308 subsonic

[mosigdude]

Only thinking out loud here, and I have never tried this, there may be reasons not to... but that's why I'm replying, maybe someone already has.

Some talked about reducing the case capacity by filling with epoxy or purchasing cases that had been specially manufactured to do so. The problem with the epoxy or modeling plastic seems to be a lack of consistency (air bubbles and such) and the frailty of the filler (i.e. pieces breaking off and getting stuck in the suppressor) The problem with the manufactured cases seems to be availability and expense.

Would it be possible to weigh a small quantity of lead shot, melt it in the case, allow it to set, the re-drill the flash hole to the desired diameter, standard or enlarged. It seems that the lead would be more malleable than most epoxies and by weighing it, the case capacity could be reduced semi-scientifically.

The potential problem I see in the beginning is having to drill the flash hole smaller than the primer and having to use a special decapping pin to remove spent primers. Obviously, only neck sizing would be possible with the lead filler taking up the lower portions of the case.

It would be nice to be able to make 308 cases with similar capacities as the 300 Whisper, this would make load development at least a little easier.

If no one else has tried this, I may give it a run, I really have no need for a subsonic 308 since I have the whisper, and suppressors are illegal in MO anyway but curiosity has now gotten the better of me. If you have, post up with your results.

[mosigdude]

Ok, after posting that, I couldn't take the suspense. In the last 10 minutes, I made 5 reduced capacity 308 Cases. I changed direction just a bit, here's what I did:

I filled one 308 case full with #9 shot (smaller would be better to reduce the air space between pellets, but #9 was the smallest I had) I then poured the shot out of the 308 case into a 300 whisper case. The remaining shot that did not fit was the approximate difference in volume between the two cases. I weighed the difference and it was approximately 220 grains of shot.

I then drilled the flash hole of the 308 cases to 1/8 (.125) inch. I noticed that a 10-penny finishing nail was nearly the same size as this hole.
I lightly oiled several of these nails and inserted then into the flash hole with the head in the primer pocket. I then weighed and placed 220 grains of lead shot in each case.

I used a pair of vice grips to snugly hold the portion of the nail that protruded from the neck of the case. I held the nail centered in the mouth and snug against the primer hole, snug enough to form a seal. I then used a standard propane torch to heat the base of the case until the lead melted (less than a minute each)

I then let the cases cool naturally (instead of quenching, which would cause them to be brittle) and lightly tapped out the nails. (if you do this, make sure the sharp portion of the nail isn't mashed out larger than the shaft before you insert it, otherwise it will get stuck as you tap it out). This eliminated the need to re-drill the flash hole.

The way it looks:
Each case appears to have the same volume. The flash hole appears as uniform as can be expected, it isn't "machine" accurate, but appears as good as any factory case. I'm guessing and hoping that the taper of the case will hold the lead "plug" in place firmly, or at least solid enough to prevent powder from getting between the case head and the plug. Finally, the case capacity is approximately the same as the 300 Whisper, giving me a good idea on approximate start loads.

I think I'll grind the point off of one of the same nails and use it as a manual decapping rod, then disassemble my 308 sizing die to size only the outer dimensions of the case first, then reinsert the expander only deep enough to pass through the neck for reloading. This should allow me to load without buying a neck-sizer only (only since I don't currently have one).

No doubt, if this works, the cases will degrade faster than those of solid brass or aluminum since the lead is much softer, but I'm hoping I can get somewhere between 5 and 10 loadings each before much degradation is noticed.

I'll keep posting after I get some loads tested... chrono reports will be slower to come since I shot the chrono while testing whisper loads a few weeks ago (read "Anyone had this problem" if you're curious).

[mosigdude]

Update:

I loaded 5 rounds of only one load, more to evaluate case performance than anything else. I loaded 9.0 grains of H110 under a SMK 168 with a federal 210 Primer at an OAL of 2.800.

First, the 220 grains of lead does not, as I had previously thought, fill the case to allow 300 Whisper capacity, it is still much larger. I was not taking the volume of the flash hole into account.

All 5 rounds were fired from a Remington 700 Tactical with a 20" 1/10 twist barrel. This rifle is usually very capable of 1/4" CTC groups without much effort.

All 5 rounds were definitely subsonic, although, as stated above, my chrono is down so I can't comment on actual velocities.

in 2 of the 5 rounds, the lead broke free of the case and moved to the front of the case, although nothing appears amiss except for this and it did not appear to come forward with enough velocity to deform the case. There is no evidence of fragmentation of the lead that I added to the case and it still appears intact, although moved.
None of the cases showed any indication of excessive pressure.

