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 Post subject: What cartridge will an AAC 762 SD handle?
PostPosted: Fri Jul 09, 2010 12:14 pm 
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I bought an AAC 762 SD can, that is still being processed by the ATF. I have the QD on my AR10, but was going to use it on several other guns as well. My question is..................What is the largest cartridge I can safely use it on? Would this can hold up to a 300RUM, and a 300 Win mag? I don't see any specs on the website about safe pressures for the can.

Any insight???

Thanks.

Les


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 Post subject: Re: What cartridge will an AAC 762 SD handle?
PostPosted: Fri Jul 09, 2010 12:48 pm 
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viewtopic.php?f=2&t=59611&hilit=.300WM

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 Post subject: Re: What cartridge will an AAC 762 SD handle?
PostPosted: Fri Jul 09, 2010 1:16 pm 
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Does anyone know the pressures for a 30-06, 300 win mag, and 300RUM? in say 22, 24, and 26" barrels?


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 Post subject: Re: What cartridge will an AAC 762 SD handle?
PostPosted: Fri Jul 09, 2010 2:48 pm 
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Don't know for different bbl lengths. But SAAMI specs for chamber pressures are listed as:

7.62x39 45,000 psi
30-06 Springfield 50,000 cup (copper units of pressure)
300 Win Mag 64,000 psi
300 Weatherby Magnum 65,000 psi
308 Winchester 62,000 psi

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 Post subject: Re: What cartridge will an AAC 762 SD handle?
PostPosted: Fri Jul 09, 2010 4:51 pm 
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Armorer-at-Law wrote:
Don't know for different bbl lengths. But SAAMI specs for chamber pressures are listed as:

7.62x39 45,000 psi
30-06 Springfield 50,000 cup (copper units of pressure)
300 Win Mag 64,000 psi
300 Weatherby Magnum 65,000 psi
308 Winchester 62,000 psi


While pressure is a factor, another thing to consider is powder charge, as you can see, the 2 mangums, are similar to .308, but, "typical" loads of .308 are using 40-50 grains of powder, "typical" loads for 300 WM uses 65-75+ grains of powder. I'd almost venture to say that charge volume (assuming similar speed powders) would be a better indicator of compatibilty then chamber pressure. All the 300 win mag loads I'm browsing online are using much more of a slower powder, which means greater muzzle pressure. Look at using hunting ammo in a M1 Garand, and how a slower burning powder, even with similar charge weights and velocities can hose stuff up.


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 Post subject: Re: What cartridge will an AAC 762 SD handle?
PostPosted: Sat Jul 10, 2010 12:09 am 
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CKOD,
You're right, but the measurement for your idea is muzzle pressure. A 308 with 24" barrel versus a 300 WM with a 24" has proportionally lower muzzle pressure because of less powder burned. So the answer is to use muzzle pressures to discern what is safe for the designed suppressor. A 300 RUM with a 30" barrel has 10,150 psi muzzle pressure, and a 308 with an 18" barrel has 10,600 psi (both using a 150gr bullet at max chamber pressure loads).

The problem is when some knucklehead asks if they cut their 300 RUM to a 20" barrel to make a homemade flamethrower, are they OK to use their 308 suppressor? They are not (it would have 16,000 psi muzzle pressure). So suppressor manufacturers say their's is made for 308, which covers all normal barrel lengths for 308 with regards to muzzle pressures.

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 Post subject: Re: What cartridge will an AAC 762 SD handle?
PostPosted: Sat Jul 10, 2010 12:10 pm 
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I plan on getting a 762SD soon too. I'd like to put it on a 25ish caliber rifle one day. Maybe a 6mm Remington or a 25-06. A 257 weatherby is the ultimate round for that size, but something tells me that would be way too much presssure for that can.


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 Post subject: Re: What cartridge will an AAC 762 SD handle?
PostPosted: Sun Jul 11, 2010 4:21 pm 
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call AAC


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 Post subject: Re: What cartridge will an AAC 762 SD handle?
PostPosted: Sun Jul 11, 2010 4:38 pm 
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.308 is the max for the 762-SD

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 Post subject: Re: What cartridge will an AAC 762 SD handle?
PostPosted: Mon Jul 12, 2010 10:01 am 
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MAJ MALFUNCTION wrote:
.308 is the max for the 762-SD


This post on the AAC blog seems to suggest otherwise.
http://www.aacblog.com/?p=6796
Image
Why would "even 30.06" be mentioned in same paragraph if not factory allowed?


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 Post subject: Re: What cartridge will an AAC 762 SD handle?
PostPosted: Mon Jul 12, 2010 11:44 am 
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Quote:
So the answer is to use muzzle pressures to discern what is safe for the designed suppressor.
Yes, but is there a reliable and affordable way to measure muzzle pressure (particularly as a curve over a very short period of time)? We can reliably and precisely measure muzzle velocity of the projectile with an inexpensive chronometer. But how do we measure muzzle pressure, as opposed to calculating an estimate from a table of calculated chamber pressures and burn rates for a particular combination of caliber, powder, projectile mass?

