First loads

[Lucius Willson]

Ok, I posted on here a month ago or so about starting reloading. With the help of forum members here and taking an NRA reloading course I have reloaded my first rounds of 300 win mag.

After finishing following the manuals overall length of 3.340, the rounds look short. I measured the lads of my gun using a hornady overall length gauge with a modified case with my 195 gr Seirra Tipped MatchKing. Measuring this 5x and taking the average I found the average OAL to be 3.583 2.873 (using odrive).

My question is where should I set the length? Should I use the manuals specs of 3.340 or something shorter than the lands?

thanks

 

[sdneil]

Trust your tools...if doing right....book does not know your chamber

 

[spife7980]

If youre confident that you found the lands correctly and not actually a jam length you can start at them and work your way back.
If starting at the lands makes you longer than your magazine length then start at mag length.
Pressures will be highest when you have the bullet jammed into the lands and lessen as you back off of them. So if you start at them you can be more confident of your max charges and then work without worry. If you start off away from the lands and increase powder you need to be cognizant of the fact that you will be increasing pressures.

 

[Fotheringill]

Listen to the above.
Also, if you are not using the rounds in a semi or a bolt with a magazine, be aware that the OAL doesn't mean much, but the measurement from base to ogive means much more.

Good luck. Your nose is now down the opening of the rabbit hole. Don't fall in too quickly.

 

[Depart123]

Factory chambers in 300 winmag regularly have 0.25" jump or more to the lands from factory length. I load my 208 Amax to 3.420". In my chamber that leaves 0.050" to jump, which the 208 has no problem with.

 

[Lucius Willson]

If youre confident that you found the lands correctly and not actually a jam length you can start at them and work your way back.
If starting at the lands makes you longer than your magazine length then start at mag length.
Pressures will be highest when you have the bullet jammed into the lands and lessen as you back off of them. So if you start at them you can be more confident of your max charges and then work without worry. If you start off away from the lands and increase powder you need to be cognizant of the fact that you will be increasing pressures.

So what your saying is, When measured with a chronograph if the pressure is to high on the lands, the velocity will be a lot higher that what would be expected and I should back down?

 

[spife7980]

So what your saying is, When measured with a chronograph if the pressure is to high on the lands, the velocity will be a lot higher that what would be expected and I should back down?

Well sort of, a chronograph doesnt measure pressure, it measures velocity. Typically they are directly corrolated but you can have high pressure without high velocity depending on cartridge, powder, component and assembly. And not all chronographs can be counted on to be accurate either. So dont go off of those numbers to help you identify issues.

The way I picture it in my mind is that when you are off of the lands a bit there is a space for some pressure to escape around the bullet before it engages the lands and seals off the bore. Further back from the lands means you have more room that the pressure can escape through. So if you find a load off of the lands you are getting some leakage for lack of a better term. When you put the bullet up to the lands you eliminate some of that leakage and it could spike your pressures.

Work through your loads from low to high and keep an on your brass to check for signs that you are over pressure, primers flowing, the case flowing into the ejector hole, swipes etc. as you go to higher level charges.

Read this article and then read it again before you shoot https://www.primalrights.com/library/articles/understanding-pressure

 

[grovey]

I'm no pro, but the advice I see being given to you is this.....
If you're working up a load that you'll be feeding from a magazine ... in most cases your length will be dictated by available mag length and you'll be jumping to get to the lands. If you're just bench shooting, you can single feed the rds without being constructed to a certain mag length.

If you're single feeding THEN you have the option to load to or into the lands. With that option ( and if you plan on tweaking the load by moving the OAL ) you're better off starting with the bullet touching the lands and and shortening the OAL to find the sweet spot. Starting back say 0.25 from the lands with a warm load and then lengthening the OAL into the lands will raise the pressure and can create an overpressure situation.

 

[C.E.Smith043]

Ok, I posted on here a month ago or so about starting reloading. With the help of forum members here and taking an NRA reloading course I have reloaded my first rounds of 300 win mag.

