Group size at what range?

[Fiftydriver]

Freebird63,

I am not upset of offended by your comments in any way, just offering another side of the conversation. Sometimes posts on line come off as heated comments, not the case here at all, just a discussion and I have taken nothing you have stated as a challange to me at all.

I am just saying that there is something to bullet consistancy as it travels over distance and when shooting high BC bullets at high velocity and out of a fast twist barrel, it is very common to see the group size measured in MOA drop and often drop significantly as the yardage increases. Thats all.

Now if that does not happen, obviously your rifle does not like that bullet and you will likely not see this happen with conventional weight for caliber bullets and especially not with light for caliber bullets.

Good discussion.

 

[Camshaft]

I have seen groups tighten on my .300rum, it will shoot 210SMK's at around .450" at 100 yards, and 1.90" at 500yds. The 210 SMK is right around 1.5" long and does seem to stabilize better at extended ranges, I think stability factors have a lot to do with this also. In my rifle this bullet is leaving with a 1.9 stability factor.

 

[steelhead613]

My ultra mag doesnt shoot bergersworth beans. Tried everything. Same powder charge, more or less powder, different seating, different primers and so on. She just doesnt like bergers.

 

[Camshaft]

Mine either, nor did it like 208 a-maxs which blew my mind, but it loves 210 and 240 SMK's and the 165 GMX's i hunt with, thank God!

 

[Fiftydriver]

The A-Max bullets have a very similiar velocity limit as the Bergers. In most cases, if a rifle likes Berger bullets, it will also shoot A-Max bullets very well, that is IN MOST CASES. Nothing is written in stone.

To the other end, if a rifle does not like the Berger, it often does not like the A-Max either.

The SMKs have a much thicker jacket then either of these other two match bullets and that is why on average, it will shoot acceptably well out of most rifles and chamberings, even high velocity ones with good accuracy. I have not found the velocity ceiling of the SMK bullets in approriate for bullet twist rates and believe me, I have TRIED VERY HARD!!!

I have driven the 107 gr 6mm SMK to +3600 fps with fine accuracy, same with the 142 gr 6.5mm SMK at 3550 fps, the 175 gr 7mm SMK at 3600 fps and the 210 gr SMK at +3450 fps.

I have yet to see a SMK dust except for some 80 gr 22 cals that were shot out of a Lilja 3 groove barrel chambered in 22-6mm AI going well over 3550 fps. In this case, they were simply over spun and the 22 cal SMK jackets are thinner then the others.

 

[sambo3006]

We've had the discussion about smaller moa groups at longer ranges many times here on LRH. Kirby used a good example in his earlier post. Notice that he never said that the actual measurement of the groups in inches got smaller as the distance increased. Merely that they didn't get much bigger, hence the smaller moa. This makes perfect sense with the "going to sleep" theory on long bullets.

On the other hand, when somebody claims that their rifle shoots 2 inch groups at 100 yards and 1 inch groups at 300 yards, that is where I call "bull". That is not physically possible assuming shooter error is eliminated. What Kirby describes doesn't violate any laws of physics. Thanks for the input as always, Kirby.

 

[Mikecr]

It's rubbish

Just for the sake of conversation, how do you explain that a rifle can shoot 1/2 moa groups at 100 yards, 1/3 moa groups at 300 yards and 1/5 moa groups at 500 yards?

Someone slipped us 'Smart Bullets' that self correct for any angular errors that occurred -earlier in their flight.

To put that into actual inches. This particular rifle averaged 0.7" to 0.8" ctc three shot groups at 100 yards. Shot between 0.9" and 1.1" groups at 300 yards and has shot SEVERAL sub 1" ctc three shot groups at 500 yards.

Well, unless it's said smart bullet conspiracy, it must be something else (like parallax). Why couldn't it just be parallax?

I have seen this with many rifles, also, the longer the bullet, the faster the twist, the faster the bullet is driven, the more dramatic this group size reduction can be when measured in MOA.

These same factors follow systems used for ever longer ranges. But I do get apparent tighter moa with distance shooting using 50gr FB bullets from a 223(14tw~3600fps). In fact I have always shot tighter MOA with distance, with any gun I've developed loads for(to a point). My son does not with the same guns. But he doesn't wear glasses either..
At any rate, this isn't ballistics. It's shooting.

This is really a moot point, until the rifle in question is properly tested from a solid shooting position, we can not begin to say why the groups are increasing in size.

If the 'question' was why groups increase downrange, then everything about this thread should really be questioned. Is there anyone who doesn't understand that groups usually open with range? C'mon, this is a long range hunting site…

 

[Fiftydriver]

Mikecr,

Wow, Usually can follow your comments but that post was out there.

