308 WIN subsonic tips for first timer

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oldscot3

New member
As soon as some components come in, I'll be working up my first subsonic loads for 308 Win. using Sierra 220 gr. Round nose bullets on top of Trailboss.

I've been researching the process, reading and watching You Tube vids, and have found some "tips" that are somewhat different from normal reloading procedures. For instance some guys recommend drilling the flash holes out and using magnum primers.

The one that really caught my attention though, was the use of lube. A particular individual suggested that some subsonic loads might get stuck in the barrel and not even exit without lube. He used a little bit of Crisco on conventional copper jacketed bullets. Hummm... I don't know about all that. Seems like if lube really were necessary it might just be for starting loads and something better than Crisco should be used. Perhaps Imperial sizing wax, or a lube used on lead bullets.

Is there someone here with subsonic loading and shooting experience that cares to weigh in?
 
I don't do that, but internet information unless from a reliable source can be extremely hazardous.

There were a series of failures in the 20s or 30s with match shooting team that resulted in blown up guns because someone told them grease made them more accurate!

My take is you don't put anything on the bullet or in the barrel period, be it Crisco, butter or Coconut oil on up to synthetic grease period.

At best its going to turn it into a gooey mess (Crisco and the like) at worst it could created an issue that blows up in your face. To think that a low temp substance is going to improve things is way beyond the pale.

If you want to shoot sub sonic go with cast lead and the gas checks, the price paid (casualties) from learning how to use lead bullets have occurred far in the past and now those are well proven.

The is a large group of knowledge shooters as opposed to internet experts out there using cast lead.
 
Drilling the flash holes and using magnum primers isn't generally necessary with Trail Boss but it won't hurt anything either. It can help with using small charges of fast pistol/shotgun powders (Unique, Red Dot, etc) that don't have enough fill to lay consistently in the case. If you find that your charge of Trail Boss isn't producing consistent velocities, pick up some Dacron and use a little fluff to keep the powder charge in a consistent position.

Don't lube jacketed bullets. It won't help, and is an invitation for grit to stick to the lube and then grind up your bore.

Good luck with your workup.

Jimro
 
Greased bullets were common in cupro-nickel jacket days. The problems in the 20's were with an experimental bullet of Townsend Whelen's that was issued as National Match ammunition just one year. It was plated with tin to cut copper fouling out (cupro-nickel jackets were particularly bad about this, leaving lumpy spots in the bore, which is why they were later replaced with the ultra-low zinc brass called gilding metal). The tin, though, cold-soldered to the cases, raising start pressure hugely. Some bullets were found in the pits with the case necks still attached. Needless to say, that over-size bullet raised pressure a lot. When the tin bullet was issued, since it was its own anti-fouling device, they instructed shooters not to dip the bullets in their customary grease pots. When these high pressure loads blew guns up, Hatcher reported that in every instance an open grease pot was among the shooter's equipment on the line.

Obviously the real villain in that case was the tinned bullets, but the grease will have raised the pressure enough further to cause the burst, but it would have been a case of being the straw that broke the camels back, and not the primary cause, as Hatcher claimed. I think his emphasis on that was an attempt to save face. In those days the Army supplied the rifles fired at the National Matches, so as long as only the gun was damaged and not the shooter, they probably didn't see it as any real harm being done back then. Today the shooter would sue, claiming psychological trauma of some kind. Mainly, the kind that missing out on a large settlement produces.

Anyway, the British kept on using grease even with gilding metal bullets for a long time. They also liked to run .309 groove diameters with 7.62 NATO in Palma and other long range shooting, and that left a little extra room. I don't know if that's still common today or not, but it was for a time.

Board member Slamfire lubricates cartridges today for longer brass life. Some of that will get into the bore. It will raise pressure, but not as much as some assume. With a load of Trailboss, which will be running under 30,000 psi, raising it some is unlikely to cause a hazard. However, if this is a high end custom rifle, I personally would be hesitant to subject any hand-lapped precision bore to extra stresses even if it it weren't outright unsafe.

There are alternatives. The moly and hBN coatings will lubricate a bullet without getting fluids involved. I, personally, would go one of those routes before I would use grease.
 
