Why does some ammo shoot differently?

[Broge5]

Even to me this sounds like a dumb question, but I still don't have a clear answer.

I often see people posting that some ammo shoots "more accurately", and to find the ammo that shoots best for me. Or that X brand shoots "low and left", etc.

I understand different brands have different grains, standard or +P, etc. But, I don't see how the first shot would be affected unless it is just poor ammo meaning anyone would experience the same issue at least given a particular gun.

Are they talking about how follow up shots are affected by how much recoil a particular brand or type has, or do some brands just not hit the x for some people? If so, why?

[frankie_the_yankee]

There are so many different factors that affect accuracy in a given gun. The precise dimensions of the barrel (both diameter and length) and the diameter of the bullet. The dimensions of the case. The relationship between the twist rate, bullet weight, and velocity. The type/shape of the rifling. Bullet construction (lead or jacketed). The length of the bullet's "driving band" (the part that engages the rifling). And of course, the powder charge and primer characteristics. (And I've probably left a few out here.)

Some of these combinations work more consistently than others. Also, some types or brands of ammo exhibit more variation in some of these parameters than others do.

[Broge5]

I see.

Would it be correct to say that if a brand/type of ammo shoots "low and left" etc. for someone, that the same brand/type would shoot the same for me - at least if I were to shoot his gun?

I ask because the posts seem to imply that different ammo shoots differently for different people. From what frankie_the_yankee posted above, I can certainly see how this could be the case due to everyone having a different gun, and maybe that is exactly the point.

[frankie_the_yankee]

How one grips the gun can also affect the point of impact, and the consistency of the point of impact.

[seamusTX]

Most of this type of commentary comes from benchrest rifle shooters, who are trying to shoot multiple rounds through the same hole at 100 yards or farther.

For practical pistol shooting, it's something best left in the cow pasture.

- Jim

[frankie_the_yankee]

Most of this type of commentary comes from benchrest rifle shooters, who are trying to shoot multiple rounds through the same hole at 100 yards or farther.

For practical pistol shooting, it's something best left in the cow pasture.

- Jim

I did a couple of turns with The Minuteman Project a couple of years ago.

The rules specified handguns only. No long guns allowed. (They wanted everything to be concealed at all times so we wouldn't resemble a "militia" type group.) So I decided that if I couldn't carry a long gun, I would learn to shoot my 1911 accurately out to 100 yards. I found it was do-able with practice.

At those ranges, consistency of point of impact is important.

[Stupid]

Assuming you are using the same rifle/gun under the same wind and earth rotation speed (joking), there are 4 things that you must consider:

1. bullet (weight and type) - how fast it flies and turns due to its weight and type difference
2. case (weight and type) - how much initial room it has to ignite the powder
3. gun powder (propellent type) - how fast it burns and expands - actually, how fast can this push the bullet
4. primer - how the powder gets ignited

Each item above has a ton of different types and makers. The 4 combined will give you unlimited (almost) number of ammo variations causing the difference when you shoot.

If you are looking for consistency, a reloader/manufacturer must firstly control all 4 factors.

Even after all these 4, there are probably 3 more to consider:
1. is the case crimped? - mostly looking for consistent neck tension holding the bullet.
2. is the bullet is perfectly centered in the case? - again, consistency.
3. temperature - it can greatly affect some gun powder.

[srothstein]

And one of the things that will affect how well the ammunition shoots, that has not yet been mentioned, is the consistency of the ammunition manufacturing process.

If each cartridge has a slightly different amount of powder, to use just one variable, each bullet will have a slightly different impact point. Add in each of the possible variables, such as brass quality, bullet weight, bullet seating, crimp strength, etc. and you get a wide possible spread of hit points from one box of ammo.

Now, to be honest, since I am not match shooting, the difference between ammo that holds to a 2 inch group versus ammo that holds to only a 3 inch group is not a problem for me. But, this is why long bench rest shooters try to use match ammo, and why match ammo is higher priced. To get the consistency takes time and work, and that equals money.

[KBCraig]

Assuming you are using the same rifle/gun under the same wind and earth rotation speed (joking),

Artillerymen don't joke about rotation of the earth. It's a serious factor in fire solutions.

There was a question about the first round, versus the rest of the magazine. Two things can contribute to first-round inconsistency. First, inconsistent seating of the round, and/or differing deformation of the bullet during chambering. This is best solved by inserting the mag while the slide is closed, then loading by quickly racking the slide. This approximates the seating that results from firing a round and having the next round picked up from the magazine.

The next factor is inconsistent grip. It is very, very hard to be consistent between the grip you establish before drawing, and the grip you have when firing second (and subsequent) rounds. It's very natural to have some shift between the first and second rounds. Your goal as a shooter is to overcome natural tendencies, and establish consistent repeatable patterns. This comes with practice, practice, practice. Then more practice.

[dude]

This is best solved by inserting the mag while the slide is closed, then loading by quickly racking the slide. This approximates the seating that results from firing a round and having the next round picked up from the magazine.

KB, can you explain your thinking on this point a little more? It seems to me that, as long as I don't ride the slide forward, the seating of the round will be identical whether I release the slide using the slide stop, sling-shot a locked-open slide, or rack a closed slide. In other words, regardless of how or when the slide gets opened, it's only the mechanics of the slide closing that comes into play in seating a round, right?

[Broge5]

Cool. I have learned a lot more here than I had expected.

My original thought was when JoeABC stated, I have a X brand 1911 and x bullet brand/type shoots "low and left", could I assume that it would shoot "low and left for me and everyone else.?

Now I understand that the differences not only in different brands of guns, but the variances of tolerances in the same make model could give different results. (gun related)

So, there are numerous Bullet related mechanical variances causing bullets to hit at different points. If I am correct, these are not shooter related, and therefor any shooter using the identacal gun (not just same make/model) will experience these variances with a given brand/type of ammo.

However, a given brand/type of bullet may give different results to different shooters of the identical gun due to shooter related variances such as grip, etc. I guess this explanation may not be PC, but it answers my question.

Thanks everybody for the input.

[KBCraig]

This is best solved by inserting the mag while the slide is closed, then loading by quickly racking the slide. This approximates the seating that results from firing a round and having the next round picked up from the magazine.

KB, can you explain your thinking on this point a little more? It seems to me that, as long as I don't ride the slide forward, the seating of the round will be identical whether I release the slide using the slide stop, sling-shot a locked-open slide, or rack a closed slide. In other words, regardless of how or when the slide gets opened, it's only the mechanics of the slide closing that comes into play in seating a round, right?

In some pistols, the top round is in contact with the underside of the slide. That changes the mechanics.

[dude]

This is best solved by inserting the mag while the slide is closed, then loading by quickly racking the slide. This approximates the seating that results from firing a round and having the next round picked up from the magazine.

KB, can you explain your thinking on this point a little more? It seems to me that, as long as I don't ride the slide forward, the seating of the round will be identical whether I release the slide using the slide stop, sling-shot a locked-open slide, or rack a closed slide. In other words, regardless of how or when the slide gets opened, it's only the mechanics of the slide closing that comes into play in seating a round, right?

In some pistols, the top round is in contact with the underside of the slide. That changes the mechanics.

OK, I understand now.

I had always (in my 1 year of experience) pictured the top round of an inserted magazine being just as it is when I see it outside of the gun. But of course it's not. It's being depressed somewhat by the bottom of the slide and only pops all the way to the top when the slide is opened.

Still learning...