XCR Forum banner
1 - 5 of 5 Posts

·
Registered
Joined
·
6 Posts
Discussion Starter · #1 ·
Bear with me as i don't know much about 545 but I'm going to own one soon enough.
Would 545 coming out of a 7.5" barrel have less pressure (or at least a smaller or flatter pressure curve) than 556 out of a 7.5" or would it have more pressure?
I see gunsmiths say less pressure overall since their 545 ar15 builds require much larger gas ports, but i understand that pressure curves could have a "spike" (the aks74u is 8.1" and i haven't heard of it having trouble with any suppressors)
Curious about whether a 556 can, that is able to handle 556 out of a 7.5" barrel like the thunder beast (or others) is able to handle 545x39 out of the same length.
I've heard of bubba ar15 conversions not having enough pressure to cycle even after opening the gas port a ton but that's usually out of longer barrels with gas ports further down,
don't know if I'm actually gonna do it since it might be unsafe but I am curious if its possible.
 

·
Registered
Joined
·
534 Posts
Since you can adjust the gas on the. cad you will be fine as long as the can is rated for a barrel that short.

I’ve got a can on my AKS74u and it’s fine. A little gassy but it works. Eventually I’ll get that adjustable KNS piston.


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
6 Posts
Discussion Starter · #3 ·
Since you can adjust the gas on the. cad you will be fine as long as the can is rated for a barrel that short.

I’ve got a can on my AKS74u and it’s fine. A little gassy but it works. Eventually I’ll get that adjustable KNS piston.


Sent from my iPhone using Tapatalk
good to know, but I'm more worried about damaging the suppressor than damaging the xcr. the xcr is a tank and is adjustable, I'm worried about a possible pressure spike at 7.5 thats right around the first baffle of the suppressor (most likely area for damage or rupturing). I assume 545 burns less powder than 556 (but i guess it could just be burning quicker) Since i can't find a pressure curve table anywhere for most 5.45 im going off on a limb that 545 has a smaller pressure curve and therefor = a 556 can thats rated for a 7.5" 556 barrel is technically rated for a 545 7.5".

I own a 7.5" 556 barrel so I ideally would like to buy 1 can for both barrels
 

·
Registered
Joined
·
2,576 Posts
Not an engineer so FWIW...

I don't think any pressure differential is going to be enough to matter. Commercial 5.45 tends to be on the weaker side. I've not shot any of the hornady stuff but would assume 7n6 is going to be hottest stuff you can get without loading your own. I've not ever heard of a 556 can having trouble with 5.45. Besides the pressure, some of the barrel restrictions are related to ensuring a stable projectile. If there is a slight increase in wear over 5.56, I don't think you'll notice unless your one of the few who has the time/money to shoot a "lot".

I've shot 5.45 in a couple of 74s, XCRs in 16 and 10" and ARs in 10.5 and 16" with the adams conversions. I had to open up the port on the barrel of the 16" with the adams but that's pushing the short stroke system so it was to be expected. The rest of my AR/XCR shooting has been suppressed and wasn't different enough from 5.56 to be of note.
 

·
Registered
Joined
·
534 Posts
The can, unless it’s aluminum or some cheap thin titanium will not rupture. Worst case is you get baffle erosion. This can be mitigated by having an appropriate blast chamber, heavier duty first baffle material (inconel for example) and a muzzle device to help calm the blast. A direct thread with a small blast chamber is going to be bad for baffle erosion.

As long as the can is rated for 556 short barrels, it should be fine. But I would run a muzzle device mount to help with erosion. Especially if you’re shooting corrosive ammo.


Sent from my iPhone using Tapatalk
 
1 - 5 of 5 Posts
Top