Battle Rifle and Designated Marksman Rifle in One

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Battle Rifle and Designated Marksman Rifle in One

Post by Neptune Glory » Tue Jun 20, 2017 11:53 pm

Just gonna leave this here... consider the possibilities with a .308 semi-automatic rifle:

https://youtu.be/d4t5XkVQGGo
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Re: Battle Rifle and Designated Marksman Rifle in One

Post by RickOShea » Wed Jun 21, 2017 12:05 am

You must really like that video....

viewtopic.php?f=109&t=119697
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Re: Battle Rifle and Designated Marksman Rifle in One

Post by brothaman » Wed Jun 21, 2017 11:07 am

I'm not willing to give up mobility for 308 power. If I need that kind of power I am willing to grab a long bolt action and juice it all out of a 24" barrel. If I need a compromise then I'll run an AR-15 platform in 6.5 or 6.8 or just grab some 223 topped with Barnes TTSX or another brand's equivalent. Now,.. If I know that I'm going to shooting a whole lot past 300 yards, I'm might reconsider the .308. If 80% of my targets are under 300 yard, then I'm not taking on more weight.

I hate that Devo Optic. It's chunk. Bulky in the worst ways. What's the difference between putting all of the optic inline versus hang it half of the right side of the rifle. I'd rather sport a traditional format magnified optic and top with a RD. I find a slim rifle much nicer to carry. If you're sporting full mall ninja regalia then I'm sure that "hanging all over the place" devo is going to be "snaggy" Especially for wrong handed operational types. There are some things that I've found to be nearly absolutely true since I started posting on this board. 1. Warning shots are stupid, 2. the AR or AK + High Cap pistol combo is the only real choice, and 3. Keep your rifle simple.

What do I know, though? I'm just a shooting nerd with a keyboard.
Last edited by brothaman on Wed Jun 21, 2017 12:49 pm, edited 1 time in total.
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Re: Battle Rifle and Designated Marksman Rifle in One

Post by RonnyRonin » Wed Jun 21, 2017 12:32 pm

Brothaman pretty well summarized my feelings.

As a wronghanded person I can confirm that I do not want that optic, super excited to try it in Cabelas and took me way to long to figure out why I couldn't see anything. Even a snooty "right" handed person that wants to be able to switch shoulders should think twice.

From recent playing around I decided that as long as the main optic goes down as low as 3X I could live with either point shooting or offset irons for anything too close to use that (which turned out to be at least closer then 20yds), and I could save the money and weight for the offset RDS that always seemed like the bees knees.

If the logistics game for 5.56 wasn't so strong I could justify 6.5g as a compromise caliber, but not .308.
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Re: Battle Rifle and Designated Marksman Rifle in One

Post by 00dlez » Wed Jun 21, 2017 12:46 pm

Looked up the scope, but after seeing the cost and bulk off the side of the rifle... I'm with brothaman... Pass.

That said, it did make me think that a "bi-focal" scope could at least be interesting... I tried a google search but most of what I am getting is questions about using scopes while wearing bi-focals. I did find a low info article about the "Eagle-Eye 3.5" (http://schweitzeroptics.com/bi-focal/pr ... gle-eye-35), though... Seems less bulky at least, but 3.5x doesn't really do much for me, and neither does the $2,000 price tag. I can't help but think even a scrub like me could find a serviceable solution for half the price.
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brothaman
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Re: Battle Rifle and Designated Marksman Rifle in One

Post by brothaman » Thu Jun 22, 2017 7:07 am

RonnyRonin wrote:...Even a snooty "right" handed person ....
...If the logistics game for 5.56 wasn't so strong I could justify 6.5g as a compromise caliber, but not .308.

:clownshoes: Wrong is the Opposite of Right!

I do agree on the 6.5G comment. It's a big compromise unless your purpose is Hunting or Target shooting. It's 'spensive. The only time My 6.5G rifle sees light is for Zero Check and hunting. And right now its in pieces.
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Re: Battle Rifle and Designated Marksman Rifle in One

Post by FOG3 » Thu Jun 22, 2017 11:22 am

https://en.wikipedia.org/wiki/Mk_12_Spe ... pose_Rifle
https://en.wikipedia.org/wiki/M110_Semi ... per_System

The thing about the DMR concept is that rifles that address that tend to be on the heavy side, and in turn there's a reason why the Designated Marksman is a member of a squad and dedicated sniper teams tend to be two man teams. Teams which tend to find and setup in a position to do their work.

