204Ruger

Hey guys, first post but big question. Was working up loads for the model 12 savage and ran into a very odd thing. I cleaned the barrel and fired 2 foulers. Shot a group of 5 32gr SBK loaded .204 in the case and 1 tumbled. group was 1.25 not good. Fired 5 39gr SBK loaded .204 in the case and it was good .404 group. repeated this test after cleaning with 2 different powders and got the same results. the 32gr bullets will tumble and the 39gr bullets will fly good. Is this not backwards of what should be happening. 32gr vel averaged 4140fps and 39gr vel averaged 3810. The rifle is a 204 Savage Model 12 FLV, 1 in 12 twist, 26" tube, heavy barrel.

What do you mean by "Tumble" are you saying they are not grouping and even keyholing, where as the 39 grn don't ? If that is the case, then the load you have for the 32 grainers is not allowing a accurate group, where the load for the 39 grn is. By the way what is the twist on your rifle ? That might have a bearing on the matter.

You are correct, the 39gr SBKs shoot good but the 32gr SBKs are not stabilizing because they are key holing. But with a 1 in 12 twist that should be the other way around I think. The vel on both bullets with 3 different powders is good with no pressure signs. And the 32s will have 1 out of 5 key hole with 1.25 grouping at 100yds, not very good.

Yes, that is strange. Usually the 32's do well and even the 39's in a 1/12 twist. The 40 grainers usually don't shoot worth a darn in a 1/12. Can't answer your issue, with this. And the Sierra BK's are a fine bullet in most every 20 caliber bore.
However I would check the crown on that rifle, for the ever so slight damage.
And hopefully someone, will chime in with some information that may help you out. Bill K

You could try a different brand of 32g bullets, or go up to the 34g dogtown HP's, they shoot well in my Savage FV12 204R.

Just grasping at straws here, but did you verify the twist with a cleaning rod or otherwise?

OK, I have been trying to find the problem and with the help of a bore scope I think I found it. The first 6 to 8 inches of the rifling has a carbon and copper build-up, a dull gray and shinny copper look, that I cannot even tell is there just looking through the bore. Also there is a carbon ring in the throat. So it appears that the cleaning that I have been doing is not so good. The smith recommends using a product called IOSSO, it"s a bore paste that will remove the copper and carbon I hope. I will clean like a crazy man today and tomorrow will try it out, hopefully with good results. Have any of you used this stuff and if so what were your results? He also said I should stay away from any bore cleaner with ammonia, hoppys, sweets, and some others, I normally use hoppys copper solvent.

The dreaded CARBON RING strikes again!! Go to the carbon ring thread. JB Bore Paste will help.

Hey guys, It worked, I cleaned for 4hr using the bore paste that the smith give me. There was some nasty looking black junk that just kept coming out, I thought I had been doing a better job of cleaning. Shot the rifle today and it's back. Using 3 different powders I got some pretty good groups all at 100yds, 32gr SBK, N-140, .434", at 4018 fps, 39gr SBK, N-140, .502", at 3752 fps, 32gr SBK, R10X, .435, at 4158 fps, 39grn SBK, R10X, .301", at 3864 fps all pretty good for me. I also tried N-530 but didn't like it as well as the others. I think it is time to work on seating depth and see what happens. It is amazing at how that carbon ring will creep up on you. THANKS for your advice it really helped.