Started reloading 357 mag. I’m getting some pretty big differences in my OAL. I would think it has to be the bullets since my die isn’t getting adjusted but I’m going for 1.590 according to my manual but they are coming out 1.580-1.6. I have never had that much variation with any bullet in any caliber. I have shot Missouri bullets for awhile now in 9mm and 45 ACP and I might get .003 differences occasionally from bullet differences in OAL. With these being shot in in a revolver I wouldn’t think it would be a problem as long as they fit in the cylinder right? These are very light loads for 357 mag. I’m not worried about high pressures at all. These are brand new dies that I took apart and cleaned before setting up. Could something in the die being doing this or just variations in the bullet? All the finished bullets look fine and crimp is in the cannelure. Just don’t understand why such a big difference. These are 158 LSWC from Missouri bullets.
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357 Mag OAL
- Thread starter ECM4
- Start date
NoSecondBest
New member
First of all, they won't hurt a thing as long as the cylinder rotates without binding. They are a light load. Second, you may not have the right seating plug in the die for the bullet you're using. Each die comes with a plug for flat topped bullets and another plug for more "pointed/rounded" bullets. Your LSWC should be using a flat seating plug. You may have some lube on top of the bullet or on your verniers giving you variation in measurement. Also, the bullets may not be "flat" on top...they might have some variation. Lead bullets aren't always perfect in form. If you clean your dies out and try some jacketed bullets and they don't have this much variation, you'll know it's the bullets and/or bullet lube.
What press? What dies? What bullets?
Basically, I would check for:
Press flex - some presses just flex. This is a lot of variation for flex alone.
Dies - RCBS seating dies have given me way too much variation. I just wish I had spent more time diagnosing why. When clean, they were fine, but as lube built up, then seating depth would vary.
Neck Tension - sometimes bullets are too small, powder or air pressure push back when seating, then you get variation, burst neck tension should not allow this. Old cases with a lot of shots on them can do this. Some cases are thinner or don’t size as well.
Basically, I would check for:
Press flex - some presses just flex. This is a lot of variation for flex alone.
Dies - RCBS seating dies have given me way too much variation. I just wish I had spent more time diagnosing why. When clean, they were fine, but as lube built up, then seating depth would vary.
Neck Tension - sometimes bullets are too small, powder or air pressure push back when seating, then you get variation, burst neck tension should not allow this. Old cases with a lot of shots on them can do this. Some cases are thinner or don’t size as well.
Old_School
New member
I'm with @NoSecondBest. Seating plug not matching the nose profile would be my first guess.
Also, are you seating & crimping simultaneously in the same die? Sometimes that can cause variations in depth.
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Also, are you seating & crimping simultaneously in the same die? Sometimes that can cause variations in depth.
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Jim Watson
New member
Seating plug vs nose is the leading suspect.
I would also look hard at the bullets, measure crimp groove to nose and see if they are all the same. Are the noses really all exactly the same shape?
The Magma machine caster runs eight double cavity molds, so there are 16 places for small differences in cavity to creep in.
Are you loading mixed brass?
Neck tension and press flex can generate differences.
I would also look hard at the bullets, measure crimp groove to nose and see if they are all the same. Are the noses really all exactly the same shape?
The Magma machine caster runs eight double cavity molds, so there are 16 places for small differences in cavity to creep in.
Are you loading mixed brass?
Neck tension and press flex can generate differences.
I’m using Hornady lock n load single stage press. I’m fairly positive I put the flat nose seating plug in the die. I will have to double check when I get home. I had them both out cleaning them. I may of put the wrong one in by mistake. All my brass in that batch was once fired Winchester brass. I’m also seating and crimping at the same time. Thanks for the responses on things to check. I will double check the plug.
buck460XVR
New member
Sometimes if you have tight neck tension, the soft nose of the bullet can be deformed when seating. Depending on the difference of neck tension between cases, the amount of deformation can be different, thus giving a difference of OAL. Mixed brass and brass of varying length will give a different amount of flare, which can contribute to a difference in neck tension. How many times the brass has been worked/reloaded can change the hardness of the brass, thus changing the amount of elasticity and the amount of neck tension.
As long as your crimp is ending up in the middle of the cannelure every time, your have the same amount of bullet in the case and the same amount of case capacity. Thus, a little variance in OAL due to bullet nose deformation, is not going to make a bit of difference.
As long as your crimp is ending up in the middle of the cannelure every time, your have the same amount of bullet in the case and the same amount of case capacity. Thus, a little variance in OAL due to bullet nose deformation, is not going to make a bit of difference.
Two thoughts come to mind:
First, LSWC bullets do leave a residue of lead shavings, and bullet lube in the seating die that needs to be cleaned out regularly. If you didn't flare your case mouths adequately, this can be a problem quickly. But a good flare, where there is zero scraping of the bullet's bore riding surface will eliminate much of the build up which equates to varying OAL's.
2nd: If you're loading from multiple head stamp brass, you might see a difference in case length between the various manufacturers. Hornady does load some of it's ammunition in .357 with under-length brass for example. When building up a load, I use only one brand of brass, preferably from one lot number. And I trim that brass to the same OAL with a Lee Cartridge trimmer chucked up in a drill press. This results in a uniform crimp, one of the essentials for accurate handgun ammunition.
HTH's Rod
First, LSWC bullets do leave a residue of lead shavings, and bullet lube in the seating die that needs to be cleaned out regularly. If you didn't flare your case mouths adequately, this can be a problem quickly. But a good flare, where there is zero scraping of the bullet's bore riding surface will eliminate much of the build up which equates to varying OAL's.
2nd: If you're loading from multiple head stamp brass, you might see a difference in case length between the various manufacturers. Hornady does load some of it's ammunition in .357 with under-length brass for example. When building up a load, I use only one brand of brass, preferably from one lot number. And I trim that brass to the same OAL with a Lee Cartridge trimmer chucked up in a drill press. This results in a uniform crimp, one of the essentials for accurate handgun ammunition.
HTH's Rod
FWIW; I have been reloading for revolvers since '69. I have seated 99% of the bullets I use to the crimp groove or cannelure and disregarded book OAL. I can't remember measuring any OAL dimensions, but maybe in the early '70s did so out of curiosity. As long as they fit the cylinder they are OK. Many of my handloads produced were very accurate as consistency is more important than book OAL.
I have found keeping the seating die clean of lube is a major consideration for consistent bullet seating (I don't have any lead shaving as I flare my cases and for some use a Lyman M die);...
I have found keeping the seating die clean of lube is a major consideration for consistent bullet seating (I don't have any lead shaving as I flare my cases and for some use a Lyman M die);...
I have seated 99% of the bullets I use to the crimp groove or cannelure and disregarded book OAL. As long as they fit the cylinder they are OK.
Yep!
Don