SBR/Powder Burn Rate

JHB · 01-09-2014, 10:10

Question to the masses. I have searched this forum and have found nothing on point with my question. If I overlooked it well , It happens.

Am building an SBR and will install my Surfire Can which I think is probably the best can available IMHO and I agree with TR that it is one of the most quiet, rugged and depenable cans on the market and I own two other brands.

So my question is this, if using a QD Surefire (or any can for that matter), on an SBR platform, has anyone experienced any excessive wear on the muzzle brake or other QD divice and or the can itself?

I am referring to burn rate of powder. If shooting in a shorter barrel, I have heard and to some degree believe that there is a percentage of powder that is not burned off completely, therefore when using a can/suppressor, the remaining powder is being burned off inside the can or at the QD device thus leading to excessive wear and potential failure. I do not expect much of a problem using the Surefire however I wanted to ask the question.

What do the masses say?

Snaquebite · 01-09-2014, 10:39

Based on what I know (I'm not a ballistics expert) the powder that is going to burn is fully burnt within the first few inches of the barrel.

Max_Tab · 01-09-2014, 12:35

I'm no ballistics expert, but I believe 5.56 was designed arround an 18 inch barrel and the powder burns all the way to the end. That is why the shortie is so much louder and brighter when fired compared to longer barrels. The 300 blackout was designed around an 9 in barrel so all the propellant is burned up within the first 9 in.

**The Reaper** · 01-09-2014, 12:44

Quote:

Originally Posted by Snaquebite

Based on what I know (I'm not a ballistics expert) the powder that is going to burn is fully burnt within the first few inches of the barrel.

IMHO, it depends on the powder, and the barrel length.

If you are handloading, a faster burning powder should burn more completely in a shorty and probably give better velocity as well.

I have not observed any significant wear on the Surefire comp adaptors to this point.

I suspect that the suppressor itself will get hotter as the unburned powder combusts inside of it, and more wear will occur within the can. The degree of excessive wear will depend on the suppressor design and materials, as well as the degree of combustion of powder inside the can.

TR

Snaquebite · 01-09-2014, 12:58

Quote:

If you are handloading, a faster burning powder should burn more completely in a shorty and probably give better velocity as well

Agree. And based on that the burn distance down the barrel would even be shorter. Correct?

JHB · 01-09-2014, 13:09

TR, Yes I handload, and I have thought about (cautiously) working up a load using pistol powder. I know there has been great discussion on this practice to build subsonic loads for the 5.56 community when using cans but still enough back pressure/gas to operate the action. IYHO, do you think SUREFIRE is capable of handling this pressure and if so have you heard howmuch wear is "too much" before a rebuild/replace of a can is warranted? I am not going to use the SBR suppressed all the time but would like to have a "bench mark" going into it so that after many hours of making noise or at least reduced noise while drinking with the TS, I will know when enough is enough.....LOL.....

**The Reaper** · 01-09-2014, 13:35

Quote:

Originally Posted by Snaquebite

Agree. And based on that the burn distance down the barrel would even be shorter. Correct?

It is, but the standard powder for the M193 and M855 loads is optimized for a complete burn in a 20" barrel.

The standard 5.56 powder charge will not completely combust in a 14.5" barrel of an M-4, much less anything shorter. It doers not burn in the first few inches of the barrel. Hence the first round designed to work better with the carbine, the MK 318 MOD 0 “Cartridge, Caliber 5.56mm Ball, Carbine, Barrier”. That round does have a faster burning powder charge.

Quote:

Originally Posted by JHB

TR, Yes I handload, and I have thought about (cautiously) working up a load using pistol powder. I know there has been great discussion on this practice to build subsonic loads for the 5.56 community when using cans but still enough back pressure/gas to operate the action. IYHO, do you think SUREFIRE is capable of handling this pressure and if so have you heard howmuch wear is "too much" before a rebuild/replace of a can is warranted? I am not going to use the SBR suppressed all the time but would like to have a "bench mark" going into it so that after many hours of making noise or at least reduced noise while drinking with the TS, I will know when enough is enough.....LOL.....

