7saum Reamer Print

[Crowe284]

I seated a Berger 180 hybrid with the bearing surface/boatail junction a gnats *** above the neck shoulder junction and sent a couple dummy rounds in for a reamer print to be created. Attached is what I got back. Freebore says .115....this seems short as compared to what I have seen others run with the hybrid on a long action. Am I handcuffing the performance I could get out of the long action with this amount of freebore? Most guys seem to be running .180-.188 freebore for the hybrid from what I have read.

 

[NEMTHunter]

That would be close I would think. After all you did send in a dummy round to get teh reamer drawn up. This bullet has a bearing surface of .430 So if they give you a free bore of .115 That would be .315 left to go in the neck BUT you seated it about .324 in the shell Maybe a touch less. So what they did should fit the dummy round you made. my guess is they made it just like the dummy round you sent in. so that would be right against the lands.

7mm Berger 180 Hybrid specs are OAL 1.527, BT length .245, nose length .852, Base to Ogive .768, With a bearing surface of .430.

 

[Crowe284]

So....would you have done anything different?

If the bullet like to jump I'm eating up more case. Should I give myself more "room"??

Why is the .180 freebore so popular with the hybrid? Seems like you wouldent ha e a whole lot of bearing surface in the neck and not much room to chase the lands. I'm new at this....all other rifles have been built with sammi reamers.

 

[Crowe284]

Can you also explain what you mean by
"BUT you seated it about .324 in the shell"

 

[NEMTHunter]

You could go out to a .130 free bore and still have plenty of neck tension. Unless your shooting out of a semi auto.

For whats it worth the 300 win mage has a neck length of .264 and it has plenty of neck tension. If you had a .166 free bore in you 7mm you would have the same amount of bullet touching the neck as the 300 win mag does. Just food for thought. Also you can control neck tension by your ex-pander ball. Smaller makes more neck tension and bigger is less.

If it was me i would try for more free bore.

 

[NEMTHunter]

Can you also explain what you mean by
"BUT you seated it about .324 in the shell"

Let me try it this way. Might have been bad wording. Sorry about that.

Ok you said you seated the bearing surface just a hair above the neck shoulder. by the print the neck is .324 for the reamer. Thats why I said about .324.. From how you said it I can only guess that the bullet is close to .324 in the neck. It might even be .315 IF they gave it a free bore of .115 to match exactly were the bullet is seated in your dummy round.

 

[Crowe284]

Gotcha. How much more would you go for?? Sorry for all the questions but I just get one shot at this! Thank you.

 

[NEMTHunter]

Gotcha. How much more would you go for?? Sorry for all the questions but I just get one shot at this! Thank you.

I understand that for sure. If it were me I would go for a free bore of .150 . It would give you room to play with seating depth. Plus still have enough meat so as the throat weres you can move the bullet out farther to make up for the difference.

 

[Crowe284]

Cool, that sounds better. I assume that I can just tell Manson to extend freebore to .150 without sending in more dummies?

 

[Crowe284]

If I move freebore out to .150 which is .035 longer, I assume I can just add .035 to my original dummy measurement using comparator to get OAL touching, correct?

 

[Buttermilk]

My 7 SAUM has 0.140" freebore. I think that would be about perfect for a Berger 180.

I shoot Berger 168 VLD's from my XP-100. Freebore is a bit long for that bullet if I want maximum bearing surface inside the case neck and still touch the lands.

 

[NEMTHunter]

If I move freebore out to .150 which is .035 longer, I assume I can just add .035 to my original dummy measurement using comparator to get OAL touching, correct?

That in theory should be correct.

Cool, that sounds better. I assume that I can just tell Manson to extend freebore to .150 without sending in more dummies?

That would be correct.

 

[Edd]

If you want the bullet to contact the lands, don't change it. A .035" change will increase the case capacity about one half of a grain. That 1/2 gr isn't handcuffing your performance. Your real long action handcuff isn't your freebore, it is using that cartridge in a long action.

 

[Crowe284]

Thanks for the replies guys. I think I am going to extend the freebore some on the reamer.

To each their own Edd.