Sionics 11.5 barrel w/ reduced gas port function report.

**JG007** · 01-02-16, 02:04

Please explain, don't many try to use as heavy a buffer as possible especially with a suppressor?

**BufordTJustice** · 01-02-16, 11:38

Originally Posted by tom12.7

You may want to look into the system further. A 11.5" carbine gas 5.56 AR using a normal 5.56 chamber, throat, and bore can use less gas with normal 5.56 ammo with the LMT carrier A5/ rifle like action in the A5H2 range without a sound suppressor. While I agree that the combo with with an A5H4 has desirable characteristics, some of that can change with the addition of a can.
The added can may not be as desirable in operation with an A5H4 porting than without a can. I will grant you that I am not familiar with your exact combo. Most testing was done with KAC, AAC, and Surefire. Even with each's traits, it's worth considering that it may be worth your time to look at the A5H2 gas when a can may be is involved for use without it to have the operation qualities in use with only the addition of more mass when it it is used.

I'll certainly consider that when I get my Saker. I'll test all combos. However, this heavier buffer is defying convention right now. And the difference between the H4 and H2 is both noticeable and preferable so far, sans can. We shall see.

But I can tell you which has the slowest unlocking for a GIVEN cyclic rate, and it's the heaviest buffer used with the e-carrier.

**jerrysimons** · 01-02-16, 12:15

Originally Posted by tom12.7

You may want to look into the system further. A 11.5" carbine gas 5.56 AR using a normal 5.56 chamber, throat, and bore can use less gas with normal 5.56 ammo with the LMT carrier A5/ rifle like action in the A5H2 range without a sound suppressor. While I agree that the combo with with an A5H4 has desirable characteristics, some of that can change with the addition of a can.
The added can may not be as desirable in operation with an A5H4 porting than without a can. I will grant you that I am not familiar with your exact combo. Most testing was done with KAC, AAC, and Surefire. Even with each's traits, it's worth considering that it may be worth your time to look at the A5H2 gas when a can may be is involved for use without it to have the operation qualities in use with only the addition of more mass when it it is used.

I think this is the same thinking along the line of Grant's best suppressed SBR thread. In a nut shell, tune the gas setting for ejection but not quite lock back without can attached then add a can and it is right on with the added back pressure. This is for a predominantly suppressed use. Would the same principle apply for BTJ? Tune the gun in the same way but with a little added margin unsuppressed because his will be more mixed used. Grants thread focuses on gas settings and back pressure as the main variables reciprocating mass remaining the same. Tom brings up reciprocating mass as the variable to rely on for mixed use. Which variable has the most influence in the system? With gas tuned for an A5H4 unsupressed and the addition of a can leads to less desirable cycling vs a tune for an A5H2 unsuppressed with more desirable cycling after a can is added but using an A5H4 buffer on the A5H2 gas setting, then given the added back pressure from the can being the same for both, which variable makes more of a difference, mass or gas?

I think SIONICS 11.5" carbine barrels are .076" gas port. I would be the reduced gas-port is right at .070-.071". Note that is the crane spec for a 10.5"barrel used exclusively with 556 pressure ammo. As BTJ illustrates in the thread, even with the reduced gas port, there is still a good bit of margin for function built into the reduced gp sizing. Which just goes to show you how crazy over gassed .083" 11.5" carbine barrels are!

**tom12.7** · 01-02-16, 12:47

Originally Posted by BufordTJustice

I'll certainly consider that when I get my Saker. I'll test all combos. However, this heavier buffer is defying convention right now. And the difference between the H4 and H2 is both noticeable and preferable so far, sans can. We shall see.

But I can tell you which has the slowest unlocking for a GIVEN cyclic rate, and it's the heaviest buffer used with the e-carrier.

If you tune it for the A5H4 without a can, the delay is less when a can is introduced. Unfortunately, theres really no way around that.

**BufordTJustice** · 01-02-16, 14:12

Originally Posted by jerrysimons

I think this is the same thinking along the line of Grant's best suppressed SBR thread. In a nut shell, tune the gas setting for ejection but not quite lock back without can attached then add a can and it is right on with the added back pressure. This is for a predominantly suppressed use. Would the same principle apply for BTJ? Tune the gun in the same way but with a little added margin unsuppressed because his will be more mixed used. Grants thread focuses on gas settings and back pressure as the main variables reciprocating mass remaining the same. Tom brings up reciprocating mass as the variable to rely on for mixed use. Which variable has the most influence in the system? With gas tuned for an A5H4 unsupressed and the addition of a can leads to less desirable cycling vs a tune for an A5H2 unsuppressed with more desirable cycling after a can is added but using an A5H4 buffer on the A5H2 gas setting, then given the added back pressure from the can being the same for both, which variable makes more of a difference, mass or gas?

I think SIONICS 11.5" carbine barrels are .076" gas port. I would be the reduced gas-port is right at .070-.071". Note that is the crane spec for a 10.5"barrel used exclusively with 556 pressure ammo. As BTJ illustrates in the thread, even with the reduced gas port, there is still a good bit of margin for function built into the reduced gp sizing. Which just goes to show you how crazy over gassed .083" 11.5" carbine barrels are!

I know from purely unsuppressed use that the H4 buffer has a smaller change in cyclic rate and a smaller change in recoil pulse between ultra weak .223 and really hot 5.56 pressure ammo like independence.

I'm going to apply this observation to suppression in light of Grant's thread. My hypothesis is that the heavier A5H4 buffer will reduce the degree of the over-gassed position WITH suppressor after being tuned for operation WITHOUT suppressor. We'll see.

**BufordTJustice** · 01-02-16, 14:27

Originally Posted by tom12.7

If you tune it for the A5H4 without a can, the delay is less when a can is introduced. Unfortunately, theres really no way around that.

Agreed. But my hypothesis is that the delta between suppressed H4 and unsuppressed H4 is going to be smaller than the delta between suppressed H2 and unsuppressed H2.

**Iraqgunz** · 01-02-16, 15:32

Just to add some additional information to this. The first batch of barrels was done for a specific client (local SWAT) that wanted to replace their Über-heavy 11.5" piston guns. The goal was to trim weight, reduce gassing and maintain reliability with their duty ammo. They also stated that these would only be used with suppressors and the likelihood of shooting without one was very slim. However, we wanted to ensure that they would run un-suppressed in an emergency.

Once we had the basics down we then used a variety of port sizes and conducted testing with several types of ammo and buffer combinations. The end result was a suppressed SBR that would cycle and function with a wide variety of ammunition, and utilize standard components (no adjustable gas block).

**BufordTJustice** · 01-02-16, 16:41

Originally Posted by Iraqgunz

Just to add some additional information to this. The first batch of barrels was done for a specific client (local SWAT) that wanted to replace their Über-heavy 11.5" piston guns. The goal was to trim weight, reduce gassing and maintain reliability with their duty ammo. They also stated that these would only be used with suppressors and the likelihood of shooting without one was very slim. However, we wanted to ensure that they would run un-suppressed in an emergency.

Once we had the basics down we then used a variety of port sizes and conducted testing with several types of ammo and buffer combinations. The end result was a suppressed SBR that would cycle and function with a wide variety of ammunition, and utilize standard components (no adjustable gas block).

I can confirm it was fully reliable and impressively smooth even with no throttling via the gas block.

The profile is great. The gas port is probably ideal for MOST users who intend to suppress their carbine.