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AR Hunting, Preparedness and Survival
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Jon W

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Reply with quote  #1 

While I've been reloading for the past 5 years, I still consider myself a novice of the science. I feel confident in my abilities to load 5.56, 308win, and 45acp and to modify and analyze loads for greater performance, consistency, and accuracy. These are obviously some of the easiest calibers to load and I'm glad I cut my teeth on these. They are fun calibers to tinker with and expect a reasonable degree of performance, but as I investigated the 6 and 6.5mm ar offerings, the intrigue was to much to bear. Thought I had settled on a 6.5 Grendel build, then I discovered 6mmAR. However the Grendel is nothing to turn a nose at, and at some point I will build one, the 6mmAR seemed to be what I was really after. Great velocities, high BC bullets, with a very good variety of bullets. A no-brainer wild cat option for sure. First question is this: I know this chamber has many different names to date, but are they all using Robert Whitley's chamber specs to make the reamers for these or are there slight differences in them? PTG will make go-no-go gauges as a special order, but the 6.5 Gendel ones should work shouldn't they? Necking down 6.5 Grendel brass looks easy enough with a bushing die, but Harrison has stated that Hornady will be producing custom dies soon, wonder if there is any update on this news?(got to get one of his 6mm Predator barrels ordered before he is out of stock again). Anyway, I have many many more questions regarding the 6mmAR but will save them for future posts. Would love to here your opinion and experience with this round.

 

Jon

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204 AR

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Reply with quote  #2 
I have a little experience with 2 different ones, I have a BHW 243 lbc with approx 1800 rounds and a ARP 6 pred, probably 300 rounds now, maybe not that many. Both 8 twists.  Both will shoot 85s/87s at about 3k fps, which is as heavy as I have. I use 87 gr vmax in the lbc as I got a pile of them dirt cheap, but they don't work so well in the ARP barrel. They seem to be slightly too "fat" for the throat, leaving tell tale copper before the lands in the throat, as seen through a bore scope. Sierras mic slightly smaller and work beautifully, holding groups to 500 so far you have to see to believe. 8208 is what I use in both cartridges.

I use bushing dies, ending up with a .267 bushing. Hdy brass works fine as is, but I have a bunch of Norma I got a good deal on and it needs a couple thousandths turned off the necks to work well in the ARP barrel. Not a big deal and you end up with very consistent brass.

I love these little rounds, I looked at it the same as you and love the bullet options. I figure barrel life with the way I shoot to be around 3k rounds at least. There is some slight alligator hide starting in the BHW barrel at 1800 rounds. 
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Jon W

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Thanks for sharing your experience 204 ar. The more I researched, the more info I have discovered regarding the six. At first look, had no idea this and it's variants were so popular, but understand now why. Looks like my retirement income is going to take a hit tinkering with this one. Got a trued upper and bolt carrier coming from arp tomorrow, guess I better get a 6 pred barrel before they are out of stock again. All reports I've read, Harrison has made a lot of guys smile with the level of accuracy they have been able to achieve. I read of one bad experience with a BHW 243 lbc, but it appeared to me the guy had initially overlooked some sound loading practices and was chasing his tale as a result. Maybe it was barrel related to,  I don't know. I guess my biggest question still, is regarding head space. What are you using for head space gauges, and how do you know where you are at with your initial sizing until you have fire formed brass? Can you tell I'm new to this? I know it's a good practice to purchase barrel and bolt at the same time but finances don't allow presently, but I just want to know anyway.

Jon
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204 AR

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Reply with quote  #4 
No headspace gauges here, I just use the brass to tell me. Size a couple down and see if they chamber. At this point there is no realistic way to stretch them anyway and there is usually 8 to 10 thousandths of head space IME. After firing measure with the headspace gauge so you can set your die to set the shoulder back 3 to 5 thousandths is what I like. 

Yeah it's tempting to grab another Predator barrel while he has them. The fact the throat is so tight is a bit of a concern as there are a lot of bullets that are very snug in that barrel.
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Jon W

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Reply with quote  #5 
Got it. I guess I was overthinking the process a bit, coupled with a little trepidation regarding a wild cat cartridge. This however, has got to be the easiest one to start with. I was just afraid I would get excessive head space on the first firing but I'm sure I can get'em dialed in. I guess you don't have much choice initially.

Now, regarding the tight throat. Do you mean it's a bit on the short side, or the leade angle a little steeper into the rifling? Please school me.

Jon 
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204 AR

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Reply with quote  #6 
No the length is very similar to my BHW, within a few thousandths. It's tight on the diameter. Meaning a bullet that measures .243 diameter actually rubs all the way around. As if the reamer was ground too small. 

I'm not really complaining as it shoots really well with the sierra 85's but it could cause issues if you didn't realize what was going on. Other bullets will chamber, but extraction of live rounds is pretty sticky.  I had this same issue with a custom chambered 270 wby. When Hdy bullets didn't work in it I started measuring bullet diameters with a mic and found Hdy's are typically 3 or 4 ten thousandths fatter than some others.

Honestly if you bought one now I doubt it would have the same issue. Different reamers and all.
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Jon W

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Reply with quote  #7 
Thanks for all your help 204 AR. Good info to help me get started when I get my barrel, dies, and reloading components. 

I bought a couple ASC magazines to see how they would function. Out of the box, not very well in my estimation. If a guy wants to spend a little time finessing them, I think they can be made to function very well. I had a box of Hornady Grendel ammo sitting around so I started to tinker with them. When I get a little time, I will post a few pics and what slight mods were performed to make the rounds slide out smooth as butter! 
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Reply with quote  #8 
The chamber I use in the Predator is a 243LBC, They have a .243" diameter throat. A .243 inspection pin slides in so they are at least .243". Most bullets are .2425. Some like Sierra are a full .243.  If the bullets are .243 and the throat is .243 they will touch. Touching is what they should do to align the bullet on the bore. If you can't pull back the charge handle on a loaded round there is a problem.
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204 AR

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Reply with quote  #9 
I can extract the Sierras easily, Hdy's will extract with the charging handle but not easily. They are not jammed into the lands. Resized brass is measured then tested to ensure sufficient shoulder set back so that isn't the issue. Hdy brass works well as is, Lapua works also but Norma needs a couple thousandths shaved off the necks to easily chamber and extract and get good accuracy. 
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