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 Post subject: Re: What cartridge will an AAC 762 SD handle?
PostPosted: Mon Jul 12, 2010 8:50 pm 
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10mmPhil wrote:
MAJ MALFUNCTION wrote:
.308 is the max for the 762-SD


This post on the AAC blog seems to suggest otherwise.
http://www.aacblog.com/?p=6796
Image
Why would "even 30.06" be mentioned in same paragraph if not factory allowed?


Maybe AAC is expanding the range of calibers the can covers, but the last time I talked to the all knowing Mers, it was .308 and below.

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 Post subject: Re: What cartridge will an AAC 762 SD handle?
PostPosted: Tue Jul 13, 2010 2:17 am 
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Armorer-at-law,
I use the Quickload program and calculate the muzzle pressures. It's close enough for me and is quick and easy to calculate for different barrel lengths and bullet weights. Using Quickload for 308 for example, its calculated velocities are within 20-30 fps of chrongraphed velocities for loads. The max chamber pressures calculated in Quickload also match what I see in my rifles, where I start getting heavier bolt lift or flattening primers. Therefore, the calculated muzzle pressures are likely accurate too.

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 Post subject: Re: What cartridge will an AAC 762 SD handle?
PostPosted: Tue Jul 13, 2010 10:48 am 
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I bought an '08 762SD with 18T and it's always been rated for 30-06.

That's one of the reasons I bought it in the first place.

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 Post subject: Re: What cartridge will an AAC 762 SD handle?
PostPosted: Tue Jul 13, 2010 11:18 am 
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Thanks, johndoe3.

I have a Rem 700 in .30-'06 I want to suppress, but I think I going to wait for a 300SD to mount on it.

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 Post subject: Re: What cartridge will an AAC 762 SD handle?
PostPosted: Tue Jul 13, 2010 4:26 pm 
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The 762SD is not 30-06 "approved" period. Neither is the Cyclone + Cyclone-K. I asked and was told 308 and 260, 30-30 but not a 30-06, 300 H&H, or the 30-06 AI (which was the intended host with a 24-26" barrel)

Mike told me NO.

I have worked up Quick Load #'s for Mike many times and sent them to him regarding SBR's so I understand Muzzle Pressures. But still the amount of powder in a 30-06 is more than the 308. Maybe that is why .. or people my think a SBR 30-06 is OK.

58gr - 61.5 gr of powder in a typical 30-06 vs 45 gr- 56.5 gr for the typical 308, a good 10 gr more powder on average. The 308 is around 52.8K CUP and the 30-06 is 50.8 K CUP

I thought the Cyclone and 762 SD were OK on a 30-06 but apparently I was wrong when I asked. I wanted to use it on my 300 H&H and the 30-06 AI I plan on building.

I would suspect a 30-06 would not bother a SD or Cyclone in a 20"+ barrel ... But what AAC says is what it is.

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 Post subject: Re: What cartridge will an AAC 762 SD handle?
PostPosted: Tue Jul 13, 2010 7:23 pm 
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johndoe3 wrote:
Armorer-at-law,
I use the Quickload program and calculate the muzzle pressures. It's close enough for me and is quick and easy to calculate for different barrel lengths and bullet weights. Using Quickload for 308 for example, its calculated velocities are within 20-30 fps of chrongraphed velocities for loads. The max chamber pressures calculated in Quickload also match what I see in my rifles, where I start getting heavier bolt lift or flattening primers. Therefore, the calculated muzzle pressures are likely accurate too.


Highly complex engine modeling software is usually very close to reality these days, so I'd be surprised if such a simple system would be off by much. But, as they say, "garbage in, garbage out..." I'm not sure I'd feel safe knowing that such an arbitrary claim (.308 good, but not 30-06) is being made without other variables being accounted for (garbage in, garbage out?). Not bashing, it's just eye-opening to know that more complete destructive testing has evidently not been completed. If, for instance, Company X says 300 Ultra Super Deer Slayer Magnum is safe for a can, but don't give you a barrel length and powder charge baseline, or at least a muzzle pressure estimate, then how do we know they've done their homework?


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 Post subject: Re: What cartridge will an AAC 762 SD handle?
PostPosted: Wed Jul 14, 2010 10:40 am 
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Quote:
But, as they say, "garbage in, garbage out..."
That's my concern. I trust the formula used. But if the data used to calculate the muzzle pressure is based on chamber pressure data that is calculated -- not measured -- for a particular load that was calculated from a different load, I'd like to know how far back in the calculation process a measurement was taken. That is, a particular amount of a particular powder with a particular burn rate was measured. Then, the pressure for other amounts of powder is calculated or "adjusted" for other factors. At what point were the figures we use as "known" measured vs. calculated?

