too much chamfer= bullet setback?

[ffgats]

Greetings,

I got my new Giraurd case trimmer( 223) and want to ask you If I overdid my chamfering. , With my old die set up I never had a problem(bullet setback) with my finish ammo and nothing was change except that this time I was using my new trimmer. No crimping was done before to my rounds, I know that crimping will not do anything on the neck tension. If I may add, my OAL for the 155 gr. is around 2.244, could this be might be culprint for the setback? its seated a liitle bit long? ,WFT was used before my Giraurd.

thanks

by the way my( MIX) case ID averages 202-203, OD- 242-243

Edited February 3, 2014 by ffgats

[dauntedfuture]

Chamfer has nothing to do with set back. 155 is quire heave for .224 bullets. I doubt that your inside diameter is .202 or .203, you would not be able to get the bullets in there. In general the OD on your loaded ammo is .224+ 2x the neck wall thickness. You size the brass so its about .002-.004 under size for a SEMI AUTO, so that's .220-.222. With a Bolt gun you can get away with .001 under if you like. Crimping does effect neck tension, it adds to it. Pull a bullet with and without crimp and you will see that crimp=more.

[Hi-Power Jack]

, my OAL for the 155 gr. is around 2.244,

I'm guessing that should be a 55 gr bullet, not a 155 grain bullet??

[ffgats]

sorry gents. its 55gr.

I reduced my OAL to 2.200 from 2.244 and with luck the setback was eliminated. just a side question what kind of force do you apply for the thumb check, I almost use my whole upper body weight. thanks

[dmshozer1]

sorry gents. its 55gr.

I reduced my OAL to 2.200 from 2.244 and with luck the setback was eliminated. just a side question what kind of force do you apply for the thumb check, I almost use my whole upper body weight. thanks

Load some rds. Measure over all length. Put one rd. in a mag. Put the mag in your gun with the bolt locked back. Hit the release to chamber the rd. Eject the rd. Measure it to see how much the bullet has set back. I allow .003 to allow for the tip of the bullet

to be deformed from hitting the feed ramp.

Works for me.

[Alaskapopo]

Chamfer has nothing to do with set back. 155 is quire heave for .224 bullets. I doubt that your inside diameter is .202 or .203, you would not be able to get the bullets in there. In general the OD on your loaded ammo is .224+ 2x the neck wall thickness. You size the brass so its about .002-.004 under size for a SEMI AUTO, so that's .220-.222. With a Bolt gun you can get away with .001 under if you like. Crimping does effect neck tension, it adds to it. Pull a bullet with and without crimp and you will see that crimp=more.

Too much crimping can reduce neck tension. I no longer crimp and I have better results now than when I did crimp with regards to accuracy and bullet set back. What was happening is I would apply (too much crimp knowing that now) The crimp was at the cannular and the bullet would move back and forth on the cannular. Now that I stopped crimping they are all firm and don't budge.

Pat

Edited February 7, 2014 by Alaskapopo

[ffgats]

The SAAMI specs for the 223 rem from the base to the shoulder 1.438, some of the factory rounds I measured at 1.442. I am bumping shoulder of my brass to 1.445 using Sinclair bump gage and thats when I experiend some set back if I set the OAL 2.244 BUT they are fine when seated at 2.200( 55gr.Hornady BT with cann). would it be a good idea to follow the SAAMI SHOULDER lenght?

As mentioned before it all started when I was using my new Giraurd trimmer.

[Doc Hunter]

The Giraurd trimmer sets its length based on the shoulder. So differences in shoulder set back, will effect trim length, unless you reset the trimmer die.