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Subject: 6.5 Grendell vs 6.8 SPC controversary
Your Gunny    3/1/2007 12:51:19 AM
I have been testing both 6.5 Grendell and 6.8 SPC cartridges in both AR-15 and bolt action formats for more than a year. I have been benchrest shooting and reloading since 1963 and feel that I have a ligimate voice in this issue. First the availability of ammo and brass. Both are available from moe than two sources. That to me makes them viable candidates for military applications. I have built one rifle each on AR-15 actions and Remington Mod 700 actions. All four rifles delivered excellent results. However, the 6.5 Grendell versions displayed better groups at distances more than 300 yards. At 400 yards the 6.5 Grendell will group 1/2 the best group that the 6.8 SPC can perform. It appears that the 6.8 SPC is limited to distances of about 250 yards. The 6.5 Grendell is very accurate in both formats from 100 yards to 400 yards and further. I have many targets fired at 400 yards that are less than 1/2 MOA. Where as the best 400 yard target with the 6.8 SPC is less than 1 MOA. Test Data and target photos are available. Regards, Yer' Old Gunny
 
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doggtag    gunsmiths are always welcome   3/1/2007 7:47:59 AM
Thanks for the info, Gunny.
In your personal opinion, do you believe the recoils of the Grendel & SPC are so much heavier than the 5.56, to the point you feel that extended firing is going to take its toll on the shooter?
I've heard/read that this is one of the frowns on adopting either as a service cartridge (aside from the major costs involved to convert to a new caliber).
 
(to me, the recoil issue sounds like superficial whining more than anything, or is it actually that noticeably different?)
 
What barrel lengths do you use on the AR15 actions for each?
Do you reload your own ammo?
If so, have you found better bullet wt/powder load ratios than what's available on the market?
 
Do you have plans to examine the SSK 6.5mm MPC and see how it compares?
 
Thanx again.
 
 
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Horsesoldier       3/1/2007 9:45:51 AM
Recoil on 6.8 Rem SPC is noticably more than 5.56mm, but not stout enough that I would consider recoil a problem for military use.  I put a hydraulic buffer in mine in place of the standard (and weighted for 5.56mm) buffer and it is almost as quick handling as a 5.56mm M4 on controlled pairs, transition to other targets, etc.
 
I'd personally say there's no real advantage in 1/2 MOA versus 1 MOA rounds at 400 meters when either one is going through a service rifle that is, itself, going to be capable of anything up to 4 MOA accuracy and still within government specs.
 
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RockyMTNClimber       3/1/2007 5:31:25 PM

I have been testing both 6.5 Grendell and 6.8 SPC cartridges in both AR-15 and bolt action formats for more than a year. I have been benchrest shooting and reloading since 1963 and feel that I have a ligimate voice in this issue.
First the availability of ammo and brass. Both are available from moe than two sources. That to me makes them viable candidates for military applications.

I have built one rifle each on AR-15 actions and Remington Mod 700 actions. All four rifles delivered excellent results. However, the 6.5 Grendell versions displayed better groups at distances more than 300 yards. At 400 yards the 6.5 Grendell will group 1/2 the best group that the 6.8 SPC can perform. It appears that the 6.8 SPC is limited to distances of about 250 yards. The 6.5 Grendell is very accurate in both formats from 100 yards to 400 yards and further. I have many targets fired at 400 yards that are less than 1/2 MOA. Where as the best 400 yard target with the 6.8 SPC is less than 1 MOA.

Test Data and target photos are available.

Regards,

Yer' Old Gunny

Bullet weight? Magazine cap? Piece weight/lb v. 5.56x45?
You are getting great performance! How would you compare them to the 7.62 Nato? (I bet you have a similar set in that caliber)
 
Check Six
 
Rocky
 
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Professor Fickle       6/17/2007 11:56:11 PM

I have been testing both 6.5 Grendell and 6.8 SPC cartridges in both AR-15 and bolt action formats for more than a year. I have been benchrest shooting and reloading since 1963 and feel that I have a ligimate voice in this issue.
First the availability of ammo and brass. Both are available from moe than two sources. That to me makes them viable candidates for military applications.

