Thanks Chris,

I'm working on a 20" AR "hunter" 7mm ARk for one of the guys (Tom) that was on the hunting trip, should work great on whitetails....The loads for the 7mm ARk out of a small pattern double-stack AR are running up over 90% of a 7-08 24" bolt-gun ....I've built four 7mm ARks including a CZ bolt-gun, which looks like my daughter has laid claim on it so I guess at some point I'll end up doing one for myself....It shoots pretty sweet, the last three 100yd groups I shot with it Sunday were one ragged hole...






The 7.62 is one of the 20" Noveske barrels from the early barrel run, I think I posted a couple pics of it a while back....20" 1:12P, 1 1/2# Jard trigger, 110 TSX @ 2,650fps

The green .25 is my daughters rifle, she put a thread up on it a while back, but between school and a bunch of other stuff she hasn't got to post on it since...18" 1:12 McGowen, JP trigger, 80gr TTSX @ 3,000fps



Both the 7.62 and .25 were loaded to 2.250"




the 7.62 has a Mark IV 4.5x14 TMR, ran most the time around 9~10 power, took the shot on the doe @ 14 power

the .25 has a Nikon 250 BDC 3x9, used it on 9 power

Thanks again,

Kurt

While on the hunting trip a few weeks back, Tom and I started knocking around ideas for a AR build for him.....he had a Olympic 300 FB a few years back, so
he wasn't new to the AR but was looking for something with more power and already had in mind for him what would be a good whitetail cartridge
( 110 to 120 gr @ 2,800 to 2,900 fps), from much success taking several deer with his really neat Mauser..... told him I thought we had just what he was looking for.....

So over the last week or so I started pulling the parts together to build him a 20" 7mm ARk......



Ended up going with a barrel blank manufacturer that I had only bought two other barrels from, the previous two shot real well ( like .8 at 200yds ) and so did this one.....
It is a 20" 1:10 .875 block.........probably gonna be where the next 7.62x40 barrels come from ....

Started with reduced loads and worked up 110 TNTs a little over 2,800 fps, still a mild load with the 2230....were grouping .500" at 100yds with a low round
count on the barrel so things looked really good.....with the 110 TTSX  or 120 Noslers this will be an easy 300 to 400 yd capable whitetail black rifle....A little
more tuning and it will be ready for the next hunt....



c'mon Tom, it ain't that difficult .......and no,I didn't hide your golfcart....I would never do that ....you must of forgot where you parked it....

Really impressed with todays trial run, .500 in 100yds with bulk drop load is unreal. Just wait til barrel is broke in and start pushing bullets back and forth this should become a real tack driver. Your load data and consistency are dead on (no pun intended).Numbers are dialed in.Thanks so much for the help. I never forget where I park the golf cart, it was your jungle juice that influenced your placement of my transportation, now fess up.

"KILLIN END THIS WAY >>"

Love it...

Hello 762x40,
Do you have load data for the 257AR Kurt? I was wondering what the difference is with the 25x40.

25ARk (7.62x39 or Grendel parent case)
.25x40 (.223 parent case)

yeah....just not in front of me right now, I just got out of the most stupid ass movie I've ever seen....skyline

ARk = AR platform k = kurz  (short, shortened 7.62x39 or grendel brass)......c'mon AR Kurt ?  even I think that would be a little narcissistic

The 25 ARk shoots really great, it's just not that much of a hot-rod.....other people have their version out there so I hadn't posted much on it ( 257TED, 25 Grendel, 25 PPL, etc....)

just comparing a velocity node.....the 25ARk will push a 100gr SMKs over 3,000fps with 30something grains of 2230....the .25x40 will push a 85BTBT over 3,000 fps with 20something grains of 1680...

Thanks for the data. The comment on the name was not intended to be narcissistic. It was intended as a compliment to you as the designer. (ie. PPC)

I put a little smiley face  thanks...

The .25 shoots good and everything, but on the Grendel case, and also the .223 case to some degree, can be a little difficult to hot-rod...

Out of a common 16 to 20" barrel, to hit a velocity/energy datum point, loads that have to be pushed to the edge to hit that point with the .25, are effortless with the 6.5 or 6.8....the .25 can make up a little with BC using those useless long bullets ,  but at the ranges I shoot at ~ 200yds, BC becomes nearly a moot point...

I thought it was pretty funny .....Tom gets the credit for that one.....The engraver I use now has gotten used to strange requests, guess that's part of the fun to custom parts....

