Building a quiet SBR and a cartridge to make it worthwhile.

[plant.one]

Leaving? You're crazier than I thought you were. The meat loaf is too good!

[thezoltar]

"I can feel a rant coming on about the problems of posting on the internet, innovation, fun stuff, dangerous stuff, and personal responsibility coming on so I'll leave that for another thread."

Ah Dellet, you make me chuckle and I feel I know exactly where you’re coming from intellectually.

A question from a lifelong math challenged mind. Are your pressure numbers from published sources, measured sources, mathematically extrapolated from charts, etc? I like to know if I’m reading science, experience or witchcraft, not that I’m disinclined to believe anything.

I like the Hornady #9 edition also but maybe for a reason that some others may not have stumbled across. This manual seems to me to be more conservative in its numbers than quite a few powder or bullet manufacturers. A safe place to start for new entry into a particular cartridge.

I agree about powder weight/volume vs bullet/shape/length. This cartridge has introduced a few new considerations about the many choices of components. I first ran into this when trying to load mid weight (+-150grn) bullets over different powders. It quickly became obvious that there was a bullet versus powder volume competition inside the case. I’m still searching for that perfect powder volume/bullet weight combination here. It’s a bit of a challenge for me because my 16" rifle seems to be most accurate at higher velocities but won’t always accept the charted powder by volume. I guess a different powder choice will help me here. Still searching…

All these comments and I’m still not purpose loading for my short gun. I guess I better get started.

[dellet]

"I can feel a rant coming on about the problems of posting on the internet, innovation, fun stuff, dangerous stuff, and personal responsibility coming on so I'll leave that for another thread."

Ah Dellet, you make me chuckle and I feel I know exactly where you’re coming from intellectually.

A question from a lifelong math challenged mind. Are your pressure numbers from published sources, measured sources, mathematically extrapolated from charts, etc? I like to know if I’m reading science, experience or witchcraft, not that I’m disinclined to believe anything.

I like the Hornady #9 edition also but maybe for a reason that some others may not have stumbled across. This manual seems to me to be more conservative in its numbers than quite a few powder or bullet manufacturers. A safe place to start for new entry into a particular cartridge.

I agree about powder weight/volume vs bullet/shape/length. This cartridge has introduced a few new considerations about the many choices of components. I first ran into this when trying to load mid weight (+-150grn) bullets over different powders. It quickly became obvious that there was a bullet versus powder volume competition inside the case. I’m still searching for that perfect powder volume/bullet weight combination here. It’s a bit of a challenge for me because my 16" rifle seems to be most accurate at higher velocities but won’t always accept the charted powder by volume. I guess a different powder choice will help me here. Still searching…

All these comments and I’m still not purpose loading for my short gun. I guess I better get started.

Pressure estimates from a reasonably reliable source. Quickload. You start plugging in published loads that have tested pressures listed and you get an idea of it's accuracy. It's like anything else, tells you when you should test the load in a Remington 700 action before trying it in your AR It's been a very valuable tool for this type of experimentation. One thing it will do is chart the pressure curve so you can tell how much pressure you will have at the gas port, but not volume.

Sometimes it's seat of the pants. For your 150 loads I would try MP300. No published data for that weight bullet. Powder is not in my version of Quickload. This will be from memory so don't take it as a good starting point. 20 grains under a Berger 155.5 at 2.255 was just over 2100 fps in a 16" barrel. Started with new Norma brass and quit counting after 16 firings of the same brass. I have no idea what the pressure was, but I got about half that many firings using 21.5 of 1680 with an estimated pressure of around 55,000 and comparable velocity. For me tho the 1680 was more accurate. It also seems to perform better under compression.

Here is Accurate's data for 1680 and 150-155 weight bullets
150 SIERRA HPBT MK 19.4 1,895 21.6 2,086 51,553 2.150
150 SIERRA FMJBT 19.5 1,877 21.7 2,057 54,564 2.140
155 SIERRA HPBT MK 18.6 1,817 20.7 2,010 49,099 2.190

http://www.accuratepowder.com/wp-conten ... t_Data.pdf

One of the other things Quickload does is when you work up a load it will chart a +/- percentage table. That gives you a reasonable idea of what you can expect for a slower or faster lot of powder, the program generally takes the middle ground.

