Polish underfolder has bad case of 1st and last round flyers

[Float Pilot]

I took the Polish under-folder out to the range today with my limited ammo supply.

She functioned flawlessly... It even fired with the end of a broken pencil floating around in the action. ( I was using it as a bolt hold open to make the other folks at the range more at ease while we went cold. )

Originally she was shooting 2 feet to the left and two ft high.
I now have her shooting in the black ( 8 inch black circle at 100 yards) , but I ran out of ammo before I cold get here where I want her to shoot. I am now 2.5 inches to the left of point of aim....at 100 yards.

My sight tool had a hard time moving the new parts over for windage. This sight is super tight.

The Tapco trigger is only 3.5 pounds, but it just slides along and then goes off. There is no stage before break.

Plus the folding stock leaves much to be desired for a proper cheek weld. I ended up folding my gloves over the rail as a cheek rest.


I noted that this rifle (carbine) has a real problem with throwing the first and last rounds from the magazine to a different place on the target.

I shot some TULA 122 grain ball, some Wolf 122 grain HP, and some old Chinese Ball ammo with a weird copper powder wash all over the entire cartridge.

At 100 yards the 122gr FMJ TULA was the best, the group was 1.25 inches excluding the first and last rounds which went 4 inches away..

The Wolf 122 grain HP did a 2.5 inch group with the two flyers (1st and last) 5 inches away. (in the same direction as the Tula.)

The Chinese stuff gave me a 3 inch group with the 1st and last round flyers 5.5 inches away.

I fired 60 rounds of the Chinese stuff to make sure the rifle would function. It works alright, but the Chinese ammo has a large velocity spread due to inconsistent powder charges. So every now and then one round would hit 10 inches low and another would go 6 inches high...
The primers on the Chinese ammo were much softer than the Russian primers.

I think I need to try to polish the Polish feed ramp, that usually helps the 1st and last round flyer problem. Also another mag might shoot better.

 

[Rob G]

The Tapco trigger is only 3.5 pounds, but it just slides along and then goes off. There is no stage before break.

Tapco triggers are single stage. If you'd like a two stage you'd need an Arsenal trigger. If you want to really play with it you can get an adjustable trigger from Red Star Arms.

Plus the folding stock leaves much to be desired for a proper cheek weld. I ended up folding my gloves over the rail as a cheek rest.

Paracord. Lots of guys wrap their underfolders in paracord to help with the cheek rest. I'm told it works well.

My sight tool had a hard time moving the new parts over for windage. This sight is super tight.

Not really a direct answer to this but if moving the rear sight isn't working for you, or you'd just rather not, then there is an alternative. You can put an RPK rear sight on your Polish underfolder and those are windage adjustable on the sights themselves. Lots of guys use them for this reason.

I know nothing about 7.62 ammo (I have a '74) or issues with flyers so unfortunately I can't offer you any advice on the rest.

 

[wally]

You can call them flyers if you insist, but IMHO its just the way AKs shoot, 4-8 moa is pretty much about it with comblock ammo.

On the few times I've fired 30 rounds from the same lot of 7.62x39 ammo off sandbags at the same point of aim, it appears to me there are at least two group centers (bimodal dispersion) as if they merge the output of two production lines in packaging operations, which greatly opens up any "groups". I've really no way to tell if its the ammo or the gun, but Wolf FMJ on my 7.62x39 AR will generally do 2-3 moa off sandbags and I've never really noticed any bimodal dispersion.

I think I need to try to polish the Polish feed ramp, that usually helps the 1st and last round flyer problem

IMHO a waste of time. If your Ak is set up right the bullet never touches anything, the cartridge shoulder bounces off the "bullet guide" and kicks the bullet up and in towards the bore. There really isn't any feed ramp on an AK.

 

[Float Pilot]

I smoothed the edges where it was obviously shaving a bit of metal during the feeding process. I will see if it makes any difference. My old Chinese milled receiver AK from many moons ago shot pretty nice groups. And of course my old VALMET M-76 shot very, very nice groups...

 

[Certaindeaf]

Load two rounds in the magazine and fire/test as normal. If the groups are the same as not, it's not "first and last" fliers. Also, doing the two rounds in the mag deal, chamber but don't fire the first.. inspect it for setback/maulage, put that one back in the mag, fire it and then inspect the "last" one as before.
Anyway, sounds like good shooting and good luck.

 

[Float Pilot]

I tried one round in a mag and did that 8 times. All those shots were within 2 inches of each other. Off in a weird place, but all together...

Then did five rounds per mag with a spotter watching through a scope.
I fired 4 groups this way.

You can almost lay the papers over each other and have all the holes in all 4 targets line up.

With Tula FMJ

1st shot 12:30 o;clock at 3 inches
2nd, 3rd and 4th shots, 9:00 O'clock at 2 inches from point of aim. (1.25 inch cluster)
5th shot, 10;30 O'clock at 4 inches from point of aim.


Then I fired an 8 shot magazine. Tula Arsenal stuff again.
The first and last shots were about in the same places,
and instead of 3 shots in a group at 9:00 o'clock, I had 5 shots all in a 1.50 inch cluster.

The Wolf HP ammo made about the same general pattern but the distances were all a little further apart.

I will try some different mags once I dig out my old ammo stash... Since the 1st and 5th rounds load from the same side of the magazine.

 

[Certaindeaf]

Well, that'd kinda bug me too.
And that wire stock in the real cold.. ouch! I wonder if you could wrap it with leather or plastic dip it just where it hits your cheek.

 

[MErl]

Just throwing out ideas:
What happens when you manually cycle a round out? Is the next round a flier like the first would have been?
Could the rounds in the mag be pushing up on the bolt causing a shift? Last round wouldn't have that shift.
Could there be a difference in how the round is chambered when manually cycled vs gas operation?
Is there any noticeable change to the round after cycling through manually vs gas? (bullet pushed deeper or off to one side?)