Tom,

I also have a 20" 7ARk, lighter contour but very similar.  What loads have you tried in it?  I have just stayed with the 120 Noslers and 2230, prints on paper nice and runs right at 2,800fps.  I just haven't had much time to work up loads.  Hoping to make a hunt with it over the Thanksgiving holiday.   Considering the 110TTSX due to some of the close shots I have had to make in the past and the Noslers blowing up, I know others are keen on the Barnes bullets.

Kurt, I might've missed it but have you posted what kind of numbers you would get with a 7mm ARk out of a 16" barrel? I'm looking for a long-range competition gun but would like to keep the barrel short and light enough to be good for shorter range run-and-gun competitions. I imagine barrel life is much better for the 7mmARk than the the 6mm AR Turbo and I just don't see myself getting what I want out of the 223 parent case at 400+ yards.


-B

I hadn't posted any 16" numbers....with a 110gr it will make a tic over 2,800 out of a 16" mid-length gas system.......

how far are you looking to shoot....the 120s have a better BC and will make major power factor if that is needed....

Most of the AR constrained intermediate cartridges have pretty decent barrel life, not much overbore there, some mechanical factors can come into play but overbore generally isn't one ....you wouldn't get into generally accepted overbore standards on the Grendel case unless you went down to around .17 cal. to .20 cal...., around ~ 1,000 - ~ 1,500 overbore index.....the larger bore 6.8, 7, .30cal on the Grendel case just help make horsepower in the frame size we're constrained by...

Depends on what you're wanting to achieve at 400yds on a .223 parent case....

the .223 is no .25STW, but it can be pretty viable in several roles......

Short answer is I'm just getting things together to jump into the competition shooting world, and in FL that will mostly mean short-range (<100 yards) run-and-gun competitions, 3-gun/multi-gun stuff. But I definitely want to explore long-range shooting (500+ yards) too, or at least have a rifle better equipped for when a run-and-gun match features a surprise 300 or 400 yard stage. Being a relatively inexperienced rifle shooter, I'd think giving myself the advantages of bigger bullet and more horsepower would be a good thing, but if I can get it out of a 223 case, or even out of the 223... I can stand being 'advised' one way or another.


-B

I don't know about others, but I went with the 7 ARk for hunting.  plenty of horsepower, very strong hitter.

What little I know about the 3-gun matches around here, most of the guys who win use .223 for speed.  The 7 ARk doesn't recoil hard by any means but compared to a .223 tuned for speed I would think you would end up paying a recoil penalty.  Unless you think you could make up for it by hitting major power.

If you're new at it I'd follow the guys in the front of the pack and do what they do for a while, the stopwatch doesn't lie.

There others here much more qualified to give you advise on 3-gun, or run-and-gun....I could maybe tell you a little about
walk around-and-hammer the hell outa somethin'

The ARks were really laid out for hunting,  I would think a completely different chamber and rifle  set-up would be needed for the rigors of competition....

I know there are some guys using a .30 cal variant on the Grendel case in 3-gun, but I think they are looking for the major power factor pay-off...we've shot and shot against  .30 cal PPC / Grendel in our bolt-guns in 'for score' competitions for years, but that's a way different world and operating pressure than 3-gun....

I just see a lot more guys using .223....

just because      

Cool. What caliber?

.25x40

Heck My brain is fried after reading this whole thing but holy crap Im wanting a 7mm ark and 25x40  whre can I get a barrell and dies for this cartridge

.25x40mm 10" barrel info.....



10" 1:12,  custom length under handguard gas systems, KX3




from 75 Hornady to 115 Berger, feeds 100% in either HK 416 and/or beta mags.....




.25x40mm, 115 Hunting Berger, 2.250" COAL




standard disclaimer: use reloading data at your own risk.

20gr. Accurate 2230, 115 Berger, 1,950 fps.

18gr. Accurate 1680, 115 Berger, 2,166 fps.
18.5gr. Accurate 1680, 115 Berger, 2,187 fps.
19gr. Accurate 1680, 115 Berger, 2,245 fps.
19.5gr. Accurate 1680, 115 Berger, 2,286 fps.
20gr. Accurate 1680, 115 Berger, 2,312 fps....with a BC of .479, it holds 1,000ft/lbs out to 200yds from a 10" barrel.....