Accuracy seemed unaffected by the 2 rounds in which the lead separated and all 5 rounds formed a cumulative group slightly larger than 1/2" CTC.

If I go forward with this idea, I will probably add more lead to reduce case capacity further. My first thought was to reduce the diameter of the flash hole by NOT drilling the flash hole larger and then using a smaller piece of wire to form the hole in the lead, however I am reluctant to do this for fear of inconsistent ignition since the entire powder charge is nearer the front of the case and so far away from the primer. Instead, I may leave all as is with the exception of adding more lead to further reduce case capacity.

I will also have to consider the cases disposable or at a minimum re-melt the lead inside each as I can not guarantee to reposition the lead filler exactly the same as it had been before separation in those cases that do separate.

I'll post more as this project progresses.

[Artful]

Interesting - if you want it to afix firmly you may want to brush the inside of the case and flux as well as changing from pure lead to 50/50 tin/lead mix so fix it better. As personal problems are keeping from shooting much, I anxiously await further reports.

[mosigdude]

Today was the last of my days off, so I followed through with my other plan and somewhat, the suggestion of Artful. This time, I used a flux and brushed the inside of the otherwise new RP cases. I had any a small amount of tin so I mixed 1000 grains of tin with 3000 grains of lead and fluxed the mixture. Then to get as close as possible to exact amounts, I made a blank mold that resembled a thick wire (just drilled with a 1/8 drill to make the mold) and cut each flush with the top of the mold. I then weighed out 220 grains again, trimming as necessary, which this time was more volume and repeated the melting process the same as before.

Same as before, the lead/tin mix separated from the case in 6/10 of the shots but group size was still good at approximately 1/2". I still do not have the chrono to measure velocities but I'm teetering back and forth as some are obviously going supersonic while others are not, I'm not sure about how consistent the velocities are but they must not have a terrible spread as I see no noticeable vertical stringing.

Also a second experiment:
I've had pretty good luck using "Power Pistol" powder in other subsonics, I thought I'd give it a try with the 308.

Again, I have almost no reference to begin with so I started at what I thought would be a mid-level charge of 8.0 grains, otherwise, same load as above, 168 SMK, RP Brass, Fed 210 Primer, 2.800 OAL. This charge fills very little of the case so I suspected that it would be very sensitive to positional changes. I opted to fill the case with 3.5 grains of loosely-packed cotton ball material. My initial thought was that this may burn with the powder and not exit the barrel. Again, I loaded only one loading with the idea of further testing if the prelim looked even hopeful.

At the range:
EXCELLENT accuracy out of the Rem 700 20" BBL Tactical 1/10 twist barrel. The group, including a cold bore shot was one ragged hole, probably in the neighborhood of ¼” CTC. I did not have comparison between subsonic and supersonic and this powder sounds much different that the H110 so I'm not sure which side of the line I was on. My guess is that this was slightly over subsonic as a comparable load in my whisper would be/has been supersonic with a 200 SMK down to 7.0 grains where it averages in the 1070 FPS range. The 308 Obviously has a larger case capacity but I think this powder burns fast enough that everything is mostly stable by the time it exits the barrel, I don't know, I could be wrong.
Although this was good news in the accuracy department, it was a no-go for the suppressor crowd, or at least those that can't be disassembled for occasional cleaning. The cotton ball does not burn up in the barrel and exits the muzzle as a fine spray that appears similar to floating cob-web, not really an excessive volume, but it’s there all the same. There really isn't much more visual effect than a little bit of smoke, but it is obvious that it isn't completely burning up. Maybe gun cotton or the puff-stuff that were talked about earlier in this thread could be substituted with better results. On the plus-side, Power Pistol burns very clean if you get at least an average crimp on the case, there was no noticeable residue in the barrel and the insides of the fired cases were still very clean. No signs of excessive pressure or indications of any other problems. Maybe next week I'll try a run without the filler to see how position changes velocities. I should have my chrono repair parts in by then. Anyone else who tries any of this, or variations, post up... I've now got another itch that needs to be scratched (I knew I shouldn't have read this thread when I saw it!).

