7" twist 6x47L - did I choose poorly?

[nvbroncrider]

I

I didn't give a freebore specification because I wasn't sure what bullet I want to run.

I'm running heavy so it works for me. Trying to maximize case capacity. I got a really accurate 280AI they put together so I think it will work fine.

 

[jaygorski]

I have some 6 creedmoors with 8 twist, I shoot new DTACs with no issues.

 

[XTR]

I have some 6 creedmoors with 8 twist, I shoot new DTACs with no issues.

According to Bryan Litz the issue for long range shooters isn't so much that long bullets won't or don't shoot well but that with marginal stability, as the spin rate decays at long range, the nose starts to yaw and you lower the effective BC of the bullet. Using barrels that provide lower or marginal stability can produce greater precision (tighter groups) at shorter ranges. BR guys know this and build accordingly.

In most cases when we have this discussion it is because we are are shooting heavy for class bullets at lower velocities to get the BC benefits at long range, so the effect is to negate the advantage we were trying to achieve.

In any case, Bryan has written a pretty good summary somewhere in the ballistics forum.

 

[FrankG]

View attachment 1000253

My 6x47 is 7.5 twist Bartlien and its perfect for the 105s, 7.0 would be just as good.

This barrel seems to be a little slow (due to the twist rate?), or it might be some other factor.

How many rounds are on it? What's your load?

Later, Frank
Bartlein Barrels

 

[SG4247]

How many rounds are on it? What's your load?

Later, Frank
Bartlein Barrels

Frank,

Barrel was at 800 rounds when this I tested the data below with both the LabRadar and Magnetospeed. Surprisingly, both instruments reported the MV at nearly identical values when both instruments were used simultaneously.

Load #1
105 Berger VLDT
H4350 36.3g
#450 Primer
2.710" OAL
Average MV 2838 from 28.5" barrel length
Checked with LabRadar and Magnetospeed

Load #2
115 DTAC
H4831SC 39.4g
#450 Primer
2.750" OAL
Average MV 2698 from 28.5" barrel length
Checked with LabRadar and Magnetospeed

#450 Primer provided best MV. Other primers tested (BR4, #41) were even slower by 10-30 fps.

SG4247

 

[SG4247]

The reason I think it is slow is:

Interpolating the MV data from the Berger manual for a 6mm 115 bullet with 39.5 H4831SC should go 2740 ft/sec with a 24" barrel.

Mine is 28.5" going 2698??

SG4247

 

[swd]

4831 is too slow for the 47 case even with 115's. Try RL16, RL17 and H4350. You'll easily find more speed with accuracy.

 

[FrankG]

Frank,

Barrel was at 800 rounds when this I tested the data below with both the LabRadar and Magnetospeed. Surprisingly, both instruments reported the MV at nearly identical values when both instruments were used simultaneously.

Load #1
105 Berger VLDT
H4350 36.3g
#450 Primer
2.710" OAL
Average MV 2838 from 28.5" barrel length
Checked with LabRadar and Magnetospeed

Load #2
115 DTAC
H4831SC 39.4g
#450 Primer
2.750" OAL
Average MV 2698 from 28.5" barrel length
Checked with LabRadar and Magnetospeed

#450 Primer provided best MV. Other primers tested (BR4, #41) were even slower by 10-30 fps.

SG4247

I only shot 115's thru my rifle but as has been posted I think the 4831 is to slow for the case capacity. I did try some Varget once and it shot well but I only tried like 20 rounds.

With 107's my load is 39.0-40.0 of H4350 and the barrel is 30" finish length and I'm hitting 3000-3100fps. I checked it thru a Oehler chronograph. That's on the shops F-Class rifle and has a 1-8 twist barrel.

My gun had a 1-7.5 twist barrel. Originally wanted to shoot the 115gr. Bergers. My load in that gun was 39.0gr. of H4350 and it was doing a solid 3000fps. I want to say 3030fps. and that was a 30" long barrel also. The gun would hold 1/3moa at a 1k but when I bumped the load up to 40.0gr. the groups would go to 3/4moa so I ran it at 39.0.

Your 36.3gr. of H4350 seems light but if your getting 2800fps and change at 36gr. of powder I don't think the barrel is slow.

Your o.a.l. is close to mine. I like to check base to ogive more than anything else. The 107's o.a.l. is 2.640" and I'm running my bullets .010" off the lands.

Later, Frank

 

[sparker]

I've never shot 115's thru mine but as has been posted I think the 4831 is to slow for the case capacity.

With 105 Hybrids my load is 41.7-41.8 of H4350 and the barrel is 23" finish length and I'm hitting 2997fps. avg. I checked it thru a Oehler chronograph and a magneto speed and they we're with in 10fps. or so.

Your 36.3gr. of H4350 seems light but if your getting 2800fps and change at 36gr. of powder I don't think the barrel is slow.

Your o.a.l. is close to mine. I'm around 2.750" depending on the bullet but I go with base to ogive measurement more than anything else and I'm running my bullets .010" off the lands.

Later, Frank

Hi Frank, what kind of delivery times are you folks running currently?
Thank you.

Scott Parker

 

[FrankG]

Hi Frank, what kind of delivery times are you folks running currently?
Thank you.

