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Posted: 6/20/2008 8:57:21 PM EDT
[Last Edit: 762x40mm]
[#1]
you got it.....was looking for a way to avoid the case cutting and fireforming step.....not so much a headstamp issue, more so a function of convenience....just a thought...the beauty of the whisper and the 40 is plentiful inexpensive .223 brass....not trying to change that, just exploring what's out there.... boy, you are right about that, Lapua brass is a work of art....I have a friend that has a TRG-42 and he only uses the Lapua brass...very nice... Starline just said that with the work load that they have right now, taking on a new rim diameter that they don't currently make wouldn't be practical....for them I guess... 40 |
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NC, USA
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Posted: 6/20/2008 10:58:51 PM EDT
[Last Edit: gdblair]
[#2]
I have a similar pet being a 6.8x43 based on the .17 remington.This 7.62x40 is just on the other side of the fence.I appreciate the fact that someone is going his own way and developing something different.Look forward to seeing more of your creation.
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Posted: 6/20/2008 11:11:16 PM EDT
[#3]
6.8x43 sounds like a neat project....how far along on it are you?....any performance data?..... 40 |
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NC, USA
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Posted: 6/20/2008 11:57:45 PM EDT
[#4]
It's still on paper while my wife is at home with my 2yr old son.As far as performance it doesn't look too bad from what numbers I get from plugging ammoguide ballistic calculator.It doesn't do anything that can't be done with other cartridges in it's class but it's mine. |
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USA
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Posted: 6/21/2008 12:37:54 AM EDT
[#5]
Afraid not, CH4D has dies for it so someone else already has made it. I apologize if you didn't mean you came up with it. Here it is listed among other 6.8 cartridges: 6.8 Improved - - F $ 78.25 - - - - 6.8 K Kadet - - F $ 78.25 - - - - 6.8 SPC Improved - - F $ 78.25 - - - - 6.8 x 43mm - - F $ 78.25 5 - - 6.8mm SPC - - F $ 78.25 5 |
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WA, USA
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Posted: 6/21/2008 12:51:00 AM EDT
[Last Edit: moose01]
[#6]
Isn't the 6.8x43 the SPC? I think what gdblair is doing different though is basing it on the 17 Rem (similar to 223 rem) rather than the 30 Rem.
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USA
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Posted: 6/21/2008 1:17:25 AM EDT
[#7]
If you look at my list there the 6.8 SPC is listed, besides the 6.8 REM, SPC, whatever you want to call it is based off the 30 Rem case not the 223. So the 6.8x43 is a 223 necked up to 6.8 (or 270) |
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WA, USA
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Posted: 6/21/2008 1:37:38 AM EDT
[#8]
I'm not following you. The 6.8 SPC IS the 6.8x43, and it IS based off the .30 Remington case.
The wildcat being mentioned in this thread is based off a .17 Remington case. I know the 6.8 SPC is based off the 30 Rem case. That's what I said in my previous post. |
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MI, USA
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Posted: 6/21/2008 6:18:30 AM EDT
[#9]
I am not sure what point you are trying to make. What are the case dimensions of the cartridges you list and what is the parent case for each of them. If there is no exact match and if the final wildcat name is unique, then we have a new cartridge. Please list your requirements for a wildcat cartridge so we can all understand what makes a one of a kind cartridge in your book. Joe |
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Posted: 6/21/2008 7:55:36 AM EDT
[Last Edit: 762x40mm]
[#10]
I say great job......and it is yours If I sat here in my shop and made a 6.5 grendel or a 7.62x39Russian with .002" less case taper....It's "mine"....I know how you feel kinda like an expecting father..... The same can be said for the 300 Whisper and 300-221.....the Whisper and it's dimensions belong to JD......the 300-221 belongs to whoever made it up....based off the same parent case, chamber dimensions slightly different.... thats why when someone comes up with a cartridge similar to the 40 with .001 difference in a case dimension and call it the 300Shout (opposite of Whisper) I'm not gonna stand on my porch and shake my fist at the sky.....Thats just how it works....by the contrary I'm going to try and do everything so no one has to go through the trouble and expense of building the "shout"....making as much of the information available, dies, barrels....compared to other things I have done in my life this is by no means a "money-maker"....If I sell all (30) sets of dies that I ordered I stand to make a whopping $500 to $600 dollars, that won't cover the expense of one R&D rifle..... but guess what.....it's mine so gdblair keep doing what you're doing and I promise your exploits will be received by "most" (previously defined) with open arms.... again, great job.... 40 and uptown1....do "most" people really like eggs? |
