Rimfire bullet speed.

[Chriswillis696]

Does anyone think that the bullets speed can make a difference on the accuracy.
I was out at the range playing around testing and trying a few things and nothing was really working for me it was throwing shoots and playing up like a second hand watch than i noticed i was using a slower speed 1052fps and i normaly use 1062fps eley match. Do u think something this little can really affect the accuracy of the rifle??

[Mulga]

So what your asking is can velocity of a projectile effect the accuracy? Yes and No. It is a difficult question to answer simply (im no expert on this matter mind you). I see taht it breaks down into three parts. Internal and external ballistics as well as human error. These are entire diciplines in thier own right and people make carears in there fields, textbooks are written on these topics.

The first part is internal ballistics or what happens before the projectile leaves your barrel. This is most relevant for the small bore (rimfire) target shooter, applicable to others as well. In a nutshell firearms can be quite quirky/finicky when it comes to what you feed them. Hand loading centerfire cartridges allows you to fine tune and find what the firearm likes and control every aspect of assembly. Wilth rimfire ammo its a matter of trying as many different types of ammo as possible to do the same. If you have ever chronigraphed any ammo before you will know 'standard deviation' (SD) of a particular load is a critial factor. For an example Winchester Z's have a large SD in the ballpark of 300 - 400fps, Win Power Point's around 40 - 80fps SD. Match ammo should have a very low SD, this is what you pay for $$$='consistency'. Now there can be enough variation between 'batches' that some small bore shooters will buy bulk of a particular batch of ammo. I have hered that when manufacturing Winchester Super Speed if a batch dosn't meet benchmark SD and velocity that batch is sold as Bushman. Whether this is true im not 100%. The point is small variation in velocity can change your point of impact.

Secondly there is external ballistics. How the projectile behaves when the projectile leaves the barrel until it reaches it end. External ballistics has more of an influence when shooting longer ranges as the laws of physics, environmental factors, projectile velocity and construction etc play a very large role. Most important of these for a rimfire shooter would be velocity , gravity and environmental variables such as wind, had between the muzzle and the target. Slower the projectile = longer travel time = more influencing factors.

Thirdly there is human error


Any how that my $0.20 worth, cant think of anything else now.

[chris.tyne]

Yes it can,it's called harmonics.






Regards Chris.

[curan]

Yes it can,it's called harmonics.

Regards Chris.

+1

As much as I respect Mulga's answer, this is the definitive answer.

The harmonics will determine where the muzzle is pointing as the projectile exits.

Chris knows by experience, but just in case you are unsure, I have a qualification in Cat 2 Vibration Analysis and a Diploma in Industrial Technology to tell me he is right.

Many variables effect rimfires, and each rifle has preferences. You have changed a variable, and it is not surprising you have noticed a difference.

regards, curan

[LoneRider]

so what your saying curan

is if i wrap a bit of rubber tape somewhere along the barrel it will change the harmonics and possibly give the ol mossy, shooting winni subs a tighter than a 50c group @ 50 yrds [roughly]?

ill give anything a go.....seriously....i will

[rubber tape is as wide as electrical but heaps heavier,black and made of rubber.its nothing like electrical or gaffa,more like handle bar tape but heavier.]

[Mulga]

Harmonics good point. It does play some role in accuracy but really is only a small part of the equation to solving accuracy issues.

If this were the major cause of in-accuracy I could tune the barrel on any budget rimfire and get it to shoot like a match grade rifle. Why waste your money on a Anchutz?

[LoneRider]

in hunting rimfires [mine anyway] ive always been happy enough with minute of rabbit accuracy [5 shots in a 50c size circle @ about 50 yrds].
if it was that harmonics played a major part in accuracy it would be worth doing.

[chris.tyne]

The biggest influence on the accuracy level of factory rifles is the price point IE you are getting what you paid for and also quality control,this one is different to that one scenario.



Regards Chris.

[LoneRider]

yeah thats understandable chris.
as long as i do my part properly,its all good.

