Finding your Lands & Grooves

P9S

P9S

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I have a Remington 700 BDL 22.250. I only shoot 5x5 aggs, never plink. I compete against myself, tuning the ammunition or rifle. This rifle has shot .3791 aggs at 100yds. Now I think the throat is burnt out.

One of the variables I've wanted to use to tune the 22.250 is the bullet relative to my lands and grooves. Touch/jam or 5, 10, 15, 20 thousands off the lands.

There are (too) many theories and suggestions to find your lands. Confusing. Smoking bullets, Hornady, Smokey Point, and lots of other difficult and somewhat expensive tools and techniques. I own one of those tools!

I had an Eureka moment when I found this youtube. Tim and Joe Duke you are my heroes!!

https://www.youtube.com/watch?v=Jv-D1mEI514

Here is a way to use my own chamber and throat to tune/measure bullet OAL as well as headspace.

I don't use my mag to feed the 700. I have a Davidson single feed ramp because I neck size only about a 1/16th just to hold the bullet. So I single feed.

I couldn't get the feel like he does on the video after taking out the firing pin. Now I've also taken out the extractor spring. This gives me the feel for go/nogo on both case headspace and cartridge OAL that he is demonstrating.

I've made go and nogo cartridges for my preferred bullet for this season. Now using my bullet comparator I can set my micrometer bullet seater for whatever testing distance off the lands I want for that particular bullet.

And I can use this same method to set my Forster bump die for headspace!!

Not sure what you do for other bolts like savage but isn't this kickass?
God Bless Texas
 
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Is that BADH Magellann?

Baffling how?

Thanks for the encouraging words - 13 vs 9,859.
Who needs new members? Your rodeo?
I missed the part what you pointed out a better, faster, cheaper method of determining head space and COAL
And where you find fault?
 
er...no. To check the depth in lands...just take a fired casing from the rifle. Make a small dimple in the neck, with just enough pressure to hold the bullet you are selecting. Gently close the bolt with the casing and bullet in the chamber. You do not need to remove the firing pin at all.

Now, as long as the bullet is not sitting too loosely, gently remove the casing and bullet from the rifle. Measure. That is the distance in which that particular bullet touches the lands. I back mine off 0.030". Now the revised number is your COL.

In terms of the throat. If you take a decent light and look down the barrel, you can see the riffling. When you have wear, you can see it too. To measure the rifling height, slug the bore with a nice soft lead ball shot a little bit bigger than the bore diameter. Measure the rifling to the bore. If you want to know the throat...don't pound it in that far.
 
sobo4303 said:
er...no. To check the depth in lands...just take a fired casing from the rifle. Make a small dimple in the neck, with just enough pressure to hold the bullet you are selecting. Gently close the bolt with the casing and bullet in the chamber. You do not need to remove the firing pin at all.

Now, as long as the bullet is not sitting too loosely, gently remove the casing and bullet from the rifle. Measure. That is the distance in which that particular bullet touches the lands. I back mine off 0.030". Now the revised number is your COL.

In terms of the throat. If you take a decent light and look down the barrel, you can see the riffling. When you have wear, you can see it too. To measure the rifling height, slug the bore with a nice soft lead ball shot a little bit bigger than the bore diameter. Measure the rifling to the bore. If you want to know the throat...don't pound it in that far.
Click to expand...

That seems a better method then buying special removal tools and removing the firing pin..
 
silverfoxdj said:
That seems a better method then buying special removal tools and removing the firing pin..
Click to expand...

It depends what information you're after. It takes a gentle hand to close the bolt on a bullet seated long without driving it forward, but it is possible and will be close enough to repeatable to find the sweet spot for accuracy. My own system varies in that I use a flat base bullet seated backwards in a normally sized neck so there is a flat surface rather than a tapered one engaging the lands, and so there is enough neck tension to prevent the bullet from pulling out when the round is extracted. As the ogive makes firm contact with the lands, particularly if the throat is getting a bit rough, it will tend to stick. But if you're tracking the throat erosion of your chamber, I can see the technique shown in the video as being somewhat more precise, although I thought he seated the bullet with a bit too much enthusiasm on the press handle.
 
The secret is in how you dimple or crimp the neck. I use a pair of pliers to just flatten the neck a bit. It provides enough tension that the bullet will be held firm enough for handling, but not so firm that I cannot close a bolt. With a fired casing, the primer pocket is already cratered, so no need to remove the firing pin.

In terms of headspace, I use a combination of plastigage, Clymer and headspace gauges. There is no guess work and I have also a built in safety check in terms of redundancy.

I primarily use this method to set the OAL for the bullet I am using and the rifle. Using teh flat base will not provide an accurate enough measurement for me as the ogive's vary with different brands of bullets, hence the OAL may be too long or too short for my preference.
 
sobo4303 said:
Using teh flat base will not provide an accurate enough measurement for me as the ogive's vary with different brands of bullets, hence the OAL may be too long or too short for my preference.
Click to expand...

Ahh, but this leads to the second part of my system. I take the bullet I intend to load, push it firmly, nose down into the muzzle of the rifle, and turn it so it scribes a line at the ogive. Based on the location of the scribed line, a precise jump or jam can be determined from the OAL of the dummy round with the flat base. The location of the ogive can be marked with a bullet comparator, but you already have the barrel.
 
although this technique would be very time consuming, i dont think there is a more accurate method for measuring to your leade. The problem with the crimped case and chamber is, you have zero feel so its very likely your going to stick the bullet in the rifling more often than not, causing the bullet to pull out of the neck, giving a longer measurement. This is remedied by repeating the process many times and taking the shortest measurement, as there would be nothing acting to push the bullet in TOO far and give a shorter reading. Setting the crimp perfectly is very difficult. Too much and you'll just jam the bullet in the lands, too light and the bullet just slides around. And its not as easy to set it "just right" as it sounds. Getting the same measurement twice with this procedure is very difficult. For me, the crimp and chamber is pretty good, but there are a LOT of variables to skew the measurement. Marking the bullet at the muzzle is completely bogus. The line itself is like 5 thou thick, not to mention ability to measure that line precisely. prepare for disappointment with that one. Hornadys O.A.L gauge is good, second best. Only problem is it simply doesnt take headspace into account. This is remedied by making your own dummy case with a fired case from the rifle. The technique in the OP takes out all variables with no cost. You dont need any special tool to remove the firing pin. The procedure is More or less the crimp and chamber improved. But thats just me.
 
When he is (what looks to be closing the bolt forward with quite some authority), isn't he pushing the bullet into the lands. I think if I was doing this test I would be very gentle on the bolt because when the bolt is pushed as far forward as possible isn't that the same as closing the bolt handle, or does the bolt handle sortof Camover like a reloading press.
 
I'm using a micrometer bullet seater die like in the video.

I said "I've made go and nogo cartridges for my preferred bullet for this season. Now using my bullet comparator I can set my micrometer bullet seater for whatever testing distance off the lands I want for that particular bullet."

Actually that's not true. Using Tim's method my die is set exactly for 'just touching'. Don't need a comparator. Now I just play with the micrometer settings to get the desired jump or jam. The nogo I will use periodically to check if (more) erosion is occurring - 3,800fps! My Nosler 52gr match can't touch!
I've been handloading this rifle since 1986 and have tried nearly all the method being described. I find this one gives me the exact measurement without going through intermediate steps that may multiply any potential measurement errors. With this method my die is set for the current condition of the rifling. And I said I'm using this same technique for setting my headspace. Your mileage may vary.

Thanks for the different suggestions. Haven't tried the cerrosafe & might out of curiosity but again it adds steps and potential for error.
 
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