer pricing on the SEI radiused groove M14 gas piston is available. That said, I have no financial interest in Smith Enterprise, Inc., just passing along one of the latest developments for the beloved M14 Rifle.

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