ak74 front trunion inside diameter

[shortround13]

I have a bulgy 74 kit (from atlantic from like January?) and my friend has a bulgy 74 kit (from classic, from like april) not sure if it makes a difference. there are some subtle differences between the two front trunions. Mine has serial #s in bare metal (parked over) and his are painted red. They both are circle 10, but the letter designators are different, mine begins with KP his begins with a BG I think. Annnndd....the worst part, if you measure the inside diameter mine measures out to like 21.95-22.00mm depending on how you hold the calipers, and his measures out to 22.10-22.15mm depending on how you hold the calipers. And, 3 different ak74 5.45 barrels that are laying around at my house slide right in without any force, as in they are to small.
Is there something I'm missing, or did some of the bulgy 74 kits have a different measurement, or did somebody along the way ream it out?
Am I better off finding him a new trunion to fit the barrel, or paying somebody with more tools and more skill to work on the barrel to fit his trunion. It's a matching #'s kit for what its worth, but I don't believe he'd be too heartbroken to save a bunch of bucks.
thanks....

[nicoroshi]

Trunnions although they all came off the same machinery vary in size.
They marked most of them with a 1-4 designation (believe the bulgy's aren't marked though). 1 being the small and 4 being large.
This is normal.
Options:
Buy an oversized barrel (they make them) or knurl the barrel journal to fit your trunnion.
This is why I recommend checking all barrel journals before you start pressing pieces on.
Very few barrels will match all the parts from any specific kit perfectly.
This is also why you'll see numbers punched on combloc barrels.
It's to tell the guys in the factory what parts to grab (they number mark all barrel parts according to size too) to fit the barrel they are working on.

[shortround13]

are you able to knurl the barrel? and what do ya charge if you can?

[Yemff]

you may be able to get an oversized barrel from kvar, I recently saw one that was a 4, it measured at 0.8705" or 22.11mm, I dont know if they would pull a specific barrel for you though, or if it would even big enough. Best bet is to probably knurl it, it shouldnt take much

[TURBOELKY]

I agree with the above. Knurling is easiest option. If you attempt it yourself, be sure to only knurl the area that makes contact with the actual portion of the trunnion. I've seen people knurl all the journal area that press fits into the trunnion, and it looks terrible!

[nicoroshi]

are you able to knurl the barrel? and what do ya charge if you can?

Sent you a PM

[kcstott]

The other thing is proper measurement technique. Calipers don't work well for ID's. Options that are accurate and in order from least expensive to most expensive follow

Gage pins.
Telescope gage and a 0-1" mic
ID mic and yes they make them that small
Bore mic
Dial bore mic
Measuring microscope
optical comparitor
CMM
Laser scanner

My recommendation is a set of telescopic gages and a good mic and some practice using them.