I am hoping someone can tell me where I should start experimenting with bullet depth in terms of how far off the lands I should be. I am loading for a new Model 10 in .308 Win.
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I am hoping someone can tell me where I should start experimenting with bullet depth in terms of how far off the lands I should be. I am loading for a new Model 10 in .308 Win.
I normally start with the bullet just touching the lands until I find a powder and a charge that shows potential, then I start playing with seating depth if need be. I have had some shoot so good that I didn't bother changing depth. Normally I don't end up too far from the lands, most within .010" but one liked it out at .050".
I should also add that in the situation of a very short bullet for a given bore where there is no chance of reaching the lands or anywhere near it, I will normally just start with the base of the bullet just above the bottom of the neck, and if that's too far in then I just play it by feel and pray a lot.
That system works for me also.Quote:
Originally Posted by bootsmcguire
Generally speaking you want to start as close to the lands as you ever intend to shoot. This will show you where max pressure is. For target shooter this means a jam into the lands. For the hunting crowd I stay .005 off. Then when you work your seating depth you will be reducing pressure as you do and dont have to worry about a dangerous pressure spike.
I have always done as boots suggested, but you will hear a few opinions that suggest pick a mid-charge and look at seating depth first, and settle on the best group size before looking at powder charge. I am going to evaluate that method next as I think it has some validity, depending upon whether seating depth or charge has the most effect on group size. One of my rifles has clearly shown depth is much more important, and working on charge first led to variable results which were not so straightforward to interpret. I believe the most important factor should be settled upon first, so that the next not-as-significant factor will be easier to evaluate in order to achieve a clear answer. In either case I use the optimum barrel time calculation to identify the powder charge region I will focus on, as this approach has shown very good insight and guidance.
Seating depth will vary with each charge. You can get almost any powder load to group reasonably by playing with the seating depth. I tried that road of finding depth first, it doesn't work.
Load long and shoot a ladder. Pick a mid charge in each node and shoot a depth test. Which ever comes out on top is your load.
I will add certain bullets like barnes ttsx shoot best off the lands. Loading close can cause serious pressure problems. I would start .030 off the lands for those. Do homework on your bullets.
I run .010 to .015 in to the lands.
ThisQuote:
Originally Posted by bootsmcguire
I've got a question about this. Sorry not trying to hijack this post. In my 10p 5R I can't load to the standard OAL
With
Hornady 168gn bthp match
Lc brass
I can only load to 2.780 before I start getting a tight bolt and marks around the bullet ogive
Is this just a tight chamber or should I get a 308 go gauge and reset my headspace? Headspace is factory set as it is.
If it chambers fine at under 2.78" then I am betting your headspace is fine, you just have a barrel with a short throat. The marks indicate that the bullet is jamming into the lands. It wouldn't hurt to double check with some gauges if you are worried about the headspace, but I'd say you just have a barrel with a short throat.
Feel free to just shoot it a bunch and the lands will eventually move their way out. ;)
My Axis seems to be the opposite. I've been loading Hornady 178gr BTHPs and when we loaded up a dummy round and chambered it, it was ~2.916". I've been loading to 2.900. I probably should've started longer if I could, but I'm not sure any longer would feed from the mag. And now it's looking like I'm going to have to shorten my load anyway. Hopefully it doesn't cause issues. I picked up a pair of 10rd mags, and it's looking like I'm gonna have to load to 2.800 or so to fit them in the mags... :( Not happy about it.
This is the way that works for me also, like Boots.
My Axis shoots the 175SMK's very well loaded at 2.8 over 44grs of IMR4064 w/ CCI200 primers.Quote:
Originally Posted by upSLIDEdown
So if one loads 15-20 thousandths off the land wether it be a long throat chamber or short throat chamber, like mine, can one expect the same results? Why is savage making different chamber throats? What are the pros and cons of each setup?
Nearly the same recipe, exactly the same results. 175 grain smk's seated to 2.8 oal over 44 grains of ACCURATE 4064 with Remington 9 1/2 primers. Better than minute of angle with the factory HogHunter barrel.Quote:
Originally Posted by LoneWolf
Quote:
Originally Posted by bootsmcguire
this ^^^^^ lol
Yes and No. Loading longer leaves less bullet inside the case and thus increases your powder capacity. So a load that is made with bullet seated out far, will rise in pressure if the bullet is seated deeper. So as always work up your loads for your barrel. In effect of the bullet towards the lands, yes it is basically the same difference, some people say that more bullet inside the case will lead to powder doing things to it like scoring the sides of the bullet before it makes it to the rifling and hurting accuracy. I think it is most likely a minimal effect but when are chasing the .1" group it could make the difference.Quote:
Originally Posted by josh_m
As to differences in barrel throats from the factory, my best guess is a difference in reamers. Perhaps one was cut on a new reamer and another on a resharpened reamer. Reamers will wear throughout a production run and possibly get swapped out for a newer one that possibly has different throat specs but is still in SAAMI tolerances. Again, those are my personal guesses just based off of logic in regards to tool life, as I am a machinist myself.
In my 7mm08, I am at .020 off of the ring lands with .25 moa at 100 yards. IMR 4064 at 42 grains and 140 Nosler Ballastic hunting tips.
As one of the immortals on another site says.
Kiss.
Find pressure.
Rock on.
I have found that nearly all of my rifles prefer that the bullet just kiss the lands.
Once I've found the lands with each particular bullet I don't change seating depth until leade erosion dictates a longer COL.
Not all chambers will allow loading to the lands and allowing enough bullet tension in case neck or enough bullet seated in the case neck. If you are bench guy and single feed then a lot of the seating depth arguements hold no real value. If you are hunter and want a repeater then you do need to consider magazine feeding and ammo handling. Regardless of your desires you really should get the right guages to measure bullet ogive to case base. OAL to the ogive is the most consistent measurement you can use for each bullet type you choose.
For me:
Step 1. Find OAL.
Step 2. Seat bullets .010 off lands
Step 3. Shoot for pressure. I step from minum in .5 grain increments to max. Load .5 grains less/off max, where pressure signs just start to show. I also do with different primers.
Step 4. Seating depth testing based on target powder charge. .010, .025, .050, .075, .100, .125
Most of my bullet choices have been VLD style bullets for long range applications. Most rifles prefered .100 off lands. However, I just built a new rifle with a Schnieder barrel that likes .050 and .075. I have not tested .025, but it didn't care a lot for .010 or less. It shot 5/8th at .010, 3/8th at .075, and almost same hole at .050 (with a magnum primer).
For me I try and not get worked up about seating depth. As long as I know my powder charge is safe I simply plan to shoot the seating depths until it all comes together. The biggest caution is whether or not your throat is long or short and how much powder compression is going on. Another example of is that of my 3 6.5-284's my Schnieder barrel is the shortest in throat by a consider margin. Again, I didn't care until I noticed I was compressing powder at .100 seating depth. If you are compressing powder just be mindful of the potential for pressure spikes.
+1--some bergers too.Quote:
Originally Posted by limige
How far off the lands? That's a loaded question if there ever was one.
^^^^ that is some good information Brent. Thanks. I'm new to reloading and this site has been a great resource.