Tiny variations, trend or not. We're talking single or near single digit extreme spreads and one shot tests. What can we really learn from that?
Barrel tuners or other muzzle devices effect on velocity and velocity stats
- Thread starter darkangel_r2
- Start date
Bill Norris
Back in the Day
I think he was shooting 3-shot groups to get each velocity listed and that still may not be enough.
Wow that is cool, damn shame our club is prohibiting brakes in matches. Tuners ok but brakes, no. Benches too close together and guys shooting big calibers with "tank" brake next to you blowing your stuff off the table, kinda ticks you off...
looks to me as if the barrel heated up the velocity decreased slightly. No brakes allowed in matches where I shoot either.
At any rate the only numbers I concern myself with these days is avg velocity and group size. I ran down the ES/SD rabbit hole far enough to decide in my shooting any differences in ES were canceled out by wind/shooting technique
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No offense meant to anyone here so please don’t take the following as rudeness, I’m just calling it like it is. This example using the same load in two different groups where one had 168fps ES and the better group was still 47fps ES is in no way a scientific comparison to what a quality firing system loaded to .02 grains is capable of.
My stuff generally shoots 15ES or less and I will tell you that moving a tuner on the outside of a barrel will have zero effect on the velocity and or ES of my rifles. It’s not possible.
I think you're right, twice.
Bill Norris
Back in the Day
And at 100 yds. which is all I have for now, I have realized that ES/SD is not a major concern either.
Can you explain this a little? Is this your example or did someone else show you this.
Can different barrel lengths with the same load produce different es/sd spreads? If barrel harmonics have nothing to do with velocity stats then any barrel length long enough to achieve a complete burn should have the same or similar velocity es/sd numbers.
Is that the case? I'm not sure. Thats why I'm making this thread.
There was a picture in that post that I quoted with details of two groups being shot, one with a jacket on and one without.
Different barrel lengths will for sure give you different velocities, it has nothing to do with harmonics, just the fact that one is indeed longer than the other. While a tuner changes harmonics it can’t change length. I keep an open mind on everything when it comes to rifles and loads etc. because just like Farmers, I’ve seen a thing or two, however there is no way a tuner will change the velocity of a bullet, statistically or any other.
Attachments
Yep I see it now.
Its velocity stats I'm concerned with in that question I asked above. Es and SD numbers not the average velocity.
Let me ask it in a different way. We know 308 win can achieve a complete burn around 20" or so. So for example if I have a load that has an SD of 7 for 20 shots in a barrel that is 30" long will it maintain maintain that tight SD if I start cutting inches off the muzzle of the gun?
I'm sure it would change some as we get close to that complete combustion length. But would it change at 29-22"?
I can’t answer that but again, we are talking about barrel length still not tuner settings which was the original question.
Thats correct its not the original question but it is a parallel if you give me some leeway to explain how they are related.
Do you agree with the following statement?
After all the powder is burnt all you have left in the barrel is a gas under pressure plugged by a bullet.
No offense taken. I figure consistent .5 - .6 MOA 10 round verticals at 300 yards for someone with my skill level and mid priced gear is about as good as I can expect. That same powder load with a 140 SMK had a ES of 11 and SD of 4. I have often wondered if I had set up my chrono too close to the muzzle and the muzzle blast caused the high numbers.
The test was to see if annealing eliminated the odd high/low flyers I had been getting with that rifle. It did but at the same time raised other questions. There had been a 15 min cooldown between shooting those two groups and the only thing that changed was I had removed my denim jacket. Both of those groups were shot with annealed cases. One of these days I plan on checking to see if changes in hold affect ES/SD
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One after the other. Only difference was the presence of the bloop tube.
It’s all good. Keep striving for more. If you’re using an optical chrony your setup could definitely be causing you fits with consistent numbers. They have to be perfect and even then are still susceptible to shadows and different light angles. Different holds will definitely give you different velocities. I can’t tell you off the top of my head how much but just compare free recoil with pinning the stock in the front rest or bi pod. It’ll show up quick but back to my original point I guess, if you’re shooting 50fps ES, anything you learn is gonna get lost in the noise.
thanks for the info on the different holds, something I suspected. I need to get into the habit of shooting in a shooting jacket, just hard to get used to in southern coastal heat in the summer. Then of course a free recoil hold is very doable with a 6BR but not really doable with a 8 pound .308 or even my .260.
On the chrono, the only numbers I trust is from a magnetospeed. The opticals have their issues as you pointed out and the Labradar will be inconsistent with vibration due to wind/muzzle blast and has to be set up at the same angle every time so that the bullet enters the transmission cone consistently
I have had some really good success with high ES/SD numbers out to 300 yards however, that is about as far as I normally chrono test. One .223 load with Berger 80's had a ES in the 70's and a 10 round vertical of just over a inch at 300
That last one looks interesting. Where does the muzzle end in these?
garandman
Bolt Gun Bodacious
Typical threaded bbl end, from what I've seen. The brake itself will often have an extra 1/4" recess the barrel seats into.
Do you know of a tuner break combo where the tuner is over the barrel and only the break is past the muzzle? Id rather not have any real constriction forward of and around the muzzle. So for example muzzle ends at red line so only open brake extends forward.
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