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

[pig ranch deadeye]

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

Thanks, that is what I thought. Can you buy a chuck for the neck as well?

 

[wonderman4]

All I wanna know is how you are getting 2900 with a 170 gr bullet in a 270 Win in a stock rifle??

 

[o2bmark]

Start with what you can't or don't want to change. If you don't intend alter the throat of the rifle (ream or rechamber) then find out 1st where the bullet you're using contacts the lands. Now if that point is so far out that the bullet would be barely be inside the case then then all of the previous comments hold which focus on available case capacity, neck tension and jump (freebore). Guidelines of how much bullet shank should be in the neck of case are just that—guidelines. l'm pretty sure I could work up a load where the bullet is seated into the lands separately and the case loaded behind it (like some artilley) that would work. In practical terms i want enough neck engagement to hold the bullet straight with usual carrying and handling. Best jump or freebore is a trial and error proposition but I like the Berger website method for finding best seating depth. I use quickload software and find it entirely useful and immensely entertaining. I play "what if" for hours at a time!

 

[Oldtime Shooter13]

I have always tried to seat any bullet at least the diameter of the bullet into the case neck. For instance .308 diameter bullet I like to seat at least .300 into the neck. This is rule of thumb that I have always used for hunting cartridges. I currently have a 6 Creed with 108 grain Sierra GK bullets that are .030 from lans and I only can seat bullets .190 into the neck. In order to get the bullets .243 into the neck would be .083 off the lans? Have not tried seating bullets this deep into the neck and shot any groups yet.

 

[StumpGrinder]

@StumpGrinder
It's Erik Cortina I think.
View attachment 251982

Yes that's him. I'm terrible with names! I can't remember my own half the time. Not to hijack the thread but I have a seating depth question. I worked up a load several years ago tha my Ruger M 77 really likes. I found some bullets that are the same profile just a little heavier. Can I expect the same over all length to work for this bullet to or do I have to do the latter test for it also? Most of my loadings in this rifle like .5 grains back from the listed max charge. I expect this to be the same.

 

[Saskquatch6]

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..

Dxlbaile - it sounds like from what you're saying that your Ruger shoots the 170gr Bergers quite well and unless it's a custom barrel I expect the twist rate to be 1:10. My experience is that 150gr is on the margin for stabilizing in a 1:10 twist 270 and bullets much heavier won't stabilize well at all and this becomes more evident as distance increases beyond 400 yards. The heavies may group reasonably well at 100 or 200 yards but begin to destabilize further down range where groups open up significantly. Just a caution- I'd confirm your rifle can actually stabilize the heavy bullets you're thinking of using properly (at distance) before investing in additional reaming etc as doing so could negatively impact its ability to shoot lighter bullets also - meaning giving the rifle a significantly longer throat could result in it not shooting anything particularly well. I'd check this out first and if all is well then continue with your plan using the 170s. Good luck

 

[dxlbaile]

All I wanna know is how you are getting 2900 with a 170 gr bullet in a 270 Win in a stock rifle??

Got a new barrel from mcGowen 1:8 twist barrel 25 inch barrel with Ramshot magnum behind it.. I can actually get 2950 but i get a stiff bolt lift and some ejector marks.. I rebarreled it just for the 170. So this is not a stock rifle now..

 

[dxlbaile]

Dxlbaile - it sounds like from what you're saying that your Ruger shoots the 170gr Bergers quite well and unless it's a custom barrel I expect the twist rate to be 1:10. My experience is that 150gr is on the margin for stabilizing in a 1:10 twist 270 and bullets much heavier won't stabilize well at all and this becomes more evident as distance increases beyond 400 yards. The heavies may group reasonably well at 100 or 200 yards but begin to destabilize further down range where groups open up significantly. Just a caution- I'd confirm your rifle can actually stabilize the heavy bullets you're thinking of using properly (at distance) before investing in additional reaming etc as doing so could negatively impact its ability to shoot lighter bullets also - meaning giving the rifle a significantly longer throat could result in it not shooting anything particularly well. I'd check this out first and if all is well then continue with your plan using the 170s. Good luck

A normal stock 270 will not stabilize the 170 berger well.. My barrel was shot out so I sent it off for re barrel. I just didn't think about needing some freebore.. Now I am definitely looking at my options.. Thanks for all the replies.