While not the bullet you are using, and expensive, Lapua's 200 gn subsonic is very accurate over trail boss and regular primer in the rifle used (1:10 twist). It is seated deeply, and really sucks up the powder space, while minimizing bearing surface. Extremely quiet suppressed.

Did not use lube, but every barrel is different. it also worked well in dirty tube.
 
I've been playing with subsonic loads for 5 or 6 years now in my .300 blackouts and .308's as well. I'm not an expert but I do know a thing or two about loading subsonics.
1. Unlike conventional reloading where you start low and work up, with subsonic it's the opposite. Start high and work down.
2. Without a chronograph you might as well be peeing in the wind.
3. I've never had nor seen the need to ruin my brass by enlarging the flash hole. Trailboss ignites just fine.
4. Twist rate is critical. About the fastest twist I've seen on off the shelf .308's is a 1/10. I've tried several .308's with this twist and Hornadys 208 A-Max's barely stabilize at 50 yards and keyhole at 100. 220 Sierrera's are iffy at best even at 50 yards. I did however have good luck with 180 grain bullets.
 
Great info, thanks TMD. I have a couple questions,
1. My calculations using Hogdgon's instructions for Trail Boss indicate a max load just under 14 grains with 70% of that being just under 10 grains for the start load. This is based on Winchester brass and the Sierra 220 grain round nose flat point that has a length just a smidge over 1.3".
2. I have a chronograph, and it will be used.
3.Based on research and advice, I think it's safe to skip bullet lubes and drilling the flash holes.
4. Berger's twist rate calculator found at their site, shows that the Sierra 220gr. round nose should be comfortably stabilized with a 1 in 10" twist running 1100 fps.

You're saying you found that not to be the case? Were you using the round nose Pro Hunters or the Match King pointed boat tails?
 
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Great info, thanks TMD. I have a couple questions,
1. My calculations using Hogdgon's instructions for Trail Boss indicate a max load just under 14 grains with 70% of that being just under 10 grains for the start load. This is based on Winchester brass and the Sierra 220 grain round nose flat point that has a length just a smidge over 1.3".
2. I have a chronograph, and it will be used.
3.Based on research and advice, I think it's safe to skip bullet lubes and drilling the flash holes.
4. Berger's twist rate calculator found at their site, shows that the Sierra 220gr. round nose should be comfortably stabilized with a 1 in 10" twist running 1100 fps.

You're saying you found that not to be the case? Were you using the round nose Pro Hunters or the Match King pointed boat tails?
Click to expand...

Trying to find my old data on .308 subs and seem to misplaced some of it. I used a Savage Hog Hunter which has a 20" barrel. With Hornady's 208 A-Max and 11.0g of Trail Boss it chrono'd at 1020fps so with a 220 slug 14g may be a good starting point. Also 1100fps will likely be supersonic depending on altitude and temperature. All I can say is try and see. Some barrels are more friendly than others. I do remember with my gun 180's around 1050fps stabilized well out past 100yrds but 220's were a no-go. Also if you plan on running suppressed definitely check for stability before using it. Baffle strikes suck.
 
I'm guessing you must have been testing the 220 Match Kings, they are considerably longer than the flat based, round nose, Pro Hunters and when plugged into the calculator don't indicate good stability at subsonic speeds.

I will most definitely bench test to guarantee stability before screwing a can on, computer calculators can provide wonderful bits of information but aren't a substitute for field tested results.

Thanks again for your input.
 
I run Missouri Bullet Company 245gr cast hi-tek coated through mine.
I only run magnum primers on all my sub loads (308 and 300 blackout.)
I get more consistent results. Especially on the blackout.
 
There are a number of speed-of-sound calculators available online. What you find by tweaking the input arguments is that it is far more dependent on temperature than on altitude/barometric pressure or humidity.

Twist rate requirements do get faster with increased air density. Moving to drier, colder, or lower altitude air all increase the optimal twist rate. It's not terribly uncommon to hear of groups opening up if not outright keyholing when a load that worked fine in summer is fired in winter weather.
 
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