I have a Dillon 550. I haven't loaded for a few months, today I decided to load a bunch but I am running into a problem that I haven't had before: The OAL is fluctuating between 1.118 and 1.131 (or there abouts). In the past I have had it dead on at 1.125 and I can't figure out what is going on with this. Can anyone point out anything to look for? I haven't taken the die out of the tool head yet to look inside of it, I thought I would ask here before I do that.
Problem: Fluctuating OAL
- Thread starter 96Brigadier
- Start date
Lead build up can happen. Also, different brass can "spring" in differing rates because of the stiffness of the brass and the internal thickness. Also, the nose profile of many bullets can vary, and lead to variations on the oal.
I'm assuming you are loading 9mm
I'm assuming you are loading 9mm
reddot said:
I am only shooting complete metal jacket bullets so no lead build up. That said, the last thing I did to the press was remove the shell plate, clean it, and reinstall it. I'll tighten it up some more, out of curiosity though, why was that your first suggestion?
What calibre? Suggestions around shell plate are great as if shell plate wobbles will effect OAL. You may want to check that dies are not loose. If you are loading 9mm, there are lots and lots of different mfgs of brass and they vary a lot in dimensions (there was an OK article in Front Site about 3 editions ago that talked about the large variations in maximum powder holding capacity). You may want to try to lube your brass to make the stroking more consistent (particularly if loading lots of different headstamps). There will always be some variations in OAL. The Dillon 550 is not as bad as the 650.
So I looked at the shell plate etc., I can't find a problem with it at all. I just finished measuring the length of the bullets AND the cases and there is a difference.
The length of the bullets themselves are different by in the neighborhood of 0.005". I found two that were that much apart according to my calipers (I'm keeping in mind that calipers are good to +-0.003). When I loaded the two bullets the shorter bullet had an OAL of 1.119 and the longer bullet had an OAL of 1.126. So I say to myself, ok, if the bullets themselves are of two lengths then perhaps that is the problem (the 0.007 difference instead of 0.005 is within the tolerances of the calipers).
BUT.. then I say to myself, the die should seat the bullet to the same depth, so wouldn't that mean the OAL would stay the same but the longer bullet would be taking up more space inside the case? (Correct me if I am wrong).
Then I looked at the cases, I'm using once fired that I bought from the local range so a mixed bag. Turns out some of the brass is about 0.839" whereas others are 0.845". Ureka I say to myself (but now I have to figure out if my downloaded rounds will still cycle the action on my Glock 22 with a slightly longer OAL). My only concern at that point is that there is no ryme or reason to the differing lengths, some brass from the same manufacturer is different lengths. Sooo, I just finished taking all of the dies out, inspecting them, re-installing, tightening, calibrating, etc. The first few rounds came out identical so I rattle off 20 and measure them all. Sure enough there is still a range, now from 1.117 to 1.125 (I adjusted the dies down a tiny smidgen on purpose so that accounts for the deeper seating of the bullet).
The only thing I can think of at this point is I have a bunch of brass that is different lengths and that is accounting for the different OAL. Does that make sense?
Second question... do you guys worry about a difference in OAL of (rounding up) 0.010 on a .40 S&W? I'm not asking so much in terms of will it fit the chamber, it is all within the recommended OAL, I'm wondering more about a difference of 0.010 in terms of available volume and as a result pressure.
The length of the bullets themselves are different by in the neighborhood of 0.005". I found two that were that much apart according to my calipers (I'm keeping in mind that calipers are good to +-0.003). When I loaded the two bullets the shorter bullet had an OAL of 1.119 and the longer bullet had an OAL of 1.126. So I say to myself, ok, if the bullets themselves are of two lengths then perhaps that is the problem (the 0.007 difference instead of 0.005 is within the tolerances of the calipers).
BUT.. then I say to myself, the die should seat the bullet to the same depth, so wouldn't that mean the OAL would stay the same but the longer bullet would be taking up more space inside the case? (Correct me if I am wrong).
Then I looked at the cases, I'm using once fired that I bought from the local range so a mixed bag. Turns out some of the brass is about 0.839" whereas others are 0.845". Ureka I say to myself (but now I have to figure out if my downloaded rounds will still cycle the action on my Glock 22 with a slightly longer OAL). My only concern at that point is that there is no ryme or reason to the differing lengths, some brass from the same manufacturer is different lengths. Sooo, I just finished taking all of the dies out, inspecting them, re-installing, tightening, calibrating, etc. The first few rounds came out identical so I rattle off 20 and measure them all. Sure enough there is still a range, now from 1.117 to 1.125 (I adjusted the dies down a tiny smidgen on purpose so that accounts for the deeper seating of the bullet).
The only thing I can think of at this point is I have a bunch of brass that is different lengths and that is accounting for the different OAL. Does that make sense?
Second question... do you guys worry about a difference in OAL of (rounding up) 0.010 on a .40 S&W? I'm not asking so much in terms of will it fit the chamber, it is all within the recommended OAL, I'm wondering more about a difference of 0.010 in terms of available volume and as a result pressure.
Last edited:
96Brigadier,
I've experienced the same thing before. You may not actually have much of a problem at all. For best accuracy you want a consistant 'jump' for the bullet from the case to where it catches the rifling. Your seating die tries to help with this by actually pressing on the bullet close to where the ogive will touch the rifling. Some jacketed bullets vary as much as you're talking about on the shape of the ogive since some manufacturers use 2 or 3 machines in parallel to produce the same lot of bullets.
After much frustration I've adopted the following procedure.
1. take an unprimed case and split the neck down through the shoulder with a dremel tool.
2. hand seat a bullet in this case as long as you can.
3. insert the bullet into the chamber of your rifle and carefully close the bolt.
4. very carefully open the bolt. you need to hold the case straight with your finger so the ejector doesn't drag the bullet against the side.
5. measure the overall length of the dummy cartridge. This is the OAL with that bullet and rifle that will be just touching the rifling.
6. repeat steps 2-5 several times and calculate an average length (use the same bullet). Then calculate the OAL you want - usually 0.015 in shorter than the length that will touch the rifling.
7. now very carefully set up your seating die so that with the same bullet you used for your measurements above it seats to the length you want.
8. now seat all of your bullets without worrying too much about the variance in OAL since the critical length which is from the bolt face to where the ogive engages the rifle will be fairly consistant.
This works well for me anyway.
I've experienced the same thing before. You may not actually have much of a problem at all. For best accuracy you want a consistant 'jump' for the bullet from the case to where it catches the rifling. Your seating die tries to help with this by actually pressing on the bullet close to where the ogive will touch the rifling. Some jacketed bullets vary as much as you're talking about on the shape of the ogive since some manufacturers use 2 or 3 machines in parallel to produce the same lot of bullets.
After much frustration I've adopted the following procedure.
1. take an unprimed case and split the neck down through the shoulder with a dremel tool.
2. hand seat a bullet in this case as long as you can.
3. insert the bullet into the chamber of your rifle and carefully close the bolt.
4. very carefully open the bolt. you need to hold the case straight with your finger so the ejector doesn't drag the bullet against the side.
5. measure the overall length of the dummy cartridge. This is the OAL with that bullet and rifle that will be just touching the rifling.
6. repeat steps 2-5 several times and calculate an average length (use the same bullet). Then calculate the OAL you want - usually 0.015 in shorter than the length that will touch the rifling.
7. now very carefully set up your seating die so that with the same bullet you used for your measurements above it seats to the length you want.
8. now seat all of your bullets without worrying too much about the variance in OAL since the critical length which is from the bolt face to where the ogive engages the rifle will be fairly consistant.
This works well for me anyway.
