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alpha_romeo_XV
11-19-2007, 11:06 AM
Some rifles were born to wear a scope … and then some others turn back into a pumpkin as soon as you pull the trigger. My “scoped” Yugo 59/66 could not hold a group better than 10” at 100 yards, bench rest.

Must be the cheap Wolf ammo? No, I tried some good Winchester and no improvement.

Must be the mount? This was not the simple drop in receiver cover replacement – the type that would obviously jar and move zero everytime the bolt slammed the recoil spring against it. No, I used a mount that installed ontop of the factory cover, with 4 bolts, after I drilled and tapped the lower receiver. Seemed rock solid.

http://i144.photobucket.com/albums/r182/wiskeypapa57/yugowscopeA.jpg

Must have been a bad scope? No, I tried 3 different scopes.

Must have been the Calif muzzle break? No, I cut the barrel and put a nice 11° target crown on it. FYI, still cycled 100% after this mod.

Then I took the scope off and just used the original iron sights. Well goooly Sarge, it held a 4’’ group with Wolf ammo. Better than my surplus M1 carbine I’ll add. WTF was I doing with a scope on that rifle in the first place. If it ain’t broke – don’t fix it. But it looked cool ….. kind of like chicks, looks aren’t everything.

Well I still wasn’t finished, put the TechSight 2000 peep sight on to get iron sights with a windage adjustment. I haven’t shot it like that yet, so the experiment continues. There is a gap between the rear sight and the receiver cover - so jarring should not be an issue. Yes, totally bubba’d, but I’m happy with the new weight/balance, sight picture, and ability to use a standard sling.

http://i144.photobucket.com/albums/r182/wiskeypapa57/TechSight2000.jpg

The mag is a 5 rnd Tapco (US made) it works well – holds the bolt back, stripper clips still work, and feeds 100%. Its takes two hands to remove/install the mag, so way slower than strippers, just used it to help with 922(r) part count. The only original/foreign parts are : receiver, bolt, bolt carrier, barrel, trigger group. Well below the 10 limit. US made are: stock, mag/spring/follower, op rod, gas piston, rear sight, front sight post.

http://i144.photobucket.com/albums/r182/wiskeypapa57/yugowtech2000rearsight.jpg

Full Clip
11-19-2007, 11:13 AM
You need to do some reading up on compliance parts. The op rod and sights do not count, so replacing them does nothing. The trigger group counts as multiple parts.
From SKS Boards:
http://www.sksboards.com/smf/index.php?topic=33369.0
Spreadsheet:
http://www.basecontact.com/library/922-r_Compliance_Worksheet.zip

Prc329
11-19-2007, 11:15 AM
I neglected to properly torque down my rings and the movement cause my 1/2 moa remington 700 to turn into a 1 moa gun. You sure it wasn't something with the scope? That just doesn't sound right.

Full Clip
11-19-2007, 11:16 AM
Double tap.

rksimple
11-19-2007, 11:34 AM
That just doesn't sound right.

+1. Hmmm?????

tteng
11-19-2007, 11:36 AM
My guess: your scope sits too high for proper cheek-weld.

rksimple
11-19-2007, 11:39 AM
My guess: your scope sits too high for proper cheek-weld.

That was my initial thought. That combined with the associated parallax issues and you have some big groups.

What kinds of scopes did you try?

Prc329
11-19-2007, 11:43 AM
My guess: your scope sits too high for proper cheek-weld.

That actually makes a lot of since. I had that issue with my M14 when I tried to scope it. Once I used my black hawk cheek piece it was better and the groups shrank. Now I just use the irons and aimpoint.

tteng
11-19-2007, 11:53 AM
Assume you have a good scope and mount: nothing rattles or float-zero. Parallax-problem should only change the center location of the group (that location should be repeatable), not the group size.
Since your cheek-weld is part of your rear-anchor as the rifle vibrates during shot, and your scope sight-line is about 1" above your iron-sight, I suspect you're not getting as solid a cradle as w/ iron-sight hold.

alpha_romeo_XV
11-19-2007, 11:58 AM
The 922r SKS link was most clear discussion I've seen - it should be useful to others, it had a specific schemetic for a Yugo. I forgot to count my US handguard. My overall total is kosher.

The cheek weld was high but by bench rest testing with a lot of accomodations, probably not paralax. I tried a 4x Leupold and 3-9x schofield without improvement.
I suspect the scope mount was flush against the back of the receiver cover when drilled and tapped, and was being tweaked slightly from each recoil. If I had allowed some gap as the techsight does, it may have been OK.
For a gun not designed for a scope mount, I caution people that aftermakert stuff may have inherent flaws or fine installation tolerances - details some vendors may neglet when taking your money.

rksimple
11-19-2007, 12:02 PM
Assume you have a good scope and mount: nothing rattles or float-zero. Parallax-problem should only change the center location of the group (that location should be repeatable), not the group size.
Since your cheek-weld is part of your rear-anchor as the rifle vibrates during shot, and your scope sight-line is about 1" above your iron-sight, I suspect you're not getting as solid a cradle as w/ iron-sight hold.

Given the same cheek and eye position, groups won't change. But with an inconsistent cheek weld (and lesser quality scopes), parallax IS an issue. The apparent POA will not change, but POI will. Point a scope, without AO, at a target 50 yards away. Leave the scope stationary and move your eye around behind the scope. The crosshairs will "move" around the target. If this is mimicked with an improper cheek weld, and the eye is in a different position every time, you will have a different POI every time.

alpha_romeo_XV
11-19-2007, 2:59 PM
I looked up a couple of articles on parallax, and now think this probably was the problem. http://www.6mmbr.com/parallax.html
If I look at the scoped rifles that I have shot well at long range, they all have either low mounted scopes, or raised stocks/added check pieces to give a correct/reliable eye position.
If adding a scope, yields an ergonomically unsound set up, then that is just as bad as a mechanically unsound device. And my observation still holds - that accuracy can be compromised with a scope. I don't own one, but the AR15 scopes that mount on top of the carry handle come to mind. Unless of course you add a check piece to your stock and bring the complete system back into parallax safe zone where your pupil is consistently in the focal axis of the scope.

jtv3062
11-19-2007, 5:50 PM
Somthing to think about, wolf ammo is either .310, .311, .312. about the same as the bore in your sks. US mfg ammo is likely .308. I would think using US ammo your groups would open up.
The groups in my Russian sks was always smaller with milsurp than my reloads with .308 bullets

tteng
11-20-2007, 8:22 AM
jtv,

I believe MN (or Brit-Enfields), SKS and AK are barrelled for .310-.312 bullets(which are available but more expensive for reloading than .308). Shooting full-loaded cartridge w/ .308 bullet out of above may gas-cut your barrell.