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Ruger 556 MPR: Thoughts?

Old 12-09-2017, 08:41 PM
  #11  
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Update: I went ahead and pulled the trigger on a Nikon BDC scope (the plain, vanilla Cabela's edition that's on sale for $99---had some Cabela's bucks saved up to put toward it). It's got a no-fault, lifetime warranty---so I can afford to cycle through some bad quality control product if need be. But I don't expect to have to; I have seen that they are generally reliable---for .223/.556 recoil, it should hold up fine. They're on all the Savage Model 11 gun/scope combos and seem to be quite serviceable.

I'll order a cantilever mount, tomorrow. I found a well-reviewed one with 6 screws on each ring; a bit of Locktite on those and should be set (plus, thanks to scanning receipts with the Ibotta app, I'll only pay $2 for it).

Last edited by younggun308; 12-10-2017 at 04:52 AM. Reason: to specify the type of mount
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Old 12-10-2017, 08:02 PM
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Many, many custom barrel makers will produce a mid-length gas system on a 16" barrel. I have a pair of Black Hole Weaponry (Columbia River Arms) barrels, 16", with mid-length gas.

The Nikon will be serviceable.

As you mentioned - stay away from the nikon mounts. They're garbage, even if they would fit with your eyebox.
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Old 12-11-2017, 05:40 AM
  #13  
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I wasn't clear: I meant an 18" barrel with an "intermediate," not a "medium-length" gas system. From what I've read, people debate over whether a rifle-length gas system (like the Ruger has) is better or a standard mid-length (which seems to be ideal for 16"). But a couple manufacturers have made a distinct "intermediate" length tailored to the 18" barrel of the SPR configuration.

Here's Noveske's gas tube for their 18" barrel:
https://www.noveske.com/products/intermediate-gas-tube.
And their barrel:
https://www.rainierarms.com/noveske-...6mm-barrel-18/

The only thing that gives me pause is I'm less-than-certain a 1:7 twist rate is ideal for non-hunting applications (where the incentive seems to be to load with heavy grained bullets, for the sake of versatility), especially if accuracy would suffer past 150 yards using standard 55-grain or even 62-grain target ammo due to over-stabilizing.

But again, I won't be worrying about that for a few years, anyway. For now, I'll have a 1:8 twist rate. By the time I'm looking to replace the barrel, there could be a lot more options in the "intermediate" gas length category.
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Old 12-11-2017, 08:32 AM
  #14  
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There's nothing particularly special about the Noveske gas length, just have to match up the tube length for physical fit. "Optimized" is a funny word, as it sounds like it means a lot, but in real world application, it means almost nothing. Here are all of the things which must be in congress for that length to be "optimized," and changing any single item from this list changes the dynamic: gas port position (length), barrel length, muzzle device, bore diameter, port diameter, gas tube diameter, buffer spring strength, buffer weight, carrier weight, bullet weight, powder used, powder charge... The Noveske is almost a rifle length, but not quite, and a mid-length with an adjustable gas block will give you better control to optimize, with a lower pressure impulse than the Noveske length.

So what might be optimal for one bullet is not for the rest, what is optimal for one powder is not for the rest. And more importantly, what is "optimal" for one application might not be for another. I run about twice the cyclic rate in my 3-Gun rifles as I do in my hunting rifles, all of them run reliably. But one kicks less, and one shoots faster.

In over 15yrs of building hundreds of AR's, my experience has been such a shortened gas system with an adjustable gas block is the real solution. You can make a short gas system run like a long one, but you cannot make a long one run like a short one.

Mid length, KAC intermediate, Noveske intermediate, it's really all marketing. A sloppily engineered solution to a gas flow and pressure balancing act. Locking into one length is just as much of a mistake as any other, and just as correct. An AGB gives you versatility to optimize the rifle to any load, powder, or bullet weight.

Your expectation for "more options" in intermediate length in the future is most likely misguided. Any custom manufacturer will cut the port position wherever you ask, but really, that's moot anyway. You'll burn out barrels every 3000-5000 rounds, and you'll replace the gas block and tube with them. The erosion which happens in the barrel happens in the block as well, the whole kit goes as one unit when replaced. Even if you did foolishly reuse the gas block, the tubes are $10. You'll be replacing a barrel for a few hundred bucks. In other words, you can pick a new gas length any time you pick a new barrel.

You've also been mislead if you feel the BCG will wear out before the barrel. I have BCG's with more than 50,000rnds on them. Many sets of gas rings, a dozen barrels, but one BCG. The upper will waller loose before the BCG would wear. It only needs replaced if your cam pin track burnishes or if the gas piston bore scorches.

