How to figure out freebore? How much is too Much??

[Russell123523]

That combo at 3.50 would be the longest you should set the bullet forward if it's throated to that you could touch and work you way down to .10 .20 .40 .60 or .80 off wherever it shoots Best But gives you the option to touch if needed and still utilizes the case capacity unless you want a weatherby freebore jump of a 1/4 inch

 

[L.Sherm]

O.P to give you an idea of your O.A.L so that the bearing surface is seated at the neck shoulder junction.
Case to neck shoulder junction is 2.156
Bullet o.a.l is 1.49
Boatail length is .254
2.156
+1.490 = 3.646
3.646
- .254 = 3.392 O.A L

I think a A.O.L of 3.40 is perfect

 

[dxlbaile]

Thanks everyone,, that will save me lots of time.. My gun shoots good right now I am just like everyone else, I got the itch to improve this if I can. I am going to go measure as soon as the snow let's up a little.. Shop is aways from the house and we got 20 inches of snow.. Going to have to dig back to the shop..

 

[FEENIX]

This is my opinion and you can take it for what its worth, I would much prefer my rifle to be able to shoot close to the lands IF that's were it shot the best than seating it out untill it will literally fall out of the neck.

^^^This!^^^

 

[MagnumManiac]

I have to ask, what length is your mag box?
I bought my Dad, and customised it, a model 77 Ruger tang safety 270 Win and re-barreled it with a 22" barrel because that's what he wanted.
The reamer I borrowed was supposed to be a SAAMI reamer, however the throat on that puts the 150gr Partition right at 3.55" touching, mag length on a Ruger is 3.4".
It still is quite accurate, just a little more jump than I would like.

Cheers.

 

[dxlbaile]

So, just measuring with calipers my mag length is 3.350 ish.. the OAL that I am shooting is 3.395 It shoots lights out with a 170 berger but.. I just want a little more velocity. This is where I am right now. The third bullet won't chamber when trying to cycle shells it touches the inside of the Mag box. this is a ole m77 tang too! So, wondering how much freebore to add?? This is .015 off the lands right now.

 

[Tommyrexx]

Just toying around with a ole Ruger m77 270 win ... I have been shooting the 170 berger at 2900 from a sami chamber but the bullets seem to shoot better longer than my mag box.. If I am going to make this thing a single shot why not give it some freebore, to free up some case capacity..?

How do you know when too much is too much? I would like to move the bullet up to where the neck shoulder junction meets.. I just don't know if this is doable or not?
I don't have the availability of a good gunsmith unless I drive 3 hours so I was hoping someone might help me out.. I really think I might gain at least 50-75 fps with the extra room in the case if I do this.. Maybe I won't..

Anyone got some great advice..??

Thanks..

I usually start working up loads for a new barrel on my match rifle at 15 thousandths off the lands. I also usually end up around there.

 

[PNWdude67]

Thanks everyone,, that will save me lots of time.. My gun shoots good right now I am just like everyone else, I got the itch to improve this if I can. I am going to go measure as soon as the snow let's up a little.. Shop is aways from the house and we got 20 inches of snow.. Going to have to dig back to the shop..

How many rounds fired though this barrel and How far are you from the lands now? My apologies if I missed this info in the thread.

 

[StumpGrinder]

One point of view is to seat close to the lands. That is not the only point of view. As in all things, there is a tradeoff.

If you don't approach the lands that can be a plus. If the bullet jumps a bit first, pressure is reduced. You can always find a load that gives a good group even if your bullet is far behind the lands. You might have to try a few loads before you find the right one. This is how I loaded the Weatherby 300 back in the sixties, using 4831. You could always find a group by experimenting with different charges. The extra free-bore is good for an additional 150 fps in velocity when loading to the same pressure limit.

I agree, in watching Eric Cordovas videos he starts .20 off the lands and moves away from the lands to find a repeatable node. This is seating the bullets deeper into the case. I would not risk screwing up a barrel just to get maybe 50 fps extra. Unless the throat is already eroded to the point it needs reemed anyway. I know competetion shooters go through 1 or 2 barrels per year and maybe you are in this group but I expect my m 77 to out live me. If your bent on reaming it anyway you might just as well reem it to AI specs, or one of the Wildcats. The mag well can be modified to fit whichever way you decide to go. If your willing to shave metal to reach your goal don't let a little wood, plastic or fiberglass stand in your way.

 

[Bobcape]

@StumpGrinder
It's Erik Cortina I think.

 

[warrbuk]

There are some guys buying a throating reamer and doing it themselves bye hand. Looks pretty easy. Tooling from PTG, and Just a lot of throating, cleaning, checking length, repeat.

How to Increase Your Rifle Throat Length With a Chamber Uni Throating Reamer - Long Range Only

Here LRO’s Ryan Furman shows show the procedure to lengthen your rifle throat free bore using a Uni Throating free bore reamer. To discuss this review or ask questions please go HERE

www.longrangeonly.com

Google it there are more videos

 

[pig ranch deadeye]

There are some guys buying a throating reamer and doing it themselves bye hand. Looks pretty easy. Tooling from PTG, and Just a lot of throating, cleaning, checking length, repeat. Google it

Does a throating reamer also make room for a longer neck? Or would that require a separate reamer, a neck reamer? I once ran a .300 Weatherby case through the .300 Win Mag die and it created a .300 Win Mag case with a nice, long neck. So I was thinking why not make all of my .300 Win Mag brass out of .300 Weatherby brass and make use of the long neck for the 200 grain Nosler Partition?

 

[warrbuk]

Does a throating reamer also make room for a longer neck? Or would that require a separate reamer, a neck reamer? I once ran a .300 Weatherby case through the .300 Win Mag die and it created a .300 Win Mag case with a nice, long neck. So I was thinking why not make all of my .300 Win Mag brass out of .300 Weatherby brass and make use of the long neck for the 200 grain Nosler Partition?

The throating reamer only lengthens the throat.

you would need a new chamber finishing reamer

 

[Bobcape]

Does a throating reamer also make room for a longer neck? Or would that require a separate reamer, a neck reamer? I once ran a .300 Weatherby case through the .300 Win Mag die and it created a .300 Win Mag case with a nice, long neck. So I was thinking why not make all of my .300 Win Mag brass out of .300 Weatherby brass and make use of the long neck for the 200 grain Nosler Partition?

A throating should not cut the neck length at all. Only the throat.