Got a weird issue that is really frustrating and pissing me off. When I got back into reloading last year my goal was to step it up to a much higher precision process than when I started as a teenager to get decent ammo at a good price. Here is my issue. I measured each of my guns chambers to find the distance to the lands with the bullets I would be using. I did this with the Hornady COAL tool. At issue is my 22-250. When I measured it the distance to the lands was 2.114 with a Hornady 52 gr BTHP. I compared this to my buddies and his was 2.110 so I feel pretty good about it. I bought some new bullets so I measured them to see what the distance was for them and it was about 50 thou different (2.058). Wasn't to concerned bc these bullets were the Barnes 50 gr tsx bullets and I expected some difference. Then I measured some 55 gr Sierra game kings and they were about .112 shorter(2.002). Holy cow...so I got the same bullet I originally measured with which was a Hornady and it measured 2.000. WTF?? I looked at where I have been seating my bullets which is 2.088 (26 thou off the lands from original measurement). According to these new measurements that would be jamming 88 thou which is crazy. Since I took the original measurements I have done an extensive cleaning of the barrel. My philosophy was always never mess with the barrel unless it starting shooting bad. Probably had several hundred rounds since last cleaning and it was still shooting well but I cleaned anyway. It took multiple sessions with Boretech eliminator, wipeout, and patch out and copper was still coming out so I ran some JB Bore paste and finally got it clean. The only thing I could figure is that maybe during the cleaning some residue built up between the bore guide and lands and kept the bullet from going in as far with my COAL tool. I took some carb cleaner and blasted out the chamber and followed with a smaller brush with a patch wrapped around it and cleaned everything well. Then ran an oiled patch thru and made sure all was clean. Rechecked the measurements and they were a few thou different but nothing significant. I've double checked with a different set of calipers, used different bullets, checked the tool, and can't see anything wrong. This is really aggravating and hopefully it is something stupid on my part but I'm stumped. Any thoughts? Also, if anyone shoots these bullets in their 22-250 and has the measurement to the lands I'd be curious to see what that figure is. Thanks!!

Only two things matter; does it shoot like you want it to, and does the brass come out easily.
Everything else is superfluous information.

quote:

Originally posted by dpcd:
Only two things matter; does it shoot like you want it to, and does the brass come out easily.
Everything else is superfluous information.

Pretty much my thoughts too.

I'll add this as long as I'm in a helpful mood: for most of us, jump is what we want rather than jam. Jam is ofttimes used for BR or varmint and loaded one at a time but jump is generally preferred for a hunting gun or one with a magazine. I hate spilled powder in my actions!

Usually best accuracy is obtained by having 10-50 thousandths jump with any given bullet (theyre not all the same) so I rarely concern myself with OACL but rather BTO (Base to ogive) length as long as they fit the magazine a feed well.

Yes, a dirty-dirty-200 round gun will measure differently than a clean gun. I'm ocd so usually only run 20-50 down the tube before it's cleaned again.

Zeke

Your point is my exact concern...I want to know what sort of jump I have in seating my bullets. The tool I'm using does measure to the ogive. It just seemed odd that the measurements were that much shorter after cleaning....seems like it would be the other way around. My original measurements had me seating to a .026 jump. Now the same is a .088 jam. Just don't want an excesssive pressure situation. I feel confident my original measurements were accurate but now I don't have the same baseline. Thanks for the responses

I like to know where my throat is as well.....

I like to use the same tool you use as well. Sometimes you really have to be careful and make sure that the modified case is seated very well in the chamber, wiggling and twisting. Remember it is a generic case and it was not made to fit your "exact" chamber.

That's why it is a "comparator".

Using measurements from other chambers as a reference really isn't gonna work because those chambers where cut with other reamers.

My bet is your case is not sitting the same in the chamber each time you measure, and/or your bullet is not pushed solidly into the lands each time. It takes a bit of use to get used to the feel of this tool.

I have used this setup for several years to get baselines for loading, for me it works well.

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I always use the old fashion method of obtaining the COAL for any particular bullet. It does not rely on modified cases or anything else other than a good caliper and any cleaning rod that will fit down the bore and has a flat end on when the jag or brush is unscrewed.

Close the bolt on an empty chamber and put the rod down the bore until it touches the bolt face. While holding the rod against the face mark the cleaning rod at the muzzle. Open the bolt and insert a bullet into the chamber pushing it in with a finger or pencil until it touches the lands. With the rod and finger you can rock the bullet back and forwards, feeling the bullet touching the lands and seating it firmly against but not jamming in the lands. Mark the clean rod at the muzzle again. The distance between marks on the rod is the COAL for that bullet when touching the lands. Back down from that measurement the amount of 'jump' you want.

This method works for any bullet in your particular rifle and does not rely on anything fitting the chamber or being adjusted correctly etc. Just needs a reliable caliper and yourself undertaking the task methodically.

Right; I do it the same same way that Eagle does; I don't use any fancy tools. If I care where the lands are; sometimes I do and with some calibers, it doesn't matter as there are other considerations in making the ammo, like mag length, etc.

Your lands did not move sir. Your bullet may have stopped moving sooner but if it did, it was Carbon ring and or copper in the throat at Lands start point. If your developing that Ring of Carbon and copper, it should be cleaned out. Then your "Comparator" will be happy.

Regardless of the method used to "find the lands" use great care that you measure for the bullet "touch" rather than the "jam". Measure several times to make sure you're spot-on.

Everyone has their own methods and opinions and while some say it's of little concern, it only means it is of little concern to THEM. It is a concern to me since it satisfies my OCD and allows me to make minuet adjustments to get the most out of my rids. I shoot every week and usually 2 x per week in good weather so I can see how my ammo works at say 10 thousandths vs 20 thousandths off.
Note: some bullets/guns like a bit more jump around 50 thousandths or more but a guy will never know if he doesn't tinker and shoot a ton.

None of this make much difference if you're shooting for minute-of-deer but it makes a huge difference if you're wanting to get into the 1's and stay there!

Take it for the value you think it's worth to you.
Zeke

quote:

Originally posted by eagle27:
I always use the old fashion method of obtaining the COAL for any particular bullet. It does not rely on modified cases or anything else other than a good caliper and any cleaning rod that will fit down the bore and has a flat end on when the jag or brush is unscrewed.

Close the bolt on an empty chamber and put the rod down the bore until it touches the bolt face. While holding the rod against the face mark the cleaning rod at the muzzle. Open the bolt and insert a bullet into the chamber pushing it in with a finger or pencil until it touches the lands. With the rod and finger you can rock the bullet back and forwards, feeling the bullet touching the lands and seating it firmly against but not jamming in the lands. Mark the clean rod at the muzzle again. The distance between marks on the rod is the COAL for that bullet when touching the lands. Back down from that measurement the amount of 'jump' you want.

This method works for any bullet in your particular rifle and does not rely on anything fitting the chamber or being adjusted correctly etc. Just needs a reliable caliper and yourself undertaking the task methodically.

That's a great tip,I always struggled with this in bolt & lever action rifles,thanks.

I never bother with any of these.

I load to the maximum cartridge length, as long as the bullet has at least its diameter length in the case.

For lighter bullets, I seat one caliber in and be done with it.

Donkeys years ago I used to be so finicky about these things, and discovered they did very little to improve anything.

For magazine rifles, I load so the ammo fits in the magazine.

I use the one caliber method too. I will go deeper if my loaded rounds won't chamber or fit the magazine. I do record the COL of my reloads, which measurement I use for seating when I've switched between bullets.