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LA, USA
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Posted: 6/21/2008 10:19:17 AM EDT
[#11]
300Shout......thats funny....I didn't think you had it in ya... Just a guess, since every grocery store I've ever been in carries them..... Put me down for two sets of dies and a 20" barrel....want to build a dedicated "hunter" for the 125 Noslers or 135 Matchkings. uptown1 |
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USA
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Posted: 6/21/2008 11:39:42 AM EDT
[#12]
270 - 221 Remington 1 F $ 78.25 15 U
270 - 221 Remington Improved 30 2 F $ 78.25 15 - - 270 - 221 Remington Improved 40 2 F $ 78.25 15 - - 270 - 222 Remington 1 F $ 78.25 15 U 270 - 222 Remington Improved 30 2 F $ 78.25 15 - - 270 - 222 Remington Improved 40 2 F $ 78.25 15 - - 270 - 222 Remington Magnum 1 F $ 78.25 15 U 270 - 222 Remington Magnum Improved 30 2 F $ 78.25 15 - - 270 - 222 Remington Magnum Improved 40 2 F $ 78.25 15 - - 270 - 223 Remington 1 F $ 78.25 15 U 270 - 223 Remington Improved 30 2 F $ 78.25 15 - - 270 - 223 Remington Improved 40 2 F $ 78.25 15 - - |
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Posted: 6/21/2008 2:34:31 PM EDT
[Last Edit: 762x40mm]
[#13]
I have received several e-mails about cutting and forming brass for the 40....
this is one way using tools that several 300 whisper reloaders have... * Start with a full length .223 case and put it in a case trimmer using the .22 pilot.... * Trim the case down to the shoulder / neck junction....I do mine down to the point that there is still a tiny bit of .22 neck for the pilot to center in.... * Form the case in the 300 Whisper full length sizer to the desired headspace length....if you trim the brass about .005 shorter than the desired final length, after it is formed it will grow the .005 back and come in right on the money.... 
Sorry for the crappy pics....cell phone camera.... Thanks, 40 |
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NC, USA
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Posted: 6/21/2008 7:55:47 PM EDT
[Last Edit: gdblair]
[#14]
That's it.I was looking for a case with the shoulder further up than the 222 rem and down alittle from the .223 rem. My hope would be to neck up in a couple of steps and trim to length.I wanted something like the 25 Copperhead with alittle boost... 27 Copperhead? ETA-with the 17 rem having a different shoulder height than the 221,222,223 there are no drawings for this round.(I'm pretty sure anyhow) |
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MI, USA
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Posted: 6/21/2008 8:07:23 PM EDT
[#15]
762x40 :
I trimmed a case like shown in your pics. Next expanded the neck to 6mm I.D. then to .277" and then to .308" but did not have a 300 fireball die to set the shoulder back. Takes a little time to do this but not bad. Do you use a tapered expander and do it in 1 pass or do you do it n steps also. When you get a firm price on what the die sets will run let us know. Have you tested the 7.62x40 in a 16" mid-length gas system yet. I do not know if you have someone in mind to do the barrels for you but Mike Milli might be a good one to contact. Here is a link to Mike's web site. Dedicated Technology |
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Posted: 6/21/2008 8:20:16 PM EDT
[Last Edit: 762x40mm]
[#16]
Using the Hornady full length die with elliptical expander you can do it in one quick pull.....cutting the neck with the trimmer takes the most time.....I have a small hobby lathe that I use to cut the necks off...can do it in about 10 seconds... so far it has only been tested in carbine and rifle length gas system.....the mid-length is next in line  ....thanks for the lead on the barrels...with all of the numbers I have gotten back on the dies they should be around $100.00 a set (working on getting that down a little).....pretty close to what a 300-221 3 die redding set goes for... Thanks again, 40 |
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NV, USA
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Posted: 6/21/2008 10:49:26 PM EDT
[#17]
I've got to ask a 2 part question if I may?
