Have been shooting a 7.62 AI AT for a few months & love it.

The only issue I have is the bolt gets sticky as it warms up on 'Rapid' (for a target rifle, anyway) serials after 2-3 rounds.

Basically, I have to make a fist to bump the handle open or reach over with the left to operate the bolt.

Ammunition used is factory ADI 168SMK round & no signs of pressure observed on the ejected cases.  300 rnds fired so far.

Common with them all?  Refer to factory?

Thanks in advance.

Original Post

Never seen that on mine.  Mine has a OTM Hawk Hill 6.5 creedmore on it with around 1200 rounds thru it.

A guess but could it be crap getting stuck to the bolt face or under the extractor?  

Does the problem come and go during the range session?

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Joined: 6/13/04 10:18 PM      Location:  Minnesota, USA

Look again for ejector marks on  the brass heads.  My vote is its hot ammo.  Have you chrono'ed it?  With my current work gun and issued ammo (Hornady) we have the same issue, but the load is really hot so we expect it.

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OK,  here are some fired cases plus a live for comparison:

No signs of anything on the case sides, no ejector/extractor marks.  Primers flatish.

Not chronographed yet but the ADI wonk said 2760 fps out of a AI 26' barrel.

Yesterday we did a rapid at 600m: two serials of 5 rounds in 30s.  Unlocking the bolt became progressively stiffer as rifle heated up.

Ran some drill rounds thu.  Compared to my Rem 700 it is stiffer to lift the bolt when uncocked.

Examined the bot heads & locking recesses: clear and clean.  The extractor assy had

TravisJr posted:

Definitely not common to them all. I suspected a pressure issue until I got to the part of your post that negated that. Do you have appropriate grease on the locking lugs?

 

some hard cosmoline(ish) stuff on the arm exterior

In comparison, my partner/spotter in yesterday's shoot was finger flicking the bolt of his 6.5CM Tikka though all of it...and he beat me: got all 10x of his rounds off in the rapid without losing sight of the target.  I  managed 6x & and had to do a total reacquire each shot.

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Back Spin posted:

Stock barrel or aftermarket barrel? 

I had an AT with a Kreiger barrel which had a tighter chamber and had heavy bolt lift with MEN 147 ball. The stock barrel didn’t have any such issues. 

Stock standard AI AT.  Only change I have made is cerakoting some butt screws & rear QD sling mount after noticing they were prone to rusting.

JS7SFGA

Ditto. Moly grease on the back of the lugs?

TravisJr posted:

Definitely not common to them all. I suspected a pressure issue until I got to the part of your post that negated that. Do you have appropriate grease on the locking lugs?

Nope: a very light oil on the bolt body, bolt head wipe dry.

Your recommendations?

You want some form of grease (not oil) on the locking lug surfaces, especially at the back as JS7SFGA pointed out. There are many gun-specific products out there, but I have used Mobil 28 aviation grease for years to good effect. A full tube will cost you about $25-$30 and last approximately until the sun burns out. Or you can buy smaller syringes packed by third parties, like this one at Amazon: https://www.amazon.com/Mobil-2...21164D/dp/B00XIQHOAW

Dry lugs can lead to galling and could well be the source of the problem you describe. 

Not sure.  When the rifle fires, a tremendous amount of rearward pressure is applied to the locking lugs against the action, hence the need for lubrication on the rear surfaces of the lugs. You want a high-temp, high-pressure grease to withstand that operating environment.  I don’t have any experience with graphite grease,  but a quick Google search makes it look like it fits the bill.

ANYTHING is going to be better than running it dry. 

JS7SFGA posted:

Ditto. Moly grease on the back of the lugs?

That's what I do on my Winchester 70 Long Action.. my grandson (5) can run the bolt with two fingers....

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Might be a good idea to check the freebore in the chamber, as well, ideally with the same projectile as the ammo you're using. I use a Hornady OAL gauge for checking chambers on my barrels. You might be bumping the lands just enough that it's getting too tight as the chamber heats up. A  good friend of mine recently had the same issue with a 6 Creedmoor custom, and that was the only thing we could figure out was causing it (he didn't have a gauge handy for us to measure it, though).

