Optimum bullet seating position in a given case? *****UPDATED*****

[thefitter]

Another one of my semi vague questions...

Is there a accepted optimum seating position for a bullet in a case? Meaning- the ratio that is below the neck, in the neck and above the neck? Specifically boat tails in bottle neck cases.

Thanks

 

[Immike]

Re: Optimum bullet seating position in a given case?

Yes. You want the bearing surface in the neck and not below the shoulder junction. About 80% is ideal for most application. Mike Rattigan shows a picture in his book to not seat past the sized area with the bearing surface. I think he's right about that.

 

[fdshuster]

Re: Optimum bullet seating position in a given case?

When I spec my chambering reamers it is with my first bullet of choice touching the lands with the full dia. of the bullet (boatail not included) far enough in front of the neck/shoulder junction to put it in front of the donut that may form.

As throat erosion develops I can continue to seat the bullet further out of the case neck & still maintain a reasonable bullet to case neck contact. Especially important with cases that have short necks like the 223 Rem.

 

[thefitter]

Re: Optimum bullet seating position in a given case?

Thank you, both

 

[M-61]

Re: Optimum bullet seating position in a given case?

I thought I once read that a bullet should be seated roughly at least the to the depth of the bullets diameter. It's a long time ago and I think it may have been referring to FB bullets. I also think this was given a starting point. I don't use/need this rule but for some reason it stuck in my head.

 

[Shynloco]

Re: Optimum bullet seating position in a given case?

Let me say, I really enjoy these types of discussions and the forthcoming suggestions that employ theories of bullet seating depths and exact measurements. And I really think highly of the information I have read and re-read in Mike Ratigan's book that I have. But ultimately, I have found that all the scientific and exact calculations often evade the one variable that cannot be controlled or foretold. And that is the rifle itself. And having tried all the suggested calculations, I've boiled it down to simply letting the rifle/chamber tell me where to seat the bullet to the point where I gets the best and most consistent accuracy. And to be clear, I'm NOT knocking what anybody wrote because I believe you must feel comfortable with what works for you. Nonetheless, I REALLY appreciate both the initial question and the suggestions that follow because they make me think and oft times spark a new idea or an old idea I read about in the past and simply forget. Thanks guys!

Alex

 

[Joe Maisto]

Re: Optimum bullet seating position in a given case?

Alex;

What we do in short range BR, ( group shooting) is :
(1) go into the lands with a "blackened" bullet in a case - ( I use matches)
(2) close the bolt, remove the case and examine it CLOSELY.
(3) you will see rifling marks.
(4) if they are LONGER than they are WIDE, seat a bit deeper so the marks
are ONLY as long as they are wide .
(5) Now you have a "start" position in which to test fire 3-5 rnds. for accuracy.
( you will need wind flags for this)
Most I know that shoot this game for accuracy are off the lands
anywhere from .002-.015 , depending on where that particular barrel
shoots the best.

Hope this helps.

Joe

 

[thefitter]

Re: Optimum bullet seating position in a given case?

The reason I asked this is I'm designing a reamer for a new build. I wanted to know what the fundamental proper position of a bullet was within a case.

What I have not decided on yet is where to set up the start of the lands with this bullet positioned in the case as described. Jammed, jumped?

Is it better to back off the lands and seat deeper into the case? Assuming that I will not be giving up necessary powder capacity.

Or is it better to move out towards the lands and lose bearing surface in the case?

thanks

 

[Old Navy]

Re: Optimum bullet seating position in a given case?

Why not ask the reamer maker for his recommendation? Later! Frank

 

[thefitter]

Re: Optimum bullet seating position in a given case?

I suggest to set up for 30-thousandths of movement, based from a 015-Off to 015-In seating scenario, from the longest bullet you are planning to try.
For with in this movement range is where typically best accuracy is found.

If it is for a long neck cartridge, go more yet like 025-OTL to 015-ITL, or even more yet.

My 2-cents
Donovan Moran

See this is why I come here, guys that can comprehend what I'm trying to understand even though I don't do a very good job explaining my question.

Thanks!!