What is the operating pressure of the 7.62X40? Part 2 would be what is it's case capacity in comparison to the 7.62X39? I think it might be harder than you think to get 2,700 with a 110 in a 16". Just My opinion. |
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Posted: 6/22/2008 5:01:13 AM EDT
[Last Edit: 762x40mm]
[#18]
The SAAMI Maximum Average Pressure for the .223 Remington parent case is 52,000 C.U.P. The SAAMI Maximum Average Pressure for the 7.62x39mm parent case is 50,000 C.U.P. Doing a comparison with de-mineralized water the case volume of the 7.62x39mm is around 33.5 grains of H20....the 7.62x40mm a little over 30......this varies slightly depending on the brass manufacturer with either cartridge..... The only two rifles of the same barrel length that I have shot similar loads in is a re-barreled CZ527 in 7.62x39mm 20" 1:12 twist.....and the 7.62x40mm 20" 1:12 twist.... 7.62x39mm 110 Hornady V-Max 27gr Accurate 1680 = 2,590 fps 7.62x40mm 110 Hornady V-Max 26.5gr Accurate 1680 = 2,700 fps roughly 100fps difference...these loads were shot roughly 3 years apart.... The Accurate 1680 is one of my favorite powders to use in the 39 and 40....good velocity low pressure.... I couldn't find where I said you could get 2,700 fps with a 110 out of a 16" barrel...please advise.... please check out this link for more on the early development on the 40 (39mmUSA)...It also has load development and growing pains we went through with the rifle length gas system....7.62x39mmUSA (.223 parent case)......one of the very first loads we tested was with the 110 V-Max right at 2,675fps.... Thanks, 40 |
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USA
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Posted: 6/22/2008 12:22:40 PM EDT
[#19]
Some people talk about headspace issues with the 35 Whelen because of it's slight shoulder. The 35 Rem is another. Looking at your cartridge pictures this round too has a slight shoulder. Have you had any problems with that what so ever? I would think this more of a problem in a semi automatic rifle because the bolt on an AR15 does slam the cartridge pretty hard into the chamber.
Another question, why not choose the bullet caliber to be .243, .257, .264, .277, or .284 rather then the .308 to have a higher BC bullet? Why didn't the military look harder at round like the one you speak of rather then the 6.8 SPC? I can understand the aspects of the sub sonic application of say the 300 Whisper, but it's the upper velocity range and trajectory that I question. |
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NV, USA
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Posted: 6/22/2008 12:27:58 PM EDT
[#20]
I may have mistakenly read that you were getting that velocity from a 16". I apologize for any misleading on the barrel length.
