New builds, 7.62x39mmUSA kinda like a 300/221XL

[kurtz]

A couple builds I have been working on for a while and some range results from the weekend....

The first is built from DPMS components, 20" Noveske 1:12 twist rifle length gas system chambered in 7.62x39mmUSA, JP adjustable gas block, Leupold M3....25.3 grains of A1680 under a 110 V-Max = 2675fps...25.3 grains of A1680 under a 125 TNT = 2530fps....as far as accuracy I didn't bring any targets with me to the range....centered up on the 200 yard gong 20 rounds made a nice brite spot about the size of a quarter...
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The second is built from a combination of DPMS and Olympic components and began life as a 300 fireball....was recently rechambered in 7.62x39mmUSA....the original pistol length gas system under the handguard was removed / plugged and set up as a carbine length system....It's a hoot to shoot with 25 grains of A1680....a little more BOOM than the original fireball loads
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The 7.62x39mmUSA compared to 300/221 and .223 Rem
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The 7.62x39mmUSA compared to a 300/221 in a mag
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The 7.62x39mmUSA is based on a .223 parent case..it uses standard bolt face and mags....as in my 300 fireball barrel, I hand re-chambered it with the longer reamer.....here is an old thread from 07 talking about the developmenthttp://www.quarterbore.net/forums/showthread.php?t=1481

I left a reamer and headspace gauges with John Noveske if anyone is interested in having a barrel cut.....PTG also has the print on file....Its been a little work getting there and the only powder I have tried is the A1680 but I guess thats part of the fun....

[jarhead1086]

I notice that the case length is longer than the bottom of the shoulder on the .223 case. You have to open up the case to achieve this obviously. I recently got a .300-221 die for my Dillon trimmer and now making cases is easy in one step to collapse the shoulder and trim. It does take another step to deprime since the trimmer dosen't have a stem, but I prefer having a primer in when I tumble to keep crap out of the pocket. This is much faster and easier than opening .221 Fireball like I used to do. This is a potent .30 you have in a light efficient package, very cool. Half the powder of a .308 and most the punch. Any feeding problems? Have you tried P-Mags or Beta mags?

[kurtz]

I have a small hobby lathe that I use to cut my brass down with....it has a three jaw chuck with aluminum jaws that I cut enough taper and a back-stop in to fit the .223 case....I ground a parting tool that comes in perpendicular to the shoulder just shy of the neck, it cuts clean enough that I haven't had to de-burr any cases yet....the rough cut cases are cut about .010 shorter than desired then ran through the die (I'm using a Hornady expanding button) you get the .010 back in length and end up at 1.540"...

To date they have digested 110 V-Max, 110 Sierra (hollow point varmint), 110 Hornady PSP, 125 TNT, 125 Rem. PSP out of DPMS mags with Mag-Pul followers with no stoppages....I have not tried the Beta or P mags..I do have a couple of the HK mags on the way out of curiousity that I'm going to hopefully try this weekend....

The 16" carbine cycles very positive, you actually get a little tingle in your shoulder after twenty or so rounds.....the 20" with rifle length gas system cycles a little more slugish, almost delayed to the point of short-stroking, but I'm going to tune on that a little... If I had it to to do over, I think I would try a 20" barrel with a carbine length gas system...

kurtz

[JFettig]

Very cool! I was considering the same expereriment, doing this instead of building the .300/221 I'm building now. I had designed my reamers and started making the dies but had some issues and wanted a gun done. Mine were .1" longer than .300 whisper, looks like yours are longer.


Jon

[kurtz]

Hi Jon,

The case length comes in right at .200" longer than the 300/221 depending on what you trim the 300/221 at (1.330 to 1.400).....the powder column with A1680 increased from 20grains to 25grains....the shoulder of the new round was blown out to the max that my redding 300/221 neck sizing die would accomodate without touching the outside of the shoulder and still leave a few thousandths taper in the overall length of the case....

when I re-chambered the 300 fireball there ended up being two very slight (.002 to .003) areas of transition that are noticable in the fire-formed brass...one about 3/8 of an inch forward of the base and another about .050 in front of the shoulder....the tolerance of my reamer was a little smaller than the olympic one and you end up with the two areas of transition...the one in the neck is taken care of when it gets neck sized...

