.

thoughts on grouping

hadjiihadjii Member Posts: 971 ✭✭
Today I went out and fired 4 rounds through my 300 RCM. The bullet was a hornady 165 gr. SST. Powder was 51.0 grains of H4895. COAL was 2.850. Over the chronograph, the 4 shots were as follows: 1)2755 2)2792 3)2784 4)2770. Avg velocity was 2775.

Temp was 90 degrees with a south wind at 15-20 mph. I was shooting pretty much straight north. I fired the first 2 shots, which were intersecting and 3" to the 6 oclock position of the point of aim. I let the barrel cool for about 5 minutes while I walked to the target and checked point of impact and grouping. I then went back to the bench and fired the next 2 shots, which were 2 1/2" to the 12 oclock position of the first 2 shots and 3/4" apart from each other.

Point of aim for all 4 shots were the same spot. just looking for some thoughts on what may have caused the 2nd 2 shots to be that far from the first 2. The barrel on the rifle is floated, so no pressure points, rifle is also pillar bedded and the action is bedded as well. Trigger is timney and crown has also been recut.

I should mention the first 2 shots were from a cold barrel, meaning coming out of an air conditioned house. Not sure if that has any bearing on the shot groups, but thought it needed to be mentioned. I brought the rifle back in the house and will let it cool completely and try it again and see if it does it again.

Any thoughts would be appreciated. Thanks in advance.

WANTED MAN; That was an awesome response. Ever thought of becoming a moderator on this forum?.........Just sayin.

Comments

  • bpostbpost Member Posts: 31,137 ✭✭✭✭
    edited November -1
    The heat and bedding issues could do that. Bore fouling getting settled in might be causing it too. I have a 22 BR barrel that drove me nuts, when clean and cold it tossed the first shots HIGH. I now leave it dirty for up to 100 rounds and it shoots fine. Go figure.
  • RobOzRobOz Member Posts: 9,195 ✭✭✭
    edited November -1
    Maybe they will tighten up when you get closer to max.
  • midnightrunpaintballermidnightrunpaintballer Member Posts: 2,233 ✭✭✭✭✭
    edited November -1
    cold bore/clean bore will do that on the foulers. Next time you take the rifle out, let it warm up to outside temperature first. Then shoot 3 shots to foul in (if barrel is clean and free from copper) then shoot a 5 shot group immediately. Let barrel cool and shoot another 5 shot group. Adjust scope then if needed.
  • iceracerxiceracerx Member Posts: 8,807 ✭✭✭
    edited November -1
  • AmbroseAmbrose Member Posts: 2,717 ✭✭✭
    edited November -1
    Glad to see you're back to testing your .300 RCM. I've got to get mine back to the range again. I haven't fired it since last fall. I took it along with a .300 WSM, a .308 Norma Mag. and a .30/.338. I often quit early when shooting stuff like that!

    As I recall, one of your projects with that rifle was to down load it for a youngster. I tried a load consisting of a 150 Hornady BTSP, 50 gr. IMR4895, WLR primer. Velocity was 2628 fps, it grouped quite good and recoil was 16 ft/lbs (compared to 27 ft/lbs for full load). 165 gr. factory loads are quite fast @ just over 3100 fps from my rifles 22" barrel.
  • hadjiihadjii Member Posts: 971 ✭✭
    edited November -1
    Thanks for all the replies and input. I will try the advice given about fouling and letting the barrel warm up and see what happens. The distance I was shooting was 100 yards, by the way. sorry I didn't mention that.

    Ya Ambrose, I'm at it again with this rifle. My other 3 rifles are pretty much settled in with the reloads I've worked up. They are a 257 Roberts, a 264 win Mag, and a 375 Ruger. I ordered a Mcmillan stock for my 264. Not sure what I was thinking there, but it sure is going to be a nice stock. It is a Sako Varmint style milled out for a Ruger 77 MII.

