OAL & comparator question

[moonbogg]

Measuring cartridge OAL to lands and will back off .020 to start. See following cartridge OAL dimensions for different bullets and take notice that the OAL's are nearly identical for the different bullets, but when measured with a comparator the dimensions are different. I rechecked these sizes about 10 times for each one, using different bullets from the box to arrive at an average and to make sure I was confident of the numbers.
I suspect that the OAL's are the same because the ogive designs happen to intersect the barrel ID at nearly the same location from the tip of the bullets. I suspect that the comparator dims are different because the ID of the comparator insert is slightly smaller than the barrel ID, and will arrive at different distances on the ogive from the tips as the ogive curvature intersects with that smaller diameter in a non coincidental fashion (unlike the barrel ID landing at the same spot). Is my reasoning sound and my conclusion correct? First time reloading here.

.223 savage 12.

69gr SMK
2.367 oal
1.983 comp

55gr blitz king
2.367 oal
1.972 comp

53gr vmax
2.363 oal
1.922 comp

[stangfish]

:o hmmm!

[yobuck]

i have never used a comparator so im ignorant as to their use. i just close the bolt on a partialy seated bullet
and work it out from there.

[CharlieNC]

It would be interesting to measure just the bullet alone for OAL and distance to ogive using your comparator; then you could see if it all "adds up".

[missed]

Bullet shapes and ogive locations are going to vary with different bullets. I have measured the chamber with each bullet. I have measured the bullet alone with my comparator also to confirm. You should see a SMK 175 & 168 right next to each other there is a huge difference in oal but the ogive location is the same.

[moonbogg]

I also soft seated each round, multiple times to check that way. I just can't believe the coincidence that the OAL would be the same for three totally different bullets, yet each bullet still touches the lands. Thanks for replies.

[stangfish]

COAL only matters for your magazine. What tools are you using to measure with.

[granite1]

I don't understand why you can't believe it. You made the measurements. The #'s don't lie. What are you concerned about?

[moonbogg]

I don't understand why you can't believe it. You made the measurements. The #'s don't lie. What are you concerned about?

I feel the same way so I went with the numbers but since its my first time I wanted to ask. Today I tested 70 rounds of 69gr SMK and I reached two conclusions. First, 22.2gr appears to be the most accurate. Second, my trigger control sucks and I saw plenty of evidence of that. I shot two 5 shot groups for each load to get a good comparison and they were all different, ranging from about 1 1/2" or a bit worse, to as good as about 1/2" with the same load.
The last group of the day hardly hit the target circle at all, and that was the load I tried a different shooting technique. I put no pressure on the rifle and let it recoil freely and the group sucked. I have no cheek weld at all as the stock is low profile. The gun always seems to yank off to the left after each shot. I am a confused noob who needs better technique, but at least the loads worked well. I used mix brass brands for this, all shot from my gun previously. So there may be some variation there. I want consistent 1/2-3/4" groups at 100. Also, I am trying to figure out why I can be zeroed at 100 but the gun shoots a few inches to the left at 200. I really hope my scope isn't crooked.

[yobuck]

first things first and that would be technique. learn to shoot well with a rimfire then move on.

[missed]

Work on a bunch of dry firing to make sure your squeezing the trigger the same way every time. If the gun is jumping one way or the other think how your pulling the rifle or how your shoulders are. Cheek weld, I have made a Kydex riser for all my rifles so my head is in the same spot over and over again. The left at 200 how were the winds that day? I have Strelok ballistic calculator on my phone and tablet, tremendous help ranging and windage. The last time I shot there was enough wind that I was having to compensate almost 2 feet left at 400 yards.

[moonbogg]

Work on a bunch of dry firing to make sure your squeezing the trigger the same way every time. If the gun is jumping one way or the other think how your pulling the rifle or how your shoulders are. Cheek weld, I have made a Kydex riser for all my rifles so my head is in the same spot over and over again. The left at 200 how were the winds that day? I have Strelok ballistic calculator on my phone and tablet, tremendous help ranging and windage. The last time I shot there was enough wind that I was having to compensate almost 2 feet left at 400 yards.

