More help with my 6.8 build. Got some questions before i get too deep in this thing.

[hobgob]

Hey, So I finally got around to building a lower for my RRA 6.8 upper. I intend to turn this thing into a hunting/targer practice rifle. I have a few questions before I get too deep into this thing. I bought the rifle in February of 2009. I finally got it in September of 2009. Its a mid length A4. I know the website now says the uppers are in spc II. But I believe back when I got mine they were still chambered for the original SAAMI. Can anyone confirm this? How hard is it to upgrade to the newer specs? Also, the barrel is 16inch chrome lined. Since this is for hunting/mid range plinking would it be worth it to upgrade to an 18 or 20 inch barrel? And is the mid length gas system the best way to go? Also, on my first range trip I found out that this thing doesnt like SSA ammo(110gr prohunter) but shot Hornady TAP(110gr) just fine. I read that the usual remedy for this is a stronger trigger spring. I will most likely just buy a new trigger eventually, but in the mean time, what spring should I buy, if any? Also, if the chamber is SAAMI and and not spc II, what ammo should I stay away from? I have some 120gr hornady custom in bound. Finally, some pics. BTW, I posted this at 68forums as well, but reposted here because thr gets a bit more traffic.

 

[Tirod]

It's wouldn't be wrong to ask RRA what they shipped. They would know better than anyone.

I'm finishing my 6.8 build, using an ARP barrel and bolt. To get a really good package together takes time and research understanding how it all fits together. Target shooters will suggest the shorter leade on the SAMMI spec is more accurate, and that loads under the maximum perform more accurately, so there's little to gain changing barrels unless you handload and can push the margins to get over 3,000fps. And then it needs to be asked, will a deer or hog in ethical range be any deader?

SAMMI has a shorter leade, a reamer can easily lengthen it. What we don't know is what twist. Early specs were the same as the .270, 1 in 10, the SPCII spec shows 1 in 11 or slower does better. That's using hot tactical or handloads, tho. Most ammo is SAMMI, the added incremental increase in power and speed won't come from shooting that.

So, it boils down to just using the 40% increase in power anyway, as the little incremental increases all need to be there to get much of anything. That goes to barrel length, too. The 6.8 was originally designed for the 14.5" barrel, 16" IS already longer. Going to 18" won't really do much, shooting the hotter loads would deliver more.

That's the reality, most of the differences are really single digit percentages, not huge increases, and a deer shot with either probably won't show any difference.

Mid length gas is appropriate for a 16". Boils down to shoot it enough to find out what ammo the barrel prefers, there's no guarantee which will be most accurate. Save the money toward an optic and use it, it will do well. Swapping uppers or changing barrels would be like selling last years Mustang because this year it has a few more horsepower. It's not easy breaking even financially, and about all the seat of the pants difference would amount to is having more new car smell. Street performance would be indistinguishable.

If it has to be a showcase of the latest technology, good luck, it's a constantly moving target. As an effective tool, it's more powerful than 5.56, which is the real point, and if that's what is needed, it will deliver.

 

[longdayjake]

My question is whether a reamer would work in this case since the bore and the chamber are chrome lined. I know all that really gets cut is the leade but I just can't see how it would be good for the reamer or for the barrel to cut into the chrome lining. I think you are stuck with the barrel you have. Also, just make sure you steer clear of the SSA tactical loads and you should be okay.