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mgraham112
11-26-2009, 11:25 PM
I have put between 100 and 200 rounds through my ssk upper as of today, but I am having some real issues with vertical dispersion. I am using 220SMK on top of 11.0g of W296 and rem 91/2 srbr primer. Grouping is wonderful when the velocities fall into the same bucket, but with a 5 shot string, they can range +-70fps which is causing me a vertical group that ranges 6".. I need to try a different powder and I hope that this will cure me, but I was wondering if what other people were experiencing in fps and deviation/spread with their particular load. My next powder is N110 which from what i have read is ideal. I dont know if I should try different bullets or not. I am up for any suggestions.

Rikky Lee
11-27-2009, 02:23 AM
I had exactly the same problem with the 30BR and heavy bullets - check out the threads in the other list on non-Whisper cases.

The cure is going to a faster powder. For me this was an expensive and time consuming venture but I did borrow small powder lots from shooting buddies to try.

Alleycat
11-27-2009, 09:32 AM
Is 11grs subsonic? My gun would be crackin. If you are transonic you would be having issues. Do you have a chronograph? If you don't, try 9.2grs of VV N110.

Romeyo
11-27-2009, 02:24 PM
Which barrel lengh does it have? I heard that barrel friction plays a serious roll when shooting jacketed bullets at subsonic velocities. I would keep the barrel as short as possible/necessary.

Rikky Lee
11-27-2009, 04:56 PM
Barrel length does have an effect on velocities and juggling the powder charge to get the magic 1050fps correct.

But vertical dispersion and velocity variation is a classic indicator of the powder being too slow for the charge/case.

mgraham112
11-30-2009, 10:21 PM
the barrel is a 16.5 from SSK. The velocities with 11.0 have ranged from 1250 (highest) to 1004 (lowest) with varying temps. What's weird is that the 1250 came on a day which the temp was 35 and the 1004 came on a day that was 65. very odd..... The barrel only has 100 to 200 rounds through it, so i am wondering if the velocity will settle down with a few more rounds through it....

Rikky Lee
11-30-2009, 11:14 PM
No the barrel will not settle down. The velocity spikes are normal with the temperature changes if you are using the wrong powder (see http://www.sengpielaudio.com/calculator-speedsound.htm to see how the air temp affects the speed of sound). You might like to build a little table of air temp versus speed of sound.

Environmental issues also affect perceived noise but that is a separate issue.

How to deal with this - powder choice is the first challenge. Have you tried a faster powder yet?

mgraham112
12-01-2009, 09:03 AM
nah, this is the only powder i have tried. I have to place an order this week for more powder and I'll get some faster ones and see how they work. Any recommendations so i dont waste any money? I have never tied any AA powder in any of my guns so I am not familiar with them. suggestions would be greatly appreciated

Spook
12-01-2009, 10:28 AM
VVN 110 works nicely:smile:

Rikky Lee
12-01-2009, 03:43 PM
What Spook says.

Also try to borrow faster powders from shooting buddies as you only need a small amount and everyone loves shooting a Whisper in return.

Fritzcat
12-01-2009, 10:00 PM
I have just started loading for the whisper a week ago. I developed loads for the 762x39 and Win 296 was the best powder for sub-sonic, Horn 220gr RN and 9.5gr Win 296 gave me around 1050fps and was shooting 2" and less at 100yds with a .308 bullet out of a .310 barrel 16".

Fritzcat
12-01-2009, 11:38 PM
Going by the Sierra Loading Book you are loading in the 1150fps range and this may be your problem. It shows 10.7 for 1100fps and 11.7 for 1200fps. It shows 9.8 will give you 1000fps with a 10" contender barrel, try it.

fasttwist
12-01-2009, 11:58 PM
fritzact what kind of rifle and did it cycle.[7.62x39] how about an expanding 225 grain .310 bullet.

Fritzcat
12-02-2009, 11:29 PM
I call it my AR47, AR 16" with 1x10 twist and carbine gas length. It cycles, but the second box of Horn 220 RN started hanging the nose sometime so I started loading some 200gr speer SP. I opened the gas hole .015 more to cycle these. So I started putting a 220 RN in chamber and 200SP in mag to hunt with. They have the same POI.