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Posted: 4/6/2007 2:48:52 PM EST
I want to try shooting Major power factor in 3-gun and I would love to do it with an AR-15 based weapon.  Now I could certainly buy and AR-10 and easily make Major with 308 but if I could just buy and new upper for my AR-15 lower that would be the cheaper route.

FYI power factor for USPSA is calculated as bullet weight (grains) X velocity (fps)/1000

Rifle Major Power Factor (PF) is 320.

From my research is seems that 6.5 and 6.8 cartridges fall just short of Major as most loads seem to top out at about 300PF.  458SOCOM and 50 Beowulf easily make Major PF but are serous over kill and those big cartridges really hurt magazine capacity.

So is there a cartridge that is compatible with an AR-15 lower that falls between 6.8 and 458 SOCOM?  Living here in Ohio I will probably not see too many stages with targets beyond 200 yards so a supper flat trajectory is not mandatory.

Thanks
mcb
Link Posted: 4/6/2007 4:17:07 PM EST
You might check out the ballistics on the 30 HRT.  Marty from Teppo Jutsu might be along to give a definite answer.

http://www.teppojutsu.com/

The only other options I could think of are the 7.62x39, or someone here was talking about trying a 7.62x39 "Improved" that might just put it over the top.
Link Posted: 4/6/2007 5:35:54 PM EST
According to Arne (competition shooting sports) the Grendel can make a power factor of 320

Click Here

Post #7
Link Posted: 4/7/2007 4:46:55 AM EST
Thanks guys.  looks like I need to take a second look a 6.5 Grendel.

Thanks
mcb
Link Posted: 4/7/2007 9:01:51 AM EST

Quoted:
According to Arne (competition shooting sports) the Grendel can make a power factor of 320

Click Here

Post #7


 I have no doubt you can get a 6.5 too make major. I have serious doubts that you are going to get a bolt to live when you do. M9
Link Posted: 4/7/2007 11:30:44 AM EST
What about 300 whisper?
Link Posted: 4/7/2007 5:11:24 PM EST
I've read that 6.5 Grendel with 130 grain bullets out of an 18" barrel will do it. Henning Wallgren does it, but I don't know his barrel length.
Link Posted: 4/7/2007 6:02:59 PM EST

Quoted:

Quoted:
According to Arne (competition shooting sports) the Grendel can make a power factor of 320

Click Here

Post #7


 I have no doubt you can get a 6.5 too make major. I have serious doubts that you are going to get a bolt to live when you do. M9


No problem with the bolts unless you try and push the 6.5 Grendel beyond pressure limits.  

If you try to get 120gr or less bullets to make 320 you are likely exceeding pressure.  123gr bullets make 320 right around 50,000 psi max load.  

Heavier than 123gr make MPF 320 without a problem and a few can do 340 for competitions that use that as MPF.

Over at www.65grendel.com/forums there are several guys working up MPF loads.  They are having a difficult time when they try to do it with a 120gr round.  Heavier is ok.  Look at the pressure safe reloading tables that Bill Alexander published - the listed Max loads are actually below 50k PSI (due to Bill's over cautiousness) and many of the heavier bullets make MPF.
Link Posted: 4/9/2007 9:24:11 AM EST

Quoted: I've read that 6.5 Grendel with 130 grain bullets out of an 18" barrel will do it. Henning Walgren does it, but I don't know his barrel length.


Wallgren's loads are hot! Kids: Don't try this at home!

John

| 6.5 Grendel: World's Best Combat Cartridge |
Link Posted: 4/9/2007 10:54:12 AM EST
Well, I guess if I was a professional shooter with sponsorship, swapping out a $60 bolt now and then wouldn't be a problem.
Link Posted: 4/10/2007 4:45:23 PM EST

Quoted:
Well, I guess if I was a professional shooter with sponsorship, swapping out a $60 bolt now and then wouldn't be a problem.


 No its not, but a bolt breaking in the middle of a winning string & he will be looking for a different rifle. M9
Link Posted: 4/11/2007 7:25:26 AM EST
Link Posted: 4/11/2007 7:43:23 AM EST
Link Posted: 4/12/2007 6:11:22 PM EST
If 30 HRT is an option, another 3-gun shooter asked the same question and our reply was:

Quoted:
Marty,
What kind of velocity are you getting with 150/155 gr and the 168 gr. loads from the HRT. Say barrel length is 18".

