AMU still testing new cartridges

[TAZ]

The 6.5mm round has a lot going for it for sure. You can have pretty damned accurate loads and rifles that can reach out to 1000 and at the same time you can have very solid anti personnel rounds. 123gr SMK moving at 2600fps is nothing to sneer at.

While I don't see these things becoming main stream any time soon, I would like to see more development put into them. The polymer case is intriguing for sure as it could be a serious cost reduction to brass if done correctly.

There is also a lot of truth to the whole OPM concept as well, but if given a choice of how my tax $$ is spent. Better this than welfare.

[Blute308]

What's the deal with wanting polymer cases?

Wasn't that concept tried a decade or two ago and found to have major problems?
If cheep polymer cases were viable, I would think the current manufacturers would already be flooding the market with polymer ammo. (It would be much cheaper than sourcing brass)

?

[jbjh]

What's the deal with wanting polymer cases?

Wasn't that concept tried a decade or two ago and found to have major problems?
If cheep polymer cases were viable, I would think the current manufacturers would already be flooding the market with polymer ammo. (It would be much cheaper than sourcing brass)

?

Off the top of my head:

Cost. If you're reloading several thousand rounds a year, not a huge chunk of change. If you're manufacturing millions...every little bit adds up to real money. Brass comes out of the ground and is a hassle to do (just because we have a lot of experience with it, doesn't mean it's easy). Procurement from mines, refining ore, etc...Not to mention the fluctuating price of the commodity itself. Hell on budget projections.

Weight. Brass, compared to poly, is heavy. And when you ship by the ton, you can get more rounds on a pallet/gallon of gas used. More rounds carried by individual soldiers as well.

Longevity. Corrosion and oxygen are ammo's enemies when it comes to storage. Poly is temperature stable, doesn't oxidize, and keeps air away from the powder. Heck, you might not even have to gum up the necks and primers to waterproof, depending on how the poly cases are made.

Profit! You figure this manufacturing process out, and EVERYONE is going to pay you a license fee. All of NATO and anyone else you think you might like to do business with.

Smokeless powder and sliced bread will pale in comparison.

[RyanB]

The G1 BC of a Sierra 107 in that velocity range is .406. Not fancy but workable.

[T2C]

Is the .264 cartridge based on the .264 Winchester Magnum? What chamber pressures would have to be managed by the weapon system?

I would like to see someone develop a modified .260 Remington cartridge by using the 7.62x39mm as the parent cartridge instead of the .308 Winchester. The .260 projectiles have proven themselves accurate and a 7.62x39mm case would be more compact than 7.62x51mm brass.

[jbjh]

Is the .264 cartridge based on the .264 Winchester Magnum? What chamber pressures would have to be managed by the weapon system?

I would like to see someone develop a modified .260 Remington cartridge by using the 7.62x39mm as the parent cartridge instead of the .308 Winchester. The .260 projectiles have proven themselves accurate and a 7.62x39mm case would be more compact than 7.62x51mm brass.

That's exactly what the 6.5 Grendel is.

[constructor]

Is the .264 cartridge based on the .264 Winchester Magnum? What chamber pressures would have to be managed by the weapon system?

I would like to see someone develop a modified .260 Remington cartridge by using the 7.62x39mm as the parent cartridge instead of the .308 Winchester. The .260 projectiles have proven themselves accurate and a 7.62x39mm case would be more compact than 7.62x51mm brass.

No, the 264 and 277 USA cartridge design is based on a slightly shortened 6.5 Carcano case, .450" dia. 55,000PSI max pressure. The USA cartridges have apx 42gr capacity or 6 more than the Grendel/264LBC. The AMU believes it will take a cartridge of that size to beat the ballistics and terminal performance of the 308 while keeping recoil and weight to a minimum of 20% lighter than the 308.

If they go through with this they will develop new lead free bullets. We have already seen bullet designs for each caliber with the same BC(.500-G1 or .250 G7). Proportionally they are the same only the weight is different. The .264 is apx 112-115gr and the .277 118-120.

[pinzgauer]

That's exactly what the 6.5 Grendel is.

Yep, the majority of my Grendel shooting is done with IMI (lapua?) 7.62x39 brass.

This was one of the big wins with Grendel during the shortages, readily available brass. That and it can be made on steel case production line with minimal changes, like the current Wolf Grendel ammo.

I understand the request, but it sure feels like we are headed down the 40sw path... Just download 260 until a real breakthrough occurs in poly case. Use current mags & rifles even if it's not quite as efficient weightwise. The difference in case weight between 260 and the proposed AR-12'ish cartridges in brass has to be minimal. (AR-12'ish being halfway between ar10 and ar15 in length and pressure)

Or just go to full pressure Grendel with stronger bolt/receiver extension... I'd have to think bolt gun/AR-10 pressure Grendel would be close to what they are asking for. (Maybe still shy on case capacity)

[T2C]

No, the 264 and 277 USA cartridge design is based on a slightly shortened 6.5 Carcano case, .450" dia. 55,000PSI max pressure. The USA cartridges have apx 42gr capacity or 6 more than the Grendel/264LBC. The AMU believes it will take a cartridge of that size to beat the ballistics and terminal performance of the 308 while keeping recoil and weight to a minimum of 20% lighter than the 308.

If they go through with this they will develop new lead free bullets. We have already seen bullet designs for each caliber with the same BC(.500-G1 or .250 G7). Proportionally they are the same only the weight is different. The .264 is apx 112-115gr and the .277 118-120.

55,000 max pressure would make it easier on the weapon system than some other options. I am of the opinion that if the AR platform could launch a 110g bullet at 3,000 fps, it would shoot flatter than the .308 and have decent terminal ballistics.

What would the new .264" cartridge gain in the way of magazine capacity over the .308?

[constructor]

55,000 max pressure would make it easier on the weapon system than some other options. I am of the opinion that if the AR platform could launch a 110g bullet at 3,000 fps, it would shoot flatter than the .308 and have decent terminal ballistics.

What would the new .264" cartridge gain in the way of magazine capacity over the .308?

27 of the 6.5 or 6.8 x 45 cases fit perfectly in a 25 round Pmag, it is like the feed lips were made for them. Since the SCAR 17 went through the complete approval process, it is lighter than most 308s and they have been using it in combat there is a pretty good chance that will be the platform they use. The 2 test rifles I have chambered in a similar but brass case version will push a 123gr 6.5 to apx 2700fps out of a 16" barrel and a 130gr 6.8 to the same velocity out of a 16" barrel. 110gr bullets should hit 2800 in the 6.5 and 2850-2875 in the 6.8 version.