[Scoop]

Here's a .308 load for all you 12-twisters out there. I have had excellent luck with the Berry's 150 Plated FN bullets in my 12-twist Remmy SPS Tactical. The load I settled on is 6.8 gr of Titegroup (case-position insensitive) in LC89 Match brass (weighed to 1 grain extreme spread, but no other match case preps) lit by a Fed 215M primer. COL is 2.635 which keeps the bullets about 35 thous off the lands. I put a light crimp on with a Lee FCD die. This load averages 1020 fps in my rifle with SWR Omega attached. It feeds reliably, is stable and is consistently MOA or better. Oh, and the bullets are CHEAP to boot

Standard disclaimer: Use at your own risk. Start higher and work down.

[Artful]

Originally Posted by mosigdude

Although this was good news in the accuracy department, it was a no-go for the suppressor crowd, or at least those that can't be disassembled for occasional cleaning. The cotton ball does not burn up in the barrel and exits the muzzle as a fine spray that appears similar to floating cob-web, not really an excessive volume, but it’s there all the same. There really isn't much more visual effect than a little bit of smoke, but it is obvious that it isn't completely burning up. Maybe gun cotton or the puff-stuff that were talked about earlier in this thread could be substituted with better results. On the plus-side, Power Pistol burns very clean if you get at least an average crimp on the case, there was no noticeable residue in the barrel and the insides of the fired cases were still very clean. No signs of excessive pressure or indications of any other problems. Maybe next week I'll try a run without the filler to see how position changes velocities. I should have my chrono repair parts in by then. Anyone else who tries any of this, or variations, post up... I've now got another itch that needs to be scratched (I knew I shouldn't have read this thread when I saw it!).

Very good to know - I think the trick will be to add more lead to reduce volume further - one of these days when I can I'll come back to this with lead filler. Have you thought about a bulkier powder like RedDot?

[mosigdude]

I played with red dot in the whisper quite a bit and had very inconsistent results. I seemed to have a LOT of really slow( -300 fps or more) cold bore shots and a huge deviation in velocities from shot to shot thereafter. There may be a way to make it work, I didn't try it in the 308 loads. I would be thrilled if I could find a good red dot load, however, since I have a stupid-huge personal stash of the stuff left over from when I was loadng shotgun.

[mosigdude]

Scoop,
Good info! I'm out of new 308 cases right now and I usually start with new ones for load development so I haven't tried the titegroup in 308 yet. I overlooked it completely as an option in the beginning since it has such a fast burn rate but your post made me re-think this.
Since I was out of new 308, I picked up a can of titegroup and worked up a sub load for the 5.56 AR. I loaded 3.2 grains of Titegroup in a RP .223 case with a CCI standard small-rifle primer, standard flash hole, and a 60 gr. Hornady V-max to a COL of 2.235". The only case work I did was trimming and used no filler over the powder.
I still don't have my chrono repair parts so I couldn't check velocity, but they are definitely subsonic and very accurate at 35 yards (It was very rainy today and I couldn't go to the long range) with one ragged hole, no stringing, and no pressure signs. I only fired 10 rounds but they seem to be very clean as well. Obviously they don't cycle the AR, but I was just looking for a low-noise pest-control round anyway. Thanks for sharing the find!
I'll be playing with titegroup in 308 next, I can't wait to see how it works in my rig with 1/10 twist and a little heavier bullets. This could be the answer we've been looking for (well, me for only a week or so, but some for longer)
Thanks again, Ill post results as I get them!

[Scoop]

Originally Posted by mosigdude

Scoop,
Good info! I'm out of new 308 cases right now and I usually start with new ones for load development so I haven't tried the titegroup in 308 yet. I overlooked it completely as an option in the beginning since it has such a fast burn rate but your post made me re-think this.
Since I was out of new 308, I picked up a can of titegroup and worked up a sub load for the 5.56 AR. I loaded 3.2 grains of Titegroup in a RP .223 case with a CCI standard small-rifle primer, standard flash hole, and a 60 gr. Hornady V-max to a COL of 2.235". The only case work I did was trimming and used no filler over the powder.
I still don't have my chrono repair parts so I couldn't check velocity, but they are definitely subsonic and very accurate at 35 yards (It was very rainy today and I couldn't go to the long range) with one ragged hole, no stringing, and no pressure signs. I only fired 10 rounds but they seem to be very clean as well. Obviously they don't cycle the AR, but I was just looking for a low-noise pest-control round anyway. Thanks for sharing the find!
I'll be playing with titegroup in 308 next, I can't wait to see how it works in my rig with 1/10 twist and a little heavier bullets. This could be the answer we've been looking for (well, me for only a week or so, but some for longer)
Thanks again, Ill post results as I get them!

Hope it works out well for you. Titegroup is definitely the best of the powders I've tried for the sub loads in .308