20gr. Accurate 1680, 100 SMK, 2,476 fps.
20gr. Accurate 1680, 85 Nosler, 2,535 fps.
20gr. Accurate 1680, 80 TTSX, 2,577 fps.
20gr. Accurate 1680, 75 Hornady, 2,510 fps. this load is a good indicator of the weight range of 1680 in the 10" barrel, 10gr lighter bullet but lower velocity....

given my druthers, the 80 TTSX right at 2,700fps from the 10" would be my go-to......but it does have a pretty good "pop" even with the KX3.......

Those are some very impressive numbers from a 10" barrel.  I've been working up loads for my .25-223 and have to say it seems the .25x40 is more efficient as you are getting velocities in a 10" that I'm seeing in a 16".  I've also noticed that in the .25-223 AA1680 is inconsistent and a bit fast for the .25-223 but seems to work very well in the .25x40.  I get 2300fps with 20.0gr of 1680 with a 100gr SP and 2500fps with 20.0gr of 1680 with an 87gr HotCore.

Are these differences due mainly to the location of the shoulder?  I know you mentioned somewhere along the way that the shoulder location and case size affected the rise to peak pressure and I'm wondering if that is what is at work here.  Would that make the cartridge better with the faster powders which in turn makes it more efficient in short barrels?

Just curious how you work your voo doo...  

Here's an older post on 1680 from 2009.......





VooDoo....I never posted any info on that one....it's still waiting in the wings....I'd like to get my hands on a Knight PDW to chamber it in, but that'll probably never happen.....

Of the five bullets fired in the 10" the only one I would consider near a max load is the 115.....plenty of performance left in the others....some of the the loads go up over 23 grains...

Some people discount using a 2" slower twist barrel with the .25, I'm not one of them.....land .251" - .2515" helps....


From the 7.62 thread but it applies here also.....



The gas system length and diameter on the 10" are a little unique, used as a tuning tool I've seen where it can add as much as 50fps on some barrels...not much, but when you add it to other refinements a 100fps can be realized in the 10" barrel, which is significant compared to similar cartridges in the same length barrel....

I sold a couple .25 reamers a while back so there are a couple guys out there making them, may see them here.......I heard the 7 is in the process of being copied, so keep your eye out for that one....

I've made several local.....was at the range Sunday putting the finishing touches on a friends 7ARk.....looks like it's gonna be his go to whitetail rifle......easily pushes the 110 Barnes at 2,800fps, which is ideal for the ranges that he shoots at....

If the weater holds, I'm gonna do a little more .25 10" barrel testing......was approached by a SBR manufacturer looking to get a .25 running for them, pretty interesting project............so far the 80TTSX and the 85Nosler are looking very good.....

GB, you ever get that 6.8 running?

I recently built a 18" that was pretty neat....have it shooting over 3,000fps with a couple different 85 and 90 loads....

10" .25x40mm info......

20gr. Accurate 1680, 85 Nosler, 2,537 fps.
20.5gr. Accurate 1680, 85 Nosler, 2,565 fps.
21gr. Accurate 1680, 85 Nosler, 2,633 fps.
21.5gr. Accurate 1680, 85 Nosler, 2,649 fps.
22gr. Accurate 1680, 85 Nosler, 2,676 fps.
22.5gr. Accurate 1680, 85 Nosler, 2,730 fps.


20gr. Accurate 1680, 80 TTSX, 2,577 fps
22.5gr. Accurate 1680, 80 TTSX, 2,731 fps

21gr. Accurate 1680, 87 TNT, 2,597 fps






Not the best 100yd group I've ever shot, but considering it's a 10" barrel with a 6oz muzzle device and a mil-spec trigger it ain't bad....

Kurt , it's set to take it's maiden voyage next month for my son's 5th birthday. He'll be sqeezing his first trigger on a Rem 510.

If there's anything you need to hit the birthday voyage timeline let me know..........

don't figure I'll be doing this much longer.....so....... 'mi casa et su casa'

I'll try and keep this anonymous as possible......