 

[thefitter]

Re: Optimum bullet seating position in a given case?

I suggest to set up for 30-thousandths of movement, based from a 015-Off to 015-In seating scenario, from the longest bullet you are planning to try.
For with in this movement range is where typically best accuracy is found.

If it is for a long neck cartridge, go more yet like 025-OTL to 015-ITL, or even more yet.

My 2-cents
Donovan Moran

I'm back and ready to set up the dummy round to send off to JGS. To recap it's a 7mm RSAUM in a long action. Bullet is Berger 180 hybrid. Which I believe would be considered a long neck bullet, right?

I know I need to keep the bullet .030 away from the neck shoulder junction.

dmoran has given some good advice on what to allow for movement. My question is do I seat the bullet right at .030 + .025 = .055 from the neck shoulder junction and then tell JGS to make it + .015 to be into the lands?

Or do I seat it .030 + .025 + .015 = .070 from the neck shoulder junction and then tell JGS to make that length into the lands?

In my mind it all adds up the same but what would be more accurate for JGS?

Thanks

 

[searcher]

Just need to find what your gun likes by trying anywhere from .015" into the lands (bolt guns) to as much as maybe .060" off the lands in increments of .010". Use starting loads when initially going into the lands and work up incrementally. Take the best load and fine tune on both sides of this measurement twice , in increments of .002". As mentioned earlier - use wind flags on the calmest day you can get out, preferrably early A.M. Look at Berger Bullets website for their load development tips and thoughts on bullet seating depth. All I have found is that most of my many guns like bullets seated close to (within .015") to the lands and a few excell at .005" to .015" into the lands. The only exceptions on my rifles are when it comes to shooting all-copper bullets - then you may experience best accuracy with moderate jump (perhaps .040" or so). Weatherby rifles and some particular calibers have also been said to like a lot of jump, though I have no experience with them. When mating the ideal bullet to your gun, there are so many variations in bullet lengths as measured from the base to the ogive, experimentation is the order of the day.
Have fun and good luck!

 

[Steve Blair]

Tell JGS you want a .200" freebore for 180 Hybrids. You will be where you need to be.

 

[thefitter]

Tell JGS you want a .200" freebore for 180 Hybrids. You will be where you need to be.

Why would that be preferable than going off the dummy round for freebore length?

Thanks

 

[Steve Blair]

Tell JGS you want a .200" freebore for 180 Hybrids. You will be where you need to be.

Why would that be preferable than going off the dummy round for freebore length?

Thanks

[br]
My development indicates that larger Hybrids, 180 7mm and 230 .30, produce best results at .015-.021" from leade contact. One barrel worked best at .029". Providing a dummy round to Dave is fine, just seat the bullet .030" longer than the point at which the shank clears the neck-shoulder junction and you should be fine. A .200" freebore will keep you free of the doughnut and allow some seating depth flexibility. Either way will work.

 

[barnesuser28]

i would have the rifle throated for the 195 berger when it comes out. Ask for about .240" freebore, i went with about .270 on my 284 win.

 

[Steve Blair]

You will also need an 8.5" twist for the 195.

 

[thefitter]

You will also need an 8.5" twist for the 195.

I have a 1-8 twist barrel for this project. thanks

 

[Steve Blair]

I have a 7-270 WSM reamer with the .233" freebore that Dave Kiff recommended. I originally calculated it at .232" based on Bryan Litz's released drawing of the 195 Hybrid. Dave indicated that .233" was what he was recommending and I went with that. Not that .001" freebore difference means much. [br]
Magnum cases, like 7mm WSM and 7-270 WSM, have the capacity to use slower and bulky single base powders like H1000 and N165. H2O capacity in the 80 grain range is close to ideal for those powders and 195 bullets. 68-72 grains is about right for faster powders like H4831, H4350 and 7828, with 180 Hybrids. Not that other combinations cannot work, but near ideal usually makes it easier to develop a forgiving, stable load.

 

[300meter]

I was once told by a reliable gunsmith that the base of a boat tail bullet should not extend into the case past the neck/shoulder junction. Not sure this is correct, what do you guys think?