220 grain HPBT Sierra Match King .308 Load????

Rugerno1shooter · September 9, 2007, 02:01 PM

Well here is a weird thought. Would it be possible to load a .308 with a 220 grain bullet to subsonic levels? I know that subsonic .22lr ammunition does well due to the fact that is more stable in flight than the supersonic ammunition which as to break the barrier twice (once upon entering supersonic and once when leaving supersonic speeds). There seem to be a fair number of sub sonic center fire cartridges out there (the whisper family).
So would it be possible to do that with a simple .308 load with a say 220 grain Sierra HPBT Match King bullet? Or would there be issues other than the COL that would prevent you from doing this? Has anyone ever done this? If so what were the results?

Thoughts?

Thanks
Pat

Jim Watson · September 9, 2007, 02:24 PM

Rifling twist: The .300 Whisper has a 8" twist for 240 gr SMK. I don't how what it would take for a 220 SMK.

Case volume: It is more difficult to get a subsonic load from a big bottleneck cartridge.

The usual rationale of highpower target rifles is keeping the bullet supersonic all the way to the target. Same advantage as subsonic, no turbulence at the Mach, with less wind deflection downrange.

But hey, you might be the one to make it work.

Rugerno1shooter · September 9, 2007, 03:52 PM

Jim,
So essentially the .308 case is not conducive to subsonic loads. You would need to straighten out the case so that it ended up firing a much larger diameter bullet.

Twist rate aside could you launch a 220 grain pill out of a .308 case with much success? Obviously the powder capacity would be much less due to the length of the bullet (unless you had some custom reamed chamber). You would probably be looking at about 2200-2300 fps (depending on barrel length). I noticed that they actually have data for 200gr SMK and 200gSGKs. So it seems as though even though it could probably be done that it wouldn't work too well and you'd end up having to use a powder like IMR4350 or something similar to get reasonable performance?

Just musing during my study breaks!!!
Pat

Trapper L · September 9, 2007, 04:31 PM

We have a silenced 308 in a Remington that shoots subsonic ammo in about .5" group at 100 yds. I haven't tried any farther than that because that's not what we use it for. It's used for night hunting hogs. Might give TTI Armory a try. We have several cases of their ammo in subsonic loaded with a 170 gr RN. I've never chronoed any so I don't know the actual speed but it works. I can only assume that the RN bullet is more stable at subsonic.

http://www.ttiarmory.com/

Jim Watson · September 9, 2007, 04:41 PM

I know there are people shooting 210 gr SMK in .308 at long range.
Heavy loads in strong actions and loooong barrels make it work.

I know there are subsonic .308s from custom loaders as above and at least one European maker. There was a guy selling loading procedures for subsonic rifle ammo - not live ammo, just instructions - on ebay. He got sneered at considerably on the gun boards but I noticed nobody publicly described what was required for free.

Roundnose bullets would be easier to work with in standard guns because it is bullet length, not weight, that determines stability and rifling twist needs.

crowbeaner · September 9, 2007, 07:41 PM

You could try some IMR SR 4759 powder loads. It is specifically designed for reduced loads, and backing down the powder charges .5 grain at a time may work. Here in Clintonia average law abiding people cannot own such niceties as suppressors and full autos. They are limited to LEOs and military, and some of the gummint types. Evidently the powers that wannabe and are think that honest law abiding TAXPAYERS aren't trustworthy enough to own such things. That is why we still have the onerous and totally asinine Sullivan law with it's current unavailability to citizen subjects of NYC areas. Good luck with the project and enjoy the research. My $0.02. CB.

shannon68 · April 17, 2009, 11:50 AM

I roll my own to use with my supresser. I learned the recepie from the company who got it forom the seals. Its large rifle match primer,IMR4198 powder 12.5 grns with 220 grn round nose flat base bullet. Boat tail won't stabilize.works grate very very quiet. when load on top of powder insert a small stirafoam disck about a 1/4 in. thick and push it down jently to take up space so no miss fires.