Back to the 150 bullet challenges because it applies all over. There must be around a 100,000 +/- 3 different 150 grain .308 bullets add in the 147, 155 and 155.5 grain options and it really gets confusing. A bullet comparator and knowing bullet length, bearing surface and seating depth is the only thing that keeps you safe.

As much as I joke around, I do try to keep things safe. I have had a couple of near misses over the years. Each time it had nothing to do with the materials I was using except the fact the guy using them screwed up. I double charged a load once, another time I did not empty or label the powder in the hopper of the dispenser. Burn rates are different and create different pressures I guess and my memory is not always clear after a week

One last thought on commercial ammo that applies to 300 Blackout more than any other cartridge. Talking to Paul from Maker bullets, he gave me this tidbit. The industry standard for loading commercial subsonic ammo is that it has to function reliably, in the worst commercially manufactured firearm for the caliber. Hopefully there is a little wiggle room when your done for accuracy.

Some how the company slogan that says "We can proudly say we can run the worst" just doesn't seem right.

[realtreehunter]

..

[John A.]

I have a question for you guys.

One thing that I seldom see discussed is the primer choice. I'm sure you've probably got a favorite.

Have any of you noticed more port noise with certain primers than others?

For the main reason in semi's when the cartridge is ejecting.

Granted there is going to be a lot going on in the chamber already as the brass is ejecting/ejected.

Another question, does one brand of primer tend to get more velocity than others in the same loads?

Less than others?

[rebel]

I have a question for you guys.

One thing that I seldom see discussed is the primer choice. I'm sure you've probably got a favorite.

Have any of you noticed more port noise with certain primers than others?

For the main reason in semi's when the cartridge is ejecting.

Granted there is going to be a lot going on in the chamber already as the brass is ejecting/ejected.

Another question, does one brand of primer tend to get more velocity than others in the same loads?

Less than others?

John as far as the noise thing I doubt the primer makes much difference. I have used cci 400, 450 and BR 4s. Winchester SRPs as well. I have found that the 450s give me a bit more consistent velocity, probably due better/hotter ignition.

[TMD]

I've played with SR and SRM primers and found that with SRM primers I get slightly higher velocities (10-20fps) but more importantly I get lower SD's.

[Srussede]

Dellet,

What was you loading mistake that cost you the barrel, bcg, etc... I'm just starting to work up my first loads. Have you tried #9 with 208's and 225's if so what were charge weights and velocities. I'll be trying these out of a Lilja 9.5" 7tw. Any input would be appreciated.

Building a quiet shooting SBR or pistol, is a whole lot more than screwing a suppressor on a short barrel and grabbing a box of subsonic ammo off the shelf. In fact that will lead to a big disappointment.

There have been a lot of threads over the years looking for the quietest suppressor and quietest powder. These threads number in the hundreds it seems and are only outnumbered by the number of posts that say my gun is loud. Well that's not completely true. (The top asked questions are probably, Why won't it cycle and Why are my case mouths dented).

Let's start right off with, if you want a quiet SBR, do not load with 1680. It's loud, it's dirty and basically just disappointing to work with. Save it for heavy supers, or use it if you are just learning to reload until you have some experience and can deal with the possible side effects of faster powders.

The next thing to be aware of is that the quietest loads, can be the most dangerous and unpredictable to work with. They require fast powders at low case fill rates and many times reach the same firing pressures as many supers. Double charging a load is certainly possible . The pay off is a reasonably hearing safe load that can be fired indoors without ear protection.

Suppressor choice, or build style come into play. Mono cores like Gemtech's purpose built 300 can, tend to have a pretty good first round pop. This can negate all the work you put into your build and handloads if used in an emergency situation, no ears inside.

Finally all of this is a waste of time if the whole system is unreliable. If you can not do at least two successive mag dumps and have the bolt lock back on empty each time, then you are no where near having a reliable setup.

Let's start with the basics.

There are way too many variables for the "quietest subsonic load". The basics won't change, but if you are doing a purpose built rifle, it can be very quiet and reliable.

First, what is counter intuitive is to leave the gas port as small as possible, or run an adjustable block. This will reduce port noise. No sense making it quiet at the muzzle just to have it louder at the other end. There is no reason to have a pistol length port over .100" and plenty of reasons to have it less.

