My 204 OCW test with 39 gr SBK's *UPDATED*

Quote:I noticed the primers (CCI 400) had a weird extruded ring around where the firing pin struck, is this a pressure sign?,,,,Not so much a pressure sign as it's possible that there might be a little excess room between the firing pin and the firing pin hole in the bolt face....

While I use a different powder (W-748) with the 39gr SBKs in my .204s, both shoot the best with 26.3gr charge weights...

This is five from 100 yards (1/2" Squares) and I've never found reason to play with them since...
 
Here are my targets and primers:





From left to right: 26.2, 26.7, 26.9, 27.0, 27.1, 27.3, 27.4, 27.5, 27.7. No visible pressure signs.


Here is a close up of the extruded primers and punched primer:


I wasn't too concerned with the punched primer at 27.7 because that's a max load and I more than likely wasn't going to run something that hot, but then I punched a primer at 27.1, this is deterring me from working up a hotter load than 26.2 especially because it is grouping well. If I stick with 26.2 gr of H4895, am I going to see a significant difference in performance (on groundhogs) out to 400-500 yards than I would if I ran a hotter load? Basically I'm asking if I should go back and try this again even though I punched primers? I have OCD as I'm sure a lot of you do and I'm also a perfectionist. I sometimes annoy myself because everything I do has to be perfect no matter what it is so understandably I really hate the idea that I'm leaving more performance on the table, but I also don't want to run a potentially unsafe load.
 
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Your groups are very good at 25.6 26.1 and 26.3. Try these at 200 yards and see what is the best for your gun. Speed doesn't do you any good if you can't hit anything at those yards that you want to shoot P.D.'s. Your higher loads don't seem to be as good as the ones I listed above.

If you want to continue to try the higher grains of powder, then I would find a gunsmith to work on your firing pin? Just my thoughts. Rudy
 
I ran some # through a ballistics calculator. At 400 yards the difference between a 3700 fps and 3500 muzzle velocity is 2.4 (200 yard zero)inches so on a standing woodchuck with no wind the lower muzzle velocity should not be an issue. Wind drift increases 2.1 inches with a 10 mph 90 degree wind at 400. Playing the wind is going to be trickier than drop. Sierra gives bc of .287 when + 3600 and .270 when velocity is 34-3600.
 

I had the same problem with my Rem 722 in 6X47 I switched to the CCI450 primers and never had a problem again.

Try magnum primers the cups are stronger.
 
Originally Posted By: KyleWoodsHere are my targets and primers:





From left to right: 26.2, 26.7, 26.9, 27.0, 27.1, 27.3, 27.4, 27.5, 27.7. No visible pressure signs.


Here is a close up of the extruded primers and punched primer:


I wasn't too concerned with the punched primer at 27.7 because that's a max load and I more than likely wasn't going to run something that hot, but then I punched a primer at 27.1, this is deterring me from working up a hotter load than 26.2 especially because it is grouping well. If I stick with 26.2 gr of H4895, am I going to see a significant difference in performance (on groundhogs) out to 400-500 yards than I would if I ran a hotter load? Basically I'm asking if I should go back and try this again even though I punched primers? I have OCD as I'm sure a lot of you do and I'm also a perfectionist. I sometimes annoy myself because everything I do has to be perfect no matter what it is so understandably I really hate the idea that I'm leaving more performance on the table, but I also don't want to run a potentially unsafe load.

Do you have any velocities to go with the groups? 26.7 - 27.1 seem to be consistent in the vertical aspect but velocities would help verify this. I would not focus on one group to determine next step. A lot of times that tune window can be very small and slight changes like a tenth of a grain of powder high or low can put you out of the tune window and this is why velocities or paying attention to the vertical grouping on each side of the good group is a good indicator of a good powder node. Some will say its hard to determine vertical at 100 yards but with careful study and practice it can be done. Without velocities its a lot of trial and error but can still be done.
 
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