Velocity difference right vs left barrel

Buck51

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Curious what you guys are getting in velocity difference right vs left barrel. I bought a Marcel Thys 470 NE and am just getting started with Load development. The ammo that came with the rifle was loaded by Superior but other than bullet type it has no load data. It Shoots about 4” low and an 1 1/2” right At 50yds. Regulation is good at under 2”. Almost touching and not crossing. Velocity out of right barrel is about 60fps less than left barrel. Getting about 1960 right and 2020 left. 500 grain TBBC. I’ve got the 3rd edition of Graeme Wrights book and he states this is in the good range. Curious what others are getting.
 
Gotta love that it's working for you!

For me, in the 470, with LabRadar, Nosler solids and DGX bonded have been very consistent between barrels - usually within 15- 20fps. Had some bigger variance with Barnes solids, but not enough data to blame the bullets.

If they are accurate and regulating, I think 60fps would be insignificant.

Keep us updated! Good luck.
 
Every barrel is unique in its own way. A velocity difference by 10 or 20 fps is normal.

If you record the velocity for at least 10 shots from each barrel then you can establish the mean difference. A 60 fps mean difference seems high but then I am not familiar with the maker's rifles.

A different bullet may produce more or less velocity difference.

Since your rifle regulates, I would not worry about any difference in velocity between the barrels.
Duplicating that load may however give you something to think about. If it were me, I'd pull the bullet, weight the powder charge, photograph the powder kernels to compare them to other known powders, record the color of the primer (copper or silver), and measure the capacity of the brass. Record all that data. Then, along with a couple good loading manuals, you will have a starting point.

Good luck!
 
Every barrel is unique in its own way. A velocity difference by 10 or 20 fps is normal.

If you record the velocity for at least 10 shots from each barrel then you can establish the mean difference. A 60 fps mean difference seems high but then I am not familiar with the maker's rifles.

A different bullet may produce more or less velocity difference.

Since your rifle regulates, I would not worry about any difference in velocity between the barrels.
Duplicating that load may however give you something to think about. If it were me, I'd pull the bullet, weight the powder charge, photograph the powder kernels to compare them to other known powders, record the color of the primer (copper or silver), and measure the capacity of the brass. Record all that data. Then, along with a couple good loading manuals, you will have a starting point.

Good luck!
I am hoping to develop a load using available components. I haven’t seen any TBBC for sale in 470. Appreciate the advice and I will document the superior load the best I can. I hope to develop a load that gets both barrels in that 2050-2100 range. I’ve purchased several options to begin with and like the idea of RL 15.5. From info I’ve read on the forum it is a good powder for 470 and felt recoil is supposedly less. Thanks for your input.
 
Curious what you guys are getting in velocity difference right vs left barrel. I bought a Marcel Thys 470 NE and am just getting started with Load development. The ammo that came with the rifle was loaded by Superior but other than bullet type it has no load data. It Shoots about 4” low and an 1 1/2” right At 50yds. Regulation is good at under 2”. Almost touching and not crossing. Velocity out of right barrel is about 60fps less than left barrel. Getting about 1960 right and 2020 left. 500 grain TBBC. I’ve got the 3rd edition of Graeme Wrights book and he states this is in the good range. Curious what others are getting.
Is that 60 fps consistent? Could “part” be normal variation between cartridges?
 
Curious what you guys are getting in velocity difference right vs left barrel. I bought a Marcel Thys 470 NE and am just getting started with Load development. The ammo that came with the rifle was loaded by Superior but other than bullet type it has no load data. It Shoots about 4” low and an 1 1/2” right At 50yds. Regulation is good at under 2”. Almost touching and not crossing. Velocity out of right barrel is about 60fps less than left barrel. Getting about 1960 right and 2020 left. 500 grain TBBC. I’ve got the 3rd edition of Graeme Wrights book and he states this is in the good range. Curious what others are getting.
I doubt it is the rifle but your reloads that are the variable.
 
Curious what you guys are getting in velocity difference right vs left barrel. I bought a Marcel Thys 470 NE and am just getting started with Load development. The ammo that came with the rifle was loaded by Superior but other than bullet type it has no load data. It Shoots about 4” low and an 1 1/2” right At 50yds. Regulation is good at under 2”. Almost touching and not crossing. Velocity out of right barrel is about 60fps less than left barrel. Getting about 1960 right and 2020 left. 500 grain TBBC. I’ve got the 3rd edition of Graeme Wrights book and he states this is in the good range. Curious what others are getting.

Congrats on buying one of the few "new best maker's" double rifles! I was talking with a friend about this concept in the wee hours of the morning today.

First, what causes the variance? If you've established its always the case that one barrel is lower velocity than the other, it indicates that one barrel is tighter due to machining irregularities. What can you do to close the speed difference? You can open the tighter barrel to slow the velocity. That is operating under the assumption that a pressure spike from the tight barrel results in increased velocity. The ways to do that without damaging the rifle in a manner that lapping could do would be as follows.

Meticulously clean the tight barrel with all the good stuff. Shooters choice / Sweets, then wipe out, etc. Rotating through all the brands may dissolve stuck particles in the bore or rifling that is restricting the bullet. After that, you can use a bronze brush rolled in bronze wool, with a cotton patch soaked in JB Bore Paste and Kroil. 50 strokes, then a full cleaning. Do this up to three times. You haven't lapped the barrel, but you certainly have attempted to remove microscopic debris and burrs that may result in lower pressure.

