Barrett XM-109.... smoke and mirrors?

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[ARCHIVED THREAD] - Barrett XM-109.... smoke and mirrors?

Posted: 3/28/2006 4:30:26 PM EDT

The 2600 FPS claime that Barrett makes in refference to his 25mm x 76mm round out of a 17.5" barrel doesn't seem possible. The round is more like a grenade round then a rifle round and compound that with the fact the barrel is a mere 17.5". 1600fps would be more realistic given the rifles attributes wouldn't it?

Physics wizards help me to understand this round if you wouldn't mind.

Posted: 3/28/2006 5:03:07 PM EDT

[#1]

I fired the first rifles made for Aberdeen. I don't think the 2600 fps is correct. The reciol is pretty strong, about like a sporter weight 300 WinMag.
The trajectory is pretty rainbow like from the charts I remember seeing.

Posted: 3/28/2006 5:15:19 PM EDT

[#2]

Quoted:
I fired the first rifles made for Aberdeen. I don't think the 2600 fps is correct. The reciol is pretty strong, about like a sporter weight 300 WinMag.
The trajectory is pretty rainbow like from the charts I remember seeing.

Tony why didn'y they use the barrel length the M-107 uses for this round? I mean you'd get better accuracy (yea I know most ammo going through this beast will be of the AoE type but still), higher MV, and would aide in reducing recoil as well.

Tony, wouldn't you think a Serbu Shark type brake would be better for this canon or no?

Thanks
Larry A.

Posted: 3/28/2006 5:38:33 PM EDT

[#3]

Quoted:
Quoted:
I fired the first rifles made for Aberdeen. I don't think the 2600 fps is correct. The reciol is pretty strong, about like a sporter weight 300 WinMag.
The trajectory is pretty rainbow like from the charts I remember seeing.

Tony why didn'y they use the barrel length the M-107 uses for this round? I mean you'd get better accuracy (yea I know most ammo going through this beast will be of the AoE type but still), higher MV, and would aide in reducing recoil as well.

Tony, wouldn't you think a Serbu Shark type brake would be better for this canon or no?

Thanks
Larry A.

Muzzle brakes become more effective as the barrels get shorter as pressures at the muzzle are higher.

Could have something to do with it. A short barrel might be the only way to manage to get some recoil absorbing properties out of the brake. With such a large bore pressures probably drop pretty quickly with each additional inch of barrel length traveled, lots of volume in the bore to allow pressures to drop.

Do you try to add weight to reduce recoil through a longer barrel with more steel in it? Or do you try to use the muzzle brake to reduce recoil while keeping weight minimal?

Posted: 3/28/2006 6:13:31 PM EDT

[#4]

Quoted:
Quoted:
Quoted:
I fired the first rifles made for Aberdeen. I don't think the 2600 fps is correct. The reciol is pretty strong, about like a sporter weight 300 WinMag.
The trajectory is pretty rainbow like from the charts I remember seeing.

Tony why didn'y they use the barrel length the M-107 uses for this round? I mean you'd get better accuracy (yea I know most ammo going through this beast will be of the AoE type but still), higher MV, and would aide in reducing recoil as well.

Tony, wouldn't you think a Serbu Shark type brake would be better for this canon or no?

Thanks
Larry A.

Muzzle brakes become more effective as the barrels get shorter as pressures at the muzzle are higher.

Could have something to do with it. A short barrel might be the only way to manage to get some recoil absorbing properties out of the brake. With such a large bore pressures probably drop pretty quickly with each additional inch of barrel length traveled, lots of volume in the bore to allow pressures to drop.

Do you try to add weight to reduce recoil through a longer barrel with more steel in it? Or do you try to use the muzzle brake to reduce recoil while keeping weight minimal?

True, this would normaly be the route to take, but considering they are trying to reach out to 2000+ yards I would think the length of the barrel would be more valuble then the weight savings, don't you? The M-107CQ is 5lbs lighter than the full sized M-107 and has a 9" shorter barrel. The XM-109 with a 17.5" barrel weighs 33 lbs, so it would be reasonable to expect a 8-9lb gain if the XM-109's barrel was increased by 11' to bring it up to the M-107's length right? Or am I under-estimating the weight gain?

Larry A.

Posted: 3/28/2006 6:20:12 PM EDT

[#5]

The chamber pressure of the 25mm round is very comparable to 12ga rounds. A longer barrel wouldn't be of any use.

Posted: 3/28/2006 6:39:55 PM EDT

[#6]

Quoted:
The chamber pressure of the 25mm round is very comparable to 12ga rounds. A longer barrel wouldn't be of any use.

Correct as usual.

Posted: 3/29/2006 3:36:21 AM EDT

[#7]

Quoted:
Quoted:
The chamber pressure of the 25mm round is very comparable to 12ga rounds. A longer barrel wouldn't be of any use.

Correct as usual.

Thanks Chris.

Posted: 3/29/2006 3:40:53 AM EDT

[#8]

It makes perfect sense. Most large bores operate more effeciently due to the base of the projectile having so much more surface area for expanding gasses to push against. That and the 25mm round doesn't appear to have a huge powder capacity, doesn't appear to look like something from a 20mm anti-air cannon atleast.

Pressures should drop pretty quickly as that projectile travels down the barrel. I wonder how fast the powder is, probably surprisingly quick in comparison to something like 50BMG powder.

Posted: 3/29/2006 3:42:57 AM EDT

[#9]

The powder is pretty slow burning actually. Some .50 Match shooters are using it for reloads. I forget the name of the powder.

Posted: 3/29/2006 6:43:16 AM EDT

[#10]

Quoted:
The powder is pretty slow burning actually. Some .50 Match shooters are using it for reloads. I forget the name of the powder.

Don't you need a minimum of a 34" barrel before you can even get a good burn on 20mm powders when the pressure in the chamber is at rifle lvl's ? I thiought I read that somewhere...

Posted: 3/29/2006 4:46:17 PM EDT

[#11]

No, all you need is the 18" of barrel for the type 25mm that is used. Think a 40mm M203 round just shrunk down a bit.

The muzzle velocity is 1350 fps.

Posted: 3/29/2006 10:28:09 PM EDT

[#12]

Quoted:
No, all you need is the 18" of barrel for the type 25mm that is used. Think a 40mm M203 round just shrunk down a bit.

The muzzle velocity is 1350 fps.

Learn something new every day.

Thanks for the info Tony, uglygun.

[ARCHIVED THREAD] - Barrett XM-109.... smoke and mirrors?

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