Quarterbore.Net Forums

mgraham112 · #1 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 · #2 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 · #3 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 · #4 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 · #5 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 · #6 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....