What cause accuracy and inaccuracy in a pistol round?

[Joshboyfutre]

So, as I understand it the reason a rifle bullet will be accurate is when it leaves the barrel at the proper time that coincides with barrel harmonics it gets the same point of aim for its flight. So as we are tuning our loads up and down we are basically looking for the perfect timing for the bullet to leave the barrel. My question is this. What factors play into accuracy for a pistol? Does a 3 or 4 inch barrel have the same effect to the extent that it effects accuracy? Something is happening as we increase from min to max and the groups tighten then open back up. Just curious is all. Couldn't find any articles or anything on this subject that was specifically about pistols, both revolver and autos.

 

[rodregier]

I doubt that resonance is a factor in pistol barrel accuracy since it's so much shorter than a rifle barrel relative to bore size. (i.e. very stiff for resonance).

 

[Walkalong]

Quality bullets and a quality barrel. Then a powder charge it likes. And of course a gun that's put together well.

 

[Blue68f100]

With a simi-auto the lockup has to be the same every time for the best accuracy. Very few guns lock up the same from the 1st round to the last. With a revolver it's a little different but lockup has to be the same between all cylinders. This all goes with a quality barrel, fitted correctly.

Then theirs the ammo, have to find the combination it likes.

Pistols are a lot harder to shoot for accuracy than a rifle. With such a short sighting plane, short barrel any movement impacts the accuracy. This is with a specially built BE gun capable of producing 1 1/2" groups at 50 yrds or better. Those that shoot BE competition out to 50 yrds develop a skill that most don't acquire. For most of us were happy with a 2" group at 10 yards or COM.

 

[WestKentucky]

The biggest factor in pistol accuracy is the platform from which the gun is fired...the shooters hands. There are other things that do play into it though, barrel lockup in autos, cylinder lockup in revolvers, weight of the gun (heavy minimizes lock time motion) and then barrel length does help by speeding up the bullet which helps keep vertical spread minimal, but the biggest thing with barrel length is sight radius.

 

[jmorris]

What cause accuracy and inaccuracy in a pistol round?

Most often, the person pulling the trigger.

There are a number of unlimited "guns" that are very accurate with barrels that are shorter than normal for rifles.



After the person pulling the trigger, sights would be the second largest factor for pistol accuracy. I have taken a "reasonably" accurate Ruger Mark II and put a 1.5x scope on it and shot 10 into 3.5" at 100 yards. I never shot that accurate with the factory sights.

 

[243winxb]

Accuracy in a pistol round (ammo)

Bullets make a difference.

 

[Bart B.]

In a nutshell, handgun accuracy is primarily repeatable alignment of bore axis to line of sight. Semiautos shoot most accurate when this is attained. Of course, good barrels and bullets always help, but even average stuff shoots very accurate in good barrels going back into battery exactly the same for each shot.

Revolvers' barrels are always repeatable in their alignment with the line of sight. But their chambers vary enough for each shot in their alignment with the bore, so they're less accurate. Best accuracy I've heard of for S&W K38's and Colt Python's is a bit over 3 inches at 50 yards with Remington .38 Spcl wadcutters.

I've seen 5-shot test targets of M1911's shooting Remington 185-gr. semi wadcutters in the sub 2" range at 50 yards. Same for rebuilt S&W 52's shooting Remington .38 Spcl wadcutters.

And single-shot Hammerli .22 rimfire free pistols shooting 3/8" or less test groups at 50 meters.

Before SSGT Bill Blankenship won the Nationals in the early '60's, he was given three M1911's to test. He picked the one that tested worst for accuracy in a machine rest because it had the best trigger.

 

[kerreckt]

Mostly, the shooter.

 

[jmorris]

These are the 50 yard test targets for the two barrels in one of my SVI pistols.



If the guy pulling the trigger was not a tremendous factor in accuracy, I should be able to reproduce what the machine did.

 

[Bart B.]

jmorris,

Thanks for the pictures. I knew handguns were much better these days when built the right way, but had never seen proof.

I assume those groups are typical of what the barrels do.

 

[murf]

there is the shooter, the firearm and the ammunition.

ammunition - consistent bullet construction and perfectly balanced bullet (hornady xtp), consistent bullet tension in the case and consistent crimp for revolver ammo, good consistently manufactured cases (starline).

firearm - precision built (tolerances kept to a minimum), weight (heavier is more accurate), quality barrel.

shooter - taken out of this equation by using a ransom rest. the shooter inputs the most variation into the shooting equation.

the biggest detriment to the accuracy of pistol rounds when compared to rifle rounds, is velocity. run a pistol round out the muzzle @ 3,000 fps and you have a contest.

murf

 

[jmorris]

It might be better to talk specifically about an issue or we will get lost in theory and still have less than ideal results.

You could have a bore that never moves at all realitive to the sights and still not have the accuracy of others pistols.



If you are trying to get your group under 5" at seven yards, you load is likely not the problem. If your trying to go from 1/2 MOA to 1/4 MOA at 100 meters just about everything becomes important.

 

[Bart B.]

Nice comparison, jmorris. Well done.

I remember when that scoped gun first came out. 'Twas oft times claimed to be a hybrid; a rifle barreled action fitted to a handgun grip held and fired with one hand.

