survivalshop

11 deg. is pretty common crown.

Scratches are probably from the locking lugs on the barrel extension. As said , when the gas system seals , your rifle will function better. Not holding back can also be the bolt stop & it may need tweeking ,if problem keeps happening. Using a 308 bolt stop ?

Forming dies . Some are multi step dies to get the case where you want it or designed to be . Are you a hand loader ? Most major die & custom die manufacturers will make pretty much any die you want & can come up with spec's for. Take the 300BLK cartridge , you cut a case down & use a forming /sizing die to make the finished case. It is a simple process.

Yep, same happens to mine . If you have a STD trigger group , any of the spare parts kits are good . Just get them from a known good manufacturer & they come in handy. If you have a custom trigger , the trigger/hammer springs may or may not change your trigger spec's if you need to use them , but the other parts are very usable. Try to get a kit that has things like , extra firing pin , extractor/spring, gas rings , stuff like that . I think my 308 kit was from DPMS , I can take a photo of it , I think it has not been molested.

I have not read any thing of the MK III ,but there other one has good reviews as said . looks good.

Here's a photo of my DPMS upper & gas tube , look at where it is . This rifle runs flawlessly & I'm going to try to get your photo side by side to compare ,but its pretty close.

Robocop gave a very detailed account on what goes on in the barrel. The 16 will have no problem out to 500 yrds & beyond , it is a .30 bullet & weight helps down range . Check this thread out if you already haven't , I give some chornograph comparisons between my 16 & 20 , the 18 will of course, come out some where in between . http://308ar.com/forum/accurizing-the-308ar/why-shorter-barrels-may-often-be-better-article/

As 98 said , you have to measure /compare from the seating flange of the barrel extension . Looking at your photo's , as said , the extension on the 308 is longer ,but the distance from flange to gas port should be the same . Your photo's have a misleading comparison between the two . Measure from the extension flange to the gas hole ( where it seats on the upper receiver )of both barrels (same gas system lengths ,of course ) What is the length of the gas tube you are using , by its self ? The one in my hand is close (15 1/8 " ,with tape measure )to the same Jgun has .

Wouldn't any AR barrel be the same ? They all have the same gas systems in them ,be it carbine , mid or rifle , 5.56,300 BLK , 6.8, 308. The difference would be barrel/extension dia. & chamber length . We are using the same parts of the gas system , so the distance should be the same ,no ?

OK , that's a little too much info! I also have some one to send it to. Too bad I can't take it to hunt camp .

Nice ! Why the mid length for 308 & rifle length for 223 ?

Any update ?

When installing or removing any muzzle device , the use of barrel blocks , clamped in a vice on the barrel is the only way to remove or install muzzle devices . The set screws on the GB are not meant to hold with that kind of pressure needed to work on them. Any properly sized GB (barrel dia.@ gas block attaching point )will work with the 308 or as said an adj. one. You can make or change any AR to the specs you want & they do get on the heavy side when you add a HB to them .

As said above , what use do you want out of it . Pmag is one reason to get the DPMS ,match trigger is one for Armilite , if it comes with it . You have said you want to change the hand guard on the DPMS , do you plan on any changes to the Armilite , if you buy it ? In a sense, it is less expensive to buy a complete rifle ,but if you already want to change it , the price goes up ,because you are adding to it already. I think you will find , most that buy complete rifles , change the configuration soon after purchasing it . Keep that in mind & you may be able to come up with one or the other that will cost you less in the long run . There are parts available for both types , to change configurations if you want . Just don't listen to the ones who say , "this is the only one & the best ", they have blinders on .

bump

WoW , he shot its head off !

If you are a handloader , you can use a wide variety of bullets for the .30 also. The bullets available now is just astounding , compaired to just ten years ago. I have seen Elephants downed with an FN in 762x51.

My complaint is , I don't have enough money to build all of them I want or like . That's the way it is for all the AR's I want, so I can't hold it against them .

This would work till you can afford the one ya want . http://www.natchezss.com/Category.cfm?contentID=productDetail&brand=MI&prodID=MIBK81001A&prodTitle=Millett 4-16x50 Tactical Riflescope SF Illu. Mil-Dot Bar Reticle ATAC w/Flip-Up Scope Cover

Well , I've not seen that one before . How many more out there with a hole all the way through ? I have at least five different manufacturers gas blocks in there & a std front sight & none of them have a hole through them . I guess once the gas tube sealed, it wouldn't matter . Different barrels , gas blocks & tubes , I can't see the sight shoulder on both barrels being out of spec. or both gas blocks . I 'm going to assume you have a rifle length gas system or are you saying even with two different gas systems ( different length barrels ), the gas tube is in the same position in the upper receiver. A partialy pluged gas hole will do the FTE , you are sure the gas holes are lined up . The rifle length gas tube in my hand is 15 1/8 " long with in +- .

You would have to compare the non working gas system to a working system ,meaning all the components . If the gas tube is too short , not far enough in the carrier key , it would cause a timing problem & under gassed. Were the 20" & 16" both same length gas systems ? Were you using the same gas block/tube on on both barrels ? I would look as has been said , gas tube length, gas block configuration( out of spec., holes in the wrong place or too deep into block ) , & definitely check the upper 's spec's compared to another. If you need measurements ,we can help. UHH, gas block on back wards ? I think they only have one entrance for the gas tube. <dontknow>

I have my glass's made with safety glass not only for work , but for shooting & reloading . Safety glass's are a must for both endeavors. I have only used the primer pick up tube for my Dillon once ,just to see how it worked . I use a Lee hand primer for a lot of reasons & now I have one more . Static elect. seems like a plausible reason , but its too easy to put a lot of pressure on the primer stack in that pick up tube , if one is not moving easily when filling it . Its one thing I don't like about the Dillon & why I don't use it . This is an odd Kaboom story. May never know what really happened. Good post ,Jgun.

AS far as the bullet being unstable , I don't believe that would be the case . In most cases , it is some thing making the bullet act that way . some thing with the barrel ,crown or path of the bullet . Different ammo with different bullet weights & shapes or configurations will and can cause different points of impact , some dramatic. Mass produced rifles ,no matter what they are made with or made by , can have an occasional out of spec component(s) . I say that only because you can not leave any possability out of the equation when dealing with a potential problem like this (new rifle ). I would do , as you are , deal with the inexpensive things first & check the out come . The scope & or mounts can cause funny things to happen , but the bullet being unstable is kinda odd. The range of harmonics of the different ammo can cause different results.

OOOOH the pressure , the pressure , I can't take it any more !

Taking off any little screws in the field , would not be one of my favorite past times . Now a lever or some kind of release would be more like it , some thing that you would not have to unscrew & potentially lose . Just look at some of the Belt fed quick change bbl's ,now & past .