[pug]

Nice job. They say great minds think alike :smile:. Very close with my 308R2. The 16" carbine is my favorite although I am contemplating cutting the 20" down to a 10" pistol.

300/221 vs. 308R2

[kurtz]

Hi pug,

Glad to see your projects are moving along as well....I find myself shooting my carbine more also, it has performed well right from the start.....the rifle length system is pretty sensitive to which load I'm using, the gas system on it seems to like the hotter loads ( above 2500 fps)....thinking about opening the port up a little to get some use out of the adjustable block...

went to the range today and tested a few loads:

22 grains H110 125 TNT = 2540 fps
22 grains H110 125 Nosler BT = 2550 fps
22 grains 4227 125 TNT = 2440 fps
25.2 grains 1680 125 TNT = 2525 fps

Also tried one of the HK 416 mags, pretty 5.56 specific..

Picked up some winchester 296 on the way home to give a try...my pet load right now is the 25 grains of 1680, has worked well from the start...

my target velocity with the 125 nosler was 2500 fps and I hit it today with the H110 but the cycling was a little weak in the 20" barrel, guess it's a little too fast burning or need a bigger port....

good to hear from you again, I have been out of the loop for the last few months...keep us up to date on your builds...

kurtz

[pug]

I think my rifle port was at .097" the last time I checked. Found the same thing that these capacity cartridges are a little sluggish ported in the rifle position. I couldn't use any powder faster than 1680 in the 20 or it would borderline function but your 16 might like the W296 with the 110s and 125s. If your cartridges tend to roll inwards as you fill the mag try some Thermolds. They have shallower ribs like the Grendels and the rounds will stack straight down.

I am going to turn my attention away from the guns now and concentrate on ammo components. People are going crazy and I need to pick up all of the LC brass while I can get it and the M193 projectiles cheap. There is still a supply of 308 penetrators but i had better move quick or they will be long gone also.

[kurtz]

my rifle port right now is .093...borderline with everything except the 1680...the carbine if I remember right is .078 and works great....

I know what you mean about components...ya wanna hear something funny, I built my first super-sonic 300-221 around the 125 TNT because at the time, a little over a year ago, you could find them for around $50.00 per 500..now they are nearing $100.00 per 500, just a year later...

The gun store that I went to today is not known for having much in the way of reloading components but they had 2000 small rifle and 2000 large rifle CCI at $15.00 a box...I bought them all...Gander Mountain Sporting Goods got in a load of small and large rifle primers earlier this week and is retailing them at $38 bucks a box, unreal...

thanks for the info on the gas port and the mags....good luck with the component harvest....

kurtz

[kurtz]

went to the range today and tested a few loads in the 20" 7.62x39mmUSA

20 grains lil gun 110 V-MAX = 2720 fps
20 grains lil gun 125 TNT = 2515 fps
22 grains lil gun 110 V-MAX = 2736 fps
22 grains lil gun 125 TNT = 2555 fps
25 grains A1680 110 Sierra hollow point = 2650 fps

the 110 Sierra hollow points and the 125 TNT are producing under 1" at 100 yards with A1680 out of the 20" 1:12 noveske....a full case load with the A1680 has a very low standard deviation, so far less than 15 fps...

kurtz

[JFettig]

What velocities are you getting out of a 16" barrel?

Jon

[kurtz]

Hi Jon,

When I started out on the two builds I had 125 grain TNT target velocities of 2400fps for the 16" and 2500fps for the 20" in mind.....and hit both using right around 25grains of 1680.....there hasn't been much time to go to the range in the last couple weeks to try any loads other than what are listed in the thread for the 20".....

