Building a prs rifle, trying to determine cal, 6.5x47 lapua or 6.5 creedmoor

[Gamesniper19]

My Coach's 6XC match load runs around 2800 with a HBN coated 115 DTAC. It's kinda pokey. He's up around 1800rds on the barrel now and it's starting to throw flyers. We're putting it through one last match and then pulling it and putting the new one one. My .243AI load ran 3200fps with 115's and made 1300 before I was beyond mag length on a loaded round. It still groups great though. I've since replaced that barrel with a 6XC running 2980 with HBN coated 115's.

Fast 6mm's are THE ticket for when you have to spot your own shots. Recoil is super low even when you're running them sick fast. If you don't need that then there are definitely barrel life benefits to be had in a less overbore setup. I personally like 7mm. Bullet weights around 180gn can get BC's in the very high .600's, actually nearer to .7 than .6. Pushed to fairly modest speeds they have a great supersonic range and the extra mass makes for a nice whack on the target so hits are easier to hear. My 7mmRM is absolutely boring to shoot under 1000yrds.

This is exactly the shooters conundrum...BC and speed versus follow up and shootability
A 130 grain berger target has a BC of 562, i picked it cause I could load it a bit faster without added recoil over a 140 and there is a definite unmistakable splash on steel with that bullet weight versus the 6MM
A 108 grain ELDM has a BC of 536 - which is close to the 6.5 BC and if you choose the 6.5 CM - powder charge diff is negligible

My question is how much recoil diff are you all seeing from the 6MM to the 6.5MM creed with nearly the same case and charge?

 

[BallisticsGuy]

Recoil is a function of rifle weight, how much mass you're pushing out of the muzzle and the square of how fast it's going. The powder charge is actually part of the mass going out of the barrel so it's part of the recoil calculation. So, if you were to push a 140gr 6mm and a 140gr 6.5mm at the same speed from the same weight of rifle, the recoil would be identical.

The actual numbers are simply calculated with the formula RECOIL ENERGY REMAINING = ((velocity in fps*((bullet weight in grains/7000)+1.75*(powder charge in grains/7000)))^2) / (rifle weight in pounds * 64.348)

If you take a 140gr 6.5 and push it at 2850 from a 12lbs rifle with 40gn of powder, you'll make about 9lbs of free recoil. If you simply drop the bullet weight to 115gr then recoil drops to 7lbs. It's a not insubstantial amount. For comparison, the same rifle shooting a .223rem at the same speed with 25gr of powder and a 75gr bullet would generate about 3lbs of recoil. The average .308 makes around 11lbs (168gr @2700 w/44gr powder).

 

[Gamesniper19]

Recoil is a function of rifle weight, how much mass you're pushing out of the muzzle and the square of how fast it's going. The powder charge is actually part of the mass going out of the barrel so it's part of the recoil calculation. So, if you were to push a 140gr 6mm and a 140gr 6.5mm at the same speed from the same weight of rifle, the recoil would be identical.

The actual numbers are simply calculated with the formula RECOIL ENERGY REMAINING = ((velocity in fps*((bullet weight in grains/7000)+1.75*(powder charge in grains/7000)))^2) / (rifle weight in pounds * 64.348)

If you take a 140gr 6.5 and push it at 2850 from a 12lbs rifle with 40gn of powder, you'll make about 9lbs of free recoil. If you simply drop the bullet weight to 115gr then recoil drops to 7lbs. It's a not insubstantial amount. For comparison, the same rifle shooting a .223rem at the same speed with 25gr of powder and a 75gr bullet would generate about 3lbs of recoil. The average .308 makes around 11lbs (168gr @2700 w/44gr powder).

Perfect - than what you are saying is that with equal weight rifles - the 6MM and 6.5 would recoil similarly.
When you were giving the accolades to your 6MM i assumed you based on your post it might recoil less than the 6.5. If not, why not go with the 6.5 with a 140 grain bullet - higher BC's and yes you have to add a few more clicks DOPE but 2x barrel life - as you stated with the less overbore portion.