    I've pretty scrapped the idea of downloading the 300 RCM. I put my daughter on my 257 Roberts, and she really likes it. Just hope she doesn't like it too much. LOL. I discovered there is a company here in central Iowa that does cera-koting, so I think I'm gonna have it cera-koted this fall. Turnaround is about 7-10 days at a cost of $150. I could be wrong, but it seems the rifle doesn't like the H4895 too well. I think I will go back to using Hunter and R-19. Seems like I had the best luck with them. I tried 10 ways to Sunday to get the 300 RCM to shoot 150 grain speer mag-tips, and no way could I do better than 1 1/2" groups at 100 yds. Moving up to 165's was substantially better, and even better yet with 180 gr. swift scirocco's, averaging under an inch for 3 shot groups. Thinking about trying some IMR 4064. Any thoughts on that powder? Seems to do well in my 257. Thanks again for the responses. Seems I always get good advice here.
  • JustCJustC Member, Moderator Posts: 16,038 ******
    edited November -1
    if the barrel was spotless clean inside, that will give the "wandering" fouler shots until it "fouls in". Some barrels exhibit this trait more than others.
  • RobOzRobOz Member Posts: 9,195 ✭✭✭
    edited November -1
    That Hybrid 100V looks good with 165-180 grain bullets.
  • FrancFFrancF Member, Moderator Posts: 35,278 ******
    edited November -1
    quote:Originally posted by JustC
    if the barrel was spotless clean inside, that will give the "wandering" fouler shots until it "fouls in". Some barrels exhibit this trait more than others.


    I would concur with that. Another thing to consider that might be a factor for him maybe. At my range I need to lug all my crap up hill to the range at a considerable distance. My heart rate is cranking pretty good for at least 10 min and it takes a few to get relaxed and settle in.

    Just a thought to consider.
  • wanted manwanted man Member Posts: 3,276
    edited November -1
    quote:Originally posted by hadjii
    Today I went out and fired 4 rounds through my 300 RCM. The bullet was a hornady 165 gr. SST. Powder was 51.0 grains of H4895. COAL was 2.850. Over the chronograph, the 4 shots were as follows: 1)2755 2)2792 3)2784 4)2770. Avg velocity was 2775.

    Temp was 90 degrees with a south wind at 15-20 mph. I was shooting pretty much straight north. I fired the first 2 shots, which were intersecting and 3" to the 6 oclock position of the point of aim. I let the barrel cool for about 5 minutes while I walked to the target and checked point of impact and grouping. I then went back to the bench and fired the next 2 shots, which were 2 1/2" to the 12 oclock position of the first 2 shots and 3/4" apart from each other.

    Point of aim for all 4 shots were the same spot. just looking for some thoughts on what may have caused the 2nd 2 shots to be that far from the first 2. The barrel on the rifle is floated, so no pressure points, rifle is also pillar bedded and the action is bedded as well. Trigger is timney and crown has also been recut.

    I should mention the first 2 shots were from a cold barrel, meaning coming out of an air conditioned house. Not sure if that has any bearing on the shot groups, but thought it needed to be mentioned. I brought the rifle back in the house and will let it cool completely and try it again and see if it does it again.

    Any thoughts would be appreciated. Thanks in advance.

    EDIT too add paragraph breaks, making reading easier.


    Within your tale you introduced so many variables, and consequently trouble spots, as to make it practically impossible to even begin pinpoint (Read: GUESS AT)a single causative factor...begin by eliminating variables, and go there from there, would be my advice...
  • rawiron1rawiron1 Member Posts: 57 ✭✭
    edited November -1
    Mixed headstamps and shell length variances can add to your problems. If the trim length is let's say 1.650" and max is 1.660" you'll want to keep the shells +/- 0.002" in that range. When one shell is 1.650" another is 1.660" and another is 1.655" etc. accuracy is going to suffer.
  • MobuckMobuck Member Posts: 11,548 ✭✭✭
    edited November -1
    Variation in butt to shoulder contact will produce similar results with any of the harder recoiling rounds. Even a slight change in how you resist recoil makes a big difference. I've seen a 12" change in POI at 300 yards from a hardly noticeable tightening or loosening of the shoulder/back muscles.
  • Hawk CarseHawk Carse Member Posts: 4,296 ✭✭✭
    edited November -1
    Agree with Mobuck, likely "Shoulder mirage."

    Fire two shots off the bench, check the target, come back and hunker back down on the bench.
    You probably did not get back in the same position and the target told you so.
  • hadjiihadjii Member Posts: 971 ✭✭
    edited November -1
    Thanks Mobuck and Hawk Carse. I am believing you're right. Operator headspace is out of adjustment. What I coould really use is a couple of hours with a really good shooter to correct all my deficiencies.
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