 

[carbine85]

Are you talking about pistol round accuracy from a pistol or a rifle? There's a lot of differences.

 

[Joshboyfutre]

I don't think I conveyed my question properly. What I'm getting at is that if I take a 9mm, and put it in a vice, and load three different loads using the same bullet weight, powder etc. etc. One slow one average and one hot, usually one load is gonna be noticably more accurate than the other two. Which ever one isn't important. Taking all outside influences out of play, some loads will be better than others. Why? Is the bullet spinning at a certain aa to stabilize it? Is it leaving the barrel at the perfect time? Is it black magic? Lol. This is just me wondering how something works. Simpily curious.

 

[jmorris]

One slow one average and one hot, usually one load is gonna be noticably more accurate than the other two. Which ever one isn't important. Taking all outside influences out of play, some loads will be better than others. Why? Is the bullet spinning at a certain aa to stabilize it? Is it leaving the barrel at the perfect time? Is it black magic?

Black magic. No, it's just variables and lots of them. In your above "hot, average and slow" hypothetical you are only accounting for a single variable. Another would be "long, average and short" bullet seating depth or "CCI, Federal, Winchester" primers or "FMJ, Plated, wax lubed" bullets or "W231, N310, HS-6" powders and countless additional variables.

If it were something that was exact for every 9mm that delivered ideal results under every condition we would have "A load" that everyone uses. If you bought two "Identical" firearms except for different serial numbers and loaded them with the exact same ammunition you won't get identical results. Again, attributed to hundreds of variables from if someone was having a case of the "Monday's" to tool erosion or a combination of tolerances that stack one way or the other.

This is why a particular load may be ideal for one firearm and mediocre in another.

Same thing goes for twin children or even rocks in a river, it's a lot harder to make things identical than to make them different.

The BOSS system is an attempt to be able to "adjust" the firearm to the load vs the load to the firearm.
http://www.browning.com/support/frequently-asked-questions/tune-boss.html

 

[Joshboyfutre]

U mention getting two gunsthe same make with different serial #s with the same ammo getting different results. The question I have been driving at is why? I am well aware that different variables cause differences in accuracy, what I'm asking here is... Why? What is physically happening to cause the two guns to shoot the bullet differently. With a rifle its gonna be harmonics mostly from my understanding. Small variances in the metallurgy cause the barrels to vibrate just a little differently, causing each to have its own prefered load. Whats the main factor in a handgun. It just seems like there wouldn't be such a difference in pistols performance because the short barrel is vibrating a lot less.

 

[243winxb]

Different amounts of the same powder may unseat the bullet at a different time?? The pressure curve would change. Sort of like from this link. See "To much Primer" http://www.shootingtimes.com/ammo/ammunition_st_mamotaip_200909/ The 9 mm part.

 

[jmorris]

Why?

Because no matter how hard we try, we can't make everything identical. As soon as things are different, well they are different and they will give different results.

It just seems like there wouldn't be such a difference in pistols performance because the short barrel is vibrating a lot less.

Think about how many parts there are in a pistol. Now how many could you alter and have an effect on performance? Now if you can't make them identical, they are different and effect performance differently.

 

[rodregier]

If you're chasing accuracy in 9mmx19 and reload, I would commend the 125g HAP (Hornady Action Pistol) projectile. It's a simplified version of the XTP for a reduced price. (Less mfgr steps = lower cost). I really enjoy them punching paper in a Glock 17.

Bill Wilson also sells it as a custom loading with an accuracy guarantee.

http://shopwilsoncombat.com/9mm-Bill-Wilson-Signature-Match-125-gr-Hornady-HAP-1075-FPS-5-Barrel-100_Box/productinfo/A9-125-HAP/

"The Signature Jacketed Match 9mm load has been extensively tested in 1911 style and other high-performance firearms and is the most accurate 125 grain 9mm ammunition available. We guarantee the Bill Wilson Signature Jacketed Match to shoot 25 yard, ten-shot groups through a fixed barrel testing device of under ONE-HALF (1/2) INCH-GUARANTEED."

 

[Walkalong]

I have no doubt the HAP is an accurate bullet, but at that price I wonder how much Wilson sells.

 

[Nature Boy]

I wonder how much Bill Wilson Signature Jacketed Match loads would be without Bill's signature?

 

[buck460XVR]

I doubt that resonance is a factor in pistol barrel accuracy since it's so much shorter than a rifle barrel relative to bore size. (i.e. very stiff for resonance).

Take a revolver and rest the front of the barrel on sandbags, shoot and then shoot it again with the front of the frame resting on the bags. The difference can be quite dramatic.

Still, every gun is unique and what it likes to eat and how well it spits it out can vary. Every gun has it's own capacity for accuracy built in, then comes shooter proficiency and then a load that the gun likes. Of course quality bullets make a difference for the most part, as is finding the velocity to drive them that the gun prefers. Then there's that issue of what is real accuracy. Big difference between a SD gun's accuracy @ 3 yards and a hunting revolver intended for 100 yard shots.

 

[jmorris]

Bullets can make a considerable difference. Like this 10 shot 100 yard group that not even all 10 plated 147's hit the paper.



Vs a 10 shot 100 yard group using Winchester 115 gn JHP bullets.



That said there are more 9mm's and people that won't do that well than there are that will.