Optimal velocity x caliber x barrel length

[dttheliman]

Potentially a dumbass question , however I am new to 6.5x47L and wondering considering barrel life /brass life etc - if there are optimum speeds one should push a round to for example ,
with a 140gr Berger Hybrid Match / Lapua brass, H4350 (and CCI450) all chrono'ed , I went up from 38.1gr @ 2619 through 40.8gr @2796 , no pressure signs at all , however I got two distinct nodes:
All at 100 yards of a bench 24" barrel .

1. from 38.7, 39 and 39.3gr three groups all shot basically 1 hole groups (POI differed slightly) @ 2649, 2678, 2719
2. and 40.2, 40.5 and 40.8 similarly 1 hole groups @2772, 2790, 2796

My thoughts are if my max range will never be more than 1200 yards (all I have access to) AB calculates that from lowest to highest, at 1200 yards my velocity is 1187 through 1284fps , and therefore as the numbers state I have not gone subsonic (<1125fps) over the range I would be fine in terms of shoot'ability selecting the middle of the lower node .

What say you and why - or am I over thinking it? (as usual) bearing in mind that the Lapua factory ammo 139gr runs at 2697fps .

Thanks
Tim

 

[chromatica]

I think you are being a little too optimistic. Trans-sonic instability starts to set in at Mach 1.2, not Mach 1. That means you need to be looking for the distance at which your projectile drops to 1330 fps, not 1125. I am shooting 123 gr projectiles at 2750 fps which gets me out to 925 yards. Shooting a Berger Target Hybrid at 2700 fps will take you out to just under 1100 yards.

Potentially a dumbass question , however I am new to 6.5x47L and wondering considering barrel life /brass life etc - if there are optimum speeds one should push a round to for example ,
with a 140gr Berger Hybrid Match / Lapua brass, H4350 (and CCI450) all chrono'ed , I went up from 38.1gr @ 2619 through 40.8gr @2796 , no pressure signs at all , however I got two distinct nodes:
All at 100 yards of a bench 24" barrel .

1. from 38.7, 39 and 39.3gr three groups all shot basically 1 hole groups (POI differed slightly) @ 2649, 2678, 2719
2. and 40.2, 40.5 and 40.8 similarly 1 hole groups @2772, 2790, 2796

My thoughts are if my max range will never be more than 1200 yards (all I have access to) AB calculates that from lowest to highest, at 1200 yards my velocity is 1187 through 1284fps , and therefore as the numbers state I have not gone subsonic (<1125fps) over the range I would be fine in terms of shoot'ability selecting the middle of the lower node .

What say you and why - or am I over thinking it? (as usual) bearing in mind that the Lapua factory ammo 139gr runs at 2697fps .

Thanks
Tim

 

[JBT47]

Test your loads out to the max distance you will be shooting and fine tune from there

 

[Clancy]

I think that if your SD is good and the load is safe I'd load in the upper middle of that high node (40.5-40.8) and rock and roll.

I'm in a 22" barrel and shoot varget so I don't know much about the 4350 in this cartridge.

What I do know is small groups at 100 and a consistently low SD means a lot more to me during LD than that 4 digit number.

You knew it wasn't a hotrod when you built it, right? So don't be concerned now.

140H at 2800? HELL YEA!

 

[FeMan]

My last barrel I ran with 40.2 grains of H4350 with 140 Hybrids and CCI 450's in the high 2700's. I got that barrel used so I don't have a round count. I retired the brass after 14 reloads when I rechambered but it was till amazingly tight. My new barrel likes 41.2 at 2845. I have shot my 6.5x47 out to 2500 yards and has done well.

A buddy ran his 6.5x47L in PRS matches and retired it at 4500 rounds. His last 5-shot group was under 0.1 moa at 4500 rounds! His load was in the high 2700's shooting SMKs and Hybrids.