 

[MagnumManiac]

The difference between what you state as a COL of 3.395" to where the bullet shoots best, unless I missed it I didn't see the measurement listed, is how much longer your throat needs to be.
I turned up some gauges that are the same ID as the barrel bore so I can measure the ogive length precisely. So in my vernier I simply measure backwards and take that number away from the OAL of the bullet.
I can then work out freebore length using that figure.
Most bullet comparators can be used for that measurement too.

Cheers.

 

[tobnpr]

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.

This.
I skipped to the last page of the thread- and this was my thought when I read the initial post.

Similar thread recently- keep in mind that your throat is gonna erode- and since you seem to like to load hot (your entire reason for doing this is more velocity), that only exacerbates it.

How much have you already increased your COAL chasing the lands?
If you throat long based on the bullet being seated as far out as practical, and your optimal jump- you're essentially done. No more room to chase them- your jump will only increase.

It's one thing to throat longer in order to use heavier bullets, or changing ogive types that requires it- but you're chasing a hypothetical.
There's no guarantee that increasing your case capacity slightly will increase your velocity- and it could potentially be less accurate.
I've rarely found the hottest/fastest load to be the one I end up with.

 

[pig ranch deadeye]

This.
I skipped to the last page of the thread- and this was my thought when I read the initial post.

Similar thread recently- keep in mind that your throat is gonna erode- and since you seem to like to load hot (your entire reason for doing this is more velocity), that only exacerbates it.

How much have you already increased your COAL chasing the lands?
If you throat long based on the bullet being seated as far out as practical, and your optimal jump- you're essentially done. No more room to chase them- your jump will only increase.

It's one thing to throat longer in order to use heavier bullets, or changing ogive types that requires it- but you're chasing a hypothetical.
There's no guarantee that increasing your case capacity slightly will increase your velocity.

Ok, thanks for explaining. So apparently it was simply bad engineering when Weatherby put .750 freebore in the earliest .300 Weatherby mags.

 

[StumpGrinder]

This.
I skipped to the last page of the thread- and this was my thought when I read the initial post.

Similar thread recently- keep in mind that your throat is gonna erode- and since you seem to like to load hot (your entire reason for doing this is more velocity), that only exacerbates it.

How much have you already increased your COAL chasing the lands?
If you throat long based on the bullet being seated as far out as practical, and your optimal jump- you're essentially done. No more room to chase them- your jump will only increase.

It's one thing to throat longer in order to use heavier bullets, or changing ogive types that requires it- but you're chasing a hypothetical.
There's no guarantee that increasing your case capacity slightly will increase your velocity- and it could potentially be less accurate.
I've rarely found the hottest/fastest load to be the one I end up with.

I have found that with both my Ruger M 77 mark II rifles, with stainless steel barrels, they like at or near max loads. One is in 308 and the other is 243. Maybe it has something to do with the stainless steel???

 

[Ckleeves]

Ok, thanks for explaining. So apparently it was simply bad engineering when Weatherby put .750 freebore in the earliest .300 Weatherby mags.

It's .361 now looking at their prints. .750 is insane if that's what it once was. Maybe it was back when velocity was king, accuracy wasn't priority #1 and the bullets we have today weren't even a thought. Even .361 is longer then I would want in a 30 cal.

 

[pig ranch deadeye]

It's .361 now looking at their prints. .750 is insane if that's what it once was. Maybe it was back when velocity was king, accuracy wasn't priority #1 and the bullets we have today weren't even a thought. Even .361 is longer then I would want in a 30 cal.

Yes, exactly. The philosophy was just hit that elk anywhere in the heart-lung area with as much bullet energy as you can. In other words, high velocity. The early Weatherby philosophy saw no requirement to cover three shots at a hundred yards with a dime. The Nosler Partition 200 grain was preferred as it held up under the stress.