 

[Lapua54]

I won't be traveling across the country attending events but want to compete in the local North West area. I already have used the MDT stocks on both my hunting and .308 precision rifle, so I will be going with their new stock. Like most people I don't have all the money in the world to put into this rifle but want to know if it's worth chambering this for the 6.5x47 Lapua or the 6.5 Creedmoor. I realize the price difference is significant but is it worth it due to its superior performance at long range or is this just me being too picky about a caliber that essentially is the same in performance?

https://www.gunsamerica.com/digest/...LN1YyM9REi1xYrmvIdGiUhWUgplT8crWNdRcnKswO15Ig

 

[tuscan]

Perfect - than what you are saying is that with equal weight rifles - the 6MM and 6.5 would recoil similarly.
When you were giving the accolades to your 6MM i assumed you based on your post it might recoil less than the 6.5. If not, why not go with the 6.5 with a 140 grain bullet - higher BC's and yes you have to add a few more clicks DOPE but 2x barrel life - as you stated with the less overbore portion.

Only if both were pushing 140 gr bullets at the same speed would the recoil be equal.

But, heaviest bullets for 6mm are 115 gr, therefore, the 6mm has less recoil

 

[Satterlee Scott]

Which 115 6mm has a .313g7?

I run the 115 RDFs they will be out soon. the 115 DTAC are as high as .320 depending on barrel and twist.

 

[Satterlee Scott]

The 147 eld-m has a g7 of .351. When propelled to 2800, a 115 with a .313 g7 at 2950 doesnt match it in wind drift. It's close however and you'd probably never know the difference. 2 moa elevation difference at 1000 yards. I run the 6.5 because I dont want to have to change barrels every 1200-1500 rounds.

I've shot a bunch of the 147 never even got close to .351 in my rifles. Best I ever got in a barrel with those was .331

 

[Creedmoor shooter]

I've shot a bunch of the 147 never even got close to .351 in my rifles. Best I ever got in a barrel with those was .331

Interesting. I use the 4dof and I ran them at 2825 and they hit dead on at 1000. The 140 eld is the only one I've taken past and theres no doubt the bc on that bullet is true.

 

[Satterlee Scott]

It's pretty common for the 6mm shooters at out club to check velocities when they approach the thousand round mark. While accuracy/precision testing may look OK, it's not been uncommon to see a drop off in velocity and increased ES which can effect the long range scores. I believe this is a driving factor behind the popularity of the quick change barrel systems that are gaining in popularity. I will say that the bulk of our shooting is in the hot(80-90F) months and barrels do get quite hot. Perhaps this is a contributor to the shorter barrel life in my area.

Velocity for me usually starts to fade at 1400 but with some quick changes to powder it settles back in for another 400 ish. Guys give up on their barrels too soon but I can shoot off my back porch so load development and refinement takes me minutes

 

[Satterlee Scott]

Interesting. I use the 4dof and I ran them at 2825 and they hit dead on at 1000. The 140 eld is the only one I've taken past and theres no doubt the bc on that bullet is true.

I check my BCs to 1740 or further. 1000 yards is a good place to start BC validation

 

[Canhunter35]

Interesting. I use the 4dof and I ran them at 2825 and they hit dead on at 1000. The 140 eld is the only one I've taken past and theres no doubt the bc on that bullet is true.

It's odd, but in my rifle the 143 and 147 are running very similar bc, but since switching to a new lot of 143s I had to bump my bc from .303 to .310 to make it work at 1180yds

 

[Satterlee Scott]

It's odd, but in my rifle the 143 and 147 are running very similar bc, but since switching to a new lot of 143s I had to bump my bc from .303 to .310 to make it work at 1180yds

I have 2 lots of 6.5 creed factory ammo and one runs 140s at .303 the other is .319 there is quite a flux from lot to lot and barrel to barrel. BC is very twist rate and bore diameter sensitive

 

[Creedmoor shooter]

I check my BCs to 1740 or further. 1000 yards is a good place to start BC validation

Unfortunately where I live 1500 is about the max feasible distance. I generally run my drops at 600 then 1000 to validate then go out from there. 1454 is as far as I've been able to find a spot to shoot. The 140 held true for me that far but after that I have no idea.

 

[Canhunter35]

I have 2 lots of 6.5 creed factory ammo and one runs 140s at .303 the other is .319 there is quite a flux from lot to lot and barrel to barrel. BC is very twist rate and bore diameter sensitive

Yeah and with my lot of 147s I was down to .312 but that kind of a ballpark, I had 100 and that got me close enough for 1/2 mile shooting I never bothered fine tuning it