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Posted: 5/21/2013 6:19:15 PM EDT
| What type of variance should I be expecting in OAL using a RCBS rock chucker? I'm loading up my second batch of .270 ladder tests after not blowing my face off with my first batch and I was just curious as to what you guys consider acceptable. I'm shooting for my max OAL of 3.25 and I'm getting 3.251- 3.2485. So what type of deviation is normal? |
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So, exqueeze as my math is sometimes in question but that's 0.003 variance ? That is easily accounted for in ogive to tip variance between bullets, not only is that about as good as it gets, to get any better you'd have to seat off the tip and you don't want to do that.
dc. |
| Ok thanks, this is my first adventure, and they shot well but since everything is about minimizing variance I thought I would ask. I was thinking it could be the polymer tip on the bullet, or even whether I put all 200lbs of sexiness behind the handle, or just 190. |
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I just loaded my first 10 rounds of 9mm - Rocky Mountain 124gr RN plated bullets in Winchester brass on a Hornady LnL AP. I'm getting larger variances than the OP however. These first 10 rounds vary from 1.150 to 1.1575 (1.150 was what I was shooting for). That's a variance of up to 0.0075. It's under the allowable max length of 1.169, but is that much variance OK? Is it typical for a progressive press? My goal is to reload for IDPA, so I don't need uber-match grade cartridges. My only real concern is - are variances this large safe?
All 10 rounds drop into my Lone Wolf 9mm barrel with a nice satisfying "clink" from the neck hitting the front of the chamber. -bob Edit - maybe I found the answer to one of my questions? In this thread, CBR900 said: Quoted:
OP: you want the LONGEST OAL that feeds in your gun without touching the rifling. Why? -longer OAL generally feeds better in many guns, including the Glock and 1911s (however, the 75 seems to be the exception here). -longer = lower pressure and that = safer, longer lasting brass, and easier on the gun -longer gives a slight safety advantage in the even of a bullet set back -longer generally means better accuracy To test, make up ONE dummy round (no powder or primer) and see how it feeds in your gun. Check to make sure the rifling does NOT touch. Load it in the mag with other rounds to make sure it won't bind up. So I'm guessing that means the variance is safe, so long as the rounds fall between my desired OAL of 1.150 and the max allowable OAL for 9mm. Is that correct? |
| OP, not sure if you understand how a rifle bullet is seated and why COAL varies, read this thread |
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As MCR suggested read, do some Internet searching, because there have been thousands of pages written on the subject over the years...on the lands vs off the lands, jumping vs jamming, is still a debate and many variables come into play...but jamming works, and so does jumping, depending....
Keep in mind that in general, not always, over all length (OAL) is used to represent diamensions that will fit into the mag and/or what will chamber, but is different than case overall length (COAL) Some othe things to consider: Shape of the bullet is very important because as the bearing surface of the bullet changes distance to the lands change Neck tension on the bullet can also change chamber pressure How does the gun head space Is the load a compressed load, is it close to max/min Again do some research and, Good shooting to ya.... FUBAR-6 Wounded Warrior Alumni |
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