The average person with a AR-15 tactical rifle is probably better served by simply buying some 77 Sierra Matchkings, or close competitors, and mixing that in with other ammo options. For instance having a marked magazine loaded with them.

If you run these through a ballistic calculator you'll find due to the higher Initial Velocity and reasonable BC, these tend to shoot flatter than the 6.5 Grendel wunderwaffe loading out to the distance you're reasonably using either. Hence why after the Mk. 262 load was adopted rumblings about the Grendel, and the SPC, died down.

If you're shooting something like a 175 grain 308 loading to extended range, mind that you need to be setup in a fashion where pulling off the shot where the potential added range of that load matters, and that's not going to be a freehand shot by any stretch of the imagination. Also mind that high magnification scopes have a narrow physical space where you can actually see through them properly, which is part of why things like AimPoints are preferred for more common engagement ranges.

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Re: Battle Rifle and Designated Marksman Rifle in One

Post by brothaman » Thu Jun 22, 2017 12:05 pm

The Grendel was mentioned as a compromise. No one called it a cure. Ballistics and power are 2 different things. With a 200 yard zero, the 6.5G drops 7 inches at 300 yards while laying down 1100 ft/lbs. The 5.56 with the same zero drops 5.2 inches at 300 yards makes 750 ft/lbs at the range. Hence, the compromise part. Whaddya want? Power or Ballistics. The Trajectory difference is negligible out to 300. But, out to 400 the 6.5 drop is 20" vs the 556 dropping 24". And the 6.5 is still push nearly 1000 FT/lbs. The 6.5 G just gets better the farther you shoot. Both of those from a 16" barrel. Your MK262 will never do what 123 gr Grendel will do. But I don't think that its has to inside the 300 yard envelope.

But,.. I'm with you. The average/any person is better served to just stick with the 556. I don't even think 77 grain ammo is a necessary. I think any 62 gr soft point that your 556 rifle will shoot well is all one needs. Its cheap. Easy to find. Most factory ammo shoots well enough. Definitely good enough for 300 yard shooting of whatever. If the majority of your targets are beyond 300 yard, the make a compromise.
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Re: Battle Rifle and Designated Marksman Rifle in One

Post by FOG3 » Fri Jun 23, 2017 2:50 am

brothaman wrote:The Grendel was mentioned as a compromise. No one called it a cure. Ballistics and power are 2 different things. With a 200 yard zero, the 6.5G drops 7 inches at 300 yards while laying down 1100 ft/lbs. The 5.56 with the same zero drops 5.2 inches at 300 yards makes 750 ft/lbs at the range. Hence, the compromise part. Whaddya want? Power or Ballistics.
Why does it seems like no one on the internet passed High School Physics?

Power is the derivative of Energy vis-a-vis time, the British Imperial Standard unit you're referencing is ft-lbs ala Force[lb]xDistance[ft]**, and it is a measure of Energy. Speaking to the Potential Energy of a round is daft because Potential Energy not only doesn't translate perfectly into useful Work in this case, it by definition never can per the Laws of Thermodynamics.

As terminal ballistic failure modes are dictated by velocity, there is no reason for anyone to ever care about the precise ft-lb of a bullet for napkin calcs as it tells you nothing of value. Without extremely complex computer simulations it is computationally impossible to translate Energy into Work, and Work is the only thing that matters on that accounting side of things.

Along those lines from what I remember of the publicly available testing docs from the US Army's evaluation, the Norma Scenars that Alexander Arms were pushing to make the external ballistics of the Grendel look as good as possible had a pronounced problem of not initiating tumbling reliably, meaning the expected wound profile would tend to be an icepick style permanent wound cavity. Something that's not unreasonable to expect from a line of high end target bullets heavily optimized for a high BC. In turn the velocity of the Grendel at the muzzle tends to fall below what's considered the floor to initiate rifle high velocity wounding factors, ala 2,500 fps, so given a strong tendency to not tumble it's terminal ballistics will tend strongly resemble what you'd get out of a 25 ACP pistol firing solids.*

Of course you can drop from Norma Scenars in 6.5mm to bullets that may actually have good terminals, but those bullets won't have the "wonderful" BC and "wonderful" advertised external ballistics. I remain at a loss why anyone humors the Grendel at this point. Alexander Arms either never thought through what they were doing with it, or were little more than scam artists.***

The 77 grain Sierra Matchkings on the other hand showed a good tendency to tumble and their improvements in frag threshold criterion basically invalidated the 6.8 SPC, which had been developed specifically for that criterion.

