Subsonic .308 load with 200 gr. bullet

[TZaun]

I was asked to find out if it is safe to shoot 7.0 gr. of Red Dot behind a 200 grain bullet in a .308? I ran it on QL and it says it would be around 1150 fps, 20,000 PSI, and 35% case fill. The gentleman wants a subsonic .308 load to shoot with a can on the end. From what I researched, most guys use Trail Boss. He has a bunch of Red Dot and wants to use that, if he can.

 

[DaveTooley]

Trail Boss gives you much greater case fill. I wouldn't use Red Dot.

 

[rammac]

Red Dot creates a situation that could be bad. When you use too little of powder mass there exists a possibility that the primer flame will engulf all of the powder and ignite it in one big flash. QuickLoad calculates powder burn based on the assumption that the primer will ignite the powder at the rear of a powder column and that the powder will burn progressively along the length of that powder column. Powder that burns in a controlled progressive burn will produce pressure in a progressive and controlled manner with only a small percentage of the total powder column producing expanding gases (pressure) as the column burns, the total amount of powder is never ignited at one time. If the smaller amount of Red Dot ignites in big flash then you can actually produce extremely high pressure unexpectedly. I would never use a powder that didn't fill at least 50% of the case volume.

 

[cmillard]

I hope he has some twist in that barrel with that heavy of a bullet or he could have a baffle strike due to instability. I could be wrong but something he may want to consider

 

[3Ackleys]

I wouldnt use red dot. TB is good. Shoot them through paper without the can to make sure they arent tumbling first.
I quit using my 308 for subs and moved to a 300 Blackout

 

[snowpro440]

Just use Trail Boss and your problem is solved. Never keyholed for me with or without my can on out of my savage 10fp.

 

[Dave in WI]

TrailBoss works great. But beware stabilization. Even if you have 10 twist barrel, probably will keyhole. Test without can on first!

 

[seymour fish]

TrailBoss works great. But beware stabilization. Even if you have 10 twist barrel, probably will keyhole. Test without can on first!

Use a 175. Stability issues go away

 

[MihiT]

I worked some that are *warning* outside the manual.
About 14gn of varget behind a 220gn hornady RN. In a 1:10 or so barrel.
550 odd FPE and with a trajectory like 22lr so easy to remember. If you're interested I'll check my notes and post the recipe.

I've heard many theories on "secondary explosve effect" or "detonation" however with exactly -ZERO- evidence to corroborate the stories over the last 50 years, I am happy to disregard them.

When working sub loads, work your loads DOWN and shoot WITHOUT the supressor until you get subsonic velo and check for keyholing in your targets. THEN you know the projectile is stable and can fit the Can.

 

[TZaun]

Thanks for weighing in guys. Much appreciated. When he called me today and asked about this, I knew where to go to get the answers.

I will tell him to scrap the plan to use his Red Dot, and that's a good suggestion to test without the can on. I'll bet he doesn't have enough twist.

I ran Trail Boss on QL and that sure does have a lot better case fill but no velocity to go with it.

 

[Mr.Knowit all]

I have a 1-7 twist .308 that I shoot subs out of. I also use a 200 gr. Speer HotCore bullet for my load.
My load is 11.5 gr of TB in Lapua brass, CCI 200, out of a 16 in barrel I get 1008 fps with a very low SD.
Good luck

 

[rammac]

...I've heard many theories on "secondary explosve effect" or "detonation" however with exactly -ZERO- evidence to corroborate the stories over the last 50 years, I am happy to disregard them...

While I've found nothing that explains how smokeless powder detonates in a cartridge case I have found quite a bit of proof that single and double base powders CAN and in FACT do detonate and cause catastrophic damage.

I found one study entitled;
"DETONATION VELOCITIES OF SINGLE AND DOUBLE BASE PROPELLANTS"
BY Ken Okada, Tomoharu Matsumura, Yoshio Nakayama, Hisashi lguichi, Masamichi Ishiguchi, Toshihiko Uchikawa, Tetsuya Sawada, Kazushige Kato, Akihiko Yamamoto, and Masatake Yoshida

The conclusion of which was;
"...we found that smokeless powder can be detonated."
"...the DV (Detonation Velocities) of single and double base propellants...were identified as 3624 ms and 4134 ms."


Another study
"DYNAMIC COMPACTION OF POROUS BEDS"
BY H. W. SANDUSKY T. P. LIDDIARD

Another study that shows that this issue has been studied by many countries in the world is;
"Smokeless Propellants as Vehicle Borne lED Main Charges: An Initial Threat Assessment"
BY Special Agent Steven 1. Beggs Bureau of Alcohol, Tobacco, Firearms and Explosives Office of Strategic Intelligence and Information Counter Terrorism Division

All of these studies explain that all smokeless powders can be detonated with the proper initiator. They explain the process by which detonation occurs. From the research I've done it seems that smokeless powder detonation has been studied for decades with some information pointing to an awareness of this issue since at least 1944. Studies discuss the deflagration to detonation transition (DDT) process. In one report they explain that studies done with closed containers haven't been conducted to any great degree so they can't really explain how it happens in a cartridge case.

