How to get bullet to contact rifling

laxd211 said:

Hello all,

I was wondering if anybody could tell me how to find the seating depth that will allow the bullet to JUST come in contact with the rifling. I remember reading in an old Sierra manual about smoking a dummy cartridge and chambering it, but I am a little fuzzy on the details and would great appreciate any help.

If it means anything, I'm shooting 168 gr. SMK w/RE-15 out of a .308 bolt action.

Click to expand...

I do not know how to post links, but Sinclair International has an overall length gauge tool that I bought. It is a stainless rod with two sliders that adjust on it.
You install the bullet in the chamber up to the rifling,push the adjuster rod up to the base of the bullet,push up one slider, and lock it down. You then install a full length sized/dead primed case into the chamber, turn the rod tool around, install rod up to the back of said case, and lock down the other slider.
You then mic the distance between the sliders, add the length of the bullet, and that is the length of that load,from the base of the case, to the rifling.
Seat your bullets .010" to .015" deeper than that+you are good to go.
Check Sinclair's web sight for the tool--IMO it is worth it..I have checked-.223 Rem.,22-250 Rem., 6MM Rem., and .308 Win. calibers with good success.
Hope this helps..Bill..

Take a resized case and cut it so the bullet is held snugly, but still can move. Push a bullet into the case so it is really long. Press it into your chamber with your fingers. The rifling will set the bullet back. Take it out and measure it. Put your new chamber length gage in your die box for next time.

Here is a photo of a 10mm. Same idea for your 308.

You may never reach the rifling if your rifle has a standard chamber.

+1
Many modern rifle chambers have more like freebore then leade!!
It's a lawyer thing to keep pressure in check.

The old tried & true method is to seat a bullet long and smoke it with a candle flame.
(Or color it with a Dry-Erase marker)

Then keep seating deeper a little at a time and re-smoking until the rifling leade stops rubbing the soot off the bullet.

That smoke method will tell you everything a $100 buck guage will tell you.
Without the Chinese Algebra involved.

rc

I load to mag length. Same accuracy with less work.

Yep!

Interesting that the most accurate factory ammo made in the world, like Federal Gold Medel, Black Hills Match, and all Varmint ammo from everybody, is loaded to SAAMI standard length or less.

With no regard to reaching the rifling leade.

If you do everything else right with your reloads, contacting the rifling is the least likely to matter one way or another.

rc

You can get the Hornady, formerly Stoney Point, OAL Gauge. It uses a modified case that has the primer pocket enlarged and threaded and the neck is slightly oversized and screws onto the end of the gauge which then has a pushrod that you use to push the bullet forward until it hits the lands. At that point, you lock down a thumb screw on the pushrod so it doesn't move and extract the gauge and cartridge. Sometimes the bullet gets stuck on the lands, but that doesn't really matter. Just tap the but of the rifle on the ground and it will fall and then drop it into the modified case and it will fall until it hits the pushrod and you'll have your OAL for that type of bullet at the lands of your rifle.

You may never reach the rifling if your rifle has a standard chamber.

Click to expand...

+2. And you will NEVER reach the rifling if your rifle is a Model 700.

Don

Rarely does seating to the lands give you an advantage, and actually can create pressure spikes with certain loads, when the bullet needs to engrave into the rifling without any jump.

I'm aware that some benchrest shooters advocate pushing the bullet into the lands when feeding a round, but they usually are dealing with a custom cut chamber and leade.

Allowing a bit of a jump, I use .020", will not affect your accuracy, and give you an honest read on the case in development, IMO.
As noted, many factory chambers won't allow you to get near the lands unless you are using exceptionally long heavy bullets.
Your COAL needs to fit your magazine, unless you're using a single shot.



NCsmitty

My Bushmaster Vmatch 223 AR15, I cannot reach the riflings even with with 75 gr bullets loaded out way longer than a magazine will feed.

With 100 gr BT in 260, I can just touch the lands if the bullets is barely in the case mouth. Not in far enough for hunting, but makes great groups at the range.

I agree with rcmodel,
To get super accurate loads you can achieve many times by simply sticking to SAAMI standards or a little bit more if the bore and/or magazine allows you. They key is that you are able to precisely replicate the length and speed spreads.

If a special purpose load is needed where you need to know the precise max COAL that your cambering allows, smoking the bullet as someone suggested is a great method. Also a marker will do the same w/o a flame.

I never ever touch the lands and after I find out the Max. I back out at least 0.010". If you are worry about starting pressure the best way to achieve this is using a light crimp. I consider this one of the most important aspects of consistent spreads and I keep mine with the spread differences in the single digits many times. Lee makes a great die that is call the lee factory crimp and even bullets w/o canelure you can apply a very light crimp to achieve that desired start pressure. When I say light I mean light otherwise what you will do is deform the bullet and that means inconsistent results and potentially unwanted pressure spikes.

Another important aspect though is that you will need as many measurements as many different bullets you are intending in using. Bullets have different design and secant/ogive profile so they will touch the lands at different lengths.

So the best thing to do is, after you find out the max. value write down the COAL for that round with that bullet and then go a recreate one. Save it as a dummy/template to be used to faster setup your seating die.

