6.8 SPC Forums banner

1 - 11 of 11 Posts

·
Registered
Joined
·
59 Posts
Discussion Starter #1
If and this is a very large if, the military ever got around to adopting a cartridge that has most of the 308 capability and handier like the 5.56, is there an in between length cartridge that could fill both needs and be the all around cartridge???

What case length would be needed? I would assume something exactly in between the 7.62 and 5.56 in length and have the same taper so as to not require the curved mag like an AK. I would also think that the caliber would be something like 7mm. The optimum bullet weight might be between 120 and 140 grains, or it might not. Do we already have a case like that or would one have to be designed? It would also have to be an in between case head/circumference.

Remember, this is an imaginary 'new' combat weapon that is a start from scratch design which might or might not look like an inbetween AR-15 and AR10. This would shoot almost as soft as the 5.56 and hit as hard as the 7.62 at distance.

Let your imaginations range free, but please don't turn this into why anything we have already is 'good enough'. There are too many strong opinions out there on both sides. This is a clean sheet and barring any large advances in plasma watt rifles, this will be a traditional case/bullet arrangement.

Cold, Paulo, TimW....If this is not in the proper forum, please feel free to move it elsewhere.

Just wanted to see ideas and have a good discussion of cartridges. Everyone, have fun dreaming and thinking about what would you do if you had the keys to the cookie jar???


Kelly :mrgreen: :mrgreen: :mrgreen:
 

·
Registered
Joined
·
2,318 Posts
Doc has brought that up on ARFCOM. I forgot what it was called, but it used a 7mm bullet and the case was intermediate length.
 

·
Registered
Joined
·
441 Posts
Paulo hit it Cris Murray the creator of the 6.8 has already done that. IT is the 7mm Murray whihc is a necked down 7.62x45 to 7x46. All the range and energy of the 308 with less recoil and fit in a AR size weapon with good SBR performance.
 

·
Registered
Joined
·
59 Posts
Discussion Starter #4
Paulo and TimW,

Thanks alot!!! :D :D Found this post over on Arfcom:

"DocGKR:
Fortunately, while at USAMU, Cris Murray, one of the co-designers of the 6.8 mm SPC simultaneously developed an assault rifle cartridge, with none of the platform imposed design compromises that limit both the 6.5 mm Grendel and 6.8 mm SPC. This an idealized assault rifle cartridge, the 7 x 46 mm, offers better range and terminal performance than 6.5 mm Grendel, 6.8 mm SPC, or any other common assault rifle cartridges, including 5.45 x 39 mm, 5.56 x 45 mm and 7.62 x 39 mm. Since the 7 x 46 mm is based on the proven Czech military 7.62 x 45 mm cartridge, it has an established record feeding and functioning in both magazine and belt-fed full-auto fire. Likewise, recoil appears manageable and weapons remain controllable in FA fire, just as with the Czech cartridge. In addition, the 7 x 46 mm is optimized for shorter barrels and larger magazines than the heavier, bulkier, and harsher recoiling 7.62 x 51 mm/.308 cartridge. The 7 x 46 mm is truly the best assault rifle cartridge developed to date.

The main problem is that the 7 x 46 mm cartridge OAL is a bit too long to fit into the M4/M16 or other 5.56 mm size weapons/magazines, yet it does not need a receiver/magazine as large as those used by 7.62 x 51 mm/.308 platforms such as the M14, Mk11, M110.

As a result, the 7 x 46 mm requires new weapons--envision a rifle sized a bit larger than the AR15, but smaller than an AR10/SR25.

As you can see, 7 x 46 mm offers outstanding terminal performance very similar to 6.8 mm; 7x46 mm is just a bit better.

Both the 6.8 mm SPC and 7 x 46 mm were conceived and developed entirely by experienced end-users based on identified combat mission needs and end-user requirements as approved by their Commanders. Both the 6.8x43mm and 7x46mm were developed by the same design team at the same time. From day one everyone involved in this effort has acknowledged both cartridges, however, a decision was made to pursue deployment of 6.8mm initially, as it offered a more expeditious solution for improving current combat capability by simple, inexpensive modifications to existing weapons, while 7x46mm required new weapons platforms for optimal performance.

Again, bottom line:

-- 6.8 mm SPC is the best available solution to rapidly upgrade current 5.56 mm weapons.

-- If given a clean slate of paper and substantial development funds, the clear and obvious best cartridge for new design weapons is the 7 x 46 mm, as it offers greater soft tissue terminal performance, better intermediate barrier penetration, and greater maximum range and long distance performance than traditional assault rifle cartridges like the 5.45 x 39 mm, 5.56 mm, 7.62 x 39 mm, as well as the newer 6.5 mm Grendel and 6.8 mm SPC. "


Looks like Chris M has already thought of that one!!!!!!! :mrgreen: :mrgreen: :mrgreen:

Looking over the stats of the parent cartridge:
Base Diameter 6.8 = 0.421 ; 7mm Murray = 0.441 ; 308Win = 0.470
Case Length 6.8 = 1.676 ; 7mm Murray = approx 1.85 ; 308Win = 2.015
Overall Length 6.8 = 2.30 ; 7mm Murray = 2.50 ; 308Win = 2.80

Now the question would seem to be would that round be the best compromise of effectiveness for CQB and DMR in one weapon??? I really would like to see how one of these would do in the real world!!! :twisted: :twisted:

Does anyone know where the information about the research of that particular round might exist???

