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supertux1

Yet Another Build Thread - My First Large Frame AR

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9 minutes ago, Matt.Cross said:

The whole idea of venting gas from yet another location on the AR makes no sense to me. Ideally, you'd have as much gas as possible going towards the muzzle, with just enough going to the BCG to cycle. What's with just dumping hot gas forward of the optics/sight system when there's no need?

I think it's for specific suppressed applications where your support hand location / thermal optics aren't going to be an issue.

Probably okay for bench rest shooting in the day time with your support hand under the stock or on a vertical foregrip, but would probably suck for applications where your offhand is on the guard over the thing, or if you mind cleaning fouling from yet another part of your rifle. (The last part doesn't really bother me so much, tools not jewels.)

That being said, this is a part primarily designed for AR-15's and not our large caliber applications so there's always that. 

This guy did a lot of testing with it, fully semi-automatic and suppressed, albeit on the small frame:

JP's blocks, similarly priced and engineered for 308 do not feature this bleed off capability, 

 

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7 hours ago, jtallen83 said:

Works fine using the restrictive side of the block, just not the by-pass mode which is what the big selling point is. On restrictive mode it is really no different than others on the market.

Also when on bypass with a suppressor it blasts the can with a jet of hot gas, no big deal unless you worry about can finish or you run a cover on the can.

Good to know. Based on this, I am strongly considering one of the JP blocks which is restrictive only and will probably fit better under the handguard I want from them.

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Finished the lower tonight. LPK didn't come with safety selector detente (no, I didn't launch/lose it) so I borrowed one from an AR-15 kit. 

I launched the front takedown detente, but it bounced right off the window and into my lap. :) 

(Interesting way that one goes in through the front as opposed to the AR.)

Basic function tests work ok, nothing out of the ordinary. Silent captured spring is smooth, heavy bolt carrier group slams forward with authority. 

Coming in at 6 lbs 2 oz. unloaded no optic, no barrel or handguard yet. 

Add 3lbs for PR 22" 6.5CM barrel, 1 lb for the XL JP handguard rounds it out to a little over 10lbs

Add 5pounds for bipod and optic, this is gonna be one heavy sucker. :) 

 

 

 

 

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On ‎6‎/‎12‎/‎2018 at 8:57 PM, shepp said:

I think it goes somthing like don’t complicate poop with complicated poop

 

They didn’t sell you the under coating too did they???

Ill never forget the undercoating treatment.....bought a new 1980 vette...they were slow pieces of $hit because of all the emission pumps and crap...so my new black vette...yes I fell for it...got the undercoating treatment..holy crap...the amount of weight that that crap added to the car...and everything under there was covered in that $hit...that was one of many stooopid moments in my life !:laffs:  Wash

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2 hours ago, washguy said:

Ill never forget the undercoating treatment.....bought a new 1980 vette...they were slow pieces of $hit because of all the emission pumps and crap...so my new black vette...yes I fell for it...got the undercoating treatment..holy crap...the amount of weight that that crap added to the car...and everything under there was covered in that $hit...that was one of many stooopid moments in my life !:laffs:  Wash

4

You bought the extended warranty too didn't you? Salesman told you it'd explode and you'd be homeless if you didn't right? 🙂

 

 

So I ended up ordering the rest of the parts to complete the upper:

  • Proof Research PR10 Carbon Fiber CamGas 22in 6.5CM Rifle + 2" + gas tube. 
  • JP Enterprises RC Handguard for DPMS LR-308, XXL Length, Black JPHG3-7D-RC
  • JP Enterprises Tactical Rail Kit - 2-inch Front Sight Tactical Rail JPTR-FS
  • JP Low profile .875 2-piece Gas Block JPGS-10D
  • Thunder Beast CB Muzzle Brake (going with the Thunder Beast can)

Going to pick up some headspace gauges, crush washers, bore guide etc... other bits and tools as I need them.

I found a shitty red dot and a mildot scope in my parts box from an older rifle that will be ok for 100 yards barrel break-in.

Picked up some 6.5/.260 jags and cleaning rod from Cabela's last night. 

 

 

 

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On 6/8/2018 at 8:02 PM, supertux1 said:

Yes, iron sights. I don't really count 5.56 a real long-range precision projectile but some guys have a lot of fun accuratizing their AR-15's and what not. It is certainly a good caliber for the ranges around here.🙂

 

Just so you know, all laughing aside...  I have two 5.56 guns that will run a target at 850 yards all day long, just about with boring regularity.  They just don't miss.   I have one that will do the same thing at 950 yards...   It's a beast, with Hornady 75gr HPBT Match projectiles...  

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5 hours ago, 98Z5V said:

Just so you know, all laughing aside...  I have two 5.56 guns that will run a target at 850 yards all day long, just about with boring regularity.  They just don't miss.   I have one that will do the same thing at 950 yards...   It's a beast, with Hornady 75gr HPBT Match projectiles...  

What's your load and barrel twist? I had gotten very good results with the Hornady 75 gr HPBT, but stopped experimenting with them a while back.