Hadn't shot one over the chrony and the ones we had were 16" and less. QL suggests for an 18" at 55000 psi max pressure
155 Amax, about 2200 fps
168 SMK, about 2100 fps

155 @ 2200 should be 340
168 @ 2100 should be 353

It might work ...
Link Posted: 4/12/2007 7:53:20 PM EST

It might work ...


It will.

QL this:
16.8" barrel (I always estimate using a slightly shorter barrel for gas guns, esp AR's)
150 grain Speer faltbase SP (flatbase allows for more powder and higher initial velocity)
2.28" OAL (a little less than full magazine legnth for a conservative estimate)
33.8 grains of water case capacity (being conservative again)
1.610" case length (this reduces the useable case capacity a smidge over the default trim length)
.6 weighing factor instead of .5 (a more consevative number than the default)

This is the worst case scenario for the .30 HRT and it still makes major by a comfortable margin with half a dozen available powders with velocities from 2200-2165 fps.  Did I forget to mention I limited it to only 52k psi?

David



Link Posted: 4/12/2007 8:12:11 PM EST

Quoted:
You might check out the ballistics on the 30 HRT.  Marty from Teppo Jutsu might be along to give a definite answer.

http://www.teppojutsu.com/

The only other options I could think of are the 7.62x39, or someone here was talking about trying a 7.62x39 "Improved" that might just put it over the top.


Marty, I can't believe it took you so long to find this thread.
Link Posted: 4/12/2007 8:23:50 PM EST

Quoted:

It might work ...


It will.

QL this:
16.8" barrel (I always estimate using a slightly shorter barrel for gas guns, esp AR's)
150 grain Speer faltbase SP (flatbase allows for more powder and higher initial velocity)
2.28" OAL (a little less than full magazine legnth for a conservative estimate)
33.8 grains of water case capacity (being conservative again)
1.610" case length (this reduces the useable case capacity a smidge over the default trim length)
.6 weighing factor instead of .5 (a more consevative number than the default)

This is the worst case scenario for the .30 HRT and it still makes major by a comfortable margin with half a dozen available powders with velocities from 2200-2165 fps.  Did I forget to mention I limited it to only 52k psi?

David


Using your input, it gives 2270 odd fps using a slightly compressed load of Re10x - 340 PF, major.

We showed the round to Piatt at SHOT 05 and he didn't think it would make major ... we didn't have all the input to QL at the time ... to me, it is a round that makes sense
Link Posted: 4/13/2007 3:19:33 AM EST
I am presently shooting a 20inch barrel and would be just happy continue using that long of a barrel.  I am shooting in the Limited Division and have to use iron sights so the longer barrel helps with the sight radius.   The longer barrel will no doubt also help if I try to go Major.  It seem like several cartridge have the potential to make Major if I hand load.  It would be nice if factory ammo would make Major but I an not against reloading to make Major.

Thanks
mcb
Link Posted: 4/13/2007 1:31:40 PM EST
Marty,

Isn't the new floor for major 320?

David
Link Posted: 4/13/2007 1:55:36 PM EST
Depends on the competition, Some are 320 others 340.

What is the .30 HRT?  It fits in AR15 platform I guess.  Is it highly accurate for competition?  How does it compare at moderate range stages such as 300 or 600 yards?

The 6.5 Grendel gives an advantage over 5.56 at 600 yards but no real difference at 0-300 for accuracy and wind bucking - the other advantage over 5.56 is that you can make easily make MPF with all bullet loads over 125gr.
Link Posted: 4/13/2007 6:43:19 PM EST

What is the .30 HRT? It fits in AR15 platform I guess.


The 30 HRT is a rimless .30 Herrett.


Is it highly accurate for competition?


There isn't any magic in it, if that's what you're asking, but it should be as accurate as the amount of effort that goes into its contruction (like ANY other rifle).


How does it compare at moderate range stages such as 300 or 600 yards?


I venture a guess that none of the few that have ever been built have been shot at 600 yards.  In an AR15 magazine many VLD bullets aren't going to fit but, in theory, it should stay above the transonic range out to about 375 yards and remain supersonic to 625-675 with the available bullets.  Since muzzle velocities are 2300-2000 fps, with a 150-180 grain .30 caliber bullet, there is obviously going to be more windage and drop.