Thanks,

Kelly
 

·
Registered
Joined
·
189 Posts
I sorry for hijacking the thread and bringing up the old 6.5 6.8 thing but in looking up the 7x46 it lead me to the 6.5 web site where they where they where talking about this round and say the 6.5 would benifit from the longer dimentions my question is how much would the 6.8 benifit from longer dimentions
 

·
Registered
Joined
·
2,318 Posts
Bigdog923 said:
I sorry for hijacking the thread and bringing up the old 6.5 6.8 thing but in looking up the 7x46 it lead me to the 6.5 web site where they where they where talking about this round and say the 6.5 would benifit from the longer dimentions my question is how much would the 6.8 benifit from longer dimentions
It would allow for more powder and allow the bullets to be loaded longer. The advantage of the Grendel is that they can use longer/heavier bullets without sacrificing case capacity. If you could load the SPC bullets out to 2.4", the SPc be even better than it is.
 

·
Registered
Joined
·
59 Posts
Discussion Starter #7
This new round would be nothing like using the 7mm bullet with the 5.56x45 case. It is a totally different, much larger diameter and possibly taller (slightly) 1.80 vs 1.76 to hold a lot more powder. It would be launching a heavy 140g-160g 7mm (.284) bullet instead of a 6.5 (.264) much faster and more impact!!! :mrgreen: :mrgreen: :mrgreen:

Just have to remember, this is a dream rifle...No AR manufactured today would handle this round. It could be designed very easily, but, hasn't been done. I will have to say that the AR-10 could, but is sooo much more heavier and the 308 round recoils way too much on full auto. Just trying to think of an AR with the weight and handiness of the AR-15 with almost equal power of the AR-10...just without all the negatives!!!
 

·
Registered
Joined
·
441 Posts
Tests have been done all the way back to WWI and every time the 7mm has been shown to be the most effective caliber of bullet for a combat round period, end of story; but for whatever reason others have been picked. After WI we almost got closer to it but certain Mil figures wanted more power and we ended up with the 30 06. It should have been the .276 Pederson (which regardless of the name is a 7mm) which was what John C. Garand had setup for his M-1 Garand for which was much more inline with that was needed and and is very close to what our SPC is doing but it had a bit more powder. Then we had our best chance for the perfect round at the end of WWII with the .280/7mm British also known at the 7mmNATO and was what all the other NATO allies had thought was best but use stupid Americans couldn't bear not to be able to use out stores of 3006 left over from the war so instead of a lighter recoil manageable round we ended up with the M14 that the cyclic rate had to be so slow as to not be point in at the moon at then of a mag if FA was used. Which ended up being one of the shortest lived mil main rifle in history. Then after that failure we did the rubber band snapback effect and went way the other way to the light tiny 5.56. Now after 100 years of going back and forth and not hitting the mark it might actaully happen in the next 10-15 years as there are no stores built up etc to go to another improper round.

The .280.7mm NATO just happens to have the following specs:

Bullet Caliber: 7mm
Case Length: 1.70"
Rim: 0.473"
COAL: 2.54"
Bullet Weight: 120-150
Powder capacity:43gr H20

.280 Britsh/ 7mm NATO




7mm Murray parent case which needs only to be necked down 0.62mm.


Has more energy and velocity on target even out to 1K then the current.308 with 25-30%less reciol about 10% more then the 6.8 SPC and only 6-9 grains more powder. We got very close with the SPC only the AR mag held it back.


Now look how we have come full circle with the 7mm Murray.Same ballistics only dif is using a different parent case and only becasue its already in production and proven. But the British were 80 years ago where we should have been. Sad isn't it. This is why you always here there's nothing new in small arms cartridges as its already be done already.

Why 7mm: When you go smaller you get better vel/BC but loose wounding ability when you go bigger you get a bit better wounding but it really hurts ve BC. The reason .277 was chosen was because of the limitation in the AR. Think about it there are tons of 6.5s out there so of course the Grendel could benefit as any cartridge with less powder capacity could the problem with their line of thought is they are stuck on the 6.5 is the best caliber no matter what the data shows. There is a big difference between pointing out a rounds positives and being a cheerleader. One is blind to facts the other is based on facts. The fact is the 7mm offers the best balance balance between ballistic and terminal performance in the frame work of a military combat rifling.There are other benefits as well as the larger diameter is more powder efficient as well as in barrel erosion. It is the one caliber that can offer a 1 caliber solution to belt fed and mag feed weapons. The 6.5 is too small in mass and the 30 cal is to big. If you go right in between 6mm and 8mm or 6.5and 7.62 you arrive at 7mmor a perfect balance point. There is enough data on both the 6.5 and7.62 to arrive at this with a large degree of certainty not to mention the huge amount of testing of the 7mm round.
 

·
Registered
Joined
·
3 Posts
I would be very, very interested in a 7x46mm project. I see the 6.8 still having a role for the m4 size rifle, and the 7x46 as a 7.62 replacement... Advantages would also include less blast/recoil..

Anyone up for it? Let me know!!
 
1 - 11 of 11 Posts
Top