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3 hours ago, mineralman55 said:

What's your load and barrel twist? I had gotten very good results with the Hornady 75 gr HPBT, but stopped experimenting with them a while back.

Both 18" guns are the Mk12 Mod 0 and the Mk12 Mod 1.  The Mod 0 has a Nordic Components 1:8" twist stainless match barrel, .223 Wylde chamber, with rifle gas.  Nordic doesn't even offer this barrel anymore, and that's a shame.  The Mod 1 has a Ballistic Advantage Mk12 SPR barrel, 1:8" twist stainless match, .223 Wylde chamber, rifle gas.  Both barrels are very serious shooters.  Remarkable. 

The 20" gun runs Yankee Hill upper and lower, and barrel.  It's the 1:7" twist, NATO chamber, heavy barrel, steel, rifle gas, and it is badass.  It's just ridiculously accurate. It is one heavy gun, though.  Damn, that thing is a pig.

I've never refined the specific load for the 20", and just run the same load in all three.   Lake City NATO brass, CCI 41 primers, Accurate 2520 powder at 25.1 grains, and Hornady 75gr BTHP Match projectiles.  That load is a tack driver in those guns, and it keeps the 18" guns over 2750 fps.  :thumbup:

I want to experiment with Accurate 2495 some, and see how it does.  My backup powder (and my original loadings for these guns) was same components above, with 24.2 grains of Varget.  When Varget got scarce several years ago, I went to RL-15, and it was the exact same charge weight, 24.2 grains.  Both great loads. 

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12 hours ago, 98Z5V said:

Just so you know, all laughing aside...  I have two 5.56 guns that will run a target at 850 yards all day long, just about with boring regularity.  They just don't miss.   I have one that will do the same thing at 950 yards...   It's a beast, with Hornady 75gr HPBT Match projectiles...  

How big is the target and what are your groups like?

Does it have feeding issues with those big bullets? I've seen some long 77 grains that are amazing out of a 1:7 twist, but need hand chambering.

That bullet is gonna drop 240 inches @ 850 yards and with a 5mph crosswind, 23" left/right drift. 270ft-lbs. 

.308 Hornady 178gr HBPT @ 2600 fps drop 252 inches @ 850 yards. 5mph crosswind, 17.5" left/right, 770 ft-lbs.

6.5 Hornady 147gr ELD @ 2690 fps drop 204 inches @ 850 yards. 5mph crosswind, 11.5" left/right, 946 ft-lbs.

 

Edit: To be fair, the .308 barrel is going to last longer. 

 

 

Edited by supertux1

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34 minutes ago, supertux1 said:

 

Good to know! I'll pick a set of those up.

( I was looking at those when I was considering the M4-72 )

 

Might find them cheaper elsewhere, that was just the handiest link.

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2 hours ago, supertux1 said:

How big is the target and what are your groups like?

Does it have feeding issues with those big bullets? I've seen some long 77 grains that are amazing out of a 1:7 twist, but need hand chambering.

That bullet is gonna drop 240 inches @ 850 yards and with a 5mph crosswind, 23" left/right drift. 270ft-lbs. 

.308 Hornady 178gr HBPT @ 2600 fps drop 252 inches @ 850 yards. 5mph crosswind, 17.5" left/right, 770 ft-lbs.

6.5 Hornady 147gr ELD @ 2690 fps drop 204 inches @ 850 yards. 5mph crosswind, 11.5" left/right, 946 ft-lbs.

 

Edit: To be fair, the .308 barrel is going to last longer. 

 

 

18"x30" IPSC steel torso - man-sized target. Groups are under or at 1MOA, from all 3 of those 5.56 rifles...

However, you're gonna throw out .308 Win and 6.5 Creed numbers, and try to act like that's some kind of victory over a 5.56 gun?  You gotta be out of your mind.

You're not comparing apples and oranges.  You're trying to compare apples to hammers.  It's ridiculous. 

Did you or did you not say this:

Quote

Yes, iron sights.

I don't really count 5.56 a real long-range precision projectile but some guys have a lot of fun accuratizing their AR-15's and what not.

 

Edited by 98Z5V

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2 hours ago, supertux1 said:

Does it have feeding issues with those big bullets? I've seen some long 77 grains that are amazing out of a 1:7 twist, but need hand chambering.

You're showing what you don't know, right with that statement.  There is zero reason you can't load the 77 SMK to magazine length, and have it reliable feed right out of the magazine, and run a semi-auto perfectly fine.

So, I'd like to know what 77gr projectile you were messing with that couldn't be loaded to magazine length.

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45 minutes ago, 98Z5V said:

18"x30" IPSC steel torso - man-sized target. Groups are under or at 1MOA, from all 3 of those 5.56 rifles...

However, you're gonna throw out .308 Win and 6.5 Creed numbers, and try to act like that's some kind of victory over a 5.56 gun?  You gotta be out of your mind.

You're not comparing apples and oranges.  You're trying to compare apples to hammers.  It's ridiculous. 