If the "39" has approximately 10% more case volume than the "40" and operates at virtually the same pressure 50K vs 52K it is more likely that your "40" has a faster than average barrel.  This is one of my 7.62 x 39's, the other is a custom Sako with a 21" barrel by Bill Wiseman. I have been shooting these rifles for over 13 years and loading extensively al that time, and decades more. For my two rifles the gain per inch is about 20 ft/sec. Most of my loading agrees with your assesment of AA1680 being the best all around powder of choice. I have chronographed literally thousands of rounds with my Oehler 35P and with realistic (factory level pressures) these are my results: 110gr V-Max's 2475/2600 125gr Sierra SP, Speer TNT, R-P SP, Factory Rem, Norma, Winchester 2260/2390 147gr FMJ Win 2150/2275 150gr Nosler BT 2150/2285 165 Sierra HPBT 2075/2190 168 Sierra MK 2050/2180 175 Sierra MK 1955/2100 180 RP SP, Nos BT 1885/2035 Vita Vourhi 130 and 133 work very well with the heavier bullets. Terminal effects on deer sized animals are best with 125/150 grain sporting design (expanding) bullets. Your "40" is a pretty lady with a few special characteristics, but the velocities you seek require more pressure for volume than you would seem to have. Since I am a fan of slim and such has merit, why not a 6.5/40 with 95/107 weight bullets...??? |
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Posted: 6/22/2008 1:35:07 PM EDT
[Last Edit: 762x40mm]
[#21]
I actually have a 35 Remington levergun and havn't had any headspace issues with it or the 300 whisper and 40 in an AR platform...... several of the headspace issues I have heard or read about were attributed back to improper reloading die setting (cartridge not headspaced correctly to the chamber) .... The first 300-221 bolt gun I built did have a slightly different chamber than my SSK 300 whisper guns and required different headspaced brass....a lesson I learned as many others have the hard way...... The 40's shoulder surface area is a little larger and more pronounced (sharper angle) than the Whisper, A couple things that PO Ackley found to improve headspace issues and stem brass growth in higher pressure cartridges (higher pressure meaning the difference between sub-sonic and super-sonic in this case)..... We have all read the reports, forums, and trash mail concerning the decisions our government makes in the selection of equipment for our military....a thread on that could take pages and pages, I have an opinion, just not interested in typing that much..... This cartridge from its beginnings was invisioned as an "INTERMEDIATE" cartridge similar in performance to the 7.62x39mmRussian....a super-sonic improvement on the 300-221... If you are looking for long range performance I also wild-cat a 7.62x63mm, has been tested out to 1,150 yards....I only say this to affirm that I have a little experience with longer ranges.....and understand the difference.....also a little trigger time in "Uncle Sam's mandatory camping program" picking targets under the sunny California skies of Fort Irwin at 800 meters...anti-material that is....so I understand field testing new equipment before it gets assigned a contract number... 40 |
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Posted: 6/22/2008 1:53:37 PM EDT
[Last Edit: 762x40mm]
[#22]
I also have found 20 to 25 fps increase in inch of barrel length......with the testing I have done in a 16" AR and 110gr bullets I have no.........."desire".........to go beyond 2,600 as your velocity findings also suggest......to use a scientific term: a little too much "BOOM" for me.....I have found with the 40 that "faster powders" work better in the 16" and the 1680 shines in the 20".....
Ain't case and burn rate effiency great.....the velocities posted are tested and actual, not "seeked".....actually continuing work on a "slim" caliber for the 40......won't use the most "slick" bullets but it should work out OK.....but trying to limit my energy on one cartridge at a time.... |
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USA
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Posted: 6/22/2008 2:22:25 PM EDT
[#23]
