Powder, speed or bullet- and long range groups

cloverleaf · May 4, 2008

I dont have much chance to practice beyond 100 yds so I dont have an answer. Do 1 inch groups at 100yds always transfer to 3 inch groups at 300 and if not, why not? Is it similar to shooting 12 guage slugs at 100 yds where they tend to become unstable once the slip below 1200 fps (sound barrier?) velocity? what facotors affect long range stability, Thanks for the thoughts. CL

FOTIS · May 4, 2008

Nope almost never. What I mean is the following:

I have shot 1/2" (at 100 yards) guns at 300 yards and heve gotten 4-5" groups.

On the other hand I had a 257 WBY Accumark which I could never get under 1.3" at 100 yards. Guess what at 300 yards it shot no bigger than 2.25"....Go figure!

old #7 · May 4, 2008

I don't think that a 1" group automaticly becomes a 3" group @300yds. There are to many variables in shooting to predict group size at longer ranges. You can predict trajectory but, throw in wind, the trigger, bedding problems, a loose screw, fouling, don't forget the shooter and you will have a tough time with any predictions.
I guess in theory and in a perfect environment one could calculate long range group size based on what was printed @ 100yds. I wouldn't bet on it.

Ol` Joe · May 4, 2008

Centerfire rifle bullets do show some instability as they cross the barrier from supersonic. That point usually is a long way past 300 yards though. The groups you get at 100 likely will be tighter then 300. The wind works on the bullet for a longer period and gravity too has its way with the slight velocity differences in the different shots. Any imbalance in the bullet itself also will start to show more at longer range. Your personal little quiver that only added 0.010" to your 100 yd group will now be 3Xs as big also.

cloverleaf · May 4, 2008

Oh yeah- I should have clarified my question, although that makes it significantly more theoretical- IF variations in wind drift were not and issue and gravity was assumed a constant. CL

Antelope_Sniper · May 5, 2008

At a pure theoretical level, 1 MOA ia about 1 inch per 100 yards, so yes, a 1 MOA group is 1" at 100, 2" at 200, 3" at 300, 10" at 1000 ect.

By the same logic, 1 Mil is 3.6" per 100 yards. 3.6" at 100, 7.2" at 200, 36" at 1000 ect.

jmad_81 · May 5, 2008

I have a 270 WSM that shooots five into right around 1.25" @ 100 and last time I shoot it at 300 I got 3 shots in .485"! My 22-250 shoots right aroud half inch @ 100 and around 2.5 @ 300 on a good calm day. My 338 WM shoots right around an inch at 100 and around 3.5-4 @ 300. I think that it all depends on the gun and the shooter if wind is a non factor. Every gun, bullet, shooter, and load combinations are different the only way to tell is to find a 300 yard range or ask a farmer if you can use a field and shoot 300 yards and see what happens.

Greg Nolan · May 5, 2008

I've heard it said and seen it written that some bullet/rifle/velocity /combinations don't immediately stabalize the bullet at say 100yds. I had a 270 like that with 130 gr. Nosler partitions. 1.25" group at 100 and .78" group at 200. I don't know the science behind it but I've seen it several times with different (usually very high velocity ) rifles. Does anyone know a source for this high tech info?
Good Hunting
Elkhunt :grin:

Charlie-NY · May 5, 2008

"I had a 270 like that with 130 gr. Nosler partitions. 1.25" group at 100 and .78" group at 200."

No flame but what you have stated is impossible. Bullets can not diverge and then converge while in flight.

edh · May 5, 2008

I've read somewhere where this phenomenon may be caused by parallax. A scope may have more parallax at 100 yards than at 200 yards. This makes it possible to shoot a tighter relative MOA at 200.

Ed