Op Rod Guide shimmy

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scooby_d

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So gotta say first off, man do I love shooting my Poly M305 that I picked up about a month and a half ago! It so far has been the perfect choice for me, even with next to no shooting experience. 300 rounds downrange and nary a problem. And I'm not really sure how big a problem it is.

Broke things down to clean everything out and noticed that in my op rod guide there is about 1-2 mm of play side to side. I remember reading a post awhile back about it being important for the op rod and gas piston to be aligned but I would assume that this takes into consideration that the guide is supposed to stay where you put it when you do this.

So my questions:

1) How hard is this to fix? I'm fairly handy but don't have much in the way of a workbench (garage not quite set up yet) so relatively simple fixes appreciated.

2)Would my #### fall off if I shoot it? #### integrity aside, I'd rather not pooch things worse than they are now, so will it wreck anything else?

Thanks
 
a bit of side play is acceptable for a rack grade m14, both civillian and military rifles and normal, all things considered.
problem with the chinese variety is that most often we have found that this bit of rotational play usually gets worse with use due to crappy roll pin quality. If there is only a few milimeters of measurable play...... don't worry, your #### won't fall off ;)

in a match rifle or simply for those seeking to get the most accuracy out of thier rifle, the oprod guide is fastened in such a way that it will not move.
the benefits of this are less wear on the moving parts due to deflection caused by the oprod guide's rotation. this causes wear to the oprod's tab and bearing surfaces and also the receiver track and bearing surfaces. It can also cause , in serious cases, cycling issues and damage to the bolt roller/bolt roller stud... after many many rounds.

for accuracy we want repeatable movement of the various parts, the oprod being one of them. AND we want the oprod tube to strike the piston dead center to prevent peening of one side of the piston, which can cause cylinder wear and wear at the cylinders opening where the piston slides through.
so how do we solve this
a knurling tool if you have one or a hammer and center punch.
first remove the chinese roll pin ( i toss them and use drill rod for this pin when ever possible)
next slide the oprod guide out of the way and condition the barrel oprod guide mounting surface by making punch marks, lengthwise in rows of 3 or 4, evenly and close together all around the mounting location, or if you have a knurling tool, this is prefered over the center punch method but both are accepted methods.
apply red , or blue loctite to the punch marks or knurlings and tap the oprod guide back into position.
apply loctite to the hole and drive in your pin
next mount gas assembly and oprod, spring and guide rod
tap the oprod guide, and you may have to give it a generous wack, to position it so the piston tip's center aligns with the oprod tubes center.
let her set up for a day and yer done like dinner ;)
 
Thanks Doc! Think I am going to have to do it sooner rather than later as I was looking at it again last night after I posted and the far limit of the wiggle is still about 2 mm off of true to the piston. Couple more questions though:

1) Does one have to take the gas assembly off to do this? I have a welded on flash hider that I have to deal with still and don't really have the right facilities to deal with it at the moment (definitely on the roadmap soon )

2) Dumb question, but where would someone pick up some drill rod and what diameter would I need? 1/8"?

Thanks for your indulgence
 
scooby_d said:
Thanks Doc! Think I am going to have to do it sooner rather than later as I was looking at it again last night after I posted and the far limit of the wiggle is still about 2 mm off of true to the piston. Couple more questions though:

1) Does one have to take the gas assembly off to do this? I have a welded on flash hider that I have to deal with still and don't really have the right facilities to deal with it at the moment (definitely on the roadmap soon )

2) Dumb question, but where would someone pick up some drill rod and what diameter would I need? 1/8"?

Thanks for your indulgence
Click to expand...


1) The muzzle device does not need to come off for this repair, you just need to remove the pin from the op rod guide and slide (or tap) it forward.
however, after the mounting surface for the op rod guide has been knurled, it is much easy to tap the guide on with a long piece of the properly sized pipe if there is no muzzle device or gas cylinder in the way.

2) I just use a good quality roll pin of the proper size as well as either red Loctite or Stud and Bearing mount to semi permanently fix the op rod guide and roll pin in place after I knurl the barrel.

Be sure to check the alignment of the op rod guide as you reinstall. I always reinstall the gas cylinder and piston and op rod to confirm alignment of the op rod tip -to gas piston tail before the locktite has set up, then I install the roll pin, the op rod gude can be adjusted to proper alignment with gentle taps from a small mallet, before the roll pin is installed, of course recheck after roll pin installation.

If you have any issues with barrel indexing, address those issues BEFORE you fix your op rod guide.
 
workerunit said:
1) The muzzle device does not need to come off for this repair, you just need to remove the pin from the op rod guide and slide (or tap) it forward.
however, after the mounting surface for the op rod guide has been knurled, it is much easy to tap the guide on with a long piece of the properly sized pipe if there is no muzzle device or gas cylinder in the way.

2) I just use a good quality roll pin of the proper size as well as either red Loctite or Stud and Bearing mount to semi permanently fix the op rod guide and roll pin in place after I knurl the barrel.

Be sure to check the alignment of the op rod guide as you reinstall. I always reinstall the gas cylinder and piston and op rod to confirm alignment of the op rod tip -to gas piston tail before the locktite has set up, then I install the roll pin, the op rod gude can be adjusted to proper alignment with gentle taps from a small mallet, before the roll pin is installed, of course recheck after roll pin installation.

If you have any issues with barrel indexing, address those issues BEFORE you fix your op rod guide.
Click to expand...

yup what he said hehehe
if not removing the flash hider and gas system, a good trick is to wrap the barrel ahead of the oprod guide with a couple wraps of masking tape to prevent dings or unsightly marks on your barrel.
as for drill rod, yes 1/8th
and in abscence of finding drill rod, a 1/8 carbon steel drill bit may be trimmed to length and of course, use the shank end ;)
my second choice would be a quality roll pin, source at any of the national hardware chains, rona, home depot, ect
 
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