I've had some 35 Rems and many of my friend also and I've never seen any problems with headspace on any of them. Yeah a cartridge like the 6.5-06 is a pretty flat shooter, but the 6.5-284 seems to be more popular. A gunrag writer just done a write up on a 6x45. He had it build on a bolt rifle, but with a 20 inch barrel with prospects of building one on an AR with a 20 inch barrel. He was hoping for 2700 fps with a 85 gr bullet, I believe, but said he was disappointed when it fell short. Something like 2650 which isn't too bad. He compared it with the 5.56 loaded with the heavier bullets and they actually out shot the 6mm both for flatness and retained energy. All in all the 5.56 isn't such a really bad round. Trouble with the 7.62x39 Russian is it's a bolt breaker in the AR15. There are some other calibers too that qualify for this, a discussion we don't want to get into. I own a 6.5 Grendel and it's a pretty nice round, but I don't load it hot. No reason when I have 6.5x54 Mannlicher Schoenaur and 260 Rem. I also built me a 7.62x39 AR with that Wilson barrel mentioned. I'm a big cast bullet fan and shoot cast out of both the 6.5 Grendel and 7.62x39. They both shoot better then good with cast. My best groups at 100 yards with a 155 gr cast bullet in the 7.62x39 is .437 inches. Don't believe anything negative that you hear about shooting cast in AR's. If you load correctly there is no leading or plugging of the gas tube. In fact my bolt/carrier groups isn't any dirtier then when using jacketed plus it's much easier to clean as the bullet lube keep the carbon fouling soft. With the cast though I"m limited to short distances because of the terrible BC of cast bullets. I shoot a 140 Saecon cast bullet out of the 6.5 Grendel and it's BC is somewhat better and for the hell of it one day tried it at 300 meters. I got a 1.5 inch group which was surprising to me. It shoots under 5/8 inches at 100. It did have a lot of drop at 300 meters though. |
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Posted: 6/22/2008 2:29:33 PM EDT
[#24]
I've taken the 06 case to .375 with a .4425 shoulder(same as the Whelen) without any headspace retention issues. The 400 Whelen is the one with the reputation, although it is totally self inflicted. The shoulder OD was originally .458-.460. At some point the original design was lost, abandoned or more likely - the gunsmiths decided against purchasing or making a less than mainstream reamer and just recut the neck and throat after using an 06/Whelen reamer to cut the body. At .458-.460, I'm of the opinion that the 06 case could go to .416 without issue, but just haven't got around to doing it yet. In the event that it didn't work out, it would take about 20 minutes to cut a belt recess in the chamber and use 240 Weatherby brass. |
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Posted: 6/22/2008 2:44:58 PM EDT
[#25]
I think the heavy 5.56 loads are a great choice for someone wanting to stay with a "close to stock" set-up....pretty good BC and bullet choice.... Have not run into any breakage problems with the 40.....early on when we were pushing loads really hard checking fatigue measurements on the bolt pivot pin....I mean really hard, like seize up the action hard....If you stay within reasonable pressures as with any cartridge all the parts look good..... I have always wanted to try cast in the Whisper.....BIG, SLOW, HEAVY, SOFT = in a Whisper....40 |
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USA
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Posted: 6/22/2008 2:48:15 PM EDT
[#26]
My knowledge is when necking up the 06 that at and after .357 the problems begin such we speak. No doubt .400 would do it. |
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USA
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Posted: 6/22/2008 2:51:20 PM EDT
[#27]
With the way my 7.62 AR15 shoots cast now I'm wondering how you 7.62x40 would shoot them. I'll bet pretty dang good. Cast is very responsive to small capacity cartridges. I even have some moulds that cast 210 and 220 grain 30 caliber bullets. Would be pretty good for your Whisper. |
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USA
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Posted: 6/22/2008 2:53:21 PM EDT
[#28]
Some of the smithies say things get serious starting at .375 and above with the 06 case as far as guaranteed headspace. |
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Posted: 6/22/2008 3:08:29 PM EDT
[#29]
A question for JFA and bfarrin1.....If you open a 06 case up to say .338 or .375, blow the shoulder and case walls out to .008 or .010 case taper, with a 30 or 40 degree shoulder....would that keep the headspace pretty solid and growth down....kinda along the lines of a AI.... |
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MI, USA
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Posted: 6/22/2008 3:16:19 PM EDT
[#30]
The article on the 6x45mm was a good one as far as it went. When comparing the two you have to remember that for equal weight bullets fired at the same pressure the 6x45 will have about 100 more F.P.S. velocity and more energy at muzzle. It is not until about 250 yards that the 5.56x45mm is equal with its the Higher B.C.. So you really need to ask yourself what do I need from the cartridge to begin with, if 300 + yards is the goal then maybe the 5.56 is a better choice. However the 6x45 did not magically drop in the dirt and give up at 300 yards.
