Shorter reamer for 6.5cm handlods

[LC 6.5 Shooter]

Got my new rock creek 6.5 barrel. I handload so is the shorter 6.5cm reamer a good way to go. Looking to shoot 130g bullets with this gun. 130g ar hybrids. 130g eld-ms maybe. Does the shorter reamer help with anything. Or is the shorter reamer for longer sleek bullets like the vlds

 

[Sig Marine]

The shorter freebore will help a lot with the shorter bearing surface bullets. Whose reamer is it and what is the freebore?

 

[XLR308]

Then 130 AR Hybrid has a more tangent ogive and would probably benefit from a little longer freebore wouldn't it without having to be seated deeper to stay out of the lands ?

 

[spife7980]

A bit of both. Without specifics its tough to say what you would want.

Bullet design: the VLDs are more secant, they have shorter bearing surfaces with longer straighter noses, tangent designs are a bit more short blunt nosed with a longer hearing surface.

The bottom of the bearing surface is where the bullet stops interfacing with the case neck, the front of the bearing surface is where it first interacts with the barrel rifling. The dimensions of your bullet and chamber (reamer) will dictate how much of the case is held by the neck and your resulting measurements.

Since the secant vlds have a shorter bearing surface and a long skinny nose the point at which they interact with the rifling will allow/require you to either

1. allow you run a shorter freebore length to hit the desired amount of bullet jump with more of the bullet held in the neck and shorter over al lengths to fit in a mag but that can lead to issues if you go for heavier longer bullets at a later point in time or
2. require you to seat them out further in the case to reach your desired amount of jump and possibly limit how far you can load and thus effect your ability to seat them where you would like to in the case.

This lumps a couple different variables all in together but you can see that the lighter secant bullet will hit the rifling at a shorter loaded length than the heavier tangent.

If you had along throat and a secant bullet you might find that you run out of case neck to hold the bullet before you get to your desired amount of jump.
If you had a short throat and a tangent bullet you might find that you are having to shove the bullet deeper into the case which robs case volume and powder capacity.

 

[XLR308]

A bit of both. Without specifics its tough to say what you would want.

Bullet design: the VLDs are more secant, they have shorter bearing surfaces with longer straighter noses, tangent designs are a bit more short blunt nosed with a longer hearing surface.
View attachment 7038160View attachment 7038161

The bottom of the bearing surface is where the bullet stops interfacing with the case neck, the front of the bearing surface is where it first interacts with the barrel rifling.
View attachment 7038157


Since the secant vlds have a shorter bearing surface and a long skinny nose the point at which they interact with the rifling will allow/require you to either

1. allow you run a shorter freebore length to hit the desired amount of bullet jump which can lead to issues if you go for heavier longer bullets later or
2. require you to seat them out further in the case to reach your desired amount of jump and possibly limit how far you can load and thus effect your ability to seat them where you would like to.

View attachment 7038154


This lumps a couple different variables in together but you can see that the lighter secant bullet will hit the rifling at a shorter loaded length than the heavier tangent.
View attachment 7038158


If you had along throat and a secant bullet you might find that you run out of case neck to hold the bullet before you get to your desired amount of jump.
If you had a short throat and a tangent bullet you might find that you are having to shove the bullet deeper into the case which robs case volume and powder capacity.

That was my thoughts as well considering the two bullets he listed are more of a tangent profile and would benefit from a longer freebore.
And there's of course the issue of being able to run some factory loads depending on the reamer spec if he wanted to or needed to.

 

[Sig Marine]

My comments about freebore were in reference to the OP wanting to try 130 Hybrids. The longer freebore is a definite benefit if you are funning factory ammunition. My experience with a 6.5 Creedmoor, cut with a SAMMI spec reamer (.199 FB), was using 140 Berger Hybrids and 140 ELDs. The problem I encountered was in order to achieve the jump I wanted, the Hybrids were seated out too far and exceeded magazine length. This said, my measurements comparing the 130 vs 140 hybrids shows the bearing surface length to be the same but the 130s are shorter and probably would fit the magazine BUT be left with too little bearing surface in the case neck, at least for my taste. Chad Dixon is one of the few gunsmiths who has a couple of different reamers for the 6.5 CM depencing on the bullet you choose, one for factory with ELDs and the other for 140 hybrids and SMKs.

If I were going to pursue the 6.5 CM, I'd make a dummy round and have a reamer made for my needs BUT I'm happier with the 6.5x47L so I'll pass on having a reamer made.

 

[XLR308]

Makes sense, I haven't tried the Hybrids in the Creedmoor yet but it was on my list.
When I finish the 6.5x47 I'm working on may give them a go in it.

 

[Sig Marine]

The list of different freebores available to the 6.5x47L shooter is long. There are some shooting the 140s that like a .160 - .170 freebore while some shooting 120 grain class of bullets are starting with something in the .120 range. Others, like myself shooting the 130s and 140s, prefer a shorter freebore that allows one to "chase" the lands as the throat erodes. Personally, I like a freebore in the .140 - .150 range.

Also, the Creedmoor has a longer case which limits some of the bullets and their seating depths when shooting from magazines. Not to say you can't jump some bullets well, but sometimes there are limitations. I think there are many more shooters running ELD-Ms and Sierras with tangent ogives than Berger Hybrids or VLDs with secant or its variants in their 6.5 Creeds.