It is completely normal.
The AIA rifles use a standard Lee-Enfield type trigger, all of the L.E. models set up for two-stage flop around loose like that. You are not missing any springs from the trigger - there aren't any in the first place.
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Whenever you take your 7.62 x 39 M10 for a run, and you are going to shoot ex-military laquered cases in it , make SURE that you take a full length metal cleaning rod and a mallet with you.
I have some spares for my 7.62X39 that Evan brought to Canada last year. He left them in Vancouver and I accidentally found the person who had them and he mailed them to me.
I also have a B2 and to be honest think both of the guns are pretty decent. I can hit a regular "clay pigeon" at 300 yards so that is good enough for my old eyes.
The B2 is a great shooter even with crappy ammo, yes they are heavy and hopefully they get to produce them again.
Communication is not good but you know I'll live with that. Whenever I have communicated with AIA they have always been cordial and answered my questions.
The problem of "sticky" cases in these rifles is a function of the ammo.
The heat of firing melts a little bit of the lacquer on the neck. This will generally re-solidify BEFORE you can open the bolt and thus, extraction starts to get sticky. You will find the same happens to Norinco and BRNO / CZ bolt actions with this ammo.
AK and SKS type actions open SO fast that the case is red-hot on extraction and ejection and thus the lacquer is still soft. They still accumulate a bit of lacquer fouling, and should be cleaned "thoroughly" from time to time..
Try the recently available Russian-made grey "polymer" coated stuff; it seems to not melt in the same way.
The WORST stuff I ever encountered for this problem was the "chocolate brown" lacquered stuff that came in pale green boxes of 20. This stuff appears to have been made "for export" to non-military customers. The "dark olive" coated Chinese "surplus" ammo seems to be less of a problem too. This usually came either in ten-round strippers or bundled in the classic "plain, brown wrapper", both in big "sardine tins", two to a wooden crate.
Even some of the "copper-washed" stuff can cause problems because the copper "plating" is itself protected by a thin layer of clear lacquer.
Plain brass as per PMC or Yugo stuff , etc, is perfect.
Thanks for the info, I guess I'm going to have to get used to it but it's strange for sure.
---------- Post added at 06:07 PM ---------- Previous post was at 06:00 PM ----------
I only shoot Yugo M67 (brass) in my bolt actions & singles, years ago when no one wanted it at $150 per crate I bought about 3 dozen so I might shoot out my barrels before I run out. I save the lacquer/poly-steel cased ammo for my AKs & SKSs
I recently bought a case of copper washed 7.62X39 after fighting the surplus lacquered ammo. The copper wash works perfectly in mine so far.
People have endless trouble with lacquered steel cases in AR's too. They bare hard on the extractors of gas guns too. Especially rifles with non chrome barrels. Bruce hit the nail squarely on the head.
The problem with rotating bolt rifles is that you cannot have primary extraction. Extraction is by brute force and an extractor that engages a large section of the cart case. It would appear to me that in the AIA rifles using 7.62 x54R the geometry of the primary extraction camming angle might not be as great as that on the old No4 rifles. Therefore the leverage exerted during the lifting of the bolt isn't doing its job of breaking the obturating seating cleanly. But as BinO says, even if it primary extraction did break the seal cleanly and instantaneously there'd still be the question of the laquer residue.
We fired a Vickers converted to 7.62 x 54R recently (another no primary extraction example) and didn't experience any stricking cases after a few belts of the cheapo steel cased varnished stuff. Mind you, the barrel ain't getting much hotter than 100c. Interesting thread
One thing that confused me is I shot surplus 7.62X39 lacquered out of a CZ bolt gun and never had a issue with cases sticking, yet they do in my AIA??
The chamber is probably a bit tighter. Every barrel is different.