6.5 or 7mm?

deadeyeky · Post by **deadeyeky** » Sun Mar 30, 2008 10:44 pm

6.5 or 7mm?

thats what i want to know, what do you prefer??

6.5- longer slender bullets with high BC's, only available up to 142 gr's, (some exceptions) 93/100 rams knocked over

7mm-fatter bullets, better wind bucking ability, available up to 180 gr VLD, less selection, 98/100 rams knocked over, have heard ppl complain about the recoil of a 7br over a 6.5 br[/list]

BlauBear · Post by **BlauBear** » Mon Mar 31, 2008 8:06 am

There is probably a technical reason for the amount of interesting ballistics work that focuses on the 6.5 mm, but the Remington .260 (that originated as a wildcat Silhouette round), Lapua 6.5x47 and Grendel (?I think?) all came around to the same caliber for the same reasons - maximum accuracy and knockdown at minimum recoil. If I were man enough I'd just use a .308 but I probably couldn't take the hammering anymore.

Bob259 · Post by **Bob259** » Mon Mar 31, 2008 8:09 am

BlauBear wrote:There is probably a technical reason for the amount of interesting ballistics work that focuses on the 6.5 mm, but the Remington .260 (that originated as a wildcat Silhouette round), Lapua 6.5x47 and Grendel (?I think?) all came around to the same caliber for the same reasons - maximum accuracy and knockdown at minimum recoil. If I were man enough I'd just use a .308 but I probably couldn't take the hammering anymore.

There is always your AR

BlauBear · Post by **BlauBear** » Mon Mar 31, 2008 8:27 am

Bob259 wrote:There is always your AR

The one that isn't in .223?

Bob Mc Alice · Post by **Bob Mc Alice** » Mon Mar 31, 2008 11:12 am

Can't figure out how to vote in the poll, but put me down for the 7mm , of course. Deadeye....sounds like you got some extensive ram knockdown data there. Not to mention all that heavy lifting exersize

I assume you compiled this data from several shooters at a few matches, correct?

deadeyeky · Post by **deadeyeky** » Mon Mar 31, 2008 1:33 pm

correct, actually lol

just ballparked it, and payin attention to how many shooters rang rams, i used to shoot a 308 with a 200 gr mk for the rams, and 1 day i lost 6 of them! most of it has to do with location of hit on the animal, wind, stand condition (is it wobbly?), and a few other things

sobrbiker883 · Post by **sobrbiker883** » Mon Mar 31, 2008 4:44 pm

deadeyeky wrote: i used to shoot a 308 with a 200 gr mk for the rams, and 1 day i lost 6 of them!

I shoot 180's and 168's outta my 308 at 2525+/- fps and have failed to have any I hit stand there laughing. You must shoot some heavy rams with a helluva wid behind them!!

I voted 7mm, just because that's what my next rifle's coming as.

GregG · Post by **GregG** » Mon Mar 31, 2008 6:51 pm

Where is the 6?

Troy G · Post by **Troy G** » Mon Mar 31, 2008 7:53 pm

I am just going to use two bullets from Berger for this quick comparison.

The 6.5 BC of the Berger is likely a bit higher than the most popular choices since I assume most shooters likely shoot Sierra or Lapua on account of harder jackets and their BCs are likely in the high 5s to low 6s.

7mm 180 VLD with BC of .690 Momentum at 500 meters is 50.6 LBS-FS with muzzle velocity of 2550 fps. Wind drift is 15.82 inches

6.5 140gr VLD with BC of .640 Momentum at 500 meters is 41.9 LBS-FS with muzzle velocity of 2750 fps. Wind drift is 15.39

What 7mm bullet is going to be shot at CPT? Reduced load with 180 VLD or something in the 140gr class?

I think the 6.5 has better bullet selection with higher BC for CPT where knock down power is not as important.

I do not know how to figure out felt recoil accurately and eliminate all the variables involved.

I wonder how many targets are lost at CPT as result of a higher recoiling rifle? I think this would influence scores more than ringing the occasional ram with a 6.5.

After all my advice I have a 7TKS barrel on my Standard and a .260 on my Hunter. How is that for fence sitting.

Bob Mc Alice · Post by **Bob Mc Alice** » Tue Apr 01, 2008 9:13 am

Troy, what is the 7TKS....how does it compare to the 7-08 Rem.? What bullets are you using, velocities, etc.?

Troy G · Post by **Troy G** » Tue Apr 01, 2008 5:57 pm

Bob,

The TKS (named after its creators) uses the 6 BR Norma as a parent case, it is then improved by blowing the shoulder forward and reducing some taper.

I am shooting the older 180gr JLK bullets and I got all I could afford and get my hands on when I found out Jimmy Knox was retiring.

My ram load is said bullet and is safe in my barrel, cut with my reamer. Yes I shoot these loads in summer but do not leave them bake in the summer heat. I may just have a fast barrel and I have only chambered one barrel with it so I do not know if these results are repeatable, could also be a good lot of powder coupled with a fast barrel. My breech bolt has a small firing pin hole which is necessary to avoid blanking or piercing primers as well.

My CPT load is a reduced load of the same bullet and same powder at 2200 fps.

I only tried a 7 TKS after shooting a 6.5 TKS and thinking that I did not have enough oomph to reliably take rams given different weather conditions one may shoot in. The 7 TKS does a number on the rams and I have shot 40 shot strings using all ram loads and did not need to submerge myself in ice water after.

I played around with the TKS pre Lapua 6.5x47. I know there was other cases that were equal or slightly larger in case capacity to the 6.5x47 but I did not believe the brass quality was there. If I was re-barreling tomorrow I would likely chamber a 6.5x47 and forget about expensive custom dies and case forming.

I do not get to many competitions and shoot informal HP as a type of therapy, something about smacking steel and seeing a cloud of grey and then hearing a sharp smack or clang. Shooting silhouette also keeps ones shooting skills in tip top shape.