[curan]

so what your saying curan

is if i wrap a bit of rubber tape somewhere along the barrel it will change the harmonics and possibly give the ol mossy, shooting winni subs a tighter than a 50c group @ 50 yrds [roughly]?

ill give anything a go.....seriously....i will

[rubber tape is as wide as electrical but heaps heavier,black and made of rubber.its nothing like electrical or gaffa,more like handle bar tape but heavier.]

Sorry LR, I haven't had much time to check the forum lately.

IMO, the rubber tape might modify the amplitude of the vibration in a barrel (dampening), but not the frequency, at least not much. So while it may make a difference, there are other methods.

An old explanation I was given, the things that change resonant frequency are span, mass and stress. Think of a guitar string. By tightening a string (stress), it's resonant frequency moves higher, and you hear a higher note. Change the span by pushing a finger against the fret board, and it changes again (span). Replace the string with a thicker string of the same tension and span, and the frequency changes again (mass).

So, for a rifle barrel, the things that make the big difference to harmonics would be:
Span - changing the barrel length or putting a wedge or shim between barrel and forearm
Mass - anything that changes the weight of the barrel, the barrel tuner being an obvious method
Stress - I've heard of tension barrels, but others would be better placed to discuss their merits.

Obviously, the easiest of the above methods to alter a barrels harmonics are the tuner, or, if the rifle is favourable to it, the forearm wedge.

I totally agree with the previous posts about firearm quality, etc.

For a more technical read, try http://www.shootingsoftware.com/barrel.htm

For a more practical read, try Australian Shooter, about a year ago, when there was an article on barrel whip.

As for your wish to improve your rifle, you can try putting .005 - .010" of tension on the forearm with a wedge/shimming, and redo your ammo testing.

You could also try paper bedding with a business card. Jimbo had an yarn about doing that in AS about 5 months ago.

Both of those are low cost DIY things you can try yourself. Personally, I'd probably try the business card bedding first.

Or the high end target shooting method is a barrel tuner.

Sounds like you can do a bit of experimenting with the mossy with a bit of room for improvement, so it's worth a play.

Obviously there are a lot of very talented people on this forum that will agree or disagree with some of this post. But that's fine, I'm sure it will add to the overall amount of info to guide you.

regards, curan.

[curan]

[quote="Mulga"]Harmonics good point. It does play some role in accuracy but really is only a small part of the equation to solving accuracy issues.[quote]
Hi Mulga,

I totally agree, but as the original post was specifically about the changing velocity. IMHO it leads to the discussion of harmonics.

You are also correct that if harmonics was the only thing involved in accuracy, I would have spent fat less on my rifles.

regards, curan.

[Mulga]

I totally agree, but as the original post was specifically about the changing velocity. IMHO it leads to the discussion of harmonics.

Explain to me how harmonics changes projectile velocity?

[chris.tyne]

I totally agree, but as the original post was specifically about the changing velocity. IMHO it leads to the discussion of harmonics.

Explain to me how harmonics changes projectile velocity?

Either you didn't/dont understand the original question or are being argumentive...........................................cause no where have I seen anyone say that harmonics changes velocity.


Regards Chris.

[Brett33]

I totally agree, but as the original post was specifically about the changing velocity. IMHO it leads to the discussion of harmonics.

Explain to me how harmonics changes projectile velocity?

Just in case you really want an answer, Harmonics do not change Velocity, Further more Velocity has little / no impact on Harmonics.

The thing is the explosion causes Harmonics, causing a wave patten in the barrel, Different velocity ammo will leave the muzzel at different points in the wave patten causing dispersion at the target.

We attemp the control the wave (whip) in the barrel to reduce the vertical at the target by different velocity. I still test and buy ammo with a Extreeme spreed in velocity below 20FPS.

Brett

[curan]

Just in case you really want an answer, Harmonics do not change Velocity, Further more Velocity has little / no impact on Harmonics.

The thing is the explosion causes Harmonics, causing a wave patten in the barrel, Different velocity ammo will leave the muzzel at different points in the wave patten causing dispersion at the target.

We attemp the control the wave (whip) in the barrel to reduce the vertical at the target by different velocity. I still test and buy ammo with a Extreeme spreed in velocity below 20FPS.

Brett

Nicely put. And the your explanation is probably better than I would have gone to the effort for an answer

regards, curan