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mtka
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Posted: 10/1/2011 9:50:28 PM
Well, I had been considering the LAR-8 Predator HP as the leading candidate among the different, affordable .308 AR10 style rifles ever since I read the review in the August 2011 edition of Shooting Times. This particular variation on the .308 AR-10 type rifle addressed some of the characteristics of their design that agreed with what I'd like to see done to them. The fact that RRA had already released some alternate calibers that shared the .308 parent case was a nice touch, but not unique to this product. The biggest feature, that I perceived from the article, possibly erroneously in retrospect, was that it allowed loading rounds longer than the typical 2.80 inches. From the article:
:"...the Fal magazine is slightly longer. This gave handloaders a little room to increase overall cartridge length..." Not having a FAL magazine to actually stick some .308 rounds into, I assumed it would be significant enough to perhaps load high BC, long bullets without either giving up precious powder capacity, nor placing the ogive below the case mouth. It also said, "...it made the LAR-8's receiver almost a half inch longer than standard AR-10s." I mistakenly took this as COLs up to a half beyond 2.80. Upon loading the FAL magazine that came with my unit, that "increased overall length" is on the order of .055 inches, or 2%. Heck my AR15 magazines allow an extra 2% COL. That worth of that increase, along with $1.59 will get you a cup of coffee at Starbucks. So, needless to say, unless RRA comes out with their own magazine that offers a COL increase that's actually significant, then the main reason I bought this model, seems like a mistake. I could have just bought a regular LAR-8. The rifle still brings some nice features to the table but IMHO, not worth sacrificing the ability to interchange aftermarket parts made from companies outside RRA like you can with the AR-10 or LR-308 and possibly other brand .308s.

Looking beyond that disappointing revelation, which I made as I sat at the shooting position at the local range, putting rounds in the magazine, I proceeded to do some shoot and clean, like I do with all my new guns, whether the practice is justified or not. It's just what I do. I ran through that regimen using some 2005 Lake City XM80 ammunition I had squirreled away, right next to where my G3 used to stand. It's reliable ammunition, but not on the same accuracy plane as quality manufactured ammunition, nor quality handloads like I churn out in the name of accuracy. For the task at hand, it was just fine. Here is an image of the target I used to foul after cleanings:



Perfectly acceptable from a freshly cleaned and lubed barrel using XM80s, before dialing in the scope. I then shot some 3-shot strings from the barrel, it having been fouled and they were probably the best groups I've gotten from XM80s out of any of my .308 rifles, let alone an autoloader. The grid and bull in this 100 yard target are 1/2 inch:



I can only imagine how well it will shoot reloads, though unless some miracle happens they won't be loads that use high BC bullets or bullets loaded to the lands, should I choose to do so. I have the blessing of a fairly well appointed workshop that I spend lots of time in and I'm no stranger to modding magazines. One of my favorite mods for single stacked caliber AR15 variants is the one associated with c_bass16. If you're unfamiliar with his mod, it cuts a slot down the front that allows the bullet tips to stick through and into the groove that runs along the inside of the mag well front wall. With it, I can load AR15 rounds up to 2.40 COL, or plus 6% to get bullets of the right profile into the lands if I choose. Unfortunately, we do not have that lattitude with FAL mags due to the catch in the front that is necessary for it to stay in the mag well. The rear however has what looks like a spacer placed inside it that may be able to be removed or relieved. Time will tell.

There were zero FTFs or FTEs. Since I use a brass catcher, I do not know where the rifle places spent brass when it ejects them, but given the strength of the ejector spring, I have no doubt it throws them quite a ways away. That leads to the only objectionable behavior observed in the rifle's performance. Despite shooting modest military surplus loads (2650fps average), I got ejector marks on every round. I did not lubricate the rounds before shooting them, nor the chamber, so I'm going to guess that the ejector simply has sharp edges that cause these swipes:



I will remove the ejector plunger and stone, then polish the edge to a less sharp profile and fully expect that to rectify that minor issue. It is an issue because ejector wipes are a useful troubleshooting indicator of loads that are a little too stiff, along with extractor imprinting and case head expansion, to name a few. The tend to happen in degrees, long before the primers start flattening.

So, I look forward to many range visits as I work through different loads, hopefully cataloging some that produce excellent accuracy along the way. It's not long before our 6 months of winter sets in upon us, so there will be a gap in range reports eventually, until our 2 weeks of spring returns next May.

John "Hoot" Hill

PS can anyone recommend a forum dedicated to .308 AR variant experimentation?
mtka
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Posted: 10/18/2011 6:41:28 PM
Reference the image of the swiped heads in the previous post.

Since it occurred to every round, not only the XM80s, but several tame reloading efforts since that first time out, I assumed there was a system problem, not an ammunition problem. Searching around the web revealed many threads and posts about the same phenomena in AR 7.62 rifles. Most were generally agreed upon to be the result of over-gassing. I always wanted to try an adjustable gas block on one of my ARs, so going on good advice, I bought a JP unit. Let me say that the quality of the construction and close toleranced fit impressed me, as I've seen some poorly fitting gas blocks.