Did you or did you not say this:

 

So you are claiming you've got sub-MOA @ 850 yards (8.5" groups or under) from a 5.56 when a little ballistics math shows that even a mild wind is going to throw that exact bullet and load off 24" left or right at the target? (That was why I posted the other bullets, for comparison, because I find it hard to believe you can group as you say you can.)

I have no doubt you can hit a target of that size more than once, eventually, -it is still supersonic and stable-, but unless it's a perfectly nice day at the range I don't see very many tight sub-MOA groups happening. It doesn't matter if you shoot the thing out of a golden barrel blessed by Jesus himself with the finest powder packed up to the neck, it's still a tiny inefficient bullet going through all that air. If that's what you like to do, more power to you, I would just like to try something else now.

 

 

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1 hour ago, 98Z5V said:

You're showing what you don't know, right with that statement.  There is zero reason you can't load the 77 SMK to magazine length, and have it reliable feed right out of the magazine, and run a semi-auto perfectly fine.

So, I'd like to know what 77gr projectile you were messing with that couldn't be loaded to magazine length.

I've messed with ones that were hand loaded specifically for the chamber they were to be fired in, right up to, and into the lands. 

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22 minutes ago, supertux1 said:

So you are claiming you've got sub-MOA @ 850 yards (8.5" groups or under) from a 5.56 when a little ballistics math shows that even a mild wind is going to throw that exact bullet and load off 24" left or right at the target?

You're making excuses for wind.  I'm telling you that if you're shooting those distances, you need to know how to read the wind.  Once you've got the wind, and you adjust for it, there's absolutely zero reasons for you not to be able to get a gun that shoots under 1MOA at 100 yards, to shoot that same thing at other distances. That's called mechanical accuracy.  The rest is up to you.

If you had 77s that were loaded "right up to, and into the lands," then there's something wrong with the loading, and it wasn't out of an AR.  It might have been a bolt gun.  You don't load "up to, and into the lands."  You need a jump. Determining that jump, per barrel, is where you find your accuracy potential.

That is what I'm telling you...

Good try, though.  :thumbup:

Edited by 98Z5V

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Tux, you see this gun right here?  12.5" 6.5 Grendel.  At 845 yards, it was 10.6 mils of drop.  This thing was center-massing all the impacts on full-size IPSC steel.  That's 18" wide. So if it's center-massing an 18" wide plate of steel, is that pretty damn close to1MOA?...  Yeah it is.  I wasn't the only one to do it, either.  Someone that had never shot a Grendel before hopped on it, and put a full mag right in the same places - right in the middle of the steel.

Oh, and yes, there was wind. 5~8mph, from the right, full value...  Running a Leupold 1.5~4 scope, at 4x, no less...   :thumbup:

 

P1060143.JPG

Edited by 98Z5V

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@850 yards, 1 MOA = ~8.9 inches not 8.5

Additionally, mean average spread for stated groups were witnessed to be <6" to which is approximately 2/3rds MOA.

Saying "under 1 MOA" doesn't imply hit-and-miss MOA accuracy, it implies some humility on the part of the claimant.

Wind is a variable that speaks nothing to mechanical accuracy, only the maximum potential POI shift for a given wind speed.

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I pulled every single 77gr projectile made for .224 diameter.  None of these get loaded longer than 2.250".

22 Caliber .224 Diameter Nosler 77 Grain HP Boat Tail Custom Competition
OAL 0.980"

22 Caliber .224 Diameter Nosler 77 Grain Boat Tail HP With Cannelure Custom Competition
OAL 0.980"  

22 Caliber .224 Diameter Sierra 77 Grain Hollow Point Boat Tail Matchking
OAL 0.994"

22 Caliber .224 Diameter Sierra 77 Grain HP Boat Tail Matchking Moly
OAL 0.994"

22 Caliber .224 Diameter Sierra 77 Gr HP Boat Tail Matchking w/ Cannelure
OAL 0.994"

22 Caliber .224 Diameter Sierra 77 Grain TMK Tipped Boat Tail Match King
OAL 1.072"

Berger does 3 in 77 Gr - Match BT, Match Target BT, and OTM.
OAL 1.029"

Lapua makes 7 x 77gr projos, in the lengths of 1.043" and 0.950"

Barnes makes 4 x 70gr all copper solids that are 1.037", and they all get loaded to 2.250"...

Here's what Sierra says about the 77TMK, the longest one of the bunch...

https://sierrabulletsblog.com/2016/04/20/seating-concerns-with-sierra-tipped-matchking-tmk-bullets/

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1 hour ago, supertux1 said:

So you are claiming you've got sub-MOA @ 850 yards

For the record...  I have a bunch of them.  :thumbup:

What caliber do you want to talk about, first?...  

Edited by 98Z5V

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On 6/15/2018 at 1:26 PM, supertux1 said:

Does it have feeding issues with those big bullets? I've seen some long 77 grains that are amazing out of a 1:7 twist, but need hand chambering.

I've loaded 1000s of SIerra 77 grain BTHP and Nosler 77 grain BTHP, all to magazine length. Perfect functioning. Never had a bit of trouble.

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