Mendoza rm 600 power

[DougT]

Well, we found the problem.  WadeS and I took his AR apart tonight and the spring was broken into four pieces.  When it came out, it measured 9.5" long.  When we arranged it the way it should have been, it was 13".  Also, the pieces had wound their way into each other, creating a double-coil spring for about 1/3 of it's length.  No wonder his velocities have been in the high 400's to low 600's.  The spring seems to have been broken from day 1.  The seal and cylinder look fine.  $15 from PA should bring back mucho power.

Thanks BWANA for the advice on the trigger.

[DougT]

WadeS e-mailed JM the stock Mendoza spring dimensions and ordered what JM spec'd.  Thursday we installed the spring with the preload spacer like JM instructed.  His guide rod was a little too large and the spring was too tight.  We chucked it up and removed about 0.006" diameter and polished it.  That was just right.  We smoothed all the edges, tarred the outside of the spring, moly-greased the spring inside and guide and piston sides and reassembled it.  Chorno + 630fps :emoticon:

Yesterday we picked up some more washers and I turned the ID to the correct size.  We tried 18 washers for about 1.75" of spacer length.  It turned out to be coil-bound so we took out 3 washers.  The chrono = 645fps :emoticon:  :emoticon:  :emoticon:

I think that's about it for this gun.  We were hoping for mid 700's.  I wonder what the stock Mendoza spring would do, with no oil to combust.

[DougT]

WadeS and I went out and rezero'd our .22 guns tonight after work in preparation for a squirrel trip saturday.  We were both using RWS Superpoints.  Wade's Mendoza is definitely easier to shoot good groups than my TF-89 but lacks the power.  Below are two 5 shot groups from each of us at 15 yards.  Wade's second picture is of 4 pellets through the same hole with a "flyer".