*A 6.5mm Grendel bullet is 0.264". A 25 ACP bullet is 0.251" in diameter. If the former doesn't tumble, expand, frag, have velocity over 2,500 fps, or otherwise is able to enhance terminal balistics beyond simple icepicking the practical difference between the two is negligible. The research is pretty consistent that the temporary cavity in an icepick profile scenario has no meaningful effect.

** Mind the relationship where that comes from is an Integral.

***Something like 6.5 Creedmoor or 260 Remington is an entirely different kettle of fish. The issue isn't the 6.5mm bullet size, its pushing unsuitable bullets for role to cook the proverbial books.

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Re: Battle Rifle and Designated Marksman Rifle in One

Post by brothaman » Fri Jun 23, 2017 8:59 am

Firstly, I want to say where I screwed up a tiny bit. I had the calculator at +2 inch at 200 yard instead of zero at 200 yards. But, I did that for both 77 gr 556 and the 123 gr Grendel loads,.. so the comparison is good. I should have noticed though. The correct trajectory numbers are: 6.5G 123 Gr @ 2500 Zeroed at 200 yards drops 10 inches at 300 yards. Your MK262 usually gets a bit over 2600 fps in a 16" gun, but imma give you 2700 fps. 77 gr 556 (MK262) Zeroed at 200 Yards is down 9 inches at 300. The "power" each cartridge makes at 300 yards is unchanged. 1100 ft-lbs for the 6.5 and 700 for the Mk262. It ain't a single digit difference.

"Why does it seems like no one on the internet passed High School Physics?"


Pass it?! Fuck that, I didn't even take it. I'm a workin' man.

But, arguing definitions/semantics instead of focusing on discussing an issue is petty. You knew what I meant. You're basically saying I'm stupid 'cuz I can't won't talk purdy. Take out arguing semantics and incorrect terminology and lets just assume power means "how hard it hits". :B Discussing cartridge performance with Average Joe Trigger Snatcher, if I say 50 BMG has more "power" than .243 Win then he and I are on the same page and can carry on with the business talking about something. It's just a matter of "Do you want to talk guns or bitch about thinking you're the smartest guy to pick up a keyboard" So,.. can we also assume, for the mentally defective, that Ballistics and trajectory refers to a bullet's drop from a particular zero? Can you get down with the plebs for the sake of discussion?

"there is no reason for anyone to ever care about the precise ft-lb of a bullet for napkin calcs as it tells you nothing of value."
What? Ft-lb numbers tell you plenty. A ft-lb comparison tells you is the difference between two cartridges on the business end of shooting. Is it a small difference or a large one? A difference of 100 ft-lbs it pretty small in the rifle world. But a difference of 350 ft-lbs jumps beyond the minutiae of 2 to 5 to even 100 ft-lbs difference. The difference is 350 ft-lbs. That's not negligible. That's a big fat step up.

Napkin calculations or not a heavier bullet at certain a speed makes more "power" at distance than a lighter bullet of a certain speed. My BHW 16" Grendel (which I'm not a diva about. I think I've mentioned before that I wouldn't miss it if it were gone.) does make an average 2500 FPS with Hornday loaded 123 SSTs. I have a chronograph. I tested that shit. I will admit that the average speed most folks get for 123 gr 6.5g Hornady ammo is around 2450. It still only drops around 10" and makes over 1000 ft-lbs. My handloads allow me to push just under 2600 with CFE223. However, my best accuaracy is around 2500 with the 123s. My 129 gr hand loads still make 2500 fps. You see, I left engineering and physics class behind and did that in the real world. I have yet to see any tumbling. Maybe its the barrel. Its a 1/8 twist. I don't know if the 1/9 is the typical or if it has issue stabilizing heavier bullets. I was really only concerned with what my rifle can do. I don't want it to tumble. I'm not shooting FMJ. I want get expansion to kill animals. The bullets I'm discussing don't tumble and they do expand well. The 123s are made for shooting at Grendel speeds. But, I think some of your rambling regarding 25 cal bullets may be dependent on shooting FMJ and you mentioned "icepicking". Honestly, it doesn't matter. More "power" is more "power". You're trying to say for some reason the more isn't more. More is always more. How much more may or a may not make a thing better or worse for the effort, but more is more. More ft-lbs = better penetration. It makes a better ice pick. The farther away your target is, the better your ice pick needs to be. We can start in on sectional density numbers, but in the end it just matters that more is more.

