Minimum bullet / case seating depth?

[wolfejohne]

I am new to reloading and working up my first rounds after determining COAL using the Hornady OAL Gauges. I am working up a load for a 300 Win Mag using a Berger 168 gr Hybrid bullet. After finding out where the bullet's ogive touches the lands 2.911"' I am finding that the case engagement is very short ie. .080" on the bullet's bearing surface. This ends up with a total coal of 3.620". I understand that the overall length needs to fit in the mag and chamber correctly. I would like to know what is the minimum or recommended bullet to case engagement? I understand the interference fit between the case neck and bullet has a major effect on accuracy. I will be using neck sizing dies to control factor. As you can see I am new to this and I am sure I have over looked items but all information / suggestions are welcomed. Thanks in advanced.

John

 

[Shynloco]

wolfjohne,
In your post, you use the term," interference fit" and say you will be using a neck sizing die to control factor. I've never heard that term before and am wondering what it means. And as to the use of a Neck Sizing Die, are you saying you will be "partial neck sizing" to control that "interference fit"? Not picking on you (and understand you ae new to reloading) but I just don't fully understand what you mean. Please explain. Thx

Alex

 

[wolfejohne]

Using neck sizing die (changeable bushings) to control the neck tension.

 

[AlNyhus]

John, it's been my experience that the amount of bullet in the case neck has no effect on accuracy.

Good shootin'. -Al

 

[Erik Cortina]

John, it's been my experience that the amount of bullet in the case neck has no effect on accuracy.

Good shootin'. -Al

I have found this to be true as well.

Seat your bullet as long as you can but that it still fits in the magazine. Sell your neck sizing die and buy a full length sizing die or buy a body die and do both always to ensure proper chambering of your rounds. Learn how to properly set up your shoulder bump and you will be good to go.

After you seat bullets to magazine length, find the powder charge that works best in your rifle, then do a seating depth test by keeping your best powder charge but seating your bullets deeper by .003" on every group until you find the one that shoots the best.

 

[Shynloco]

As usual, Erik is right on target with his response.

Alex

 

[kelbro]

The general rule of thumb that I was taught was that you want a minimum of one bullet diameter in the neck. With some of the boat-tails that are out there now, the reasoning behind that guideline is lost as there will not be one bullet diameter's worth of interference fit (yes, that is a correct term).

I have violated that rule many times without any issues.

 

[expiper]

Im a dinosour that will shoot anything that work!!haha,,,,when you get down to ~.050 it is possible to pull the bullets with your fingers!!! and the ammo has to be handled like eggs,,,,they usually shoot fine but are very delicate....in your case (.080") should hold them fine...the old wives tale of "one bullet dia." is "just that"....most necks are not a full dia long....like a Dasher being .200 --how are you gona get .243 of grip?(and most bushing dies only size .180 of the neck when fully inserted),,,,Roger

 

[fdshuster]

And the BRX is even shorter, at about .180".

 

[Erik Cortina]

Based on his COAL, it looks like he might need to seat it deeper anyway to have proper fit in magazine, at that point he should have plenty bullet in the case. At that point, all he needs to do is what I suggested and he should be all set.

 

[wolfejohne]

Thanks for all the feedback! The mag on the AI AX chassis will Just take the total coal length, but may not feed with .020 clearance.

Question on sizing/case prep. I thought you did not want to work the entire case ever time. With fire (shot previously) formed cases you need to keep a watch on shoulder length and just resize the neck. When things start getting long do a full length resize and trim the total length as necessary. The dies I am using are a 3 die set with 1) neck sizer, 2) body sizer and 3) seating die. Again all feedback is welcomed, I am working in a void and reading lots of information.

 

[Erik Cortina]

You need to full length size every time. This will ensure proper chambering always. Also, f/l sizing every time ensures everything stays consistent, neck sizing does not, hence the need to f/l size at some point.

 

[fdshuster]

john: With multiple firings the cases not only stretch in length, but in width also, at the case head, right in front of the extractor groove. How many firings before it becomes a problem (hard bolt closing or if severe enough, no bolt closing at all) depends on the operating pressures.

Easiest way to prevent case chambering problems (and stopages) is to do as Eric said and just FL size with each loading. Keep the sizing to the minimum required to allow normal chambering, with maybe just a little resistance when closing the bolt, but I mean a very little resistance.

Doing this will keep your brass uniform throughout its use. Attempting to neck size only will allow differences to develop (brass is not all created equal) over a few firings.

 

[wolfejohne]

Thanks for all the advice, it looks likes full length sizing is the way to go.

 

[gilream]

John, listen carefully…these men know what they are talking about. I fell for the neck size only ruse for a long time concerning my hunting and varmint rifles. Eventually (after the 2nd firing in my experience) you must FL resize to get the case to chamber smoothly. When you do that you change the internal dimensions of the case and consistency goes out the window. I chased my tail and wasted a lot of time and effort before I learned to size the necks first with a bushing neck die or a Lee Collet Die (terrific for factory chambers) then consistently bump that shoulder .0015 to .002 thousandths with a FL body die. Redding makes a FL / Bushing Type S die that will do both in one step. FL size your cases every time…it’s the right thing to do.