On grease vs oil on the lugs, I have found it depends on the action. My Tempest action (2 rows of 3 lugs, very similar to AI) did NOT like grease anywhere. At all. A light coat of SLIP 2000 in the raceway for the bolt stop, and a bare wipe of the lugs and body OD with a lightly oiled rag is all that action needs to run like a top. My trued 700, on the other hand, needs SLIP2000 grease on the back of the lugs and a LIGHT coat in the raceways to run at its best. Might be worth playing around with different products and even combinations on your bolt and see what works best.

tsquared posted:

Maybe I missed it, but have you tried a different brand of ammo yet?    

Nope.

I dived into this...it sorta feels like jumping onto a moving coveyer belt.

I picked ADI 168SMK factory because a couple of other AI shooters here (AT & AX) said it shot well in their beasts...and at AUD1.36 by the can it was affordable consistent  alternative to screwing around finding a Load.  Basicaly a choice between compete or trial loads.

I have been trying to get to a 100m benchrest range to determine 100m zero (have shot it less than 400m once) & to try out my old 155gn BJD loads & some mil ball.  Plus practice 'rapid': my weakness.

OK- from the range today.

Put a minor amount of moly lube on the locking lugs & worked it in.

Bolt lift when uncocked is still heavier than the Rem 700...but much better than it was.  Maybe another 100 rnds or so will improve it as well.

Firing tests with ADI 168 SMK: way less sticky & did not become worse with warming up on 'rapid'-with exception of last round of two strings.

Did not get the chance to try some other factory ammo in it: got bounced onto a range staff position.

Again thanks to you all.

Cheers,

Linz

If my research is correct the AT is a cock-on-opening action. 

If your cam surfaces between the rear of the bolt body and firing pin shroud haven't been polished did you moly-grease these contact areas (including the angled cocking surface at the back of the bolt body)?  Is there any interference between the firing pin shroud and the rear of the bolt?

It will help smooth out bolt handle lift and cocking.  Grease along the sides of the cocking piece might help just a little (or not), but definitely anywhere that semi-circular extension surface where the cocking piece contacts the rear of the bolt body).

Sinister posted:

If my research is correct the AT is a cock-on-opening action. 

If your cam surfaces between the rear of the bolt body and firing pin shroud haven't been polished did you moly-grease these contact areas (including the angled cocking surface at the back of the bolt body)?  Is there any interference between the firing pin shroud and the rear of the bolt?

It will help smooth out bolt handle lift and cocking.  Grease along the sides of the cocking piece might help just a little (or not), but definitely anywhere that semi-circular extension surface where the cocking piece contacts the rear of the bolt body).

 

They certainly do cock-on-lift: you can feel it.

I should have thought of greasing the cam surfaces.  What a silly bunt.

Thanks.

We had two of our four bolts replaced by AI. They said the metal was soft and caused the same problem you are experiencing. Look at the lugs for deformation. They replaced them free of charge. Interestingly this happened on guns run by lefties. I don't know if this is caused by cycling the bolt with the right hand causing more torque on the bolt. 

bk1716 posted:

We had two of our four bolts replaced by AI. They said the metal was soft and caused the same problem you are experiencing. Look at the lugs for deformation. They replaced them free of charge. Interestingly this happened on guns run by lefties. I don't know if this is caused by cycling the bolt with the right hand causing more torque on the bolt. 

Interesting...it never occurred to me that AI might have product or QA issues.

Because of this thread I pulled the bolt from my .308 Savage and lubed/greased up the lugs, and what had been a little stiff lift really smoothed out.  Unintended consequences. Thanks LINZ for bringing your issue to the forefront as it helped me out.

Mojo/Mark
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MOJONIXON posted:

Because of this thread I pulled the bolt from my .308 Savage and lubed/greased up the lugs, and what had been a little stiff lift really smoothed out.  Unintended consequences. Thanks LINZ for bringing your issue to the forefront as it helped me out.

Haha!

Don't thank me.

Thank the SME here that freely shared their knowledge.

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