"The issue isn't the 6.5mm bullet size, its pushing unsuitable bullets for role to cook the proverbial books."
As I said,.. I've shot my rifle over a chronograph. I know where it hits at 300 yards. I know what it does. I know my limitations, too. As it relates to this cartridge, the only thing I'm cooking is venison. I didn't rely on Alexander Arms for anything. I'm not responsible for what Alexander Arms does or did. I don't own anything they make (but I do like those handguards). Technically I don't even have a 6.5 Grendel Rifle. It's labeled .264 LBC (thanks, Les). Yes, bullet selection is important. No one can deny that. But, as I can't man-up and go fight a war I'm not stuck with FMJ ammo. I think that's the rule, correct? Military shoots FMJ only? Either way, the better Ice Pick analogy applies. Your issue will Bill Alexander and the Grendel have no place in this discussion.

Now,.. all that said. I have hunted extensively with the 223. I know what it does and what it doesn't. I've got no issues with its performance. I'm happy to kill deer with 223. Even big ones, although a 200lb deer would be a monster in my area. A good soft point bullet from 55gr up to what ever is all that's needed along with a lung shot. Its not always DRT, but I've found they don't wander far. I absolutely agree with on on your original observation about 223 being the better choice for the average shooter. I'm average. I'm fine with that. I even said that the 6.5G is a compromise. It's costly. Likely more prone to malfunction in an AR as it really isn't the standard for anything. Less Carts in the mag. A little more recoil. Finding ammo in store can be a headache. No argument, if I was told today that I could only ever have one rifle for the rest of my time on this earth, It'd likely be an AR in 223. Well,.. that or a 30-30 just 'cuz I like it.
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Re: Battle Rifle and Designated Marksman Rifle in One

Post by Dabster » Fri Jun 23, 2017 12:28 pm

While it has a funny shape, that scope has some nice features. However it doesn't have half of the innovations I was led to expect at this late date. Where is the auto-range finder and adjustment? Where is the wind-detection and auto-windage? Heck, I don't even see thermal or night vision!

I realize putting all of this in something on top of a rifle will be heavy but.. but.. How are we going to defeat the robots?
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Re: Battle Rifle and Designated Marksman Rifle in One

Post by RonnyRonin » Fri Jun 23, 2017 1:00 pm

brothaman wrote: But, arguing definitions/semantics instead of focusing on discussing an issue is petty. You knew what I meant. You're basically saying I'm stupid 'cuz I can't won't talk purdy. Take out arguing semantics and incorrect terminology and lets just assume power means "how hard it hits".
I think you misunderstand his attack, he isn't playing a semantics game, he is saying that "how hard it hits" is not super meaningful information. I used to use ft/lbs when comparing ammunition but have largely stopped as plenty of different sources have convinced me it isn't all that meaningful either.

The end goal is to disrupt tissue in a terminal way, and permanent wound cavity is the best way we currently have to measure this, and ft/lbs is not strongly correlated enough to the size of the permanent wound cavity to be worth discussion most of the time. Penetration and expansion are the meaningful factors there, and while certainly ft/lbs has a correlation with penetration it still isn't direct.

