Comparison of the ballistic superiority of 6.5 CM

[doctnj]

What I mean is I enter all the information for her rifle in other calculators and it gives me matching drops. So if I put the 3k MV it gives me drops that match the 3k drops that strelok gives. We measured her MV yesterday and today so I have an average over two days plus weather. So I'll put it all in and print out a new table.
Have you ever had to true your dope to match actual performance? Litz says inside the supersonic zone, to true MV. Past that, to true bc. I just looked at berger website and I'm still finding .311 as the bc for the 140's. I re-measured her scope height also.
I think I have everything covered.
I "trued" my MV on my 260 back when we did hers, but it didn't change very much. Not 300 fps like hers changed.
I think that rubber cap crammed in under the scope, changing with temperature, moving a little every time the cap was open or closed had to have a lot off effect . I'll cut the bottom of the cap off for now and possibly get next taller rings later.

[doctnj]

Just looking at my MV's over the past few months , my original measured speed was 2827 then trued with actual poi the mv was dropped to 2716 to make the calculated match actual.
Today I remeasured and came up with 2776 as average. But these numbers were under todays conditions. I think I understand that that theory a little better.

more to come

[LongRange]

So are you using the truing part of your app? If so that maybe part of the problem.

I enter my actual muzzle velocity then shoot at distance and adjust the muzzle velocity in the bullet selection...I never enter multiple velocities or multiple BCs...I also keep powder temps close to ambient temps...my elevation only changes .1-.3 moa at any give time or day...dopes are always on.


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[doctnj]

Yes I am using the truing part of the program.

One thing I WISH I would have done was shoot, then remove the front cap, then shoot again. I cant rule out that it may not have just been a mil high this whole time and she was having to dial down to compensate. Oh well. Hind sight. Having the zero stop shims in there I can see where if bottoming out and the allen screws are not tight enough that it could easily spin down and not know it if your not paying attention to clicks.

Im always nervous about putting too much force on them. Both scopes tracked well both days. I got the calipers out and measured between holes just to make sure. I had hash marks on the lines but we were either right to the side or just below with same error down the whole line.

As far as the truing part of the software. It asks for the measurement up or down from calculated to actual point of impact. Then it gives you the option of selecting which value to change, the BC or MV. I select the MV and it then just goes back and changes that value. The next time you open the drop table it is based on the new MV.

I dont think I would know how to calculate the change with out using that.

[Rob01]

Never trued anything in a program. I put my velocity, bullet and other data into JBM and get my data. I have never been off more than .2 mils at 1000. That's max. Usually it's right on but as I run my data ahead of a match and if the environmentals change slightly it might be slightly off but .2 mils isn't bad.

[yobuck]

I really think data entry has become about as much of a challenge for at least some shooters as the actual shooting.
I can see where in some types of competition it can be very important, especially where sighters aren't permitted.
But for average joe shooter/hunter, its still best to confirm with a sighter shot if at all possible.
And frankly sometimes a first round miss is the sighter when hunting.
Especially during the rut when a buck is almost constantly moving and causing the data you entered to be now obsolete.
You cant eat couda, shouda, wouda. lol.

[doctnj]

Rob thats pretty good record. I didnt need to true my own MV. It was a good load and the numbers agreed pretty well but after seeing such a difference in the wife's numbers I measured the distance off. I was maybe 3 inches from bull at 500. Even that small of a number caused a slight change in MV. Only slight, but I remeasured actual MV Sunday and re set it back to measured. Now, hopefully, T's rifle will be on like that this time and we can forget about it!!

Also Buck, I just purchased the kestrel drop so I CAN get good data every time. I can always got out to my hunting lease and pre measure spots on the field where I normally hunt from and note the drop. The problem could be atmospherics changing the bullet performance and now you arent quite sure of the hit. Especially, if you dink up the initial data. Right now I mostly rely on the weather channel.

[yobuck]

Rob thats pretty good record. I didnt need to true my own MV. It was a good load and the numbers agreed pretty well but after seeing such a difference in the wife's numbers I measured the distance off. I was maybe 3 inches from bull at 500. Even that small of a number caused a slight change in MV. Only slight, but I remeasured actual MV Sunday and re set it back to measured. Now, hopefully, T's rifle will be on like that this time and we can forget about it!!