Barrel length also makes a noticeable difference. I have had the chance to run 7-8.5" in 1/2" increments and noise increases noticeably at each length. Shorter is louder.

Bullet choice will also be an issue. A longer bearing surface can help create back pressure and choice of material can play a role. A good example would be the Lehigh 174 grain bullet. I tried very hard to develop a load for it that met other requirements I had. Basically I chose to run Accurate #9. I had no problems getting full function using Sierra 175 and 168 Matchkings, but I had trouble with reliable cycling and locking back if the 174 Lehigh stayed subsonic. I cured it by moving to the 194. The problem was the brass, it behaves more like lead when it comes to creating pressure.

Powder choice as pointed out earlier is critical. The two powders I have ran that are the quietest and still have full function are Accurate #9 and Vihtavuori N105. N105 is slightly quieter, but needs a heavier bullet than #9.

I take a certain amount of criticism using #9. Generally being told it's not safe in low charges, you'll have high ES blah, blah, blah..... there is some truth to that and there is a great pic of a barrel and bolt carrier that gets posted a lot on the forum to drive that point home. That's my work, it was a loading error. Cost me a bolt, barrel and upper.

The other truth is that for the most part I am using data straight out of Hornady #9 for reference. The fact that the barrel is 8-9 inches shorter means that I just don't get the velocity printed. This is a big plus when loading for an SBR. You can use low end super data and have a functioning sub sonic load in an SBR.

All that said be very careful and attentive when using fast powders. All the noise it saves you, comes out in one shot when things go wrong.

Velocity matters.
There is a huge difference in muzzle pressure and pop above and below 1000 fps. There is also a difference because of the burn rates of powders. It's not always true that faster powder is quieter, experimentation is required.

What about the rifle?

There are just as many variations here, as in your load. But the main things are buffer spring and weight, carrier weight. I won't even discuss gas port size except to repeat what I said before. Smaller is better, bigger is noisier and there is never a need, that I have found to be over .100" and plenty of reasons to stay under. An adjustable gas block makes shooting supers in your dedicated sub gun much more enjoyable.

I am a fan of the JP captured set up because you can adjust both weight and spring tension. The quietest operating rifle will be the one that takes the least amount of gas to make it go. It will also be cleaner running and therefore more reliable for longer shooting strings.

I have had the chance to run a Gemtech 300BLK, a couple of Thunderbeasts 9" and 7" and a I think it was a Sandstorm?. The Gemtech was the loudest and created the least back pressure. This meant that it was the least helpful for the specific application. The most reliable, quietest on first(most important)round and subsequent shots were the Thunderbeasts. My choice would be an Ultra 7.

I am sure there are other things I have forgotten or do not know and this is meant as a general guideline or thought process to getting quiet. As always it's not the only way and hopefully others will chime in.

My purpose built SBR and dedicated load.

8" Excaliber 1/5 barrel with .097" gas port
JP silent capture w/steel weight and black spring.
LMT enhanced F/A bcg
Thunder Beast 7"

194 Lehigh
8.2 grns #9
1010 fps.

[dellet]

Dellet,

What was you loading mistake that cost you the barrel, bcg, etc... I'm just starting to work up my first loads. Have you tried #9 with 208's and 225's if so what were charge weights and velocities. I'll be trying these out of a Lilja 9.5" 7tw. Any input would be appreciated.

Got distracted, didn't have my mind on what I was doing, for maybe a minute.
viewtopic.php?f=141&t=97062

In short, I have ran everything from 178 Hornady's to 240 SMK's using between 8.2-8.8 grains. The best reference is Hornady's manual. Their data for #9 is the best, but is for 16" barrels. Start with that data, what is 1300 fps in 16" will be very close to subsonic in a 9".

[dpete]

Dellet,

What was you loading mistake that cost you the barrel, bcg, etc... I'm just starting to work up my first loads. Have you tried #9 with 208's and 225's if so what were charge weights and velocities. I'll be trying these out of a Lilja 9.5" 7tw. Any input would be appreciated.

The best reference is Hornady's manual. Their data for #9 is the best, but is for 16" barrels. Start with that data, what is 1300 fps in 16" will be very close to subsonic in a 9".

Any idea what the Hornady #10 holds for 300BLK data?