AI AT/AX308 Barrel lock screw torque

[Luvman]

I’m looking to pick up a torque linter to keep with my AT for barrel changes. I’ve read that some people have found that 55 in/lbs works better for return to zero than the factory spec 49 in/lbs.

What do you use?

 

[Scotch_egg]

I’m following this one.

 

[SSSamurai]

Just my experience, but I found that consistently torquing the barrel into the receiver made more difference in return to zero.

 

[ShtrRdy]

I didn't know some use 55 in-lb.

 

[Huskydriver]

I didn't know some use 55 in-lb.

I do. My return to zero is every time now. All I can say is test it out. I tested the torque from 49 to 65 found my groups were repeatable between barrel swaps at 55-58.

 

[blbennett1288]

Interested to see what others say.

 

[Nik H]

I figure the designers of the rifle know a thing or two...49 lbs as specified

 

[Huskydriver]

I figure the designers of the rifle know a thing or two...49 lbs as specified

I swap barrels at least 4-6 times when I shoot across 4 calibers. If your 49 inlbs returns you to zero every time great. Mine didn't so I played around with the torque setting after asking around. I agree 49 is obviously the recommended starting point but if your rifle isn't returning to zero play around with the torque. Mine is dead nuts every time returning to my primary zero now.

 

[ShtrRdy]

Huskydriver-- after you change barrels, does it take 1 or more shots to settle the barrel in?

 

[Huskydriver]

Huskydriver-- after you change barrels, does it take 1 or more shots to settle the barrel in?

No first shot is right where the zero is for that caliber. I am meticulous in mounting each barrel exactly the same each time. I snug the barrel to the action with a good pull on my wrench flat then torque the screw to the exact same place every time. Consistency in how you swap barrels is part of the key for returning to zero every time.

 

[Nik H]

I swap barrels at least 4-6 times when I shoot across 4 calibers. If your 49 inlbs returns you to zero every time great. Mine didn't so I played around with the torque setting after asking around. I agree 49 is obviously the recommended starting point but if your rifle isn't returning to zero play around with the torque. Mine is dead nuts every time returning to my primary zero now.

So you do 55lbs?

I guess I haven't really ever taken note if a different torque setting would produce a better RTZ. I only swap between 6.5 and 7.62. I should give it a shot. I have always used 49 and the adjust I make to RTZ is pretty small.

Do you have an AT/AX or an AXMC? What calibers are you switching between?

 

[Huskydriver]

So you do 55lbs?

I guess I haven't really ever taken note if a different torque setting would produce a better RTZ. I only swap between 6.5 and 7.62. I should give it a shot. I have always used 49 and the adjust I make to RTZ is pretty small.

Do you have an AT/AX or an AXMC? What calibers are you switching between?

I do 55 inlbs. I shoot a axmc using, 6cm,6.5cm,308, and 338 LM. Give it a shot and report back. I tried up to 65 in lbs and had good results too.

 

[Nik H]

I do 55 inlbs. I shoot a axmc using, 6cm,6.5cm,308, and 338 LM. Give it a shot and report back. I tried up to 65 in lbs and had good results too.

I wonder if the AXMC and AX/AT would respond in a similar way being that the tenons are different length. I will try it out next time I shoot 7.62

 

[redneckbmxer24]

Huskydriver-- after you change barrels, does it take 1 or more shots to settle the barrel in?

If this is happening the barrel isn’t seating correctly.

I recommend removing the handguard when you install the barrel and wiping down the action face of any debris, and the same with the barrel shoulder. Screw the barrel on with the butt on the floor and muzzle straight up and ideally use a wrench on the flat to just barely snug the barrel to insure a good seat. I use the wrench that came with my Borka kit usually. I also snug the action screw with the muzzle up and then go back and torque it.

With this method I can pull and reinstall the barrel every shot with no POI shift at all and no settling in.

 

[Nik H]

If this is happening the barrel isn’t seating correctly.

I recommend removing the handguard when you install the barrel and wiping down the action face of any debris, and the same with the barrel shoulder. Screw the barrel on with the butt on the floor and muzzle straight up and ideally use a wrench on the flat to just barely snug the barrel to insure a good seat. I use the wrench that came with my Borka kit usually. I also snug the action screw with the muzzle up and then go back and torque it.

With this method I can pull and reinstall the barrel every shot with no POI shift at all and no settling in.

What torque are you using with this process Sir

 

[redneckbmxer24]

What torque are you using with this process Sir

I run it at 70 in lbs. I’ve found accuracy to be better the tighter it is and IMO that’s not overtorqueing that size bolt. My AXMC I ran at 85 in lbs since that’s where accuracy was best.