You attack my comment that group moa size will decrease as range increases and then at the end of your post you say most of your groups will decrease in moa size as you increase range........ WTH!!

Your right, I have no idea how to adjust my optics to elimiate paralax. Thanks for the heads up on that one!!! WOW!!

Also, I did not say it does not occur with lighter bullets in slow twist barrels but that it is instead easier to see and more dramatic in heavy for caliber, high BC bullets shot at high velocity in fast twist barrels. Again, you say its not possible but then say it happens to you all the time..... Plus, if your getting a 50 gr bullet at 3600 fps in a 223 Remington, you need to tone things back a bit my friend!!!, your about 200 fps over where you should be at most.

Yes groups do generally open up to some degree as the range increases but they certainly do not increase in size in porportion to the range they are being shot at. For example, a 1" group at 100 yards does not equate to a 4" group at 400 yards or an 8" group at 800 yards.

Sometimes the groups increase in size, even when measured in MOA but in a top quality rifle, this increase in size is generally caused by environmental conditions we are not judging accurately or us as shooters imposing our ill effects on the rifle. Which brings us back to my original point.

"UNTIL THE RIFLE IN QUESTION IS FIRED FROM A SOLID SHOOTING POSITION WE HAVE NO IDEA WHAT THE ACCURACY POTENTIAL OF THE RIFLE OR THE LOAD IS, SHOOTING FROM A SITTING POSITION WILL NOT GIVE EVEN THE FAINTEST IDEA WHAT THE RIFLE AND LOAD REALLY CAN DO AS FAR AS GROUP SIZE."

 

[freebird63]

I do have some 210 SMK's, I don't think I have given them enuff time yet. But with hunting season less then a week away and the weather is not the best for shooting. I noticed when measuring with a comparator that the barnes tipped triple shock bullets seat different then the A-Max bullets, they must have a different diameter Ogive. but overall length is still shorter then the A-Max rounds. Its all very interesting stuff and can be quite frustrating sometimes.

 

[Fiftydriver]

Every bullet will have different OALs when they are seated to the same distance in relation to the origins of the lands. Thats why you need to reset your seating dies for each bullet and confirm distance from the lands.

 

[Autorotate]

Concepts that are difficult to absorb/understand are often put in the "witchcraft" category before we give them their due.

What if.......just what if......the progression of a accuracy/precision trend from a shorter range, to the results seen at a longer one was due to two components....

1st component....angular deflection of shot placement due to shooter/load error will continue to be manifested in a linear function at distance. i.e. I yank a shot one MOA/MIL left at 200 yards, it will now be two MOA/MIL left at 400, and six MOA/MIL left at 600, and so on....

the 2nd component...Lack of accuracy/precision due to the bullet "not going to sleep"....hmmmmm.....it doesn't seem any of our longer/higher BC projectiles are immediately stabilized in terms of pitch/yaw by the model below....

So...it would seem if one had a very precise rifle, and was an outstanding marksman, firmly grasp the fundamentals of shooting a rifle, and had consistent/precise ammunition, to minimize the effects of the first component listed above, that Kirby's results (and others) results might very well be plausible, and even accounted for by ballistic models.....

My dumbest day will be the day I'm too smart to learn....

Good luck and keep it fun! Go shoot at long range!

 

[Mikecr]

The epicyclic swerve affects above & tested by Berger, amount to corkscrewing flight well under 0.1" within 3-5yds. This anomaly in flight is damped toward unmeasurable by 100yds, even in an extreme.

There is an investigation into both opening and closing dispersions in chapter 11 of APPLIED BALLISTICS FOR LONG RANGE SHOOTING. Everything related to this thread, including my implications, is well investigated there.

 

[mphstigerfan]

Ok... Back to the original question... As was stated earlier load development should be done from a bench or from your belly with bag and bipod. That said I had a similar issue with 168 bergers and my 300 wsm. They shot 1/4 to 1/3 moa at 100 yds but at 300 they wouldn't hold 1 moa. Tried190's and got down to 1/2 moa at 100. Stepped back to 300 and again couldn't hold 1 moa. Tried their 185 target bt and got sub 1/2 moa at 100 moved back and 1.8" at 300. Unfortunately I was told the jacket was too thick to hunt with this bullet. However being pressed for time I hunted this yr with that load anyway and limited my range. I am about to try something else although I hate to given the accuracy of this load. ( recently shot a .65 @ 200 yds from my belly)
Oh well

 

[RockZ]

Interesting discussion.
At 565 yds I will work up a load that shoots 3 shots into 1.5-1.75 inches, with as little vertical dispersion as possible.