I've been spending most of my free time re-chambering a couple rifles for friends and another of mine.....I have now hand re-chambered a total of (4) 300-221 and 300 fireball rifles to 7.62x39mmUSA...this project was my first attempt at cutting chambers and have been pretty happy with the results.....it probably took more time to tool-up and cut the
receiver/T-handle bushings out of delrin than it has to cut the chambers.....polymer sucks to cut...maybe it's just my tools???

I have a new/unused chamber reamer and headspace gauge if anyone would like to join in the fun....fair price and no wait....

the reamer that I have been using is still sharper than woodpecker lips....PTG is the stuff...anybody have an idea how many barrels can be cut with a reamer before re-sharpening is needed...

Thanks for the interest and I hope to get to the range this weekend to be able to post more data....

kurtz

[JFettig]

Not sure what the problem with delrin is, its my absolute favorite thing to cut. A sharp tool goes a long way.

I'd almost be interested if I had the cash to do another barrel. This is kind of what I originally had in mind instead of a 300/221, maybe sometime in the future.

When you get around to getting those velocities, post them up, I'm interested in seeing what you get out of the shorter barrel.


Jon

[kurtz]

Got to go to the range this weekend to test a couple changes made to the 20" 7.62x39USA......I had PTG make me a new chamber reamer to try a couple new ideas.....I moved the shoulder forward .050", opened the neck up .001" and added .003" taper to the neck....The gas port that I had been trying was .093" and the rifle cycled ok but was a little slugish and would fail to lock open every once and a while on the last round with less than 25gr of 1680......

I went to the range with a bunch of 125 TNT's with 25gr of 1680, my drill press and numbered bits.....opened the gas port up .002 to .003 at a time firing 10 rounds between.....took a little time but ended up at .102 with very reliable cycling.....now that the shoulder is moved forward .050" I can now fit a little over 26gr of 1680 in fire formed brass....with more powder and a bigger gas port it brings the adjustable gas block back to use other than wide open....also noticed that opening the gas port around .010" took about 80 fps off the top-end of the 25gr loads now clocking around 2450.....

I can't say enough good about the 20" 1:12 Noveske on this rifle, rapid fire (10 rounds in about 8 seconds) from a bi-pod at 100 yards printed a group that could be covered with a quarter....very happy, thanks John....

now to work on load development for the 16"....hopefully this weekend...

kurtz

[kurtz]

went to the range to test a couple loads in the 16" and 20" 7.62x39USA


16" 1:8 Olmypic .078 gas port carbine length gas system, fire-formed brass, no signs of high pressure...

125 TNT 21.5gr 4227 = 2,230 fps
125 TNT 22.0gr 4227 = 2,350 fps
125 TNT 22.5gr 4227 = 2,440 fps
125 TNT 25.8gr 1680 = 2,430 fps


20" 1:12 Noveske .102 gas port rifle length gas system, fire-formed brass, no signs of high pressure....

125 TNT 21.5gr 4227 = 2,270 fps
125 TNT 22.0gr 4227 = 2,440 fps
125 TNT 22.5gr 4227 = 2,470 fps
125 TNT 25.8gr 1680 = 2,575 fps


I'm going to work up more loads for the carbine: 296, lil-gun, H110.......hopefully I'll have the data tomorrow...


kurtz

[kurtz]

went to the range to test a couple loads in the 16" and 20" 7.62x39USA


16" 1:8 Olmypic .078 gas port carbine length gas system, fire-formed brass...

125 TNT 22gr lil-gun = 2,540 fps
125 TNT 22gr H110 = 2,480 fps
125 TNT 22gr 296 = 2,475 fps


20" 1:12 Noveske .102 gas port rifle length gas system, fire-formed brass....