 

[Huskydriver]

If this is happening the barrel isn’t seating correctly.

I recommend removing the handguard when you install the barrel and wiping down the action face of any debris, and the same with the barrel shoulder. Screw the barrel on with the butt on the floor and muzzle straight up and ideally use a wrench on the flat to just barely snug the barrel to insure a good seat. I use the wrench that came with my Borka kit usually. I also snug the action screw with the muzzle up and then go back and torque it.

With this method I can pull and reinstall the barrel every shot with no POI shift at all and no settling in.

This is basically exactly what I do.

 

[Nik H]

I run it at 70 in lbs. I’ve found accuracy to be better the tighter it is and IMO that’s not overtorqueing that size bolt. My AXMC I ran at 85 in lbs since that’s where accuracy was best.

The 70 inch-lb value is for an AX/AT not the AXMC...right. If yes, I'll have to try it

 

[yej0001]

tagging this discussion

 

[morganlamprecht]

my experience mirrors Husky...i started out using 49in lbs and it was fine for a little while

in 2016 i was swapping between 4-5 barrels of different calibers each month, after a couple months i noticed RTZ inconsistency and groups opening a bit

upped it to 60-65 in lbs, and have been running it ever since with no issues, RTZ very repeatable

 

[Nik H]

@morganlamprecht

Was this with a short or long action (AX/AT or AXMC)? Do you think it matters?

 

[morganlamprecht]

multiple ATs

ive never used an MC long enough to have a worth while opinion on them so i cant comment on that

 

[MysizeisMAGNUM]

my experience mirrors Husky...i started out using 49in lbs and it was fine for a little while

in 2016 i was swapping between 4-5 barrels of different calibers each month, after a couple months i noticed RTZ inconsistency and groups opening a bit

upped it to 60-65 in lbs, and have been running it ever since with no issues, RTZ very repeatable

Were you tightening the barrel by hand with 60-65 or using a wrench to snug as well?

Thanks for reply’s I’m a new AT owner.

 

[redneckbmxer24]

The 70 inch-lb value is for an AX/AT not the AXMC...right. If yes, I'll have to try it

Correct.

 

[morganlamprecht]

Were you tightening the barrel by hand with 60-65 or using a wrench to snug as well?

Thanks for reply’s I’m a new AT owner.

holding the stock between my legs, butt stock on the floor and snugging tight as i could with my hands...then torquing the lock screw

 

[OH58DViper]

holding the stock between my legs, butt stock on the floor and snugging tight as i could with my hands...then torquing the lock screw

I use the same method but near the end I finish with 1/4 turn of quick turn momentum to get r nice and tight by hand.

 

[Nik H]

multiple ATs

ive never used an MC long enough to have a worth while opinion on them so i cant comment on that

Thanks

 

[MOUNTIC]

Going to try the slightly higher torque on mine moving forward. Good info here.

 

[Nik H]

I ordered a 62 in-lb PTL from Borka today.

 

[Luvman]

I’m leaning towards the 55in/lbs fix it sticks at the moment. Are the Borka Tools more accurate or better in some way?

I like the small size of the fix it sticks.

 

[Nik H]

I’m leaning towards the 55in/lbs fix it sticks at the moment. Are the Borka Tools more accurate or better in some way?

I like the small size of the fix it sticks.

Always have used Borka. Never tried Fix it sticks.

 

[kortik]

Always have used Borka. Never tried Fix it sticks.

Nik, Thank you. BTW, PTL062 was shipped today.
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Some thoughts reg. AI MC barrel change setup:

I'm not 100% certain that I'm correct, but my gut feeling tells me that AI uses flats at the muzzle end of the barrel for a couple of reasons. First, to make it easier to unscrew the barrel, particularly .338 caliber. Second, to assist with "hand tight" barrel installation. If you use even a small size wrench with these flats, something like we make and include with ATD-EFK2 and PTL049K2 kits, it is more likely that the extra leverage, provided by use of such wrench, will assist in reliably closing all gaps in a barrel thread, and then, 49 inch-lbs. should work just fine, as it is recommended by AI. "Hand tight" definition of torque, which greatly depends upon capabilties of different individuals, may be the reason why people have different experiences with different torque values, applied to the lock screw. I think the more torque is initially applied to the barrel threads, the less torque may be actually needed to be applied to the lock screw to completely secure AI MC barrel installation.

Boris
Borka Tools