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 Double Lapped, what does it mean?
Battl3fr0nt  [Member]
4/21/2008 11:49:52 PM EST
I have an Armalite and on other AR's I don't see "Double Lapped" what does this do for the gun and how does it work?
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Lapp_Dance  [Team Member]
4/22/2008 12:17:36 AM EST
It means I've done your gun, twice.









































j/k...I have no clue what it means. I get a giggle everytime I see the word "lapped", for obvious reasons.
RedFalconBill  [Team Member]
4/22/2008 12:18:05 AM EST

Originally Posted By Battl3fr0nt:
I have an Armalite and on other AR's I don't see "Double Lapped" what does this do for the gun and how does it work?


Lapping the barrel is done to polish the bore and remove any machining marks, tight spots in the barrel, and make the bore dimensionally uniform end to end.

To me, it means that ArmaLite laps the barrel twice. Once after the barrel is reamed to remove marks and then they lap the barrel a second time after it is rifled. After this, they send the Chrome-Moly barrels out to be Chrome-Lined.
Battl3fr0nt  [Member]
4/22/2008 1:45:34 AM EST
does it help with anything? and what is lapping the barrle do for the gun? and another thing I have a 1/9 twist and this guy in the military says it will shoot 77 fine.. but I read on here that after about 200-300 yard's it will not hit target..
RedFalconBill  [Team Member]
4/22/2008 2:44:51 AM EST

Originally Posted By Battl3fr0nt:
does it help with anything? and what is lapping the barrle do for the gun? and another thing I have a 1/9 twist and this guy in the military says it will shoot 77 fine.. but I read on here that after about 200-300 yard's it will not hit target..


Yes, it makes the bore smoother.

1/9" twists can shoot Sierra 77gr MK bullets...sometimes.

It depends upon air density, muzzle velocity, and lastly whether your 1/9" twist is really 1/8.5" or 1/9.5".
AtlantaFireman  [Team Member]
4/22/2008 5:39:45 PM EST
Armalite does a pretty good job with thier barrels: they finish the barrel before it leaves the factory, so you don't have to do it.
cckw  [Team Member]
4/22/2008 5:44:07 PM EST
I think they are not really "lapping" at all, perhaps ordering the barrels with an extra button pulled to help smooth it. They buy barrels from the same vendors as Bushmaster, RRA, etc.
lordmercury  [Member]
4/22/2008 6:06:16 PM EST
Lapping is a good thing,,,,,although...........
Once a barrel is chrome lined the accuracy you gained is lost. Chrome lining is not perfect in any way, shape, or form. NOT saying it will be worthless or anything like that, but if you want a true "match barrel" skip the chrome.
I have seen some good chromed barrels and have seen some bad ones.
Just my .02
new-arguy  [Site Staff]
4/22/2008 6:32:25 PM EST

Originally Posted By cckw:
I think they are not really "lapping" at all, perhaps ordering the barrels with an extra button pulled to help smooth it. They buy barrels from the same vendors as Bushmaster, RRA, etc.


source for this info?
Battl3fr0nt  [Member]
4/22/2008 10:46:21 PM EST
I do i fidn out if it is a 8.5 twist or 1/9 cuz I know it is not 9.5.. but I would like to know if it is an 8.5.. and is it always a .5 or can it just be a 8 or a 7, 9, ect ect.. cuz I know with 1/8.5 it will shoot 77 just fine for sure.. and armalite does make some of the best barrles.. and they give u good specs with them.. not just "chrome lined".. like other cheaper guns out there.. but yeah how can I check on the twist? cuz I know most rifle barrles are 1/9 pretty much all of them are now cuz it is a much better twist for lighter rounds.. and more accurte then 1/7 with anything under 69gr.. cuz my friend was shooting 62 with his 1/7 and I was shooting it with my 1/9 and I had much better groups.. even when we switched just to make sure i was just not a better shooter..
Centauro97  [Team Member]
4/23/2008 5:00:07 AM EST
If you shoot two of those abrasive covered bullets does that count?

There's hand lapping and fire lapping and I'm sure some others that crafty salesmen can use to sell a product.
RedFalconBill  [Team Member]
4/23/2008 11:08:56 AM EST

Originally Posted By Battl3fr0nt:
I do i fidn out if it is a 8.5 twist or 1/9 cuz I know it is not 9.5.. but I would like to know if it is an 8.5.. and is it always a .5 or can it just be a 8 or a 7, 9, ect ect.. cuz I know with 1/8.5 it will shoot 77 just fine for sure.. and armalite does make some of the best barrles.. and they give u good specs with them.. not just "chrome lined".. like other cheaper guns out there.. but yeah how can I check on the twist? cuz I know most rifle barrles are 1/9 pretty much all of them are now cuz it is a much better twist for lighter rounds.. and more accurte then 1/7 with anything under 69gr.. cuz my friend was shooting 62 with his 1/7 and I was shooting it with my 1/9 and I had much better groups.. even when we switched just to make sure i was just not a better shooter..


I said 1/8.5 or 1/9.5 because on a button rifled barrel there is a +/- to what the twist states.

Your 1/9" twist barrel could be as fast as 1/8.5" or as slow as 1/9.5" and still be considered a 1/9" twist.

Chrome-Lined barrels are not "cheap". The chroming actually increases the cost of the barrel.

There are numerous FAQ's thread that are tacked that explain the whole 1/9" vs. 1/7" very well.

I explained what ArmaLite meant by double lapping and I'm glad that you enjoy shooting your AR.
Ghostface  [Member]
4/24/2008 6:31:46 PM EST

Originally Posted By cckw:
I think they are not really "lapping" at all, perhaps ordering the barrels with an extra button pulled to help smooth it. They buy barrels from the same vendors as Bushmaster, RRA, etc.


I think that depends on the barrel type and caliber....
Battl3fr0nt  [Member]
4/24/2008 9:06:32 PM EST
sales man? I didnt even know much about anything when I got the gun... I just heard on here Armalite's Bushmaster and Rock river are the top guns and all they had where armalite or bush so I want with armalite.. then I found all about the lapping and stuff online.. cuz pretty much all match barrles are double or tri lapped..
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