If you have bullets for your 6.5 that shoot flat, expand and penetrate well, then that is what matters, It does sound like his critiques of 6.5 are largely applicable to FMJ only in any case.
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Re: Battle Rifle and Designated Marksman Rifle in One

Post by brothaman » Fri Jun 23, 2017 3:59 pm

I didn't misunderstand anything. Foggy didn't like what I said about 6.5g vs mk262 so he called me uneducated and then tried to beat me with terminology. That's petty. He was on my ass because he has some chip on his shoulder about Bill Alexander . Whatever. I'm saying that ft-lbs is a good data point for understanding the potential of what a cartridge can do. I'll agree, ft-lbs doesn't tell the whole story. When one starts changing bullets, that changes everything. But if you don't have all the bullets and all the loads and all the information and real world experience with a cartridge, then ft-lbs is a damned fine start for understanding what's going to happen. And, you have to compare apples to apples. You can't make a comparison like this where one has an expanding bullet and one doesn't. When you discuss wound cavity, I totally get it. But the wound cavity made by FMJ isn't going to be like that of an expanding bullet. So, then were down to discussing pure bullet performance. Ok, now let's look at it like this. Let's get away from the .264 bullet. Caliber doesn't matter for this comparison. 270 Winchester vs 6.8 SPC both shooting,.. er,.. say a 120 gr SST. Now how does ft-lb play into helping you predict what a wound cavity would look like?

And notice, Ronny,.. you and I haven't called each other any dirty names or made fun of each other. Discussion is a good thing. I might learn something.
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Re: Battle Rifle and Designated Marksman Rifle in One

Post by brothaman » Tue Jun 27, 2017 8:07 am

You know, I've been reading up on this a good bit in the last few days. There are so many factors in measuring the killing potential of a cartridge I don't think anyone will be 100% correct. I didn't realize how strongly debated the question is. But, it seems that comparisons are best when the cartridge are similar. You can try to compare 243 Win and 454 Casull . They both make roughly the same FPE. But the 243 will never expand enough to do what the 454 does. The 454 wil never do what the 243 does at distance. FPE won't help you make any decision. But, comparing Spire point rifle bullets of the same type (FMJ, JSP, etc.), the FPE has more meaning. Like comparing 308 Win with different bullet weights and speeds or say,.. choosing between 243 Win and 25-06. FPE can be a helpful bit of data there. But, there's the completely subjective stuff. Regarding wound channel. Some guys want complete pass through, some don't. Some like a cup and core bullet and some will only shoot a bonded bullet. The wound channel made by a heavy solid isn't like that of a high speed expanding bullets. A heavy solids might cause a ton of damage or it might punch a clean hole. I saw a gel test between 454 and 44 mag on the YouTube. There was actually much less disruption than I thought I'd see. Penetration differences with in 1-3 inches of each other. The gel block didn't' make a dramatic bounce and wave. But, I did see some gel test with 223 and Barnes bullets. Obviously not the penetration of the 454 or the 44, but my my did that jelly roll. I saw a 375 H&H test,.. bullet just flew out the back of the gel. For high speed small bore solids, depending on Tumble isn't the best idea. ...

Imma just stop. The variations and combinations of factors are nearly endless.
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Re: Battle Rifle and Designated Marksman Rifle in One

Post by minengr » Fri Jun 30, 2017 2:55 am

Well, it is physics.

Bullet weight, BC, MV and whatever else get plugged into an equation and it spits out the drop. All those programs are doing the physics for you. Same thing with "Power"/energy.

KE = 1/2MV^2 = the kinetic energy "power" of a bullet is 1/2 the mass of the bullet x the velocity squared. So yes, a 50 BMG shooting a 750gr bullet with a muzzle velocity of 2800fps is going to have more energy/power than a 75gr .243 going 3375 at the muzzle.

243 vs 454

at muzzle - 243, 75gr, 3375fps - 1897ft/lbs
at 100 yards - 1564ft/lbs

at muzzle - 454, 300gr, 1900fps - 1813 ft/lbs
at 100 yards - 1210 ft/lbs

Ballistics and "power" are related and there are infinite factors that come into play when making comparisons. When discussing stopping power/killing power/killing potential you open up a host of issues because I've yet to see a universally agreed upon definition. Heated discussions of wound channel, retained energy, hydrastatic shock, etc normally follow. How long has the 9mm vs 45acp debate been going on now? For me, bullet choice is more important than head stamp and placement trumps all. But it's getting late and my head hurts.

P.S. I'd never buy that scope.
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Re: Battle Rifle and Designated Marksman Rifle in One

Post by brothaman » Fri Jun 30, 2017 7:50 am

minengr wrote:... P.S. I'd never buy that scope.
That is all that matter. That scope eats ass.
But if I won it at a church raffle, then it'd be the greatest thing ever made.
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