There is no such thing as over-stabilization for 50grn bullets in 1:7" AR barrels under 20", or even longer. You'll get better stability at longer ranges with a faster twist. I shoot 50grn V-Max's from a 1:6.5" 29" high power match rifle out to 600 and 1,000yrds regularly. As long as the bullet doesn't come apart at the muzzle (some of the 32 and 40 grain bullets can, especially in cut rifles barrels), it'll be more stable down range.
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Old 12-11-2017, 09:20 AM
  #15  
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Again, thanks for the thorough feedback. It's helped clear up a lot of my misconceptions---there's only so much one can learn from reading on the internet compared to real experience. Clearly the former led me to believe some marketing hype.

Great to know an adjustable gas block with a short(and by that do you mean carbine/M4 or "pistol"?)-length tube/port position is where one should set their sights.

Great to know the BCG should last longer than the barrel (though I've heard that semi-auto ones, like the Ruger, are less durable than FA---is this also true?). My dad had a bad experience with the BCG that came with his Remington R15 a couple years back, and it might have biased my expectations.

As for stabilization, I must have been misled by something I read---that a faster rate of twist with a 55-grain will be okay at shorter ranges with a 1:7", but that "wobble" will throw the bullet off MOA more than it would otherwise, as it travels further.
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Old 12-11-2017, 11:39 AM
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As it is with nomercy, I have around 30,000 rounds through my Wilson Combat with the original BCG and on my 5th barrel. I've always used an AGB and fine tune it to the rounds built every time. If I change a powder, bullet, or even a primer I re-tune the AGB. My 6.8 gets the same treatment though it has only seen around 4,000 rounds and it's getting close to a new barrel need and will probably be going with a Black Hole for it as that .338fed of the old mans is exceptional. A lot of people are under the false impression that over gassing is a good thing, that it will ensure your operation of your system when in fact it's harder on your entire system, creates more recoil, and seriously dirties up your rifle. And if you ever put a suppressor on it, well lets just say a bad day will come soon but then you are talking about needing a heavier buffer spring as well as closing off the AGB a bit to prevent short stroking. The make it short, AR's are fun but they can be pickier than a prom date sometimes. That is if you are really serious about your hardware.
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Old 12-11-2017, 01:25 PM
  #17  
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Originally Posted by younggun308
Great to know an adjustable gas block with a short(and by that do you mean carbine/M4 or "pistol"?)-length tube/port position is where one should set their sights.
The trend in recent years has been to run a "lower pressure" position in the bore, meaning a longer than standard gas length, hence the rise of mid-length, intermediate Nov & KAC gas systems. However, these are only an advantage if used with a "dumb" gas block, and then leave the user vulnerable to lack of gas flow with lighter loads, or faster, lighter bullets (shorter dwell time. Alternatively, by running an AGB on a shorter gas system, aka a pistol length instead of a carbine length on a 10.5" barrel, a carbine on a 16" barrel instead of a mid/inter, or a midlength instead of a rifle on an 18" barrel, you can throttle the gas flow to a lower impulse. No, you shouldn't be running a carbine length system on a 20" barrel, or a pistol length on a 16", but for a couple barrel lengths where there's a decision to be made, I ALWAYS go short and add an AGB, instead of running the risk of insufficient flow on a longer system.

Originally Posted by younggun308
Great to know the BCG should last longer than the barrel (though I've heard that semi-auto ones, like the Ruger, are less durable than FA---is this also true?). My dad had a bad experience with the BCG that came with his Remington R15 a couple years back, and it might have biased my expectations.
What failure did he have with the Remington BCG? I'd be interested to hear. BCG failures are exceedingly rare. Out of spec manufacturing is far more common than wear-and-tear failures.

Semiauto BCG's will not wear out any faster than a Full-Auto design, anyone claiming such is simply lying to you. The only difference is the cut at the tail of the BCG. There is no difference in durability when used in semiauto fire, and frankly, I'm not prone to believe there's a significant difference if used for simulated full auto fire (the FA bolt typically engages the select fire mechanism, so an SA bolt couldn't be used for true FA fire, only for simulated FA, like a binary trigger, bump stock, or trigger crank). FA bolt carriers ARE popular among SA shooters and AR builders, since they have a bit of extra weight compared to the SA bolts, which slows down the recoil impulse and reduces some of the action battering. Adding an extra weight buffer will accomplish the same end. FA BCG's are REALLY popular because mil-spec mall ninjas all over the internet say they should be popular, misleading folks into thinking mil-spec and FA actually mean something important in terms of rifle function and durability in SA civilian AR's.

