.223 AR loads vs. Bolt rile load pressures ???


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10 Spot Terminator
November 8, 2012, 05:48 PM
Ok so here it is . I have loaded only for the .223 in a bolt rifle and would be the first to admit there must be more varying load data for this calibre than any other BY FAR . Enough to make you cross eyed and take double doses of Advil. I understand the the seperation of the 5.56 and .223, barrel twist rates and bullet weights they stabilize and so on, but what I need to have explained to me I guess are the guidlines for load pressures that determine a load for a given lets say an AR with a 1 in 8 twist and 20 inch barrel vs. a bolt rifle of the same configuration. I am speculating to get the AR to cycle the bolt a load would be increased slighly to equal the chamber pressure in a bolt rifle with a given powder and end up with an equal muzzle velocity ? I am asking this if anyone has seen this to be a factor of any real consiquence in load developement between the Black Rifles and bolt guns or will loads that are within pressure limits tend to perform fairly equal ( as a rule ) in both weapons ? Looking for personal expierience feedback here as I understand no 2 weapons will perform exactly alike due to a host of varaiances that can be present . There are literally thousands of load recipies available from powder manufauctures and on line these days , dozens of powders and even more bullets to pick from and Black rifle data seems to have gained the majority as of late. Understanding this should help to narrow down a persons initial powder selection and starting charge weights ( somewhat ) on a new load developement. In case you havent guessed this is what I am gearing up for once again and dont have an abundance of cash to just "buy em all an shoot em up". Look forward to your input here folks !

10 Spot

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steve4102
November 8, 2012, 06:55 PM
I am speculating to get the AR to cycle the bolt a load would be increased slighly to equal the chamber pressure in a bolt rifle with a given powder and end up with an equal muzzle velocity ?

Are you saying that the gas system in a semi-auto bleeds off pressures and will cause a reduction in velocity? To compensate for this a Semi-auto should require more powder to achieve the same velocities and a bolt action?

Not really. If it does, it's not enough for you to measure or calculate the powder increase to compensate for the gas system.

I ran a test in a Ruger Mini-30 a few years ago. I tested identical loads with the gas system shut off and with the gas system wide open. Velocities were virtually unchanged.

10 Spot Terminator
November 8, 2012, 10:09 PM
Thanks Steve,

That is exactly what I was looking for as I did not know if this was the case due to the fact I see some reload manuals ( such as Sierra , Lyman etc. ) seperating their load data between different firearms.So Pretty much ( in general ) loads for both a bolt rifle and a black rifle of equal barrel configurations should perform similarly, ( but maybe not exactly ) with a same load . Here again I understand no 2 weapons are exactly alike and may require fine tuning but you should be in the ball park. You were able to fire in both modes with the Mini 14 which removed any variables that might be encounterd passing a particular load between 2 seperate firearms. This just gives me a better starting point for a new load.

Thanks Again,
10 Spot

helotaxi
November 9, 2012, 08:38 AM
There are AR specific loads out there. Sierra has some in their manual. The difference isn't that you need a more powerful load, it's that you actually just want a slightly different load and it's one that is usually a little reduced or uses a slightly faster powder, accepting the tiny reduction in velocity that yields, to control gas port pressure.

The difference that you're looking at isn't going to make the load unsuitable for the bolt rifle in any way. It isn't centered around trying to get the AR to develop the same velocity as the bolt rifle either. It's all about making sure the AR functions reliably. Too much gas and the rifle can come out of battery a little early and it starts ripping the rims off of cases and leaving them in the chamber. Too little gas and the rifle short strokes and doesn't fully extract or eject or doesn't pick up the next round if it comes out of battery at all.

10 Spot Terminator
November 9, 2012, 11:58 AM
So helotaxi ,

If I am getting the jist of this then it seems that there is an upper and lower pressure limit one should be aware of for the AR and is why I see threads that speak of an AR bolt needing a buffer of some form as it appears to be slamming back harshly when fired. Must be cycling hot loads when this occurs. As I always cross check any and all printed load refferences between a couple different manuals before I start load work up this shouldnt be an issue for me but am glad you made me aware as I have been entertaining the idea of adding a nice black rifle to my mini armory in the not too distant future and will be careful with my loading for it . Thanks for the heads up.

10 Spot

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