Scott Parker

Scott, Depends on what your ordering and when your ordering it can be a big variable. For the most part I'm going to say a solid 6 months maybe longer right now. If you cannot wait you and they have the contour you want you can try the places on our links page like Grizzly, Southern Precision Rifles, OTM, Redhawk Rifles etc.....if they don't have the contour or twist more than happy to help you out.

If it's a odd caliber we don't run a lot of like a .375, .408 etc....then it's a timing thing. If we are getting close to a run and you place the order at the right time you could see it in just a few weeks. it's happened where guys have ordered the barrel and got it in as fast as 3 weeks. If you order a caliber like I just said and we just made the run then plan on a longer lead time.

Also if it's a odd caliber and you time it correctly and we have a order coming up for some ammunition test barrels again you could see it fairly quickly.

Later, Frank

 

[sparker]

Scott, Depends on what your ordering and when your ordering it can be a big variable. For the most part I'm going to say a solid 6 months maybe longer right now. If you cannot wait you and they have the contour you want you can try the places on our links page like Grizzly, Southern Precision Rifles, OTM, Redhawk Rifles etc.....if they don't have the contour or twist more than happy to help you out.

If it's a odd caliber we don't run a lot of like a .375, .408 etc....then it's a timing thing. If we are getting close to a run and you place the order at the right time you could see it in just a few weeks. it's happened where guys have ordered the barrel and got it in as fast as 3 weeks. If you order a caliber like I just said and we just made the run then plan on a longer lead time.

Also if it's a odd caliber and you time it correctly and we have a order coming up for some ammunition test barrels again you could see it fairly quickly.

Later, Frank

I'm looking for a 6mm 7.5" twist medium or heavy palma.

Scott

 

[SG4247]

I only shot 115's thru my rifle but as has been posted I think the 4831 is to slow for the case capacity. I did try some Varget once and it shot well but I only tried like 20 rounds.

With 107's my load is 39.0-40.0 of H4350 and the barrel is 30" finish length and I'm hitting 3000-3100fps. I checked it thru a Oehler chronograph. That's on the shops F-Class rifle and has a 1-8 twist barrel.

My gun had a 1-7.5 twist barrel. Originally wanted to shoot the 115gr. Bergers. My load in that gun was 39.0gr. of H4350 and it was doing a solid 3000fps. I want to say 3030fps. and that was a 30" long barrel also. The gun would hold 1/3moa at a 1k but when I bumped the load up to 40.0gr. the groups would go to 3/4moa so I ran it at 39.0.

Your 36.3gr. of H4350 seems light but if your getting 2800fps and change at 36gr. of powder I don't think the barrel is slow.

Your o.a.l. is close to mine. I like to check base to ogive more than anything else. The 107's o.a.l. is 2.640" and I'm running my bullets .010" off the lands.

Later, Frank

Thanks Frank,

I will try the 115s using H4350 up towards 39.0 - and see if that picks it up.

I tried the 105s up there at 39.0 - 40.0 with H4350, and accuracy fell off. Didnt check those for speed.

SG4247

 

[nvbroncrider]

Thanks Frank,

I will try the 115s using H4350 up towards 39.0 - and see if that picks it up.

I tried the 105s up there at 39.0 - 40.0 with H4350, and accuracy fell off. Didnt check those for speed.

SG4247

You might be between nodes that would be my guess.

 

[FrankG]

I'm looking for a 6mm 7.5" twist medium or heavy palma.

Scott

Scott, Nothing in stock. I'd say a solid 6 months from us direct right now. Try Bugholes (Southern Precision Rifles), Grizzly, OTM or Robert Whitley at ARX Enterprises. One of these guys should have one in stock.

Later, Frank

 

[Puzzaz01]

Great choice in my opinion. Get some of the new 110 Sierras along with Reloader 16 and have fun!

Just by chance ...... Do you have any load data for lapua brass 6 dasher using reloader 16 with the 110 or 115's?

 

[swd]

Just by chance ...... Do you have any load data for lapua brass 6 dasher using reloader 16 with the 110 or 115's?

With the 110SMK start at around 32 and work up. With Norma Dasher brass I maxed out at about 35 with a bushed .062" pin. That's a case full about to the base of the neck very slowly trickled in. This is in a .145" free bore. 32 should be plenty safe for most any bullet to start with, but this in my rifles, you know the caveats...

 

[BrandonK]

I have never waited 10 weeks for a gun barrel.

Well lucky you.lol

 

[Iowa Fox]

Great choice in my opinion. Get some of the new 110 Sierras along with Reloader 16 and have fun!

Yep! Was thinking the same thing.

 

[kevwil]

My barrel arrived last week (almost 4 months to the day), so I loaded 20 rounds just to get the scope back in the ballpark and verify the rifle is not gonna explode on me.

Initial shots with some hunting bullets made some extremely encouraging groups, I can't wait to work up some accuracy loads and see how she really shoots. First impression with this cartridge and this barrel is off the charts, I think it's my new favorite rifle.

Thanks again for all the votes of confidence.

 

[ChrisNZ]

I'm interested in your load development progress. Keep us posted.