But since we do know that detonation is a fact I'd recommend being cautious when ever you deviate from the reloading manual recommendations.

 

[MihiT]

In one report they explain that studies done with closed containers haven't been conducted to any great degree so they can't really explain how it happens in a cartridge case.

I'd say they can't explain IF it even happens.

I would say most if not all ammunition manufacturers have tried and failed to replicate it in the lab. From my reading they never have, even going down to SFA load densities. The advice remains to not load below 50% case capacity, so you can catch a double-charge. But still, no proof of small loads somehow creating an over-pressure situation.

As always, your safety is in your own hands and everyone has to determine what they're comfortable doing.

 

[BronzeArcher]

TB has been unsatisfactory for extreme spreads and accuracy in subsonic .308 loads for my friends and I. Blue Dot is much more consistent and usually accurate.

 

[Brians356]

Hodgdon lists max 41.0 grs H4895 behind 200-gr bullet at 2406 fps. Hodgdon endorses reducing H4895 to 60% of max, or 24.6 grs. This might well be subsonic, but load density will be low compared to TB. Still, if he already has some H4895 ...
-

 

[jds holler]

Many of us pistoleros have shot many thousands of hollow base wad-cutters over a charge of three grains of Bullseye or HP-38 in 38 Special or 357 Mag. Those cases aren't near half full, and I've never sploded myself. jd

 

[Brians356]

Many of us pistoleros have shot many thousands of hollow base wad-cutters over a charge of three grains of Bullseye or HP-38 in 38 Special or 357 Mag. Those cases aren't near half full, and I've never sploded myself. jd

There's a first time for everything. And it usually ain't pretty.
-

 

[mic2377]

I have used Red Dot for this, but mainly in smaller cases like 300 Blackout and 30-30. It works very well in smaller cases.

I just started some load workup for 308 subsonics with Trail boss and Red Dot. I am using 150-165 grain projectiles though due to stability concerns.

To stabilize 200-220 grain bullets subsonic, 1/8 twist is good, and 1/7 twist is better.

I think concerns for Red Dot and low case fill are a bit overblown? It is a very fluffy, easy to ignite powder, and works well at low pressures and low case fill volumes. It is a shotgun powder after all. Just my opinion...

 

[mic2377]

Also when working up subsonic rounds, start high and work down, and watch for stuck bullets!

 

[rammac]

I'd say they can't explain IF it even happens.

This is why these kinds of discussions never get anywhere. If WHAT even happens? Did you mean that nobody can prove that Smokeless powder detonates or that smokeless powder in a cartridge case detonates? If people would bother to read even one of the references that I posted you'd see that the tests that were used to determine the velocity of detonation was done by filling a tube with powder and then detonating it - kind of like a cartridge case - a tube with powder in it. Common sense should tell you that if smokeless powder can detonate and that it can be detonated reliably in a closed cylinder then it might be possible to detonate smokeless powder in a cartridge case.

Inexact comments and generalities simply create rumors that some people misinterpret as fact and then we end up with people spreading Internet crap as truth. Making a general statement like;

"...most if not all ammunition manufacturers have tried and failed to replicate it in the lab."

isn't proof of anything. Which manufacturers have conducted detonation tests? Give us a link to the reports that say that they couldn't make it work. I suspect that you don't have any proof and that you are simply repeating something that you read on the Internet. I've come across a couple of articles that say that at least ONE manufacturer has tried to create this issue but failed but those articles didn't provide any proof either, there was no link to the test or a quoted statement from the manufacturer about the test.

We can't find tests proving this phenomena either way because there haven't been any. The government isn't in the business of making sub-sonic loads so they aren't going to waste time experimenting with them, although they have conducted a lot of testing on the detonation of smokeless powder. One or two manufacturers might have run tests to prove that their powder didn't blow up a customer's gun but that's not the same as running tests to prove or disprove in-cartridge detonation. Manufacturers don't want you to use light loads, that's why most powder manufacturers warn you to not do it so why would they create a liability issue producing a report about using light loads when they've already gone on record saying that it's not safe to do.

Just because something can be done doesn't mean that it's smart to do it. It's obvious that sub-sonic loads can be built but I'm sure that most people simply use a load that someone else has already developed and whomever it was that developed that load was the guinea pig. Either the developer knew a lot about powder or he was just lucky. It's just like blended powder, it can be done, manufacturers do it, but the average layman isn't qualified to even attempt it and the cost of failure is simply too high to bother doing it. My opinion is that since nobody, including myself, in this conversation is a trained smokeless powder expert who has any facts proving that smokeless powder CAN'T detonate in a cartridge case and I know that it's a FACT that smokeless powder CAN detonate in an enclosed container, I'll play it safe and let you guys do the experimenting.