This is why I can see how the 7.62x40 can get the velocity it does, and if you want to maintain this velocity at a given pressure with a smaller dia. bullet it will have to drop in weight. Maybe to the point that the smaller bullets B.C. ends up being lower than wanted. When looking at a cartridge for the AR platform its about trade offs more than which one is better just keep the goals in sight and be realistic. Joe |
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Posted: 6/22/2008 3:25:56 PM EDT
[#31]
+100........preach on Brother Joe.....I agree 100%.....Application, Application, Application..... |
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Posted: 6/22/2008 3:41:21 PM EDT
[#32]
Is this something you've read, overheard at the gunshop or actually done? |
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USA
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Posted: 6/22/2008 3:54:36 PM EDT
[#33]
I guarantee you the 6.5 Grendel shoots flat for pretty far. More then 300 yards and out of an AR15. |
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USA
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Posted: 6/22/2008 4:00:04 PM EDT
[#34]
Bill Farrin, what am I going to do with you? Since you're the Guru of knowledge here we'll just let you answer all the questions on the forum. Bye Bye |
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Posted: 6/22/2008 4:00:56 PM EDT
[Last Edit: 762x40mm]
[#35]
The reason I asked the question earlier about blowing out the 06 is that I have one sitting on the bench.....it has a false shoulder about .200 forward of the 06 shoulder....should have it done shortly....I can be a little stubborn when hanging out at the local shops and range listening to the tale of the day...have self proclaimed smiths in the area that won't do a barrel change for the public because "that may mess with the headspace"???......usually like to have my own ammo as back-up.....gets a little expensive building one or two of everything to settle an argument but what the hell, my kid will have a neat collection one day.... 40 |
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USA
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Posted: 6/22/2008 4:04:16 PM EDT
[#36]
That certainly helps. It's not like these neck up calibers are terribly unreliable because they are not that. |
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MI, USA
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Posted: 6/22/2008 4:24:57 PM EDT
[#37]
The intent of my post was a comparison to show a concept only, not a statement of superiority over the 6.5 Grendel or any other cartridge. It is good to hear that the 6.5 Grendel works well for you, and if you shoot over 300 yards a lot it is a good choice for the AR. I personally have decided a long time ago to limit my shots to under 300 yards, and in doing so my requirements may be much different than yours. Joe |
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USA
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Posted: 6/22/2008 4:54:16 PM EDT
[#38]
I didn't mean my reply as a comparison either. In fact in my opinion the 6.5 Grendel is limitied to velocity in an AR15 because of the pressure limit of the bolt. The more positive Grendel owners will point out various other 6.5 caliber cartridges that have taken all sorts of big game. Think is a 260 Rem will zing a 120 gr bullet along much faster then a Grendel will ever do. Perhaps in a bolt rifle the Grendel would give it a run for it's money. |
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Posted: 6/23/2008 12:42:50 AM EDT
[#39]
Didn't have a chance to read all it this thread in depth as I have to get caught up on a BOAT load of Email.
First - I think this round rocks. Now, at first I was somewhat puzzled and worried about the velocities posted. When I used the supplied numbers for the 110 VMax load in the 16" upper, I got 61+ KPSI from QuickLoad. A-HA! is what some of you are surely thinking. But then I looked at the case geometry again and figured out what the truly graceful aspect of this round is. By using a caliber (.308) very close the case diameter, you have a case with very little taper and not much bottleneck - as close to a straightwall case as you can get with a bottlenecked case. The developer of QL told me in personal conversations, that one of the limits of QL is in large bore short cases. But I think the case design of the 40 has the same concept working for it: upon firing, once the first bit of powder is ignited, the bullet has started moving and with its movement, you actually have a growing "chamber". Before all the powder has ignited, the bullet has traveled and by the time the last bit of powder ignites, the effective chamber has grown quite a bit. This causes the peak pressure to be below that of the QL prediction, but IMHO is limited to certain combinations of short cases, close to straight designs OR large bores and the faster burning powders. I think this is a sweet spot of cartridge design that has not yet been fully exploited. Applying the "crutch" to QL he told me to use, it drops the peak pressure to 53,000 PSI. I think this round is one heck of winner, exploiting this not-so-wellknown sweet spot and I think it might become far more popular than anticipated. |
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NY, USA
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Posted: 6/23/2008 1:11:02 AM EDT
[#40]