That much? That could be it then for sure. I could have underestimated the wind and just ignored it. So, when pulling the trigger, should the gun recoil straight back? It seems to naturally go left every time. I thought it might be from the torsion from the bullet spinning or something.

[CharlieNC]

Typically the bullet will be off in the direction which the muzzle recoils. Moon, what are you using for shooting rest? I just started shooting prone with bipod this year and have learned a lot of technique with the 223 to manage recoil and accuracy; decent success to extent that sighting in the 300WinMag was better control with the bipod than on the benchrest in the past. Very important to set up the rifle position using your front and rear rests so the scope is on the bullseye before you apply any muscle to absorb the recoil; the so called Natural Point of Aim (NPA); this is taught extensively and cannot be stressed too much!

[stangfish]

There are some good pointers above with regards to shooting.

Wind does not just cause horizontal movement, if it is in you face or your back it can cause vertical stringing as well. On the high recoiling rifles if you loose site of your target after the shot then you may want to work on your positioning.

[n4ue]

Moonbogg. Try to find a copy of the book:
"The Accurate Rifle", by the late Warren Page. This book (although older) is a classic and I learned a lot of benchrest techniques, reloading tips, rifle tips, etc.
I use these basic skills to help all the new shooters I teach (with my rifles) and the new shooters are thrilled to be be able to shoot this good.
Of course, it really, really helps to have a nice heavy varmint rifle in .17 HMR, .223, etc, so recoil is one less thing for them to 'worry about'. ha ha
Good, safe shooting to you and yours.....

ron

[moonbogg]

Typically the bullet will be off in the direction which the muzzle recoils. Moon, what are you using for shooting rest? I just started shooting prone with bipod this year and have learned a lot of technique with the 223 to manage recoil and accuracy; decent success to extent that sighting in the 300WinMag was better control with the bipod than on the benchrest in the past. Very important to set up the rifle position using your front and rear rests so the scope is on the bullseye before you apply any muscle to absorb the recoil; the so called Natural Point of Aim (NPA); this is taught extensively and cannot be stressed too much!

I use Caldwell sand bags in front and back. Just the standard, large, square shaped sand bag in front and little bunny ears in back. I'll check out the book mentioned in one of the replies here as well.
Regarding natural point of aim, I didn't know that was called something and related to technique. Now that you pointed that out, I recall doing that sometimes, and other times not.
Will having the front sling and bipod studs in the front of the stock cause an issue? It might be unstable since that's where it sits on the front bag?
Gun is savage 12 BTCSS in .223 with Nikon monarch 5-20x44 nikoplex.
Scope mount is DNZ single piece mount with extra wide rings (tactical version as they call it).

EDIT: Just watched a video of actual bench rest shooting. I almost spit my coffee upon realizing how clueless I am! I like huge learning curves though. Lots of room for growth.

[n4ue]

One of the best things I learned from Warren Page's book was:
Every once and a while before starting the trigger squeeze, relax your grip on the rifle and rear bag. If the scope moves off target, you are 'forcing' the gun in a certain direction. When you can get the rifle so steady that a relaxed grip will still be on target, you'll see a drop in your group size. It did for me, anyway!!!
good luck

ron

[CharlieNC]

You should unscrew the swivel studs if they contact the rests; definite problem.

[blt65]

Here is my two cents worth to accurate shooting. First off Cheek Weld, Cheek weld, Cheek weld. I use a old mouse pad and cut out a section and duct tape it to my rifle. I do this until I can get a good cheek weld with my eyes closed. Open them and look through the scope, you should be perfectly aligned. Secondly make sure you have a full circle in the scope, and black area top, bottom, left or right will result in the bullet impacting opposite of it. (i.e. black on top, results in a low hit) Third, relax, get the crosshairs aligned and exhale, as you exhale focus on sight alignment and trigger squeeze the rest of your body should not exist. Then let the gun suprise you when it goes off.

[stangfish]

Secondly make sure you have a full circle in the scope, and black area top, bottom, left or right will result in the bullet impacting opposite of it.

Then you learn how to set parallax.