September 9, 2007, 02:01 PM	#1
Rugerno1shooter Senior Member Join Date: March 30, 2007 Location: VA Posts: 144	220 grain HPBT Sierra Match King .308 Load???? Well here is a weird thought. Would it be possible to load a .308 with a 220 grain bullet to subsonic levels? I know that subsonic .22lr ammunition does well due to the fact that is more stable in flight than the supersonic ammunition which as to break the barrier twice (once upon entering supersonic and once when leaving supersonic speeds). There seem to be a fair number of sub sonic center fire cartridges out there (the whisper family). So would it be possible to do that with a simple .308 load with a say 220 grain Sierra HPBT Match King bullet? Or would there be issues other than the COL that would prevent you from doing this? Has anyone ever done this? If so what were the results? Thoughts? Thanks Pat

September 9, 2007, 03:52 PM	#3
Rugerno1shooter Senior Member Join Date: March 30, 2007 Location: VA Posts: 144	220gr Jim, So essentially the .308 case is not conducive to subsonic loads. You would need to straighten out the case so that it ended up firing a much larger diameter bullet. Twist rate aside could you launch a 220 grain pill out of a .308 case with much success? Obviously the powder capacity would be much less due to the length of the bullet (unless you had some custom reamed chamber). You would probably be looking at about 2200-2300 fps (depending on barrel length). I noticed that they actually have data for 200gr SMK and 200gSGKs. So it seems as though even though it could probably be done that it wouldn't work too well and you'd end up having to use a powder like IMR4350 or something similar to get reasonable performance? Just musing during my study breaks!!! Pat

April 17, 2009, 11:50 AM	#7
shannon68 Junior Member Join Date: April 17, 2009 Posts: 1	308 subsonic I roll my own to use with my supresser. I learned the recepie from the company who got it forom the seals. Its large rifle match primer,IMR4198 powder 12.5 grns with 220 grn round nose flat base bullet. Boat tail won't stabilize.works grate very very quiet. when load on top of powder insert a small stirafoam disck about a 1/4 in. thick and push it down jently to take up space so no miss fires.

September 9, 2007, 02:24 PM	#2
Jim Watson Senior Member Join Date: October 25, 2001 Location: Alabama Posts: 18,543	Rifling twist: The .300 Whisper has a 8" twist for 240 gr SMK. I don't how what it would take for a 220 SMK. Case volume: It is more difficult to get a subsonic load from a big bottleneck cartridge. The usual rationale of highpower target rifles is keeping the bullet supersonic all the way to the target. Same advantage as subsonic, no turbulence at the Mach, with less wind deflection downrange. But hey, you might be the one to make it work.

September 9, 2007, 04:31 PM	#4
Trapper L Senior Member Join Date: November 20, 2006 Location: South Texas Posts: 804	We have a silenced 308 in a Remington that shoots subsonic ammo in about .5" group at 100 yds. I haven't tried any farther than that because that's not what we use it for. It's used for night hunting hogs. Might give TTI Armory a try. We have several cases of their ammo in subsonic loaded with a 170 gr RN. I've never chronoed any so I don't know the actual speed but it works. I can only assume that the RN bullet is more stable at subsonic. http://www.ttiarmory.com/

September 9, 2007, 04:41 PM	#5
Jim Watson Senior Member Join Date: October 25, 2001 Location: Alabama Posts: 18,543	I know there are people shooting 210 gr SMK in .308 at long range. Heavy loads in strong actions and loooong barrels make it work. I know there are subsonic .308s from custom loaders as above and at least one European maker. There was a guy selling loading procedures for subsonic rifle ammo - not live ammo, just instructions - on ebay. He got sneered at considerably on the gun boards but I noticed nobody publicly described what was required for free. Roundnose bullets would be easier to work with in standard guns because it is bullet length, not weight, that determines stability and rifling twist needs.

September 9, 2007, 07:41 PM	#6
crowbeaner Senior Member Join Date: June 4, 2007 Location: Upstate SC Posts: 1,943	You could try some IMR SR 4759 powder loads. It is specifically designed for reduced loads, and backing down the powder charges .5 grain at a time may work. Here in Clintonia average law abiding people cannot own such niceties as suppressors and full autos. They are limited to LEOs and military, and some of the gummint types. Evidently the powers that wannabe and are think that honest law abiding TAXPAYERS aren't trustworthy enough to own such things. That is why we still have the onerous and totally asinine Sullivan law with it's current unavailability to citizen subjects of NYC areas. Good luck with the project and enjoy the research. My $0.02. CB.