After finishing following the manuals overall length of 3.340, the rounds look short. I measured the lads of my gun using a hornady overall length gauge with a modified case with my 195 gr Seirra Tipped MatchKing. Measuring this 5x and taking the average I found the average OAL to be 3.583 2.873 (using odrive).

My question is where should I set the length? Should I use the manuals specs of 3.340 or something shorter than the lands?

thanks

Personally, I would start where the book says to start and work out from there. One reason is, you know the book is a safe starting point. Often times, I find a good accurate load about .050" out from the book recommendation.

 

[joshb]

Be mindful that it's a balancing act. You can raise pressure by jamming. You can also raise pressure by pushing the bullet deeper in the case and, there by reducing case volume. I learned this with my 308 and a "warm" load in a Remington with a long throat. These days, I work up a load for "mag fed" rounds after I work up a load near or in the lands. When I find a good bullet/powder/primer combo, I reduce my powder charge by 10% and start a mag feed load work up. Also keep in mind that some bullets like to jump and some don't.

 

[barefooter56]

I'm no pro, but the advice I see being given to you is this.....
If you're working up a load that you'll be feeding from a magazine ... in most cases your length will be dictated by available mag length and you'll be jumping to get to the lands. If you're just bench shooting, you can single feed the rds without being constructed to a certain mag length.

If you're single feeding THEN you have the option to load to or into the lands. With that option ( and if you plan on tweaking the load by moving the OAL ) you're better off starting with the bullet touching the lands and and shortening the OAL to find the sweet spot. Starting back say 0.25 from the lands with a warm load and then lengthening the OAL into the lands will raise the pressure and can create an overpressure situation.

Grovey,
Read how bullet seating depth can affect cartridge case powder capacity, pressure , velocity and accuracy here:
http://www.bergerbullets.com/effect...coal-and-cartridge-base-to-ogive-cbto-part-1/
and
http://www.bergerbullets.com/effect...coal-and-cartridge-base-to-ogive-cbto-part-2/
This should help.
Take care,

 

[grovey]

Thanks . I'll look that over, but I feel I have a good grasp on how keep pressures in check myself. I usually start load development at 0.20 off for single fed rds myself. So far. I haven't had a load that got crazy good by jamming. Again... even though I'm confident in my loading skills I am still learning, and believe it will be that way for many yrs to come. Someone mentioned rabbit hole?

 

[Lucius Willson]

thanks everyone. I think I am going to start with 2.73 off of the odrive where touching the lands was 2.83 and go from there. I want to go back a little to ensure I wasn't jamming the lands.

 

[Rsadams]

Just FYI , Sierra said to back off the charge 2/10ths of a grain when useing matchking data for tipped matchking bullets and work back up because of more bearing area and they also don't like to jump like regular matchkings...

 

[chop house]

Be mindful that it's a balancing act. You can raise pressure by jamming. You can also raise pressure by pushing the bullet deeper in the case and, there by reducing case volume. I learned this with my 308 and a "warm" load in a Remington with a long throat. These days, I work up a load for "mag fed" rounds after I work up a load near or in the lands. When I find a good bullet/powder/primer combo, I reduce my powder charge by 10% and start a mag feed load work up. Also keep in mind that some bullets like to jump and some don't.

as josh says... you can mostly correlate this effect with the chrono readings. when on or into the lands the bullet start pressure is higher, then as the bullet is backed off the pressure drops, until the effect of reducing case capacity takes over.

there is a series of articles on the midsouth shooters supply blog about 'jump tolerant bullet designs' put together by glen zedeiker (sp?). the quick summary is that if you are limited by mag length even though you have a generous throat, there are some bullet geometries (ogives) known to be more tolerant of long jumps. iirc it has to do with the manner in which the ogive takes the rifling. so, of course it will also then depend on how the throat is cut or worn i suppose.