Originally Posted by younggun308
As for stabilization, I must have been misled by something I read---that a faster rate of twist with a 55-grain will be okay at shorter ranges with a 1:7", but that "wobble" will throw the bullet off MOA more than it would otherwise, as it travels further.
There's no "wobble" caused by over-spinning the bullet. The only negative consequences of excessive rate of twist are 1) bullet stress, where the bullet may tear itself apart as it leaves the muzzle, and 2) extra bore drag, where the bullet can't be pushed as fast as it otherwise could be with a slower twist.

Largely, there is unstable and stable, and no such thing as "over stable". The farther you get down range, the more spin you need. Poor quality bullets are going to exhibit yaw, exaggerated down range, and those imbalances will also be exaggerated by insufficient stabilizing spin. Over-stabilization is bad science.
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Old 12-11-2017, 02:10 PM
  #18  
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Originally Posted by Nomercy448
The farther you get down range, the more spin you need. Poor quality bullets are going to exhibit yaw, exaggerated down range, and those imbalances will also be exaggerated by insufficient stabilizing spin. Over-stabilization is bad science.
So yaw is more due to the imperfections of the bullet being magnified by speed rather than due to the bullet weight itself interacting with the rate of twist?
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Old 12-11-2017, 02:19 PM
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No, and I didn't say that - I made the inclusive statement, not an exclusive one. Yaw is caused by insufficient stability, this can be due to imbalanced bullets, or insufficient spin, or both.

Poor quality bullets have more imbalanced imperfections than higher grade bullets. These imbalances will cause a bullet to yaw - period. More twist can help slow that down, so it happens farther down range.

Under-stabilized bullets, spinning too slowly, will also yaw, even high grade bullets.

My point was really to say the fools online who tout 1:7 as too fast for their bulk supply 55grn FMJ junk don't know of what they speak. Crap bullets are going to spool out down range no matter what.
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Old 12-16-2017, 07:09 AM
  #20  
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Here it is, getting acquainted with some others in the gun safe.

Took it to the range, yesterday. It certainly prefers heavier loads; 55-grain FMJ's reliably short-cycled (with the exception of Remington UMC, which only jammed toward the end of the session). To be more specific, in all cases the spent casing would eject. But with cheap steel-cased (coated with zinc) 55gr. loads the bolt apparently didn't go back far enough to pick up the next one. With slightly more expensive steel-cased 62gr. (coated with brass), the bolt picked the cartridge up somehow from the middle of the case, driving it halfway forward before obviously jamming.

But this may in part be because I had not taken the BCG apart to wipe away excess oil therein. I only cleaned the bore and wiped the lower receiver before shooting it. When I switched out my BCG with my dad's nickel-boron plated one, there was no cycling problems even using steel-cased 55gr. loads. So it's not the rifle-length gas system alone.
In any case, I always planned to use heavier bullets out of this rifle; it would on the other hand be nice to reliably cycle 55-grain FMJ's to simply break the rifle in cheaply, however---so hopefully cleaning the BCG will result in better performance. Anybody know an affordable but hotter 55 or 62gr. plinking load, though?

The best 3-shot group at 100 yards I got was an MOA from Winchester 64 grain power-core 95/5 (non-lead hollowpoint), and a 1.25 MOA using 55-grain Barnes TSX ("VOR-TX"). I'd feel comfortable hunting with either of these two rounds at this point. I got a decent 1.5-1.75 MOA group using 60-grain Nosler Partitions.
Anyone used any of these on deer out of a .223? I've heard that the Partition has a nasty tendency of splitting inside the body cavity, compromising the ability to get an exit wound. Granted, I've only heard this in the context of discussions about using the bullet in much more powerful rounds, on much bigger game (elk).

Using the Winchester, the bolt locked open on the empty mag as it's supposed to; that didn't happen with the 60gr. Nosler Partition, the 55gr. Barnes, or any other 55-grain I fired (granted, I didn't have a great sampling---didn't have time to go to the store, so I used some Silver Bear and Golden Bear 55's that my dad had, which are coated steel case with what probably figures to be a light powder load).

I have to say the recoil impulse on this rifle is incredible---I can see my hits, and the target never leaves the scope. The gas system and radial muzzle break work together great in tandem for this, especially considering how light the rifle is (a mere 6.2lbs before scope and rings).

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