Factors that affect accuracy

[Beiruty]

Please let us keep the thread civil and on topic
Here are some factors that affect the rifle accuracy, If I missed anything, please comment.

1) Bullet Jump, and seating depth consistency
2) Bullet concentricity
3) Bullet BC consistency
4) Dynamic Bullet stability, ie. speed and twist rate
5) MV consistency, i.e., lower MV SD
6) Barrel pointing to the point of impact as MV varies
7) Barrel dilation/contraction at the time the bullet leaves the barrel.
8 ) Powder temperature stability
9 ) Case bullet/interface, i.e., neck tension
10) Muzzle crown shape or the lack of
11) Muzzle device, brake/suppressor
12) Chamber lead angle
13) Chamber throat length
14) Load ratio
15) Powder burning rate consistency vs temperature
16) Powder burning rate, i.e., fast/slow
17) Case capacity consistency
18) Muzzle pressure at the time when the bullet exit
19) Primer output consistency, initial pressure consistency
20) Total rifle weight and recoil
21) Trigger pull weight
22) Level of the rifle
23) Barrel/receiver interface, i.e., action trueing
24) Bolt/receiver interface, i.e., custom action
25) Receiver/stock interface, stock bedding
26) Rifle support, i.e., front rest, bipod, bench rest, rear rest, rear bags, etc
27) Aiming apparatus, i.e., Optics clarity, mechanical turrets consistency and stability under recoil
29) Shooter marksmanship
30) Wind call proficiency and consistency.
31) Case trim length uniformity and trim length
32) Case shoulder bump in case full sizing.
33) Free recoil, or no free recoil
34) Shooter/Gun interface shooter's fit and comfort behind the rifle
35) Barrel Profile, length, weight and material quality
36) Barrel bore rifling, its quality, quality lapping no lapping
37) Bullet Profile, VLD/ELD/RDF, LRHT, Flat base BT, HP, pointed, etc
38) Bullet caliber
39) G7 Form factor
40) Shooter's psychology, i.e., meditation/yoga before the match, caffeine level, Prozac intake and dosage, etc
41) Optics to receiver interface, i.e., Scope to rings contact. Rings to base, base to rifle contact.
43) Rifle to terra firma interface, i.e., shooting on wooden/concrete bench, shooting on solid surface, sand/grass land.
44) Shooting position, Standing, Kneeling, Prone. Supported/not supported, up/down, or upside down
45) Shooting induced stress, i.e. Anxiety about good score, wind calls, next shot, other shooters,
46) Shooting under the clock. That is, shooter focus vs speed
47) Shooter's health and physique, i.e. shooter age, fatigue, pain, and suffering
48) Shooter's anxiety such as worrying about house chores, wife, kids, ex-wife, significant other person, work load, etc
49) Optics Turret angular units, MOA/MIL 1/8 MOA vs 1/4 MOA, 0.05 semi-step
50) Distance to target: Range estimation, pre-known distance, scope estimation, LRF, LRF accuracy, LRF max effective range
51) Bullet speed in flight, i.e., supersonic, transonic, subsonic and dynamic stability.
52) Weather condition, i.e., other than wind, temp, station pressure, rain, fog, snow, mirage, etc.
53) Coriolis effect, that is, GPS location of the shooter and the direction of the shooting.

 

[TylerFromMS]

Trigger puller. Barrel. Chamber job. Wind. If you’ve made the proper sacrifice to your bloodthirsty eldritch gods. All kinds of stuff.

 

[Homerange]

20) Bedding
21) The nut behind the butt's core technique must never be excluded from such discussion.

 

[Bill Norris]

(22) Jack Neary says trim length uniformity will affect accuracy in short range benchrest.

 

[K22]

The shooter!!!!

 

[Clancy]

(22) Jack Neary says trim length uniformity will affect accuracy in short range benchrest.

I was already typing this and saw your response. Case trim uniformity AND making sure your cases aren’t within 10 thousandths of the end of the neck is huge. I deliberately tested this after watching that video and cut 100 yard groups almost in half.

I’ll add amount and uniformity of shoulder setback and of course if you feed from a magazine make sure the bullet doesn’t contact anything hard before entering the chamber.

 

[Ranger188]

Not sure I understand the point of this post.

 

[davidjoe]

Number 7 got my attention on the other post as a new to me consideration. I agree, again, with that principle. Wondering though, are you saying contraction waves traverse the barrel back and forth (say from a source of pressure) regardless of whether the barrel vibrates up/down and l/r, because it is also true that the circularity of the hole in a hollow tube will change slightly if it bends. To the degree the muzzle moves around relative to the chamber, the barrel is indeed bending.

 

[JEFFPPC]

Not sure I understand the point of this post.

I feel that way about lots of posts. This one I am fine with. Although with no wind flags on the list, it's incomplete. Also a distinction between short range and long range should be made.

 

[Beiruty]

Not sure I understand the point of this post.

For the love of science

 

[Beiruty]

Number 7 got my attention on the other post as a new to me consideration. I agree, again, with that principle. Wondering though, are you saying contraction waves traverse the barrel back and forth (say from a pressure) regardless of whether the barrel vibrates up/down and l/r, because it is also true that the circularity of the hole in a hollow tube will change slightly if it bends. To the degree the muzzle moves around relative to the chamber, the barrel is indeed bending.

Exactly,

David, please see here

Barrel Harmonics Mode Shape Movies

www.varmintal.com

 

[rwj]

I deliberately tested this after watching that video and cut 100 yard groups almost in half.

Would you be so kind as to either post the video or a link?

 

[Clancy]

Would you be so kind as to either post the video or a link?

Oh gosh, I’ll try. It’s from that many part series of his on YouTube. No telling where in all those hours of talk he went over that but I’ll look.

 

[WSnyder]

Would you be so kind as to either post the video or a link?

It's in one of the Jack Neary videos. Heck you should watch them all

https://www.youtube.com/channel/UCvxDA52hlZKvbgsPapHk0hw/videos

https://www.youtube.com/results?search_query=jack+neary+

 

[Clancy]

Here it is, watch it all but the trimming part is around 9:30

 

[Bottom Fodder]

Does your gun fit you physically and your personality

 

[Beiruty]

Here it is, watch it all but the trimming part is around 9:30

Here is my video, from my channel demonstration trim length and staying below maximum SAAMI case length. Consequently, you would see the so-called carbon ring.

 

[Beiruty]

Number 7 got my attention on the other post as a new to me consideration. I agree, again, with that principle. Wondering though, are you saying contraction waves traverse the barrel back and forth (say from a pressure) regardless of whether the barrel vibrates up/down and l/r, because it is also true that the circularity of the hole in a hollow tube will change slightly if it bends. To the degree the muzzle moves around relative to the chamber, the barrel is indeed bending.

 

[Big_Daddy]

The amount of "high caffeine" coffee I drink before shooting....LOL

 

[BobbyJ]

Barrel quality and thickness. Bull barrels seem to be less finicky to different loads.
Bullet shape/design - Flat base vs boatail.
Bullet caliber. 450 bushmaster is relatively insensitive to distance to the lands and also to loads vs bottle necks like 223.
Twist rate and bullet velocity and length. Shoot too long a bullet in a 1/12 twist = keyholes and terrible groups.
Bedding and barrel free floating.

I would put Barrel at number one. Some barrels can shoot anything well paying little attention to distance to lands, neck tension etc. Some no matter what you do they are poor shooters, people spend crazy amount of time chasing lands, depth, hand sorting etc and still shoot worse than some other barrels with factory ammo.