125 TNT 26.0gr 1680 = 2,606 fps


I think I've hit a stopping point with the 16" around 2500fps...my favorite loads have been with the 4227 and lil-gun around 2350 to 2450fps.....I can probably push it a little faster but I'm not sure if the additional velocity is worth the increased pressure (wear and tear on the rifle).....2350 to 2450 is comfortable to shoot....the additional power it takes to reach the 2500 to 2550 mark is pretty noticable in the BOOM factor....

The 20" rifle handled the 125's at 2600fps great.....I think the 1680 really shines in the 20" barrel.....it's funny, in the 16" barrel a charge of 22.5gr of 4227 and 25.8gr of 1680 produced almost identical fps (around 2440fps) ....but out of the 20" with the same loads the 1680 was over 100fps faster....no pressure signs with the 26gr of 1680 and still have a little room in the case.....

kurtz

[kurtz]

went to the range today to experiment with a couple things and fire-form some brass.....

the last changes made to the chamber reamer seemed to work out pretty good...pushing a 125 TNT at a consistant 2,650fps out of the 20" with 26.5gr of accurate 1680....with a combination of a few tweaks the 20" now cycles very positive and reliable....

a pic of the revised round in a line-up (left to right: 300-221, 7.62x39Russian, 7.62x39USA, 5.56x45)...revised round is approaching 7.62x40mm

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also got a few of the 20 round pmags for shooting prone....modified them using a 11/16" bedding tool....disassemble the mag, hold the mag body vertical insert and pull down the bedding tool a few times and it cuts out both ribs at the same time....works great on the 20 and 30 round pmags....

a pic of the revised round in the pmag....

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after a few requests from the AR-15.com forum I am probably going to chamber a couple more barrels this week...most are interested in the 16" but I'm kinda starting to favor the 20"....going to start next week on another 20" with a mid-length gas system, may be a little easier to tune...

[abyssdncr]

I called Noveske yesterday...they didn't seem the least bit interested in building me a barrel that wasn't on their website. A little disappointing as Pac-Nor as them listed as the source for AR barrels.

I still would like to have one of his barrels to play with, but it sounds like it could be a long wait before they do another run of .300/221 barrels...

[MartytW]

Can you post dimensions of the cartridge? Or a link to a drawing? I am mostly interested to find out the neck diameter. Thanks!

[kurtz]

the outside neck diameter of a loaded rounnd with a 125 TNT is .328 to .330, depending what brand of brass you use.....

kurtz

[kurtz]

Range tested the build for uptown1....

He provided most of the components, we provided the barrel, mags, ammo, and put it all together...

7.62x40mm barrel #001

415

416

417

418

http://www.ar15.com/forums/topic.html?b=3&f=121&t=381685

[MartytW]

the outside neck diameter of a loaded rounnd with a 125 TNT is .328 to .330, depending what brand of brass you use.....

kurtz

Wow, that seems like a small diameter... my drawings (Ken Howell's book, as well as SAAMI prints) show .253 neck diameter for the .223 Remington. With a .224 bullet that gives 0.029 combined wall thickness (or 0.0145 each) which is in line with the "typical" value of 0.024 (or 0.012 each).

0.328 with a 0.308 bullet gives 0.020 or 0.010 each .... any chance it might be more than that?

[kurtz]

Can you post dimensions of the cartridge? Or a link to a drawing? I am mostly interested to find out the neck diameter. Thanks!

Wow, that seems like a small diameter... my drawings (Ken Howell's book, as well as SAAMI prints) show .253 neck diameter for the .223 Remington. With a .224 bullet that gives 0.029 combined wall thickness (or 0.0145 each) which is in line with the "typical" value of 0.024 (or 0.012 each).