I would NOT use pistol powder in a 5.56 rifle load. I would search the manual for 5.56 loads, and then cross-reference with the powder burn rate to select the fastest burning powder. Alternately, if you can find loads listed for the TC Pistol, they may have better burn rates for the shorty barrel. IMHO, there is little point in a sub-sonic 5.56 round. You are basically using a heavier, jacketed standard velocity .22LR round. With a good, well-running .22LR conversion unit, I have had no problems with getting good functioning with the Surefire 5.56 cans. It will put a lot of lead into the can, however, and I would not make a habit out of shooting it thru any can other than a dedicated .22LR suppressor. I probably have several thousand rounds thru my Surefire with no apparent wear, have fired a full 200 round ammo pack through one on a SAW, and seen the cans glowing well into the yellow heat range without issue, but you would have to cut one apart and destroy it (which Surefire has done) or possibly use a borescope, X-Ray, MPI, etc. to confirm cumulative wear.

Personally, I like the .300 BlackOut for a suppressed AR platform.

35NCO · 01-09-2014, 13:56

JHB,
I think you are asking a question with infinite possible answers. As TR mentioned, instead of a blanket on “SBR” powder burn rates, what is the exact length of barrel you plan on using and all your planned calibers? An answer for a typical 14.5/11/10.5/10.3 is very different than the answer for a 9/7.5 inch barrel or less. As well as all variations and curves on multi calibers. I would not want to mislead you to say something is okay, then find out you are making a 7.5 in something special. I do concur with the answers above though.

So, what is it you are planning on making?

Max_Tab · 01-09-2014, 14:42

TR I couldn't remember if it was 18 or 20in, thanks for the correction, and I agree about the blackout. A 5.56 can for reduced noise and muzzleflash works but for subsonic go with something else.

**Peregrino** · 01-09-2014, 19:40

If you want suppressed on an AR platform, build a 300blk. Then you have a suppressor for .30 cal which will also moderate to some extent everything smaller. If you only need ear safe, stick with a 5.56. If you want to adjust burn rates to reduce muzzle flash on SBRs, get one of the computer reloading programs to use ICW up-to-date manuals. I have used Quickload (http://www.accurateshooter.com/gear-...ckload-review/) and found it to be well worth the learning curve. I intend to pick up a current copy next week. Course these are my opinions and worth exactly what you're paying for them.

35NCO · 01-10-2014, 08:37

You can also use some 9mm suppressors for Subsonic 300BLK. The only down side is that you cannot shoot supersonic 300BLK out of them. Check with the manufacturer if they approve of 300BLK out of their 9mm suppressor.

In my experience I have a (very early) fat MK9 with M baffles that does subsonic 300 BLK very well. I have also had great success with an older AAC 9mm for pistols.

I would also add that from the sound at the ear and not the actual decibel measurement, I cannot hear a difference from subsonic 300BLK out of a .30 suppressor or a decent 9mm suppressor. They sound the same to me. However, some cans perform better than others in both calibers.

koz · 01-10-2014, 08:45

Email Western Powders and ask which powder for SBRs. The ballistician email's is [email]johan@ramshot.com[email]. edited: Johan is no longer at Western powders. Scott@ramshot.com Scott Ziebarth will get back to you.

I've used X-terminator with pretty good results in 11.5" barrels and 55gr fmj.

You may also look at AR-comp. it has a high burn rate percentage in a 12" barrel.

The Viper · 01-20-2014, 15:22

Got some trigger time on a friend's custom Noveske SBR on saturday. He shoots it suppressed almost exclusively due to the fact that shooting a 10.5 inch 5.56 can be like getting punched in the face. We shot it unsuppressed just for giggles and in the picture you can definitely see unburned powder exploding as it comes out of the muzzle. His suppressor hasn't sustained any damage due to this. I'm pretty sure the the inside of the silencer will have strengths and tolerances close to that of your rifle's barrel so powder burn in a suppressor shouldn't do any damage.