From the m1-m14 e-groups forum (see fourth paragraph):
From: David L. Peterson <dpeterson@r...>
Date: Tue Aug 15, 2000 9:52pm
Subject: RE: Polytech tests
Late this afternoon I decided to call Smith Ent. and see what they had to
say. I didn't catch the name of the person I spoke to, except that the
references he made indicated he was an owner/principal of the firm. It was
interesting conversation on a number of points, some of which I thought may
be of general interest.
First, they recommend hardening for any receiver less than 50 on the
hardness test. When I asked what would be the result of not doing this,
specifically about a dangerous failure, he said it was a matter of wear on
contact points. He specifically mentioned the effect of a close to 56
hardness sight adjustment on a 50 or below receiver serrations. Their
process brings it up to about 60. He said the process was $100, though
their web site says $150. About another issue, he said they don't update
their web site often.
Secondly he did speak rather disparagingly of other vendors popular on this
list in regards to their viewpoints and expertise on the subject. While
this made a negative impression on me, that doesn't rule him out as being
knowledgeable, so I continued to listen with an open mind.
Third, straight from the horses' mouth, they are currently manufacturing
receivers, and have been all along. They make only five or six at a time,
and they are spoken for the moment they're done. Price $600. Next year
they will start making them 100 at a time, and he said the price would be
$1200! I didn't get into why they would be costing so much more, as they're
out of my league.
Lastly, if you keep the Chinese barrel, it will not cause complications
later if you replace it with a domestic offering.
Turnaround is 3-4 weeks. I think he told me some other things, but it
escapes me now.
The above was "posted" in reply to:
-----Original Message-----
From: Tom Simpson [mailto:bullet@s...]
Sent: Tuesday, August 15, 2000 7:08 PM
To: M1M14
Subject: Re: [m1-m14] Polytech tests
The Chinese approach to hardening their receivers is somewhat different
from US practice, largely owing to the Chinese selecting a different steel.
The steel specified for USGI receivers is 8620, the Chinese selected what
would be a a 5000 series steel in US terms. Both are excellent steels for
this application but have different properties when it comes to heat
treatment. The Chinese receiver has a lower surface hardness but still
excelent core hardness. The Chinese reciever is "tough" and will not stretch
but if you apply a conventional hardness tester to both receivers, the
Chinese receiver will show up as being out of spec ie, "soft". You might
think that this condition might lead to accelerated wear where moving parts
come into contact but neither I nor anybody else (Clint included) have noted
this in the field, so it would seem to be a non -issue.
The Smith Enterprises solution would seem to me to be an inappropriate
fix to a nonexistant problem. Each alloy of steel has its own particular set
of recipies in order to arrive at the various desired mechanical properties
for different applications. To go back after the fact (particulary without
the provenace and tech support of the steels manufacturer) and tweak the
mechanical properties of as intricate a finished part and with the wide
assortment of sectional thicknesses as an M14 receiver strikes me as more
likely to do harm than good. I have never heard of a Smith Enterprises
reheat treated reciever being harmed by the process, but I remain leary of
the procedure.
In the meantime, I own one each, a SA Inc. receiver, a Armscorp receiver
and a Polytec reciever. Guess which one I built my "bet 'yer ass" battle
rifle on? Yup. The Chinese one.
At about 1000 rounds, the headspace has
yet to move so much as .0005".
-Tom
[This message has been edited by mbott (edited August 16, 2000).]