If the former improves it, great. If not, next step would be to use pin gauges and a bore mic to see if there is one area of the bore that happens to be tighter than it should. If that is the case, and you can localize it, then a competent barrel mechanic will lap the bore in that area, staying far clear of the chamber and muzzle of a double rifle. (this is professional's work)

The good news is your gun will be more accurate at the end of the process. The bad news is that your current regulating loads may not be correct any longer, because they probably were converging due to one barrel effectively being crooked...one barrel was yawing more by the velocity difference. If you correct the barrel problem, you may find your new regulating load needs to be a grain more or less than it is when you started.
 
Thanks for the all the insights! I need to spend A little more time at the range verifying the variation. I only fired 8 rounds my last outing but it was 54,56,60 and 61 fps more out of left barrel vs right. I’m going to give it a good cleaning as rookhawk suggests and put some more rounds through it. BTW the Buff in mu Avatar photograph was taken with the Dakota 76 in 416 Rigby I purchased from @rookhawk a few years ago.
 
Thanks for the all the insights! I need to spend A little more time at the range verifying the variation. I only fired 8 rounds my last outing but it was 54,56,60 and 61 fps more out of left barrel vs right. I’m going to give it a good cleaning as rookhawk suggests and put some more rounds through it. BTW the Buff in mu Avatar photograph was taken with the Dakota 76 in 416 Rigby I purchased from @rookhawk a few years ago.

@Buck51 congratulations on the buffalo! Also, congrats on the Dakota. Since you purchased it, its easily gone up 50% or more. Hopefully you have an heir that will own it someday after it gets a lot more honest wear and stories to tell.

For your cleaning experiment, just for fun, only methodically clean the tight barrel that is giving you higher velocity and lets see if that reduces the speed differential. If it does, report back and we can come up with some other tactics for you to close the gap further.
 
I like that idea. Hopefully get to range this weekend. I will let you know.

My son has his eye on it…(y)
 
My Merkel 140AE 450-400 3" with 60 cm barrel (approx. 23.5") shooting Hornady factory loads averages between 2000 fps ( at 5°c) and 2080 fps. (at 30°C) AND there is a consistent difference of about 20 fps between the right and left barrels. Shoots good consistent groups from both barrels despite that difference in velocity on hot or cold days.
 
I’m also getting on avg 10-20 fps difference between my right and left .375 HH with the right being faster. I haven’t tried any different cleaning procedures- both barrels cleaned the same. Still working on regulating a load but about there. Then on to the .470.

Disclaimer- As always I’m not suggesting any load for anyone- it’s just what’s working for me.
IMG_7150.jpeg
 
I am hoping to develop a load using available components. I haven’t seen any TBBC for sale in 470. Appreciate the advice and I will document the superior load the best I can. I hope to develop a load that gets both barrels in that 2050-2100 range. I’ve purchased several options to begin with and like the idea of RL 15.5. From info I’ve read on the forum it is a good powder for 470 and felt recoil is supposedly less. Thanks for your input.
i use it with great results getting regulation of 0.8 inches at 50 yards. i use Norma brass, 84 grains with Trader Keith #2 fillers and Barnes TSX bullets
 
i use it with great results getting regulation of 0.8 inches at 50 yards. i use Norma brass, 84 grains with Trader Keith #2 fillers and Barnes TSX bullets
Thanks for the info. Ithink I will give it a try. Already have some of those #2 fillers and some Norma Brass.
 
Congrats on buying one of the few "new best maker's" double rifles! I was talking with a friend about this concept in the wee hours of the morning today.

First, what causes the variance? If you've established its always the case that one barrel is lower velocity than the other, it indicates that one barrel is tighter due to machining irregularities. What can you do to close the speed difference? You can open the tighter barrel to slow the velocity. That is operating under the assumption that a pressure spike from the tight barrel results in increased velocity. The ways to do that without damaging the rifle in a manner that lapping could do would be as follows.

Meticulously clean the tight barrel with all the good stuff. Shooters choice / Sweets, then wipe out, etc. Rotating through all the brands may dissolve stuck particles in the bore or rifling that is restricting the bullet. After that, you can use a bronze brush rolled in bronze wool, with a cotton patch soaked in JB Bore Paste and Kroil. 50 strokes, then a full cleaning. Do this up to three times. You haven't lapped the barrel, but you certainly have attempted to remove microscopic debris and burrs that may result in lower pressure.

If the former improves it, great. If not, next step would be to use pin gauges and a bore mic to see if there is one area of the bore that happens to be tighter than it should. If that is the case, and you can localize it, then a competent barrel mechanic will lap the bore in that area, staying far clear of the chamber and muzzle of a double rifle. (this is professional's work)

The good news is your gun will be more accurate at the end of the process. The bad news is that your current regulating loads may not be correct any longer, because they probably were converging due to one barrel effectively being crooked...one barrel was yawing more by the velocity difference. If you correct the barrel problem, you may find your new regulating load needs to be a grain more or less than it is when you started.
Cleaning helped quite a bit. The average variation is about 20-30 fps. Out of 20 rounds I had one in the right that was 60 fps higher right vs left but I think that was the ammo.
 
At the distances you're going to use that double to good effect, a delta of 60 fps is truly meaningless.

If you were shooting F Class or National Match at 1000 yards, an ES of 60 fps would be terrible.
 
Well used douɓled wear out thr right barrel faster than the left barrel.....not sure how well used this one is though
 

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