308 subsonic

[jarhead1086]

Thanks Zooly 22. This is over priced though I think. I paid $100 for 20 CNC brass Blaylock cases. I sent a couple old cases recently to Quick Silver Manufacturing in ID for an example. I have a few ideas to make the cases last even longer than the 10 or 15 shots each that they lasted. I know we could make a better case for less money using my ideas. The biggest problem I had was getting the neck annealed properly with the thick walled body acting like a heat sink. I just have to convince somebody with an NC lathe that interest exists and make a run. I will try to get some price quotes after I model them. My Redding neck sizer has an adjustment for partially sizing the neck, so these tools are extra cost that I wouldn't use personally. You know some dummy will try to full length size one : ) I bet a bulky Trailboss load would fill up a case like this.

[Artful]

Thanks for the suggestion but I would like something other than Aluminum cases and still hope I luck into a combination that will be subsonic and group as well - Next I'm going to try other cheap bullets (170 grain RN 30-30 bullets next then 180 grainers, hopefully they will stabalize in FAL's barrel)

[pug]

Artful have you ever mic'ed the neck of your first fired case and compared it to later fired cases?

[rumlover]

308
10" encore 1/8 twist

240 SMK's with 12-15gr trail boss seems to keep me in the 950-1010 range. I just can't seem to get to the 1050 mark. Any suggestions?

[Artful]

Originally Posted by pug

Artful have you ever mic'ed the neck of your first fired case and compared it to later fired cases?

Please expand upon your question - Mic'd after first firing and again after the 5th firing of the same case? Or compare between cases fired in the same chamber with same loads? or ...?

[pug]

Just wondering if fired case #1 may have a smaller neck diameter than fired case #5 shooting five of the same loads in the same chamber. I was looking at the first round lower velocity you had posted.

[Artful]

Shot 12/15/2007 50 deg F 12 noon - winter in Arizona
IMBEL FAL 21" barrel -
7.9grn Clays with 170 Grn RN Remington 30-30 bullets
2.695 OAL - Lee factory crimp .002 - WIN Large Pistol primer.

This bullet has more bearing surface which caused the first shot to stick in the barrel. (unlubed and cold) argh

Velocities recorded after that shot warmed up the barrel.
865.6*, 789.2, 789.8, 679.2 784.3, 810.9 815.7, 793.0, 813.6, 789.6 798.6

*all shot on Grenade out of FAL with cyclone suppressor on except the 865.6 2nd shot

going to up the powder charge and try it again accuracy seemed ok but I was just shooting rocks and you had to hold over quite a bit to hit 'em (guess work but it seemed consistant) - Nice and quiet though

[Artful]

Originally Posted by pug

Just wondering if fired case #1 may have a smaller neck diameter than fired case #5 shooting five of the same loads in the same chamber. I was looking at the first round lower velocity you had posted.

Well I can check on that but doubt any difference will be found - their was a link given to me about long barrels and lower first round fired phenomina - If you want I'll find it. Their solution was to shorten the barrel to something under 20 inches I don't want to do that to my FAL

[Artful]

Originally Posted by rumlover

308
10" encore 1/8 twist

240 SMK's with 12-15gr trail boss seems to keep me in the 950-1010 range. I just can't seem to get to the 1050 mark. Any suggestions?

You could try a hotter primer, or lube the bullets / barrel. Personally I'd be happy at consistant 1010 - 40 fps won't be noticed at the other end.

[rumlover]

I'm aready using LRM primers. The problem biggest was accuracy. once I got to 12 gr (TB) I seemed to max out in vel with an average of 980ish. The range went anywhere from 860-1040. This created a pie plate group, generally vertical in nature. It filled up the cases with the 240s so I wouldn't think there would be an issue of powder placement at ignition.

I tried 15 gr of Greendot and pierced a primer. 10.5 gr in a 16" krieger got me 1050 behind a 220 RNSP, but the powder had to seated against the primer. This did create excellent accuracy, but I missed 3 deer last year because the rifle was generally pointed down (treestand) and the powder was against the bullet.

Also, I've been getting the first shot to dump on every string. Consequently, as I was shooting those loads Friday, I would wait 15-20 min between shots. Shooting 200 Speer Spitzers, 12.0 TB, WIN LRM primers, Rem Cases, 10" Encore, 1/8; I averaged 960fps with a range of 946-974. By allowing the bore to return to ambient temp (33deg) I had a better representation of actual velocities that I would find in the field and lowered the range of velocities.

I'd like to try another powder. Based on the posts I've found AA#9 or IMR SC4957 (I think that's the right powder, I'll have to check my notes). I looked up the IMR powder and it was specifically formulated for reduced velocity loads. I also came across some Accurate 2215 (?) at Gander MT which said it was also formulated for low volume loads and a hig tolerance to powder position at ignition.

Any idea what length barrel it would take to get TB to push a 240 at 1050? I don't have another 1/8 twist barrel to test with, just the 10". With a little extrapolation, I was figuring each inch would gain 7fps, but I'm not certain.

If I don't get it worked out in the next month, I'll order a 16" whisper upper. I would assume someone has found an accurate 240 load for that.