I have built one rifle each on AR-15 actions and Remington Mod 700 actions. All four rifles delivered excellent results. However, the 6.5 Grendell versions displayed better groups at distances more than 300 yards. At 400 yards the 6.5 Grendell will group 1/2 the best group that the 6.8 SPC can perform. It appears that the 6.8 SPC is limited to distances of about 250 yards. The 6.5 Grendell is very accurate in both formats from 100 yards to 400 yards and further. I have many targets fired at 400 yards that are less than 1/2 MOA. Where as the best 400 yard target with the 6.8 SPC is less than 1 MOA.

Test Data and target photos are available.

Regards,

Yer' Old Gunny

Your Gunny  In your opinion what would make a better light machine gun round(M249 modification )  6.5mm vs 6.8mm ?
I am  ~assuming~  the 6.8mm because the round seems it might be easier to insert & extract (6.5mm Geendell round is longer tip to case neck).

openions please?

 
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Jeff_F_F       6/18/2007 3:02:55 PM
For extraction purposes 6.8mm
If extraction can be resolved, I'd say grendel because of the better long range ballistics, especially in the LMG role where long range area fire is more of an issue than with assault rifles.
 
Note that with the likely move to telescoped small arms ammunition in the near future feed considerations become a non-issue, and a round with a high BC (whether 5.56mm, 6.5mm, or 6.8mm) becomes a very practical option.
 
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Horsesoldier       7/3/2007 10:45:21 AM

Note that with the likely move to telescoped small arms ammunition in the near future feed considerations become a non-issue, and a round with a high BC (whether 5.56mm, 6.5mm, or 6.8mm) becomes a very practical option.


If overall length of the round is a non-issue, something around a 140 grain 6.5mm round (heavier than Grendel is capable of firing through an AR magwell) probably provides the best external ballistics with a recoil considered as well.  (At least it seems to have worked well in the 6.5x55 Swedish Mausers for the first half of the 20th century.)  I'm not sure it would get the nod due to other considerations (even with CTA ammo, it's hard to make 140 grains lighter than, say, a 90 grain 5.56mm bullet, etc.), but would certainly be an impressive cartridge for a rifle that falls somewhere between an assault rifle and battle rifle. 
 
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Jeff_F_F       7/5/2007 11:43:15 AM
A 140 grain bullet would be almost as heavy as a 7.62mm NATO and would have better long range performance due to its higher BC. I'm not sure the weight of the bullet would be an issue. Two different rounds could be issued-one of 120 grain or lower for use at standard ranges and the other 140 grain or higher for long range fire.
 
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Yimmy       7/5/2007 11:58:42 AM

 Two different rounds could be issued-one of 120 grain or lower for use at standard ranges and the other 140 grain or higher for long range fire.


That sort of thing just doesn't work.

In the past it was common for the infantry rifles to fire a heavier charge than the cavalry carbines of the same chambering (to reduce recoil in the lighter weapons), and more recently it is common for medium machinegun ammunition to be loaded hotter, however it simply is not practical to offer different rounds for the same weapon.  The rifle would need two separate zeroes, while you would never know which ammunition type the logistics had brought up.

 
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Jeff_F_F       7/5/2007 1:36:45 PM
I was mostly thinking heavy rounds for LMGs and marksmen, and light rounds for the assault rifles and ARs. Though you could also base it on theater, for example light rounds in Iraq and heavy rounds in Afghanistan.
 
On the other hand, I don't really see the big downside to a high BC 129 grain round even for GPMGs though. The 15gr difference between it and 7.62mm NATO just isn't that big a deal and the better long range performance should make even that a completely moot point. In CQB the muzzle energy isn't so much higher that recoil should be noticably different from a 5.56mm.
 
My only objection is that I'm unconvinced that there is that much benefit right now. But for LSAT, I think it is an ideal round allowing all the KE infantry smallarms to use the same round.
 
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Jeff_F_F    Possible Smallarms Lineup of the Future   7/5/2007 1:56:15 PM
Here is what I'm thinking, assuming that the LSAT program allows sufficient weight reductions to make the OICW practical. I'm not sure this lineup depends on the use of a high BC 6.5mm round, high BC 5.56mm might be sufficient.
 
Role
Current
Future
Individual
5.56mm assault rifle
6.5 mm assault rifle
Grenade Launcher
40mm UBGL
25mm bullpup semiauto GL
Light support weapon
5.56mm LMG
6.5mm LMG
Medium support weapon
7.62mm GPMG
25mm sustained semiautomatic fire GL
Heavy Support weapons
12.7mm HMG or 40mm AGL
25mm crew served AGL
 
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