 

[Hal]

My last barrel I ran with 40.2 grains of H4350 with 140 Hybrids and CCI 450's in the high 2700's. I got that barrel used so I don't have a round count. I retired the brass after 14 reloads when I rechambered but it was till amazingly tight. My new barrel likes 41.2 at 2845. I have shot my 6.5x47 out to 2500 yards and has done well.

A buddy ran his 6.5x47L in PRS matches and retired it at 4500 rounds. His last 5-shot group was under 0.1
moa at 4500 rounds! His load was in the high 2700's shooting SMKs and Hybrids.[/QUOT

 

[Sniper338]

Test those loads way further out and you will answer your own question on which charge is better... which = what your barrel likes, which = what its gonna do range wise.

Forget about velocity, forget about barrel life, and shoot whats accurate. Precision is better than higher velocity. If you have to shoot 1200 yards all the time build another rifle better equipt for 1200, but the 6.5x47 will reach it. Drop to 120's 130's if you want more speed.

Accuracy over velocity!

Jmo, nothing more.

 

[Shynloco]

Maybe I'm misreading what you wrote, but why on earth are you testing loads at 100 yds when you intend to shoot at 1200 yds. Two very different animals that produce different results. Bullets and powder loads will produce different results. Just my .02 worth.

Alex

 

[dttheliman]

I appreciate the responses - just for clarity I stated that I have access to a 1200yrd range - not that that was the distance where I was going to shoot all the time, typically I am within the 5 to 700 yrd window + when I am bored I head down to my local range (20 minute drive, not 2 hours) which have a max 200yrd just to punch paper ..... when I am building a load up , something that is accurate at 100 / low sd etc and not ridiculously too hot for the caliber (Agree its not a hotrod cartridge) is where I like to start - before I start messing with OAL etc.

So following the thought process - I will go into the middle of my higher node and work from there.

Thanks

Tim

 

[JBT47]

I appreciate the responses - just for clarity I stated that I have access to a 1200yrd range - not that that was the distance where I was going to shoot all the time, typically I am within the 5 to 700 yrd window + when I am bored I head down to my local range (20 minute drive, not 2 hours) which have a max 200yrd just to punch paper ..... when I am building a load up , something that is accurate at 100 / low sd etc and not ridiculously too hot for the caliber (Agree its not a hotrod cartridge) is where I like to start - before I start messing with OAL etc.

So following the thought process - I will go into the middle of my higher node and work from there.

Thanks

Tim

Test your loads as far out as you can then. I've shot many bug hole groups at 100 that are pathetic at 1,000. Inversely, what shoots best at 1,000 for me may or may not shoot tight groups at 100.

 

[Shynloco]

Test your loads as far out as you can then. I've shot many bug hole groups at 100 that are pathetic at 1,000. Inversely, what shoots best at 1,000 for me may or may not shoot tight groups at 100.

Which is exactly what I was referring to. You have to find a sweet load for each distance you will be shooting if accuracy is what you are chasing. And I do understand what the OP wrote in his subsequent comments. At the same time, JBT just illustrated the importance of testing for each particular distance as I doubt shooting bug holes at 100 yds makes any shooter happy when at 1K it looks like a shotgun pattern.

Alex

 

[DirtySteve]

Looking at the info you posted I would say you are right on starting at the middle of the higher node. I am guessing you will end up at 40.6 or 40.7. Based upon the the 40.5 to 40.8 was only 6 fps! When shooting at 1000 or more speed is going to be your friend.

Just curious as to what your twist is on the barrel? I like the fastest twist barrels for the caliber I am shooting. I always go for heavier than lighter bullets. So this always suits my habits.

 

[dttheliman]

Its a 8 twist 5r bartlein - and @DirtySteve I am a fan of faster twists - I had a 260 Rem in a 9 twist that would not shoot anything over a 130 gr - when that barrel got tired I changed it for a 8 twist - and I was very successful with the 140gr , enjoyed it so much I still haven't got bored with it yet