new ammo crate = new problems

[Z-Hunter]

I was so happy with my XCR, up to yesterday...

I have a 7.62x39 rifle with all the new gizmos and it was shooting really well. Only issue was a couple stickies in the chamber every hundred or so. I polished the s** out of the chamber with Flitz and the problem disappeared. I run the rifle at gas setting 2, switching to 3 after 200 rnds or so. I usually shot Czeck surplus as well as hunting ammo from Norinco and Privi (with the same POI for all 3 rounds). Accuracy is between 2 and 3 MOA. Happy camper for almost 2000 rounds.

Yesterday I opened a new Czeck ammo crate to refill my range box and headed to the range with a clean and lubed rifle.

First round : FTE, bolt locked solid, no hole in the paper ??? ???
After using a 2x4 and a lot of force to open the chamber, I checked the rifle and everything was fine.
Second round: same problem
I then switched to 3 then 4.
At 4 I had some weak ejections (1 foot) but most of the time FTE and still no rounds on paper at 100m. Cycling the ammo by hand is smooth.

To confirm an ammo problem, I tried some rounds from the old crate and sure enough everything was fine.

After more tryout with the new ammo I found out that the POI shifted 4 MOA to the RIGHT with the same 3" accuracy.

I didn't have a chrony with me but obviously something is different with the new ammo: probably weaker than the previous crate. I say different, not bad : my 858 digest them without a hiccup but shows the same 4 MOA to the right POI

Now, I can live with a new zero for the next 1200 rounds but I have no use of a single shot rifle where a 2x4 is more important than a sling.

To me it looks like a tight chamber that was just ok with the previous ammo, but won't eat anything different.

I don't want to send it back so I'm looking at DIY solutions.
Right now I'm thinking Flex-hone but can't find the 7.62x39 model anywhere. Does anybody know the ref number or the size ?

I will go through my other ammo crates to see if I have more of the 'special XCR' one, but I'd rather fix the problem.

Couple questions:

- Why a weaker cartridge will cause the casing to stick so badly to a clean chamber ?
- Why a shift of 4 MOA to the right with the same accuracy ?

Let me know what do you think
Thx

[dont_tread_on_me]

If you have another rifle chambered in 7.62x39 try the new crate in that rifle.It sounds like you have some crap ammo if everything else you've tried so far has worked.Your chamber could still be a bit on the tight side and the ammo your using now may be somewhat out of spec,and the combination of the two is what is causing the sticking.Check this thread out,I think you can use a 308 flexhone for your application
https://xcrforum.com/index.php?topic=9141.0

[Z-Hunter]

Thank you Sir,

as I said ammo works fine in a VZ 858 with the same 4" shift in POI, doesn't even seems weaker in that rifle: casings still bounce off the roof ;D

I just checked my other crates and it looks like the previous ammo was from 1986 when the problematic one is from 1978. 1970's surplus is known for being weaker.
But I can't understand how a weak ammo can lock the chamber that bad or shift the POI to the side and not vertically.

[dont_tread_on_me]

Thank you Sir,

as I said ammo works fine in a VZ 858 with the same 4" shift in POI, doesn't even seems weaker in that rifle: casings still bounce off the roof

My apologies,I missed that somewhere.

I just checked my other crates and it looks like the previous ammo was from 1986 when the problematic one is from 1978. 1970's surplus is known for being weaker.
But I can't understand how a weak ammo can lock the chamber that bad or shift the POI to the side and not vertically

Well considering that ammo is not going to be exact even from lot to lot from a quality manufacturer,then throw in it's age,different years of manufacture,and the fact that it's a military loading,a point of impact shift is not at all surprising.It sound like your chamber is tight if that ammo works ok in your VZ.I would try a flexhone in 308 and see what happens..

[dont_tread_on_me]

http://www.brushresearch.com/brushes.php?c2=183

[aziator]

That link, get the 7.62x51 brush (or both if you want). I think I only used the 800grit when I did mine. Use the flex hone oil, and don't press too hard. It should fix your problem. You can also find my thread on getting 9" barrels to run, I ended up opening the gas post/dial on my x39 as well. You can measure yours and maybe look at that if the flex hone alone doesn't work.

[dont_tread_on_me]

You can also find my thread on getting 9" barrels to run

lol,already liked that too!

[Z-Hunter]

Thank you guys,

Aviator's post was what I used to diagnose my problem, well done.
Brushresearch is out of stock and I can't find this specific hone anywhere. I want to hit a couple auto parts stores before ordering online so if someone could measure the diameter of the 308 or 7.62 brush for me that would be great.

[Sean K.]

DON'T get the .308 brush. They have a 7.62x39 brush now from brushresearch.com.

http://www.brushresearch.com/brushes.php?c2=183

Personally, if it's that tight....I'd get the 400 grit.....but it's up to you.

As for the backorder.....not sure where else will have it in stock. Patience is key. I'd get the right tool for this job.

HTH.

Sean

[Z-Hunter]

Thanks Sean,

I just measured the brass and was going to buy the closest hone but it seems like a bad idea. I'll just wait then