Cheers,
E.

I partially resize the neck just enough to hold onto the bullet with minimal tension. I then seat the bullet to well over any listed OAL or just simply noticably longer. I recomend a dummy round not priner or powder obviously. I then try to chamber it, it the bolt won't close I seat a little deeper and so one until I'm getting s tight fit. Once I'm getting a tight fit I take a black magic market and color the bullet black and then try to chamber it watching for the rifling marks to stop appearing. Based on how much resistence and the rifling marks I arrive at a depth that is several thousandths off the lands. I have loaded a lot of rounds that are touching or slightly into the lands on a number of occasions, and honestly feel that is the optimum performing OAL and has proven so with ever bolt action I load for. The only issue I can imagine from seating like that is the round being too long to fit the magazine, which has never happened ot me.
I've heard concerns about possible pressures spiking because the bullet is up against the lands and it is being delayed from exiting the cartridge/chamber. I have found no information professionally provided from any reliable source that supports that risk.

All the above methods work just fine.

I'll list a couple more options that will also work if you're so inclined. I used to worry and ponder about the max OAL, not so much anymore.

First, you can close your bolt on an empty chamber (no case or cartridge at all) and then gently push a cleaning rod or wooden dowell down the barrel from the muzzle until it touches the bolt face. Use a razor blade to mark that point on the rod where it clears the muzzle. You want a very sharp thin and repeatable mark. Then take whatever bullet you're going to be using (each bullet will be different) and drop it into your chamber until it hits the rifling. Use a pencil to push it in and hold it tight. Put your meauring rod back down the barrel and mark it as precisely as before. The distance between the marks should be your max OAL. It depends on how precisely you can make those marks and do the measurement, but it should be pretty close. Enough to get in the ballpark. It might tell you right quick that the max OAL is either too long for your magazine or else it might be too l ong to seat in the case mouth.

Another way is to take a used unsized case and drill the primer pocket out. Seat a bullet fairly short (normal SAAMI length will do), using a pair of pliers or something to put enough crimp into the mouth to at least hold the bullet for now. Chamber the cartridge with the bolt removed and push it into the chamber with your fingers. Now take your cleaning rod and stick it through where the bolt would go, into the drilled out primer hole and continue pushing until the cleaning rod contacts the base of the bullet and push the bullet forward until it hits the riflling. Pretty much the same as the fancy measuring gauges, but I'm cheap at heart.

One more tid bit. If you use a dummy case to find your depth with, make sure thatt case isn't fitting with any resistence or it could give you a false indication of having reached the lands. I just resize the neck on a case that has deffinitely been well formed to my chamber to insure an accurate point of contact.

rcmodel said:

+1
Many modern rifle chambers have more like freebore then leade!!
It's a lawyer thing to keep pressure in check.

The old tried & true method is to seat a bullet long and smoke it with a candle flame.
(Or color it with a Dry-Erase marker)

Then keep seating deeper a little at a time and re-smoking until the rifling leade stops rubbing the soot off the bullet.

That smoke method will tell you everything a $100 buck guage will tell you.
Without the Chinese Algebra involved.

rc

Click to expand...

this is dead on.

I do not wake up in a new world everyday, if starting over everyday can be avoided, avoid the practice.

I am a big fan of the running start, I do not use up all the space available, but, it is more than nice to know the length of the chamber from the bolt face to the rifling, once the length has been (discovered?) determined it is not necessary to find over and over and over, it does not move, it has a taper and is between the large and small diameter of the barrel (30/06 is between .300 and .308).

I do not smoke the bullet, I do not shred the mouth of the case, I am a big fan of bullet hold (something others call neck tension), I want all the bullet hold I can get, back to starting over everyday, once the contact between the bullet and rifling has been determined it is not necessary to discover it ever day.

I drill the flash hole/primer pocket out to a diameter that accommodates a cleaning rod, I then size the case and seat a bullet that is to be loaded in the sized case, does not matter as to length, just make sure the bullet is seated short, then I remove the bolt, chamber the test case then use a cleaning rod to push the bullet out of the case until it hits the rifling, the rifling will imprint on the case, I then remove the case and use it as a transfer, the bullet hold of the neck (neck tension) will allow the reloader to use the test case to to set up their seater die to .000 of the lands, for those skilled in the use of tools like the height gage, depth gage and dial caliper can then determine the height of the seater stem to .000 as in off the lands, then adjust the seater stem height to seat 'off the lands. With bullet hold and when using the same bullet the test case can be used to .000 the seater stem height above the die. This method is a smart way to save money, the smart reloader that is skilled in the use of tools does not need the MICRO adjusters on seater dies.

Those skilled in the use of tools can determine the contact point between the bullet and rifling, and as I have said my favorite tool is the DATUM, others call it datum line.

I am a fan of the jump start and bullet hold and turning my seater dies into micro adjusters.

It is nice to know the distance to the lands, it sounds cool when someone says, "I seat my bullets .002 off the lands" I can say the same thing, but I don't, I want my bullet to have a running start, and when I drill the primer pocket/flash hole to avoid starting over the next day I drill the primer pocket/flash hole on at least 10 cases.

F. Guffey