Suppressors 300blk question... Please help.

[11B-B4]

I looked online for quite a while and read various threads with no real answer. There was alot of debate and what people "presumed".

I'm looking to get a custom 300blk barrel made for my LMT MRP CQB upper. I want to achieve max velocity with the shortest barrel possible. I guess im asking, how much length is needed to achieve max velocity with full power 110grain 300blk's?

If anyone could provide that info it would be appreciated... im hoping its around 12 or so inches.


Please let me know. Also if anyone can recommend a place that can either convert a 300blk barrel to LMT MRP or sells one please let me know, thanks -Evan

 

[762frmafr]

Re: 300blk question... Please help.

Max Velocity? The longer the barrel, the faster the projectile will go. To a certain point and then friction actually slows the projectile down. So for "Max Velocity", I would have to say, 34" would be the length.

 

[11B-B4]

Re: 300blk question... Please help.

<span style="font-weight: bold">Found This info on Wikipedia, should have looked there in the first place. I think it answers my questions. Thanks all. </span>

Barrel Cartridge Velocity Energy
9 in (230 mm) barrel 300 AAC Blackout, 115 gr UMC 2,120 ft/s (650 m/s) 1,136 ft·lbf (1,540 J)
16 in (410 mm) barrel 300 AAC Blackout, 115 gr UMC 2,295 ft/s (700 m/s) 1,344 ft·lbf (1,822 J)
9 in (230 mm) barrel 300 AAC Blackout, 125 gr OTM 2,030 ft/s (620 m/s) 1,143 ft·lbf (1,550 J)
16 in (410 mm) barrel 300 AAC Blackout, 125 gr OTM 2,215 ft/s (675 m/s) 1,360 ft·lbf (1,840 J)


<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 762frmafr</div><div class="ubbcode-body">Max Velocity? The longer the barrel, the faster the projectile will go. To a certain point and then friction actually slows the projectile down. So for "Max Velocity", I would have to say, 34" would be the length. </div></div>

Sweet thanks!

Alright i'll try to be as specific as possible....

Ammo manufacturers rate ammunition typically off 16" barrels or something to that extent for AR calibers.

Im curious if there is a barrel length (shorter than 16) that is very close to max velocity from an ammo manufacturers spec.

The reason I was speculating this (as many others are) is that 300blk has a large bore in relation to its small case. If anyone wants to try to provide info without being sarcastic that would be nice, thanks.

 

[762frmafr]

Re: 300blk question... Please help.

The shorter the barrel, the higher the chamber pressure for a given velocity. There comes a point where that pressure becomes unsafe. The best thing to do is give us a velocity for a certain projectile and we can tell you what the shortest barrel possible with a safe pressure. Not being sarcastic, being literal.

 

[11B-B4]

Re: 300blk question... Please help.

762frmafr:

I think the whole allure of this round is that you can shoot it in a short barrel while sacrificing only slight reduction in muzzle velocity. The data confirms this.

Also subs cycle well just like full power loads. I guess the reasons are obvious why it is well liked. however, after seeing many people with ridiculously short 300blk barrels (some as low as 6.5") I thought to myself, I consider 10" to be short so why not see if I can get a slightly compact length that doesn't sacrifice much in terms of Muzzle velocity?


50 m/s over 7 inches of barrel is fairly insignificant. I would like to achieve more closely to stock performance though so I will probably go with 11" or so of barrel. I believe the LMT CQB MRP has roughly 9" of rail space ahead of the front receiver lug. So to clear the rail you would need at least 9.5" I'm guessing.

I am planning on mounting our new RSTA can when it is finished and that needs an additional 1.95" past the rail for the muzzle device to mount so I guess roughly the minimum I will get away with is 11".

Thanks for you help though

 

[762frmafr]

Re: 300blk question... Please help.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 11B-B4</div><div class="ubbcode-body">762frmafr:

I think the whole allure of this round is that you can shoot it in a short barrel while sacrificing only slight reduction in muzzle velocity. The data confirms this.

Also subs cycle well just like full power loads. I guess the reasons are obvious why it is well liked. however, after seeing many people with ridiculously short 300blk barrels (some as low as 6.5") I thought to myself, I consider 10" to be short so why not see if I can get a slightly compact length that doesn't sacrifice much in terms of Muzzle velocity?
</div></div>

I completely comprehend what makes this round so popular. I've had this round since before it was the "IN" thing. Back then they called it a 300 whisper. Your original question was incomplete and poorly thought out. If you are shooting solely factory ammo, then the shorter the barrel the slower the round will go obviously. But, if you were going to reload, then you can tailor your rounds to you barrel. For example, if according to Wikipedia a 115 grain projectile is going 2120 fps from a 9" barrel and 2295 fps from a 16" barrel with factory ammo, then by reloading you may be able to get 2295 fps or more and still have safe pressure levels from a 9" barrel. This example is the reason for my above statements. It is also the reason that your original question was incomplete and poorly thought out. So, while you said thank you for my help sarcastically, it should have been literally.

 

[11B-B4]

Re: 300blk question... Please help.

I'm sorry that you thought I was trying to offend you, I actually did mean thank you literally.

Again, Thanks.

 

[Rancid Coolaid]

Re: 300blk question... Please help.

I ran a Whisper before getting a Blackout, and I had a can that "nested" in the rail, the first 3-4 inches of suppressor was inside the rail, shortening the overall length. If the suppressor diameter isn't ridiculous, this is a good option.

Also be aware that with shorter barrels comes louder report. I sold a 10"-barrel upper because it was much, much louder than my 16" upper. In the end, I decided 12" is a good compromise on muzzle velocity, carry length, and loudness with/without a can.

Is shooting sub and super, get a carbine length gas system, or a pistol with an adjustable gas block.

If the primary purpose of your build is to maximize velocity, this isn't the platform for you. Get a bolt gun, 16 inch barrel, and you'll be good to go on sub or super.

 

[11B-B4]

Re: 300blk question... Please help.

Thats good news as I plan on running my barrel very close to yours.

Im hoping my RSTA can will nest inside but I dont know the ID of the MRP. Im away from home right now so I cant measure it. Good to know though.

 

[rsilvers]

Re: 300blk question... Please help.