The 30 HRT is never going to compete on an even field with the major-loaded 6.5 Grendel, even in matches limited to 200 or 300 yards.  The Grendel is always going to recoil slightly faster and a caliber specific compensator will work better (more muzzle pressure to work with).  Even so, the .30 HRT could have a place, if for no other reason than its a much cheaper, easier way for people that mostly compete locally to make major.  Something like shooting 40 S&W instead of 38 Super in the old days of the 175 PF.

David

Link Posted: 4/13/2007 7:28:54 PM EST

Quoted:
What is the .30 HRT?  It fits in AR15 platform I guess.  


6.8SPC brass run through a .30 Herrett die.  Uses resized 6.8PC brass, 6.8SPC bolt, and 6.8SPC mags.  The barrel is the only part that would have to be a custom order item.
Link Posted: 4/14/2007 11:13:30 AM EST

Quoted:
Depends on the competition, Some are 320 others 340.

What is the .30 HRT?  It fits in AR15 platform I guess.  Is it highly accurate for competition?  How does it compare at moderate range stages such as 300 or 600 yards?

The 6.5 Grendel gives an advantage over 5.56 at 600 yards but no real difference at 0-300 for accuracy and wind bucking - the other advantage over 5.56 is that you can make easily make MPF with all bullet loads over 125gr.


As DocGKR commented, the SPC team looked at all variants from 22 to 30 caliber and decided upon 6.8 as it gave the performance (terminal/wound ballistics) they wanted.  For competition purposes, the 30 caliber version might make (more?) sense.

As stated, simply the 6.8 SPC run through 30 Herrett dies (Herrett Rimless Tactical).  Accuracy?  With a good barrel and handloading, it should hold its own.  It falls a little below 30 IHMSA, 30 BR and 30 PPC in terms of case capacity, but what it does have it bolts and magazines that work without issue ...  At the distances you mention the sleek 6.5 will win out ...
Link Posted: 4/14/2007 11:42:44 PM EST
Link Posted: 4/15/2007 4:35:05 AM EST
When I started work with the 7 SCAR, it appears that the longest case length that would still work in the magazines with the lighter bullets (110-125) was 1.695.

222 Rem is 1.700 and necking up would reduce the length a hair.

I would think a 7mm - 222 would work nicely perhaps for a similar round?  It would be right in line with your 7 x 40 and should be feasible from COTS brass with one pass ...

Quick run in QL suggests 2300 fps with 120 gr bullet from 16.8 bbl at 55K psi ... not enough for MPF

Yet ANOTHER caliber to add to the mix
Link Posted: 4/15/2007 4:58:20 AM EST

Quoted:

Quoted:
Well, I guess if I was a professional shooter with sponsorship, swapping out a $60 bolt now and then wouldn't be a problem.


 No its not, but a bolt breaking in the middle of a winning string & he will be looking for a different rifle. M9


Will you STFU already?  You have absolutely no friggin proof of what you're saying.  I don't know why you constantly spew your bullshit about the 6.5 Grendel.  
Link Posted: 4/15/2007 5:41:10 PM EST
After looking at it some more, I think a 30 PPC Long could maybe crack 320 with 125 grain bullets, a 20" barrel and acceptable pressures.  I think the 30 HRT could do it with 130's.

David
Link Posted: 4/17/2007 3:27:22 PM EST

mcb,

I have made major in 6.8 spc.
130gr soft point.
20" barrel upper.
going 2500 fps

I shoot 3-gun but not much USPSA 3-gun. The 20" is not that great for 90% of 3-gun stages being somewhat muzzle heavy for me.

I really wanted to shoot the 6.8 in heavy metal division but, most matches have rules that say .308 and up in heavy metal. So the 6.8 is .031 short howing
Link Posted: 4/22/2007 9:31:04 AM EST

Quoted:
Will you STFU already?  You have absolutely no friggin proof of what you're saying.  I don't know why you constantly spew your bullshit about the 6.5 Grendel.  



 I've seen a lot of broken bolts from PPC based ARs. I think you pretty well summed it up with "I don't know why?"  Nuff said. M9


 PS The answer too your question is negative.
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