Acceptable OAL variances

T

thumbs47

New member
I am having a hard time holding my OAL for my cartridges. I am not sure if I am being to pickey or if I am missing something. I have the same problem on two presses. I can run + or - .005 regularly. Everything seems to be tight. Dies are snug and there seems to be no slop in the presses. The two presses I am using are the Lee Classic Turret press and the Loadmaster. Please don't start with the the Red, Blue and Green thing. Not interested. I would like to know how I can get the tolerance closer on my OAL. This is a problem with cast and plated bullets. I check the lengths with the cal. and using a comparator. The lengths show a difference from what I originally set. Now I can run OAL's pretty close then they go off. I readjust the die and after a couple of rounds it goes way off like I should have left it alone. What's going on?

thanks for the help
 
I think that's a pretty standard thing from what I've learned from the net. It has to do with bullet variances, both in length and the ogive of the bullet, and case variances in length, and any movement in the press.
From what I've learned .005 is pretty common and even .010 is not that bad. At least I hope so, cause I get up to .010 at times although I think I'm usually around .005 to .007.
 
Thanks, that was my thinking but really didn't know. Not sure yet if it effects accuracy to much but it may. Good to know others are in the same ball park and I'm not alone.

thanks
 
My RCBS dies average .005 in AOL differences, until I thoroughly cleaned my seating die and then it fell to .003 and that's with 50 cartridges, so no big deal to me, it's hunting ammo.
I use Forster Benchrest dies for 3006 and 7mm mag, and those differences lessen to .002- .001, with 50 cartridges.
 
" I can run + or - .005 regularly."

INSIGNIFICANT
In most cases, the bullet seater works on the ogive and you're measuring the bullet tip. Depending on design and material, there can be significant differences in tip length/shape which will have little bearing on performance.
 
It also depends how you are measuring your cartridges.

If with just a pair of calipers from base to tip of bullet, you will easily get that.
 
std7mag said:
If with just a pair of calipers from base to tip of bullet, you will easily get that.
Click to expand...

Mobuck said:
" I can run + or - .005 regularly."

INSIGNIFICANT
Click to expand...

It can be very significant when loading for a firearm with a short magazine like the AR . I've found the 77gr SMK to have up to .010 difference in bullet length bullet to bullet . Although 2.260 will feed in an AR mag . I have to find the longest bullet/s and seat those to 2.260 . That means the seated shorter bullets can be as short as 2.250 . It sucks when you load up a bunch a rounds thinking you had the right depth only to get to the range and find out they wont feed from your mag . Don't ask how I know this :D
 
re:handgun only: Lyman 49th p41 speaks a bit about the seeing the +/- 0.005." If you call the various manufactures, some of them will say even out to +/- 0.007" is not a bit deal as long as you are not compressing powder, loading around max, those kid of things.
Think about buying budget bullets that do not publish oals or specific powder ranges for their specific bullet. You really don't know what the magic "exact" oal is supposed to be for your pistol chamber and the next lot of budget bullets may be different. Then if you change from manual "A" to manual "B" you will see different load data recommendations. The testing used for those manuals was their test bed, their chamber, their etc, etc.
One of the most important over looked topics is learning and recognizing pressure signs as you work up from start. You'd think there would be a manual that would spend more time on that and post lots-n-lots of pictures w/ explanations.
 
If you're within 0.005" of your ammo not working in your magazine, you really should pick a shorter length.

It's difficult to get closer than 0.01" total variance. You'll almost never get it measuring from the tip, as noted. The ogive is much more consistent but still not perfect.

The pressure you put on the press handle will change it. Even if you use the exact same force on the handle every time (you don't unless you've got a torque wrench attached to it), the seating force and minor dimensional variances in cases and bullets will cause some discrepancy.

Most bullet seating plugs are generic and don't touch every kind of bullet near the ogive. If they touch a spot that varies, and most do, you're going to get some variance. This can be fixed by simply drilling out the plug with a drill bit that's as close as possible (but slightly larger than) ogive diameter.

Ultimately though, what you've got is close enough and you can ignore it.
 
Metalgod. Good point on bringing out the mag trap. Then you think you have that perfect oal for magazines worked out then buy some good mag deal only to find out the mag isn't so sweet of a deal and the bullet needs a tad bit shorter. Learn by burn so to speak to buy known good mags.
 
"...problem with cast and plated bullets..." Handgun? 5 thou usually isn't a big deal with handgun ammo. Only matters with a rifle, if as mentioned, you're really close to max mag length or your rifle likes its bullets really close to the rifling.
Can have to do with how consistently you operate the ram. As daft as that sounds. Might be a wee bit of wiggle in the ram itself as well. If you don't move the ram to where it stops, you'll have a bit of variation.
"...find the longest bullet/s..." A 77 grain MATCH bullet should not have any length variation.
SAAMI spec OAL's used by the reloading manufacturers are NOT measured to the ogive. They're measured from the pointy bit(if there is one) to the flat bit. Metal god's 2.260" is measured that way.
 
Years ago I used to try to control OAL with respect to a Sinclar bullet comparator
http://www.brownells.com/reloading/...r-hex-style-bullet-comparators-prod83792.aspx

I gave up.

Now for targets I measure where a bullet touches the lands and where a bullet gets stuck in the lands. I aim to seat for halfway in between.

For hunting I seat a 3.34" de facto, default, SOP, OAL. The magazines are designed to be that long, plus extra for the cartridge tipping and be not wedging when rim edge to bullet tip is more than 3.34".
That started, I think with 30-06. Then the 300 Win Mag was made by shortening the 300 H&H to fit in 3.34" rifles. The 270 and everything fell into line.

The ugly exceptions:
The 7mmRemMag is not registered at 3.34", but it should have been, so I seat them that long.
The 8x57mm surplus Mausers have got a magazine not 3.34" friendly. So I mill out the magazine well so I can shoot my 3.34" 7mmRemMag ammo.

And then there those miserable 5.56x45mm NATO chambers. I hate those. The lands are beyond reach. Krieger makes a 223 SAAMI barrel for the AR15. One could reach the lands, but the barrel is heavy as a boat anchor.
 
I reload 1 basic combo ( but 2 different OALs) for 5 different .45 autos and I maintain an OAL of +.002/-.002 but will say that maintaining a OAl to that close tolerancing is definitely not worth the effort. As others state, if they go into the mag & the chamber, shoot & reload.
 
i had the same problem until I started measuring my bullets,.. all my cases were uniform.. I measured my bullets and found out that they were varying .001-.006 in lenght themselves.
 
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