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Posted: 6/7/2008 12:00:35 PM EDT
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I picked up my new build this morning and am very happy with it. kurtz over on the Quarterbore forum put it together for me over the last couple days. Earlier in the week I sent over most of the parts, he sold me the barrel, ammo, mags, a 100rds of pre formed brass, adjusted my 300-221 dies for the longer round, duracoated the steel parts, lapped and mounted the M3, and put it all together. www.quarterbore.net/forums/photopost/showphoto.php?photo=498&cat=529 www.quarterbore.net/forums/photopost/showphoto.php?photo=499&cat=529 We ended up shooting a little over a 100 rounds of various powders and bullet weights and styles. They all fed great, no FTF I usually shoot between 500 and 600 rounds a month so I was glad to find out that the .10 cent 145gr surplus M80's worked great, loaded light they clocked 2,025fps and grouped around 2". The brand name 110 and 125's did much better, even though the wind was blowing hard and I could see my heart beating in the scope. www.quarterbore.net/forums/photopost/showphoto.php?photo=500&cat=529 www.quarterbore.net/forums/photopost/showphoto.php?photo=501&cat=529 kurtz, thank you very much for doing a great job. uptown1 out |
it's a 7.62 wildcat based on a .223 parent case whereas the 300 whisper is based on the .221 case or can be made from .223, most of my Whisper brass is around 32mm. As the case got bigger through development it went through a name change from 39 to 40mm as this thread suggests. www.quarterbore.net/forums/showthread.php?t=1827 the 7.62x40 holds 6 to 10 grains more powder than the Whisper, and has less case taper, comes out of the mags really slick. I have a couple suppressed Whispers that I have now dedicated to sub-sonic use. My AR Whisper has the gas block in the pistol position, the highest velocity I was able to hit was around 2,100 fps with 125gr bullets before it started dumping primers (coming out of battery while still under pressure) this build will be dedicated to super-sonic use and was told to expect top-end velocities between 2,400 and 2,700 fps depending on the weight of the bullet, was shooting 125 TNT's at 2,450 fps today. it will also shoot 180 to 220gr sub-sonic, but thats what I'll use the Whispers forhould uptown1 |
Sounds like an awesome round. Wish it could get as popular as 6.8 and 6.5 Grendel.  If factory loaded ammo was commercially available I'd sure as hell get one.
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being the new owner of one I am now one of its biggest fans. I went to the range and tested the 125 noslers yesterday, had them clocking right at 2,500fps. The best I can figure is some where around 975 foot lbs of energy at 300 yards. It's funny you mention the 6.5 and 6.8, the 125gr nosler load produced an almost identical ballistic overlay with a 6.5 load I worked up for a friend shooting 123's at the same velocity, the 6.5 had about a .5 inch flatter trajectory at 300 yards, the two had almost identical energy at 300yds. get out much past that and the BC of the 6.5 starts to take over. I rarely make hunting shots over 100yds around here so it's all good. The more I learn and realize about the 7.62x40 the more I like it. uses inexpensive .223 brass (free if you range pick-up), broad selection of inexpensive .308 bullets, reasonable powder charge (around 20grains of pistol powder), uses inexpensive 20 or 30 round PMAGS, no bolt change, uses whisper or 300-221 dies for reloading, and good punch. A lot of the same can be said for the Whisper or 300-221, I guess thats why I like them also. the 40 does seem to out perform them in the super-sonic role, but hey, it's totaly different from them being geared towards super-sonic so it makes sense that it would. Looks like most wildcats face some of the same problems: custom brass of some kind, no set dimension specs (I was told that the 40 went through 5 or 6 chamber changes in the last two weeks, all I care about is that mine runs great).....limited ammo retail, if any...reloading is almost a must thanks for the bump and giving me a chance to soapbox. |
Seriously?  I bought a noveske 16" barrel over an M1 for the quality that I was hoping to use supersonic for hunting and subsonic when I can afford a suppressor. If I had a longer gas system would I get higher velocities in the 300 whisper? |
