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Break in ammo ?


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  Ok a friend of mine and I were discussing this. My new Armalite SASS manual states to break in the barrel and am a firm believer in it. The question is what kind of ammo and does it really matter?  I say that I can use whatever 150 grain or 147 grain 308 or 7.62 as long as I follow the shoot and clean instructions. My friend says I should use the 168 type ammo such as FGMM to break in the barrel.  What say you ? 

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I just don't understand what the difference is when using it as cannon fodder to remove the minor imperfections in the rifling. Obviously in a 1:10 twist 165-168 is ideal and that' what I will use when making bug holes in paper.  But using match grade ammo to break it in seems a little excessive to me especially at the cost and difficulty to find.  Is it the difference in bullet type and velocity or something else that I am missing ? 

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I've used the Tubb Final Finish ammo on several 5.56 builds.  I can't say if it worked or not, but those particular rifles are accurate as all hell. 

^^^ Is what I've always understood to be the best to start with, then finish off with the good stuff. I'm not sure there's anyway to prove any one method is better than the next.

Whoa hold on.....Armalite SASS and no pictures posted? >:D

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Talking about the Final Finish, brother? 


 I was taught that unless you are buying a serious match grade barrel, such as krieger, shillen, or lilja for example. That use bore scopes after hand lapping the barrel to ensure the rifling is concentric and there are no tool markings or other imperfections that is why a barrel must be seasoned, fire lapped or broke in per se'.  I understand that the twist rate of a barrel must be matched to the case length, bullet type, weight and velocity.  So I know that on a 1:10, 1:11 to a 1:12 twist the 168 grain BTHP traveling at around 2650 FPS is ideal and is the heavies load for the 1:12 twist. So how does shooting a 147 or 150 grain  PMC or Wolf or CBC at 2600-2800 FPS to just remove the barrel imperfections differ from using the 168 match grade stuff. Now I know that it will hit minute of pie plate or minute of dirt bag unlike the match grade after the barrel is broke in. I will use the good stuff to group with , I just don't understand why I would need to or want to waste good ammo. Is the lighter stuff traveling to fast and the wrong bullet type not biting into the rifling enough to remove the imperfections ? 

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  • 3 weeks later...

Just a note on the Tubb Final Finish projectiles, and kits - those projectiles are actually abrasive.  They're numbered differently, and vary in the level of abrasiveness - like sandpaper.  Shoot them in order, and it smoothes out any manufacuring imperfections in a barrel's rifling, from the rifling process.


Obviously, match grade barrels that have been final finish lapped by the barrel maker won't benefit from it as much as a "good" barrel that's mass produced, or semi-mass produced.  I've used it on the "accurate" barrels that I've purchased, that are "almost" match barrels.  Ironically, they're all Wilson Arms stainless barrels, 1:8 twist, with .223 Wylde chambers - one 16" midlength, one 18" rifle gas, and one 20" rifle gas. 

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Another note on the Tubbs Final Finish fire lapping bullets.

I used them for my .308 JP stainless steel Supermatch barrel, which I believe to be from a Wilson blank.

I bought the whole Tubbs kit which includes 5 increments of abrasive bullets, 10 rounds apiece.

I thought I'd be using all the increment groups but when I got the kit I read the instructions in detail and it stated that when used with a hand lapped match barrel, or of this sort, use only the last three abrasive compound groups. Do not use the first 2 in order more abrasive groups. So that's what I did with just the 3 lesser abrasives, in order.

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I don't even know if I believe in a break in procedure.  Because I bought a Rainier Ultra Match Barrel, I did do a cleaning after the first 10 shots. Then again when I took it home (about 50 shots later).  I think if you have a hand lapped barrel you don't even need to break it in, that's what the lapping was for after all.  


I broke mine in with handloads too, which probably goes against what everyone's procedure is :P  I can't even find any 308 ammo for sale so I said screw it and made my own.

Edited by Justintoxicated
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