A crude starting comparisson would be that of the .221 fireball vs. the .223 Remington, I only use it because there multiple sources of info on both......several of the same principals at work.......again, especially in shorter barrels.....but if the .221 fireball was on an improved case/chamber/AR action and optimum barrel and length vs. a standard dimension case/chamber/AR action/barrel  the efficency comparison of the two would be even more noticable.....and as seen in other .223 parent case wild-cats, as the caliber is increased the advantages become more noticable......

on the .223 case .22cal is hard enough to hot-rod and see the differences.....25 isn't much better, but we figured out a few combinations that work, it's not one of my favorites but it'll do....As posted earlier, 85 to 87gr I like a 14" barrel length with 1680.....and as the bullet weight goes up (100gr) the barrel length I use gets shorter for a 1680 optimized set-up........


if all the .25-223 is just a re-necking of the .223 parent case, with chamber cutting and action assembly held to average methods I can think of 8 or 10 improvements just in the mechanics that would allow higher velocities before pressure signs or false-positives for pressure present....I've been saying this since page 1 of this thread, if the brass is allowed to exercise around in the chamber you're fighting a losing battle, and I'm just not talking about headspace or fireformed brass....I probably spend more time on bolt/extension/breech interface than most people do building their whole rife, that's why it's not practical for me to build rifles on a mass level knowing there's a better way.....

From around the 18th post on the .25x40 thread:



1680 isn't the end-all / be-all powder.....but I like it, you just gotta figure out what it likes.....it's all about finding combinations that compliment each other, whether you're using 1680 or lil-gun......you can either tune the only rifle set-up you have with several different powders, or vary your rifle set-up to the powder you like to use....

I raced cars and boats sucessfully for a long time, wildcatting is no different.......all your parts have to fit, there are limits to what your equipment can withstand, anything you can do to increase those limits without experiencing equipment failure will put you ahead of everybody else.....the stopwatch or chronograph don't lie...

The internal ballistic differences of the two could fill pages here, I'll just let the external mechanics and external ballistics speak for themselves.....


The thing that I find utterly amusing is the "drafting" that has run through this thread and over into other threads ......everything from copying what I used as tag lines to how I format my load data from post to post....

"hope this helps"

"(standard disclaimer as with any wild-cat, use at own risk and work up slow)"

I began my industrial career as a fork lift driver, lol lol.....and EVERY wild-cat that I've come up with in the last six years has come from here thanks to Miss Rita:



So I guess I am truly blessed that such educated people rely and wait on my next move to inspire them.....


Psalm 23:5:  "Thou preparest a table before me in the presence of mine enemies"  my cup truly runneth over.

Rehab, The Bartender Song: "I guess I should have did something about my anger, But I never learn, Real things I don’t concern, I pour kerosene on everything I love, And watch it burn, I know it’s my fault, But I wasn’t happy it was over......."

I'm versed in either, take your pick..........................................

Thanks ,Kurt . I truly appreciate the offer.

ETA- I think I might print off this entire thread for future reference though .

Kurt :
I want to personally thank you for all the work you put into your wildcats, and the time you took to help out others. You should be proud of what you have accomplished!  

Joe

Kurt,

A couple of questions about the 7mm ARK... after just reading the entire thread.

1.  Are there reamers available for the 7mm ARK?  
2.  Are you still making barrels?
3.  Do you have to change the bolt to match the face?  I seem to remember that several pages back.
4.  I see from the pictures it looks like some 20 rd magazines.  How do they stack?  Preferred mag?
5.  Lastly, you and Bill Wilson (or anyone for that matter) looking at going the same route with this round?

Thanks,
8654

Bump for Kurt

tag for that answer  

1.  I still have it marked proprietary at PTG, have a couple things I want to look at a little more before I set it....
2. I brought a bunch of stuff up here with me during the move but my hands have been kept pretty busy lately, sounds kinda funny working in the gun biz and not getting to do much in the way of gun stuff....did get to spend last weekend at the Tulsa gun show with Bill and crew....holy cow that's a big show
3. I set my 7 ARk's up using either DPMS or Olympic 7.62x39 Russian bolts, the Olympics came with a firing pin....
4. I use 20 and 25? round C Products Grendel mags with no issues, I took all of my Grendel mags and measured for the ones with the widest rib to rib measurement and used those for the 7mm, I've seen as much as .060" from mag to mag...
5. Don't know, I think it's one helluva hot-rod....it's approaching 7-08 light loads in a AR....and I've said this before, I go through a fit / tuning / settling / break-in procedure that most shooters or rifle builders would not find practical on a production rifle....I've got a few thousand of above average loads across several of mine and others 7ARk's using the x39 bolts and attribute no broke bolts on mine or other peoples rifles to this fit / tuning / settling / break-in convention.....it just takes a while....

been seeing a few familiar names come across the "floor"....just want to say HI

Thanks, Kurt.

Sure would like to get into some 7mm ARK.  I agree, looks like a winner.  When you make the move to the market, keep us informed here.

Thanks,
8654