Ar15 interchangeability question:

[rcschummers]

My nephew just asked if his rifle that is chambered in 762/39, having a heavier hammer spring and heavier buffer, would that cause issues with a 556 upper? I think the buffer will throw off the cycling and the hammer could possibly puncture the weaker primers causing bolt face disfiguration.

What are your thoughts? Thanks.

[henmar77]

I would take a stab at answering, if i understood the questions. Is he trying to chamber 556 in his 7.62?

[Fjold]

I believe that the OP is asking if he can use a 5.56 upper on the 7.62x39 lower that his nephew already owns.

[gun toting monkeyboy]

No, it won't cause any real issues. The worst that may happen is that the 5.56 upper won't cycle because of the added resistance of the heavier buffer. I have never had that happen to me, but I suppose it is possible. Every 7.62x39 I have ever seen uses a regular AR buffer though. The heavier hammer spring won't cause any problems.

-Mb

[MKE]

I haven't had any issues swapping out my 7.62 upper with my 5.56 lower that has the Wolf heavy hammer spring. I'm running an H2 buffer and have had no cycling issues. The only problem I initially had was mis-feeds due to the C-Product mags I was trying to use for the 7.62 upper. The MWG mags have fixed the feed problem.

[2shotjoe]

Nope, I got an extra power hammer spring in mine.

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[SOAR79]

Good to know, I'm looking for a 762 upper

[rcschummers]

Sorry guys, he wants to use his lower that is set up for a 762/39 on a new 556 upper.

Seems what i have read so far indicates it should be fine?

More input would be great! Thanks again!

[negolien]

Taking a stab also.. I would say no issue. Worst case scenario would be FTF/FTE?