Noveske barrels generally perform much better than M1 barrels any day of the week. You should be able to get the velocities that you want. I have a 16-inch Noveske barrel. I can routinely get 2250 to 2360 fps with Speer 125 TNT and Sierra 125 SPT Pro-Hunter. The bullet that I am really interested in now is the 135 gr Sierra HPBT MatchKing. I have pushed this bullet to 2240 with W296. I have an Olympic Arms 16-inch barrel. The barrel has gas ports in both pistol and carbine position. I can plug the either port with a set-screw and blind gas block and use either one. With the gas port in the carbine position and I can get may be an additional 25-50 fps because of the slightly longer dwell time. If you are looking for some reloading data I have posted my results here reloadersnest.com Most of the loads listed under "Not yet verified user loads" are one that I have worked up. Good Luck |
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The 300 AR that I have right now is a SSK, has the Hi / Low gas block. Works really great in the Low position for sub-sonic. In the Hi position for supers 2,100 is about the max with the loads I tried. maybe if the Hi position had a little smaller port in it or if I used a slightly different burn-rate powder I could creep it up a little more. But I don't think I'm gonna call JD and tell him he put too big of a port in my gas block, he So Bodacious, my answer to your question, from my experience with SSK, M1, and Olympic 300 whisper barrels, would be that the carbine length gas system produced the higher fps for a given load in my rifles with the least signs of high pressure. Went back and looked up the velocities for a pretty standard 300 super-sonic load of a 125 grain Speer TNT with 18gr of H110 SSK 1:8 twist SSK pistol position 2,130 fps M1 1:8 twist carbine position 2,220 fps Olympic 1:8 twist carbine position 2,250 fps Haved pushed loads faster than 2,250 in the Olympic carbine position, but the 18gr load was the only one that I had tried across all three barrels for reference. I too am interested in the 135 matchking and also the 123 Lapua, but I'm gonna use them in the 40. with the right powder I'm hoping to get close to 2,475 to 2,500 with the 135 MK's. Thanks for the link to the load data 320pf |
uptown1....thank you for the kind words.....I've been working on a couple new projects with the 7.62x40....will post info and pics as soon as I get them done. working on a new 20" rifle, getting over 2,600fps with 125gr pills.... thanks again, kurtz |
I don't know anything about the 30HRT but, in uptown1's case, the 7.62x40 and the 300 whisper are used for different roles. The 300 whisper is far more available than a 7.62x40 and its only shortcoming will be getting the velocities that 7.62x40 can do. If you are going for a subsonic only rig I would say that 300 whisper is all you need. If double duty supersonic and subsonic is required then 7.62x40 would suit you better. That is my take on it and I am speaking for no one else but myself. |
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As Bodacious pointed out kinda depends on the application.... I currently own three 300 whispers and three 7.62x40's..... even the three 300 whispers that I own fill individual roles, one is a long barreled slow twist bolt-gun for dedicated super-sonic, another is a short-barreled fast twist bolt-gun dedicated sub-sonic, and the last is a fast twist AR dedicated to sub-sonic.... in a stop-gap all around compromise AR of the three cartridges you asked about....If you are going to suppress the rifle for sub-sonic and also run supers I have had great luck with the 300 whisper, operating envelope between 1,000 and 2,200 fps. If you are wanting to build a 30 cal AR wildcat more geared towards supers.....I'm a little partial to the 7.62x40  ....I was asked to post an informational thread about the cartridge and intend to do so but I'll list a few of the reasons here.Background: I had several whispers and found myself gravitating more and more towards super-sonic use. I don't hunt but have friends, a few with children, that use AR whispers to deer and hog hunt with.....that is where the spark came from to develop a higher energy 30 cal AR based wild-cat.... had looked at the 39mm Russian round and had considered blowing out the case to match the taper of a .223 so it would work better in slow curve mags, but that would require more than just a barrel change... There had been attempts that I knew of to neck up the full length .223 to .30 cal to use in an AR but the rounds ended up being too long to fit in a mag with 125gr bullets, single loaded in the rifle the limited case capacity didn't produce enough gas in the 30 cal bore to cycle the rifle length gas system...project was dropped I had a operating envelope in mind between 2,400 and 2,500 fps out of a 16" AR