Today, I went to the range to see how it worked and adjust it. Starting with it totally obscurred, requiring the round to be hand ejected, I noted no swiping on the head. I adjusted the screw out a few turns each shot and as soon as my observer (daughter) started seeing bolt movement from the side, the swiping resumed. It started with a sliver of a crescent moon and progressed to just like in the image before I was even getting rounds to eject. So, it appears my swiping is not the result of over-gassing. My gut feeling would be to add some inertial mass to either the bolt carrier, or more easily, to the buffer. Still, there is a nagging voice in my ear suggesting that perhaps the face of the receiver is not trued. I say that because when I first mounted my scope on the LAR-8, it shot so far to the left as to take 1 1/2 full rotations of the scope's windage knob to get it to the middle of the target sheet. Consider the fact that my scope, rings and riser move from different platforms as an entire assembly and across three other AR15s of different caliber, I rarely have to turn it more than a few clicks to re-zero. Now, I assume the factory test fires each upper before shipping it and if the technician saw unusual brass markings like I'm getting, they would put it in the "problem child" pile to be troubleshot. Is that being naive on my part? My question is should I send the upper to the factory to have them re-test it for any problems, or is that kind of malfunction considered to be my tough luck? Once zeroed, the rifle shoots great. I have about a dozen rifles that shoot great, many of which are auto-loaders. No other one does that to the case heads. Should I at least try additional weight to the buffer before worrying, or just send the upper in for evaluation? I had hoped to use it as my backup rifle when deer season starts in three weeks, but I have others stamping their feet in the stable.

Thanks,

John "Hoot" Hill
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Posted: 10/18/2011 7:02:31 PM
interesting, thank you for posting
mtka
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Posted: 10/18/2011 11:01:25 PM
I forgot to add that my LAR-8 buffer weight 4.6 ounces. Is that the standard for them as other AR 7.62 variants have a heavier buffer. I assumed this was lighter due to the longer bolt carrier weighing more? I am leaning toward trying more weight in increments until the swiping stops, or I run out of room for adding additional weight, or it won't cycle all the way with the gas adjustment at full open. In my shop, I can cast a continuous lead dowel that will fit inside the buffer, to increase the weight. I have done this in other heavy AR15 calibers like my 450 Bushmaster and .300 OSSM and to a lesser degree my 6.5 Grendel. In all cases, the increased weight reduced perceived recoil somewhat, but more importantly also reduced how badly the brass got beat up. None resulted in any FTE or FTF, nor abnormal carrier wear.In those cases, I was not experiencing ejector swipes. Just beat up rims and bodies.

Thanks for any input on this phenomena.

John "Hoot" Hill
mtka
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Posted: 10/23/2011 11:19:31 PM
Sorry for distracting the discussion, but I resoled the swiping problem. Despite preaching to younger work staff the importance of not looking for complex solutions to simple problems, the master got a refresher course. The adjustable gas block did not resolve the problem. The additional buffer weight did not resolve the problem, though it did lessen the severity of the perceived recoil while not causing any cycling issues, so it will stay for the moment. No combination of the two resolved the problem. The simple act of truing and polishing the bolt face, which was a little uneven, did the trick, even though it did not look like an issue until I examined it under the stereo microscope. Runs like a Swiss watch now and the brass looks great to boot. I was going to wait until after Deer Season in two weeks to send the upper in to have the hand guard broke free, but I'll do that this week and have decided to take the 6.5 Grendel as my backup to my 450 Bushmaster instead. Kind of a one two punch. The 450B is great for the tight north woods I hunt in and the Grendel is great for the occasional clear cuts or across some of the many beaver slews and muskegs in the area. Neither has been bloodied yet. The Predator HP can have its "at bat" next year as I doubt I will get it back in time. I shot some exploratory 150gr TTSX loads and it was nigh impossible to make them shoot worse than 1.5 MOA across a few loadings I took to the range today. They will make a great deer load next year for the PHP.

John "Hoot" Hill


mikear
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Posted: 10/24/2011 9:57:18 PM
Originally Posted By mtka:
Sorry for distracting the discussion, but I resoled the swiping problem. Despite preaching to younger work staff the importance of not looking for complex solutions to simple problems, the master got a refresher course. The adjustable gas block did not resolve the problem. The additional buffer weight did not resolve the problem, though it did lessen the severity of the perceived recoil while not causing any cycling issues, so it will stay for the moment. No combination of the two resolved the problem. The simple act of truing and polishing the bolt face, which was a little uneven, did the trick, even though it did not look like an issue until I examined it under the stereo microscope. Runs like a Swiss watch now and the brass looks great to boot. I was going to wait until after Deer Season in two weeks to send the upper in to have the hand guard broke free, but I'll do that this week and have decided to take the 6.5 Grendel as my backup to my 450 Bushmaster instead. Kind of a one two punch. The 450B is great for the tight north woods I hunt in and the Grendel is great for the occasional clear cuts or across some of the many beaver slews and muskegs in the area. Neither has been bloodied yet. The Predator HP can have its "at bat" next year as I doubt I will get it back in time. I shot some exploratory 150gr TTSX loads and it was nigh impossible to make them shoot worse than 1.5 MOA across a few loadings I took to the range today. They will make a great deer load next year for the PHP.

John "Hoot" Hill




Thanks for posting the information. I think the more info that's out there about the LAR-8 the more people will feel comfortable purchasing. I love mine BTW. Could you post pics of the buffer and bolt face (before and after if you have them)?