MartyW, I had a similar conversation with the developer os QuickLoad (QL) as well about a year or so ago. At that time I was working on pushing the 300-221 fireball to make USPSA major rifle (power factor 320) and was using QL to model some different powder and bullet load. The 300-221 fireball also benefits from the "expanding" chamber phenomena. The 300-221 Fireball does simply dose not have sufficient case capacity of push a 125-135 grain bullet to major PF. You can get major PF with 155 gr Sierra palma bullets out of a 20-inch barrel... but I wanted to get it out of a 16-inch barrel So I also started thinking about wildcatting 223 to something similar to the 30 Apache and 7mm TCU. But I came across 762x40mm and another fella on quarterbore who were doing the same thing but... they were way ahead of me. So I have been watching and encouraging them. Basically, the ballistics of the 762x40mm is a modern rimless 30-30. And the bottom line is that I am going to have 762x40mm help me build a 7.62x40mm 320pf |
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WA, USA
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Posted: 6/23/2008 2:26:21 AM EDT
[#41]
Hey 762x40mm,
What length of barrel are you planning on using when you try the midlength gas system? |
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MI, USA
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Posted: 6/23/2008 4:48:46 AM EDT
[#42]
I have heard of this myself with the 30 carbine performing better than it should with its limited case volume. So I can see how it would also apply to the 7.62x40mm with its case design. Joe |
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Posted: 6/23/2008 6:09:37 AM EDT
[Last Edit: 762x40mm]
[#43]
A 16" and 20" are in the works...... Marty......thanks for the pressure / effiency explanation.....I have had similar discussions on the phone and through e-mails with forum members although not nearly as....."elegant"...on my part...........I don't have access to Quickload so I was limited to the more traditional wild-catter means of measurement, "run it up til things go bad then back down"..... I knew the effiency had to be pretty good comparing it to 7.62x39mmRussian loads that I had worked up of similar charge......I had always attributed the absence of pressure signs to the fact that the larger bore compared to available "gas" allowed the pressure to drop very rapid in a short period of time.....a fact that makes the brass look good but longer gas systems a bitch to tune.....I really like the "expanding chamber" comparison..... Thanks all for watching and contributing...... 40 |
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FL, USA
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Posted: 6/23/2008 7:45:06 AM EDT
[#44]
I liked the expanding chamber concept too-but I don't know shit about building cartridges, or even reloading-but a few years ago I cooked up a few cartridges in my head, and this was one of them-after reading about the 6.8, 6.5 Grendel, etc.
Someone else came up a round (can't remember the name of it) but it worked with stock magazines, maintained full 30 round capacity, would fit belt links for MG's, and required no changing of the bolt-just the barrel. I don't know what happened to it, but it seems like your cartridge is the answer if the .mil wants something that isn't going to cost a fortune. Personally, I don't think they are going to adopt a different cartridge-but this round is cool. Is it available commerically, or reloading only? |
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NC, USA
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Posted: 6/23/2008 10:09:03 AM EDT
[Last Edit: gdblair]
[#45]
SSK's 6.5 MPC? (inventor of the whisper?) |
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Posted: 6/23/2008 12:25:18 PM EDT
[#46]
Mic McPhereson has written extensively about this powder ignition situation in various articles in the Varmint Hunter magazine over the years. He has gone as far as designing his own type of elliptical shouldered cartridge line, to deal with it. His testing protocals and results have been enlightening, to say the least.
Craig |
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Posted: 6/23/2008 5:57:11 PM EDT
[#47]
Right now you have to roll your own..... Started the arrangements late last week to start the die making process....a first run of (30) sets is in the works as of today.... |
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MI, USA
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Posted: 6/23/2008 6:00:34 PM EDT
[#48]
I would like to be on the list for a die set. Will send my email address by PM.
Joe |
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Posted: 6/23/2008 6:03:44 PM EDT
[#49]
Funny you mention the 30 carbine....I used the analogy of a 30 carbine on steroids a few days ago in a discussion about the 40.....I have been suprised that several of the tried and true 30 carbine bullets cycle in the 40....the sierra 110 HP is one of my favorites....should make one hell of a varmint control load..... 40 |
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USA
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Posted: 6/23/2008 6:19:48 PM EDT
[#50]
Don't be so surprised as to what load will function an AR action. I've told you I shoot cast out of three AR's. Part of my procedure for finding a good load is starting out very low in velocity and working up till I get the velocity and grouping I want. I've cycled AR's with very very anemic cast loads. On another note the French MAS 49/56, which has a DI gas system also cycles on pretty much anemic loads. On the other hand my SKS doesn't. I've come to the conclusion that it has something to do about the DI gas system. It doesn't take a lot of gas to cycle it. |
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