Also, it's easy to "over engineer" a device (make it stronger than it would ever need to be). But we are all seeking maximun performance, including minimizing size, weight and price at an acceptable useful life duration.

When I asked someone at AAC (not Mers) what I should used to suppress my .30-'06 bolt gun, I was told I should wait for the 300SD to become available. I wasn't told that other models would be unacceptable, just that the 300SD would be the best and would be available soon enough for my needs/desires.

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 Post subject: Re: What cartridge will an AAC 762 SD handle?
PostPosted: Wed Jul 14, 2010 11:12 am 
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I think if you run a heavy bullet in a long barrel in 30-06 it would probably be ok.. heavy bullet means lower powder charge , and long barrel means down pressures... (probably have to be a handloader type guy ...)

but what happens if you forget and , swap ammo fire a fast light bullet ??? kaboom????

that's probably why you would loose your warranty and support from the manufacturer.. just because the potential for error !!

I guess they have to cover their tush based on the fact that there are lots of dumb people out there and a firearm is serious business with serious consequences...


I personally run my heavy 22-250's 75 and 80 gr a-max on my m4-1000 with a 22 inch barrel , and it's nice and quiet and does not hurt the can one bit ... but Mers recommended me to use my cyclone instead (don't have it yet)


after all the m4-1000 is rated for full auto fire at no less than a 10.5 inch barrel..... it would be really hard to be as harsh on it with a 22" bolt gun 22-250 ... i'd assume the 7.62 SD is along the same lines...

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 Post subject: Re: What cartridge will an AAC 762 SD handle?
PostPosted: Wed Jul 14, 2010 11:43 am 
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What we really need is some climate "scientists" to work these numbers for us, then... :mrgreen:


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 Post subject: Re: What cartridge will an AAC 762 SD handle?
PostPosted: Tue Sep 21, 2010 6:36 pm 
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So what the official AAC answer...Is the 762-SD good to go with the 300 Win Mag?


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 Post subject: Re: What cartridge will an AAC 762 SD handle?
PostPosted: Tue Sep 21, 2010 7:17 pm 
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I don't have the "official" answer, but yesterday when they put out the info for the contract on the new Army M24E1, which is a 300 Win Mag., they have chosen the Titan to go on it. There has to be reason. Hopefully Jason or Mike will chime in.

This is the link to the M24E1 info: http://www.aacblog.com/?p=7397


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 Post subject: Re: What cartridge will an AAC 762 SD handle?
PostPosted: Tue Sep 21, 2010 9:19 pm 
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GBI96 wrote:
I don't have the "official" answer, but yesterday when they put out the info for the contract on the new Army M24E1, which is a 300 Win Mag., they have chosen the Titan to go on it. There has to be reason. Hopefully Jason or Mike will chime in.

This is the link to the M24E1 info: http://www.aacblog.com/?p=7397


762-SD and 300 WinMag is definitely a no-go.

The M24E1 is 300 WinMag, and the contract was won with the TiTAN-QD. Another good choice when available is the 300-SD. I don't know the details of the Army guns and why they went with the TiTAN. My ASSumption is to allow .338LM flexibility?

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 Post subject: Re: What cartridge will an AAC 762 SD handle?
PostPosted: Wed Sep 22, 2010 6:33 pm 
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johndoe3 wrote:
CKOD,
You're right, but the measurement for your idea is muzzle pressure. A 308 with 24" barrel versus a 300 WM with a 24" has proportionally lower muzzle pressure because of less powder burned. So the answer is to use muzzle pressures to discern what is safe for the designed suppressor. A 300 RUM with a 30" barrel has 10,150 psi muzzle pressure, and a 308 with an 18" barrel has 10,600 psi (both using a 150gr bullet at max chamber pressure loads).

The problem is when some knucklehead asks if they cut their 300 RUM to a 20" barrel to make a homemade flamethrower, are they OK to use their 308 suppressor? They are not (it would have 16,000 psi muzzle pressure). So suppressor manufacturers say their's is made for 308, which covers all normal barrel lengths for 308 with regards to muzzle pressures.


This is one of the best post on this forum EVER.

:D

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 Post subject: Re: What cartridge will an AAC 762 SD handle?
PostPosted: Wed Sep 22, 2010 6:43 pm 
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seattlite wrote:
So what the official AAC answer...Is the 762-SD good to go with the 300 Win Mag?



We do not recommend this. However, I know customers that do it on 26" barrels without problems... heck they say it sounds good.

30.06 was out and now back in on 20" barrels or longer. Sorry John, I told you no because that was the company line then...


PLEASE NOTE, the Cyclone and Cyclone-K are thinner walled silencers... they are 308 ONLY!

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