6.5 x 300 weatherby jump

[Andrewmtnman]

Hello all. I am new to this forum and recently started reloading again after 20 years. So a bit rusty. I was given a 6.5 300 W Mag that was built on a mauser 98, i believe. Loaded and shot less than 10 rounds so far. Problem I'm having is the suggested coal, 3.590", is way to long for the magazine clearance which measures 3.321". The cbto measures 3.857. So if I seat to fit the magazine, my jump would be .500 or so. That seems crazy to me. Wondering your thoughts. I have read of guys with jumps of around .200 or so. First concern is, is that a safe jump in that chamber? Second question, Is that too deep to seat the bullet in the case? I'd rather not shoot one at a time all the time.

 

[rsnell]

Since your rifle is custom made, it may not have the Weatherby chamber. Have a gunsmith make a cast of the chamber to determine if it is a true Weatherby chamber. All of the loading manuals I have only list loads for the Weatherby chamber.

 

[Andrewmtnman]

Hmmm. Good idea. Suppose its a true weatherby chamber, do you think that jump would be acceptable in terms of safety? Thanks for your thoghts.

 

[cape cove]

I don't believe there is anything unsafe about a long jump other than it affecting accuracy and pressure. I believe the standard jump on a factory Wearterby 6.5x300 is .203. Not sure but I believe this is close. JMO

 

[Andrewmtnman]

I don't believe there is anything unsafe about a long jump other than it affecting accuracy and pressure. I believe the standard jump on a factory Wearterby 6.5x300 is .203. Not sure but I believe this is close. JMO

I think I just found the freebore to be .253 by using a fired case and insterting a bullet backwards and chambering the round. The distance petruding out of the case should be the true freebore?.?.? If this is an accurate measure than I should be fine with a coal of 3.321 which is my magazine box length. Appreciate your thoughts on this.

 

[cape cove]

I checked the Weatherby site and found the freebore of their 6.5/300 to be .2037. Seating a bullet backwards will give you a ball park # but even if your chamber had a zero free bore there would still be a measurement # done your way. .253 minus your trim to length and land angle would seem to fit well with a .2037 freebore. Someone like @J E Custom could give you a better answer.

 

[J E Custom]

I checked the Weatherby site and found the freebore of their 6.5/300 to be .2037. Seating a bullet backwards will give you a ball park # but even if your chamber had a zero free bore there would still be a measurement # done your way. .253 minus your trim to length and land angle would seem to fit well with a .2037 freebore. Someone like @J E Custom could give you a better answer.

The SAMMI chamber dimension for freebore is .2645 that is to the start of the lead angle. Some wildcats have less but that Is recommended buy SAMMI and that Is what it should be.

Hope this helps

J E CUSTOM

 

[J E Custom]

I don't believe there is anything unsafe about a long jump other than it affecting accuracy and pressure. I believe the standard jump on a factory Wearterby 6.5x300 is .203. Not sure but I believe this is close. JMO

Actually the longer freebore improves the engraving starting pressure by giving the bullet more jump lowering the starting pressure and allowing more powder for the same pressure, ultimately increasing velocity, Some of the big Weatherbys have more than a half inch of freebore. If good quality ammo is loaded for these cartridges they can be very accurate. One of my most accurate rifles (A 30 x 378 Weatherby) will average 1/10 MOA. To date the best 5 shot group has been .092.

Note: If the freebore is shortened, you may not be able to use Factory ammo because pressures will climb above max and blown primers are the norm. When loaded with a lesser freebore to maximum pressure velocity will also suffer (Go down).

J E CUSTOM

 

[Andrewmtnman]

Actually the longer freebore improves the engraving starting pressure by giving the bullet more jump lowering the starting pressure and allowing more powder for the same pressure, ultimately increasing velocity, Some of the big Weatherbys have more than a half inch of freebore. If good quality ammo is loaded for these cartridges they can be very accurate. One of my most accurate rifles (A 30 x 378 Weatherby) will average 1/10 MOA. To date the best 5 shot group has been .092.

Note: If the freebore is shortened, you may not be able to use Factory ammo because pressures will climb above max and blown primers are the norm. When loaded with a lesser freebore to maximum pressure velocity will also suffer (Go down).

J E CUSTOM

I checked the Weatherby site and found the freebore of their 6.5/300 to be .2037. Seating a bullet backwards will give you a ball park # but even if your chamber had a zero free bore there would still be a measurement # done your way. .253 minus your trim to length and land angle would seem to fit well with a .2037 freebore. Someone like @J E Custom could give you a better answer.

Thanks guys for your thoughts and help. I will load up a few and see how she goes.

 

[Andrewmtnman]

In loading up 140 gr bullets, the base of the bullet sits down .235 beyond the shoulder. This is because the bullets are so long but have to be seated down that far to clear the box magazine. Is that ok?

 

[Andrewmtnman]

So I loaded up only a few cartridges and fired them today. The primers were cratered and a bit flattened. My load was 83gr H870 with 140 speer sp. It looks like the pressures may be to high. Should I drop the charge down and try again? If so, how much do you recommend? Accuracy was impressive!

 

[Rich Coyle]

First, where did you get the H870? Secondly, if you didn't feel the bolt getting even a little sticky, I would use it.

 

[Andrewmtnman]

First, where did you get the H870? Secondly, if you didn't feel the bolt getting even a little sticky, I would use it.

Lol. It came with the gun my dad bought at least 15 years ago. Not sure what I will go to when that runs out. I only have 1/4 lb left! Was looking into US869, Rotumbo, and H1000.
The bolt seemed a little sticky. Actually it may have been the cases because I recall it being a little tight seating the bolt before I shot.

 

[Rich Coyle]

Well, my.com friend, you are in luck. I have three pounds I would forward to you if you pay the haz-mat fee.

It is too slow for the stuff I load for. I would be pleased to know it went to a good home.