6mm vs 7mm

[15Tango]

For any given chamber pressure, the 300 AAC BLACKOUT is capable of higher velocity.

Meaning, the 300 Whisper(R) cannot make 2280 fps with that bullet at the same OAL and pressure.

The dimensions of these two cartridges are nearly identical - the AAC is 7/10 of a MM longer on the neck which doesn't even matter as that space is consumed by the bullet in both chamberings. They have the same parent case, therefor the same maximum pressure abilities, and the body taper is nearly non-existent in both. Case capacity also seems to be nearly identical (25 vs 26) for the two. They're both close to each other and the AAC seems to be a way of getting around using the Whisper name - they changed it enough to call it their own. The difference between the two is splitting hairs and it's obvious what the AAC makers did.

Cite your sources for thinking that the 300 AAC is somehow able to do something the Whisper isn't with equal loading lengths. If you trim the necks of the AAC you've pretty much got Whisper brass. It's somehow less capable then? Come on now.

People buy off the shelf ammo for 308 and that does not need any forming. Less than 15% of shooters reload, but factory brass for 300 AAC BLACKOUT is coming out soon at a low price.

People buy .30-06 off the shelf that does not need any forming. What's the point of that statement? the AAC will still be a novelty cartridge, it'll never be as available as 223 or as cheap. Most people that shoot popular novelty cartridges reload it or shoot very little if they don't. That AAC brass could be used to make Whisper brass nearly as easy as range pick-up 223.

 

[rsilvers]

It is not the brass dimensions that I speak of, it is the chamber dimensions - specifically the throat.

I am the project lead at AAC on the 300 AAC BLACKOUT. We never had a Whisper(R) drawing so we did not try to make it the same or different. We started from scratch. We took a Remington 221 Fireball, changed it to 308 cal while keeping the same headspace, taper, and rear of the case. To make the shoulder as significant as possible, we carefully considered the inner and outer shoulder radius, and picked a datum location which would avoid those radii. We then picked a neck diameter to allow for 223 cases to be used if someone wanted to form their own brass, but yet not too much as to maintain as much shoulder as possible. We picked a throat angle which we believed to be the most accurate, and selected a throat length to allow Sierra MatchKings to be loaded to magazine length. This throat length ended up about 0.050 longer than the 300 Fireball wildcat chambers I have seen - which is about the difference between 6.8 SPC-II and 6.8 SAAMI. Shooting full power 300 AAC BLACKOUT ammo in a 300 Whisper chamber will cause pressure to go over SAAMI max. The end result is that a 12 inch barrel in 300 AAC BLACKOUT is about equal to a 16 inch barrel in 300 Whisper, if both are loaded to 55,000 psi.

Remington brass uses an operation to make the case-head hard and so it has been tested and passed 10 reloadings. We do a light crimp on the primer to help with the military but yet it does not need to be swaged to reload. The primers are waterproofed. We anneal the case neck but don't polish out the marks so as to allow for visible inspection of annealing. We keep the shoulder kinda close to max to again, keep the shoulder as large as possible.

Yes, you can use a throating reamer and lengthen a 300 Whisper throat and have the same thing. In fact, PTG sells a reamer to convert a 300 Whisper chamber to a 300 AAC BLACKOUT chamber without moving headspace.

More info here:

http://www.silencertalk.com/forum/viewforum.php?f=128

 

[rsilvers]

That AAC brass could be used to make Whisper brass nearly as easy as range pick-up 223.

I am not sure what you mean by 'nearly as easy.' Range pick up 223 needs to be trimmed a lot, have the shoulder moved a lot, and converted to 30 cal.

What has to be done to 300 AAC BLACKOUT brass to shoot in a Whisper or vice-versa?

 

[rsilvers]

People buy off the shelf ammo for 308 and that does not need any forming. Less than 15% of shooters reload, but factory brass for 300 AAC BLACKOUT is coming out soon at a low price.