Also Buck, I just purchased the kestrel drop so I CAN get good data every time. I can always got out to my hunting lease and pre measure spots on the field where I normally hunt from and note the drop. The problem could be atmospherics changing the bullet performance and now you arent quite sure of the hit. Especially, if you dink up the initial data. Right now I mostly rely on the weather channel.

Pre shooting or pre ranging various objects at spots you hunt is as good as it gets. As a rule the rocks don't move around much lol.
There are sometimes whole seasons where we don't need or use a rangefinder, just by referring to a book of our various spots.
Also, you learn not to rely on lazer rangefinders, especially if its sunny or snowing. Have a simple chart based on an average temp and elevation
and your good to go. Minor variations with flat shooting guns wont matter much under about 700 yds anyway. You don't need to be shooting 10s, you just need solid hits good enough to win.
Rather than invest in a Kestral, id recommend spending the money on a very good lightweight portable shooting bench you kneel down next to.
Of coarse (real men) don't need them lol. That is unless their working up loads or zeroing a gun.

[psharon97]

The ballistic difference between the 260, 6.5 creedmoor, 6.5x55, and 6.5x47 are very similar. Granted the 6.5x47 will be slightly slower and the 6.5x55 will be slightly faster, but for the most part, all 4 will generate velocities that are very close to one another. None of these 4 will generate ~3000fps with a 140gr projectile.

Knowing this, I went with a 260. I had just purchased a short action from this forum, and wanted lapua brass. I also wanted the ability to easily neck up or neck down anything in the 308 family.

[doctnj]

As it stands right now I have the CM at 23 fps faster using .5 gr less for some reason. That is "as measured" with magneto speed one after the other last weekend.

[yobuck]

Why don't you try not weighing the loads for your daughters gun.
Just look in the cases to make sure you didn't miss any, and that there all pretty much the same.
Don't tell her you did that and just let her shoot as usual.
See if she still beats you. lol
I'm not joking.

[LongRange]

The ballistic difference between the 260, 6.5 creedmoor, 6.5x55, and 6.5x47 are very similar. Granted the 6.5x47 will be slightly slower and the 6.5x55 will be slightly faster, but for the most part, all 4 will generate velocities that are very close to one another. None of these 4 will generate ~3000fps with a 140gr projectile.

Knowing this, I went with a 260. I had just purchased a short action from this forum, and wanted lapua brass. I also wanted the ability to easily neck up or neck down anything in the 308 family.

ive shot 142g smks at 3075fps out of a standard 260...brass didnt last long but it can be done...130g berger hybrids are very easy to get up over 3000fps in a 260...if you want speed out of a 6.5mm RL-17 is your friend LOL.

[doctnj]

Probably would.

[doctnj]

FYI, you cant pull a 6mm bullet with 6.5 mm bullet puller no matter how tight you make it. Add another collet to the pile!

[LongRange]

FYI, you cant pull a 6mm bullet with 6.5 mm bullet puller no matter how tight you make it. Add another collet to the pile!

i pulled three 6mm bullets with a 6.5mm collet in a hornaday bullet puller last sunday.

[doctnj]

Well I put the rcbs on one last night and there ain't no way. All the gaps closed and the bullet just fell out. :( one on the way. I have around 70 to pull.

[LongRange]

thats why...i thought you had the hornady puller.

[doctnj]

Because of the on again off again rain all day, Im only going to run one test today. Thats going to be the ladder test for the daugter's 243 with the 105's. I looked around and didnt find too many cross references of common accuracy loads using the components I am using. Hope thats not a bad thing. Plan on still using the IMR 4350. running the ladder from just over mid point to just barely under max load. I should be able to find a nice load in there. I like to shoot 5 shot groups during a ladder test but my last powder charge, I only had 3 left to load. Everything else is loaded with the smaller bullets. I tried several times to pull one using many things around the house. Vice grips etc. No good So the last powder charge will only be a group of 3. Hopefully the results will be very clear on that one that three will be all that I will need.

[LongRange]

Ladder test and five shot groups?

Here's a tip....41.5g start at .015 off the lands and don't change the charge weight just adjust the seating depth.

Or follow this...which I think I already posted...

http://www.texasprc.club/preidloaddev/


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[LoneWolf]

LR keeps sharing all the secrets I share with him lol!


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