6.5-300 weatherby help

[bellboy]

So i went and shot my first batch of handloads for my mark v ultralight today.

my recipe was as follows:

6.5-300 weatherby resized brass
case trimmed to 2.820"
coal 3.717" (.070" off lands)
retumbo powder from 77-82gr in .5gr incriments
215 magnum rifle primers
hornady 143 gr eld-x

My dilemma is this, from 77-79.5 gr the velocities went down as powder increased. 77gr of retumbo gave me alarmingly low 1944fps and it decreased from there...79.5gr retumbo showed 1796fps. at first i thought maybe my chronograph was messed up so i shot a factory round through it and it displayed 3574fps and the box says 3531fps. i reached some minor pressure signs at 82 gr but was only pushing the bullet at 1907fps!! It just doesn't make sense, i found some quick load lists online using retumbo and the velocities were much higher and another source told me he was getting 3430fps from 82gr of retumbo out of the same gun. what am i doing wrong? this is my first weatherby and for those velocities to be that low maybe theres something I'm missing with weatherby reloading.

thank you

 

[Deleted member 46119]

Wow. That doesn't make sense.

What type of chrono are you using and if optical, how far away from the muzzle is it.

I am getting things I don't expect with Retumbo myself, however, not like what you are getting.

 

[bellboy]

It is an optical chrono and it was only about 2' in front of the muzzle. I've used it like that in the past with accuracy and the two factory rounds I fired were pretty much spot on with what the box says the velocity should be but maybe the retumbo causes some problems for the optical eyes as it leaves the barrel or something. I'm hoping that is the case. I had one load that printed .5" group. I guess I can try loading up some of those and shoot them at 300yd to see if the drops make sense for what the velocity should be with 81gr of retumbo

 

[Deleted member 46119]

It is an optical chrono and it was only about 2' in front of the muzzle. I've used it like that in the past with accuracy and the two factory rounds I fired were pretty much spot on with what the box says the velocity should be but maybe the retumbo causes some problems for the optical eyes as it leaves the barrel or something. I'm hoping that is the case. I had one load that printed .5" group. I guess I can try loading up some of those and shoot them at 300yd to see if the drops make sense for what the velocity should be with 81gr of retumbo

Move the chronograph out to at least 10' but you don't need to put it out at 300yards.

Retumbo has lots of residue. That is confusing your chrono.

 

[toddc]

I cant believe it was reading the factory ammo either at 2 ft. My bigger stuff needs 15+ ft to read consistently.

 

[bellboy]

Ok I will try putting the chrono out at least 10' and see what happens. Thanks for the advice, I did notice the retumbo being very dirty. What I meant about shooting at 300yd was using 100 yd zero and shooting at a large paper target at 300yd to see if the bullet drop corresponds with a 2000fps mv or a 3400fps my

 

[cacsrx1]

Diffusers usually get blown off at 2 feet .

 

[bellboy]

The diffusers are the white plastic pieces attached to the steel rods? They definitely didn't blow off, and when I said 2' it'swas more like 18" away, but I do have an accubrake on my rifle.. either way the weatherby factory lrx round worked just fine through the chrono but my hand loads with the retumbo was giving it problems. I'm going to test it at a min of 10' to see if it works better. Cacsrx1 don't you have a 6.5-300 shooting retumbo? What were your velocities with 140gr class bullets and 82gr of retumbo?

 

[cacsrx1]

The diffusers are the white plastic pieces attached to the steel rods? They definitely didn't blow off, and when I said 2' it'swas more like 18" away, but I do have an accubrake on my rifle.. either way the weatherby factory lrx round worked just fine through the chrono but my hand loads with the retumbo was giving it problems. I'm going to test it at a min of 10' to see if it works better. Cacsrx1 don't you have a 6.5-300 shooting retumbo? What were your velocities with 140gr class bullets and 82gr of retumbo?

3425fps they will go faster but that's where the accuracy was