People buy .30-06 off the shelf that does not need any forming. What's the point of that statement? the AAC will still be a novelty cartridge, it'll never be as available as 223 or as cheap. Most people that shoot popular novelty cartridges reload it or shoot very little if they don't. That AAC brass could be used to make Whisper brass nearly as easy as range pick-up 223.

You stated that if one can make brass at home by modifying another case, one would never want to buy factory loaded ammo. I gave an example where people buy ammo off the shelf even though they can reload without doing any forming, and so therefore they would be even more likely to buy loaded ammo if they could avoid making brass.

Especially since 300 AAC BLACKOUT ammo is $12.99 MSRP with a street price of about $11.50 whereas the cheapest 300 Whisper ammo was Cor-Bon at over $40 a box.

 

[rsilvers]

AAC will still be a novelty cartridge, it'll never be as available as 223 or as cheap. Most people that shoot popular novelty cartridges reload it or shoot very little if they don't.

Of course people had to reload to shoot Whisper(R). No one feels like spending $42 a box on ammo. That is why we made 300 AAC BLACKOUT ammo cheaper - in fact it is cheaper than brass-cased 7.62x39mm ammo.

Imported:
Sellier & Bellot Ammunition 7.62x39mm Russian 123 Grain Full Metal Jacket Box of 20 - MidwayUSA (http://www.midwayusa.com/viewProduct/default.aspx?productNumber=295405) $11.59
Prvi Partizan Ammunition 7.62x39mm Russian 123 Grain Full Metal Jacket Box of 20 - MidwayUSA (http://www.midwayusa.com/viewProduct/default.aspx?productNumber=373939) $13.79

USA:
Remington UMC Ammunition 7.62x39mm Russian 123 Grain Full Metal Jacket Box of 20 - MidwayUSA (http://www.midwayusa.com/viewProduct/default.aspx?productNumber=883096) $15.29
Federal American Eagle Ammunition 7.62x39mm Russian 124 Grain Full Metal Jacket Box of 20 - MidwayUSA (http://www.midwayusa.com/viewProduct/default.aspx?productNumber=371433) $15.99
Winchester USA Ammunition 7.62x39mm Russian 123 Grain Full Metal Jacket Box of 20 - MidwayUSA (http://www.midwayusa.com/viewProduct/default.aspx?productNumber=831144) $17.29

So $16.19 average for USA, which is 25% more expensive than 300 AAC BLACKOUT based on MidwayUSA prices, or 41% more if you use the $11.50 pricing that one dealer is offering for 300 BLK.

 

[flatlander]

15Tango -
I recently sold my AR15 match rifle upper in 6 RAT - not because I didn't like it, but because I've got a couple of Eliseo tubeguns (R5 in 6BR & RTS in 6.5x47), and have gotten hooked on running a bolt rifle in XC HP matches. The RAT upper had a 28" Bartliein 1:7.8tw bbl. contoured & chambered by John Holliger, and was giving fine accuracy, along with 2840fps with B105VLDs pushed by RL15.

Since I liked the RAT so much, I had John do a 24" fluted Wilson 1:8tw RAT bbl., and used it to build sort of a 'super-duper' SDM rifle. I put a LaRue 13.2 rail on an M4 upper, and used a Magpul ACS buttstock in FDE, then CeraKoted the whole rifle in coyote tan. It's a nice-handling & accurate rifle, one that I'm going to enjoy playing with. Only real downside as far as I'm concerned is the price of AA 6.5 Grendal brass - I sure don't want to lose very much of that stuff running & gunning through tactical field courses.

Though I've really come to appreciate the ballistic advantages of the 6.5x47 Lapua, 6.5x55 AI, and 284, I'd hate to give up on my Dashers & 6x47s - 6mm rifles are so darned nice to shoot after putting 75-80rds. through a 284 or 308 during the course of a day's shooting in a 3x1000.