rifle seating deapth

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litenite99

New member
i am venturing into hand loading for my AR-15 in .223 rem i have only to this point hand loaded for my handguns. i am aware that seating depth directly affects pressure in handguns does the same apply to rifles? my reason for this question is that i want to load .55 grain fmjbt bullets with cannalure and according to both of my manuals they require a trim to length of 1.750 and an overall length of 2.250. basically i cannot achieve the suggested lengths and still seat to the cannalure. when i trim the brass to 1.750 and seat to the cannalure my overall length is about 2.225 on average. anyone have any suggestions?
 
Unless you are crimping, I would disregard the cannelure. I normally load most of my AR loads to 2.260" to insure they function in the magazines and I can't load close to the lands with 5.56 chambers.

Rifles are slightly different than handgun loads. You would think that the longer the OAL the lower the peak pressure due to the increased case capacity. But with rifles, the jump before the bullet engages the lands also factors into the peak pressure. So it changes at different OAL's. There are some good curves showing peak pressure for various OAL and distance from lands. For the curves I have seen, around 0.050" off the lands is the lowest pressure, IF I remember correctly. But that was one load, one bullet, one rifle.
 
well honestly the reasoning i chose to seat to the cannalure is that i loaded some to the exact specs of the manual 10 to be exact and loaded them into the magazine and cycled the rifle 2 out of the 10 had the same issue the bullet pushed in a good ways so that immediately caught my attention. I'm not saying that i couldn't have been me or the way i have the dies set but that was the reasoning behind why i wanted to just seat to the cannalure.
 
2 out of the 10 had the same issue the bullet pushed in a good ways so that immediately caught my attention.
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bullets getting "shoved" into the case during chambering is a neck tension issue, not an OAL issue.

Feel free to seat to whatever OAL you choose, but I would expect the issue you are seeing to not be confined to any particular OAL.
 
i follow you on the neck tension any suggestions on how to fix? this is virgin brass winchester to be exact i don't know if that makes any difference. should i run it all through a sizing die? i measured it out of the box it was close to saami specs. or should i just put a bit more of a taper crimp on it and seat to a longer oal? opinions?
 
To check the amount of neck tension you currently have:

- run just the expander of your sizing die through the case neck on your new brass. This will make sure it is round.
- measure the neck OD, a micrometer with 0.0001" resolution is best, but calipers will work
- chamfer the inside of the case neck lightly
- seat a bullet to your normal seating depth
- measure the OD of the neck again

The difference between the 2 measurements is the neck tension.

The easiest way to increase neck tension is to reduce the expander OD. Pretty easy to do. Measure it first (accurately), then spin the decapping rod with the expander attached in a drill and use sand paper. They aren't that hard of steel and will sand down pretty quickly. Take off 0.001" and see if your bullets are still having set back during chambering.

The reason this works is the resizing die undersizes the neck OD during sizing (some by as much as 0.008"). Then the expander opens it back up. You just want to open it back up less. Make sure you use some sort of proper lube on the expander.
 
i did fl size the new brass that did take care of the neck tension problem only for me to realize how inconsitent the bullets i bought are. its always something! im going for and oal of 2.250 and my current oal is ranging from 2.240-2.265! its all over the place, i measured the bullets and found the problem. they are easly .15 off from one to the next:mad:. i know saami specs say for .223 that max oal is 2.260 so i guess i have some sorting to do. I deff am learning alot more since i moved into handloading for my rifles!
 
....seating depth .....pressure....like pistol
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Not really. I'm sure on some calibers it matters. My understanding is that seating depth is only a few 1000 psi.

It does affect accuracy...so, I would play with it. Your OAL sounds about right...55's are a bit short.

BTW, you don't have to crimp at the cannelure. I don't when it works to my advantage.
 
I believe sizing your brass has stretched it some which is why the bullets seem inconsistent. Measure all the brass now that it has been FL sized.
 
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