0.328 with a 0.308 bullet gives 0.020 or 0.010 each .... any chance it might be more than that?


the information I have on a .223 cartridge neck diameter shows .247 to .248....roughly 3.8 times smaller than a .458 SOCOM

[pud-knocker]

....roughly 3.8 times smaller than a .458 SOCOM

tooooooo funny eh Marty

[MartytW]

bunch of smarty pants :rolleyes: J/K

But seriously, all my drawings show .253
Cartridges of the World, 8th Edn
Designing and Forming Custom Cartridges - Ken Howell (the Blue Book)
Handloaders Manual of Cartridge Conversions (the Green Book)
Norma Reloading Manual
Just to name a few

Reason I asked originally was because I wanted to know if moving the shoulder down the case required a change in case mouth wall thickness. Now I am totally confused ... :confused:

[kurtz]

I think as brass manufactures looked for ways to cut costs and manufacturing processes became more accurate (aka: them make more money) we got thinner brass.....I have some older commercial Winchester that the case mouth wall thickness mics right at .014......A new lot of commercial Winchester that I got in last week mics right at .0115 if you check it with a less expensive caliper it rounds up to .012....so, by the time you form it and flow it a couple times it thins quick, and doesn't stand up to as many reloads as it used to.....the brass is still within specs, just on the thinner side of the spec....it's called: quality give-away ( any item sold to a customer above set specifications costs the company more money, meet the minimum spec / make the most money)

[pug]

MartytW my 308R2 cartridge is similar to kurtz except the case is 1.5" long with a .2" neck using .223 remington parent case. kurtz is right on the money saying the loaded necks run about .330" as that is the average.

[kurtz]

pug,

thanks for the back-up....

I posted a little info on another forum about the new round and.....mother fu##er

....my is this....you said this....this is this...you are this....this is better...mine is better...I know this...I read this...

thanks to 320pf for coming to my aid.....

just trying to share what is going on in other parts of the world and people still believe it's flat...I thought someone figured that one out around 1492AD...

Ma can I come home....

Thanks again

kurtz

[320pf]

kurtz,

Check your personal messages on that other site,


320pf

[kurtz]

Have some information for those who have written requesting information on barrels and dies.....

WoooooooHooooooo :nanabang:

John Noveske will be making our barrels for us!!!

A list of barrel combinations we are having made.....

20" SS 1:12 twist polygonal bore mid-length gas system threaded muzzle low profile gas block
20" SS 1:12 twist polygonal bore mid-length gas system crowned muzzle low profile gas block
16" SS 1:12 twist polygonal bore mid-length gas system threaded muzzle low profile gas block
16" SS 1:12 twist polygonal bore carbine length gas system threaded muzzle low profile gas block
16" SS 1:12 twist polygonal bore carbine length gas system crowned muzzle low profile gas block

Also having 30 sets of custom Hornady dies made.....

Thanks,

Kurtz

[Spanners]

Sorry to dredge up an old thread, but have you run any ~168gr through it?

[kurtz]

Sorry to dredge up an old thread, but have you run any ~168gr through it?


I don't generally run anything that heavy, usually 135 to 145 is where I top out....

depending on barrel length I've pushed the 135's up around 2,400fps....

[kurtz]

Bill Wilson of Wilson Combat / Tactical announced today that he is going to manufacture the 7.62x40mm




Thanks to all of Kurt's kind help we're off and running with our 7.62x40 WT project. Here's what we have coming initially.........................expect a big launch by end of first quarter 2011.

Complete ARs, uppers and bbls in 11.3" and 16.2" CAR gas, 1-10 or 1-11 twist (haven't made the final decision yet)
Loaded Ammo in both new and OF cases, will be loading Sierra 125gr PH, Nosler 125gr BT, Speer 125gr TNT and Barnes 110gr TTSX
Formed cases, both new and OF LC
Hornady dies
Case gauge
Load data


This will NOT be a proprietary caliber and access to chamber drawings and reamers/gauges will available to anyone. I hope everyone will use the same chamber spec so we will start off and remain consistent with dimensions!!!! We've settled on Kurt's final dimensions with one minor change so will be cross-compatiable with existing dies/chamber/brass.


If the demand is there we will also offer 18" and 20" mid gas too ??????

[Titleiiredneck]

looks to be a real nice! I may have to get one in the future to play with!