with 125gr bullets... Reasons It works for me: - only a barrel change required to the weapon platform, if you already own a 300-221/whisper/300 fireball barrel it can be rechambered in 7.62x40 - inexpensive brass, I purposely used range pick-up in my 40's during the development just to see what the differences were in about 10 or 12 different brands of brass - very broad range of bullet selection, have fired everything from 110 to 200 grain, works great with .09 and .10 cent surplus bullets - it's a natural progression from 300 whisper if wanting more velocity, uses the same reloading dies, just rechamber the barrel, form new brass, load and go shoot.... - no special mags required, will use standard AR mags, I and others have found with the heavy whisper and standard 40 loads that de-ribbed PMAGS work best for us. load a full 30 rounds, dump a mag without a hitch. - no bolt change needed.... - If using a .308 Winchester BDC the 40 with 125 or 135 grain boat tails is a very close match, worked great for friends estimating hunting ranges. will post more info and pics later, working on a couple new 40 builds.... kurtz as an aside....I have not been able to post any pictures or an avatar through my profile main screen, any suggestions???? |
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Very interesting round you have there. I have a 300 fireball AR myself. With this round are you limited to the lighter bullets? I can't imagine being able to seat a 200 or 220 gr in that case and still be under a COL that would fit in an AR type mag. I think a good name for this would be something along the lines of .300 Whisper (Fireball) Magnum. 
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It's concept and design is to work mainly with 110 to 145 gr bullets..... however, it will also work with heavy sub-sonics.....we have done this a couple different ways, one way is to throat the chamber a little deeper and keep a few longer seated heavy subs rounds handy (in the grip or stock) and single feed them as wanted....another way is to use 180 to 220gr bullets that have a long bearing surface and seat the bullet deep in the case down to mag length, the 220 soft nose Hawks have worked well in this application, works and cycles great, similar to the 9x39mmRussian or HK 7.62 sub-sonic, and has worked the best for me for all around accuracy with light or heavy bullets.....have also been able to load a little longer subs with metal mags over the pmags... there is a measurable difference in case capacity between the 300 and 40 but fired side-by-side sub-sonic I haven't been able to distinguish a db difference with the ear, not the most scientific but when I get a chance to put them on a meter I will.... the load density of the whisper is more suitable to sub-sonic, a little less powder burn rate angle sensitive, although the deep seated bullet in the 40 takes up a good part of the case....both my 300 and 40 AR's shoot MOA with sub-sonics.... the 300 whispers I had suffered from excessive "chamber jump" when loaded with 110 or 125 bullets.....the 300 chamber for the 220gr matchkings is set to the point that when you chamber a 110 or 125gr the bullet has to "jump" close to 200 thousandths from the case mouth before it is engraved by the rifling.....not the best for accuracy. As far as the name, it's just a mechanical designation....I also do larger wild-cats, I have a 7.62x63....a tactical rifle build that falls between a .308 and a .300 mag....will launch 220 matchkings between 2,700 and 2,800 fps.....that's about as hard as I want to get kicked  the case and chamber dimensions of the 40 are significantly different from the whisper...case taper is different, shoulder angle is different, neck diameter and length is different, about the only thing the same is the rim diameter....similar story as the 6.5grendel, 6mmPPC, 22PPC, 220Russian, 7.62x39Russian, 9x39Russian Thanks, kurtz |
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funny....in a Willie Wonka sort of way..... just to answer a couple of your questions from the voice mail yesterday, we are very happy with the last couple revisions made and are hoping to have leads on barrels and cartridge specific dies by the end of next week....this thing has moved a lot faster than anticipated, being driven by the number of requests for information.... I have been asked by a few forum members to start a 7.62x40mm FAQ....like I have said to members here and on Quarterbore this is really in its infancy, but if there is interest in a FAQ I'll pull together what I have and post it. kurtz |
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