cartridge overall length question


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lockmasteroz
October 4, 2011, 01:28 AM
So I must be a dip#%$@ or something, but I have a question about measuring my rifles chamber length. It is my understanding that .030-.070 off the lands is where I want my bullet to be in a loaded cartridge. If that is true then my C.O.A.L. is going to be excessively long. I have a Ruger M77 300 Win. mag. Can someone help explain what is right cause I feel like an idiot right about now. The load i'm making is 70gns IMR4831/Fed LRM primer and a Barnes 168grn TTSX. Please help i'm confused. Thanks Mike

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bigedp51
October 4, 2011, 02:24 AM
If your using your reloads for hunting big game then reliable function and chambering is your number one priority. Keep your ammo within normal lengths for function through the magazine. If your hunting varmints and are single loading your reloaded ammunition then experiment with bullet length.

Work up an accurate load and then try changing the seating depth, I say this because I have spent the last ten years shooting Enfield rifles that have throat errosion and seating depth is out of the question and has no effect.

If you had a brand new long throated Weatherby rifle you would never be able to touch the lands either.

KISS - keep it simple stupid and stop pulling your hair out and keep your reloads within factory limits.

gamestalker
October 4, 2011, 05:13 AM
In many high powered rifle cartridges the concept of working up an accurate load involves getting as close to the lands as possible among other necessary steps. However, the 300 Win. mag. is not as friendly in this regard because of the short neck. If you can get your OAL to within .010" of the lands without neck tension issues or magazine issues than go for it. If that can't be done with that rifle, than find the longest OAL that will facilitate neck tension and feeding needs.

Don't try to achieve this by not trimming your brass either or you will risk pinching at the mouth which drives pressures up unpredictably high. I know some reloaders who load the 300 Win. for single loading benching and some will just shoot it with weak neck tension just for the sake of accuracy. There is nothing wrong with this method but it isn't a reocmended hunting method for obvious reason.

rcmodel
October 4, 2011, 11:59 AM
It is my understanding that .030-.070 off the lands is where I want my bullet to be in a loaded cartridge. For hunting loads?
Load them to factory length.

Many of todays rifles have so much free-bore it is impossible to load to the lands, so don't bother trying.

If it will shoot good factory loads decently, it will shoot similar length handloads decently.

rc

Funshooter45
October 4, 2011, 12:29 PM
This whole idea is one of those things that some benchrest shooters do for optimal accuracy, so regular shooters figured it must be the thing to do also. Benchrest shooters will often jam the bullet into the lands, or just barely touch the lands, or back off 0.010" the lands, or whatever they have found to work for them. So naturally, a lot of folks have decided that 0.010" or 0.030" or 0.050" or some such figure is a magic seating depth.

Varying the seating depth can and will have an effect on accuracy, no doubt. But so will the amount of powder you use. They both have an effect and you can tune your load to your rifle using either or both methods. What I typically do is decide first what COAL I want. It might be industry factory standard length, or in a few cases I have taken the trouble to figure out what OAL I need to seat the bullet 0.010" off the lands. Whatever you decide, go through the OCW procedure of varying the powder weight in increments of 1% and shooting them in round robin fashion.

When you find the magic powder charge for your bullet/powder/OAL, then you might want to play with increasinig or decreasing the seating depth in small increments. Typically though the seating depth won't change the accuracy very much if you have found the right powder charge.

lockmasteroz
October 4, 2011, 05:41 PM
Thanks guys that did help alot. Its been shooting factory loads perfectly fine for quite some time now so why change. Thanks again Mike

redbullitt
October 4, 2011, 05:52 PM
Aint broke, dont fix : ) That said, I have a rifle that shoots great at standard length; it is fun to tinker though lol. It will shoot a bit better with longer loads, but I usually just use all standard so they can run in any other rifle.

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