Think I learned something new or more of a realization turning into lots of questions. New bullets to try out. I was making some food for the AR. The speer bullets coal in the speer book is quite short compared to other bullets I have done in 55g. The trim length I do with casings and putting nosler btbt bullets on the canalure puts them .005-.008 back from coal. These speer bullets, no canalure but with crimp will work I know and is a whole topic but not what I am talking about. The 2.220 in the speer book made me stop loading cause of all the variables. They will shoot fine in the R700 BOLT. Here is what got me thinking though. If each bullet 55GRAIN has different length and ogive. Then ogive to base of thethe bullet length is different. Thereby affecting charge capacity which affects everything in conjunction with my measurement in a paticular rifle for ogive position to the lands and grooves. If this is affected than the void behind the base of the bullet and the powder charge is affected. So you can't just use the lands and grooves measurement or odrive number of a rifle for most bullets because they may not have a proper seating depth. This will only be answered by using the short coal speer gives or should I use my measurement to the lands to accurise the load? The powder charge is the same but I want to know and learn more. It seems you can get lucky just putting this match together. I just want to understand what the books I have don't get into. Thanks again to all you guys here.
seating depth canundrumm!
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The difference in case volume created by different 55gn bullet bases is tiny as a percentage of total case volume. Additionally, you should work up your load for every different bullet anyway. Finally, the engraving force typically determines the initial pressure spike, the deeper you seat the bullet, the lower the pressure (to a point) because the slight increase in pressure is more than offset by the inertia of the bullet overcoming the engraving force.
Unlike a pistol cartridge which uses fast powders and typically sees peak pressure before the bullet starts to move, rifle rounds and their slower powders don't reach peak pressure until the bullet is moving down the barrel. As a result, rifles aren't as sensitive to small changes in case volume like pistols are.
Unlike a pistol cartridge which uses fast powders and typically sees peak pressure before the bullet starts to move, rifle rounds and their slower powders don't reach peak pressure until the bullet is moving down the barrel. As a result, rifles aren't as sensitive to small changes in case volume like pistols are.
This is spot on and excellent advice.
I think you are over thinking all this OAL vs Pressure stuff for your AR. The OAL listed in manuals is nothing more than bit of trivial info that tells us what length they used in testing there data, it is not a minimum or a maximum. Some reloading manuals do not even list an OAL for their loads as it is that unimportant. What is important is that you find the correct OAL that works in your rifle. Here is what Western Powders has to say about handloads and OAL.
SPECIAL NOTE ON CARTRIDGE OVERALL LENGTH “COL”
It is important to note that the SAAMI “COL” values are for the firearms and ammunition manufacturers industry and must
be seen as a guideline only.
The individual reloader is free to adjust this dimension to suit their particular firearm-component-weapon combination.
This parameter is determined by various dimensions such as 1) magazine length (space), 2) freebore-lead dimensions of
the barrel, 3) ogive or profile of the projectile and 4) position of cannelure or crimp groove.
Finding the best OAL for an AR is simple.
First, it should fit into the Mag. That's 2.260 or less.
Second, it should have at least one diameter of bullet seated into the case. That is in a 223/5.56, .224 inches of bullet should be seated into the case. Of course this is only a "rule of thumb" and rules are made to be broken, but it's good place to start.
If you start with the longest OAL that will fit the mag and have .224" into the case adjusting OAL for accuracy is as simple as seating deeper and testing for accuracy. As stated above, seating deeper will reduce pressure not increase it.
That makes sense. I have an invite to go to Trapper Johns house and shoot some rifles and learn things I imagine also. Says he has tried to get almost every book on Reloading for his reloading room he could find. I will take some pictures. Thanks for the help.
FROGO207
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I typically start at max OAL and make sure it will feed in the firearm, then develop an accurate load, finally I will vary the length of bullet/propellant to see if accuracy is able to be improved upon anymore. No I do not crimp my bottle necked rounds unless for use in a tube feed type firearm. I have not found any accuracy improvements doing so if the correct neck tension is used anyway and is just a waste of my time IMHO.
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