Overall length question

[Pighunter]

When looking at reloading 300wm Data for Hodgdon H4350 powder with 150gn bullet it shows 69gns. of powder with the C.O.L. at 3.325 to 3.340, my Remington 700 300WM headspace measures 3.577 So I'm a little confused as to what length I should seat my bullets. I've only loaded handgun loads in the past, I'm finally working up some rifle loads and want to make sure I get it right.

[charlie b]

SAAMI spec oal is 3.34. Don't know what you mean by headspace here.

A way to determine seating depth is to seat a bullet out until it touches the lands and then reduce that oal by 0.020". Some magazines will not allow bullets to be seated that long. Book load data won't be accurate at that point either. The increase in case volume will decrease pressure and muzzle velocity.

[ShooterAZ]

Yep, length to fit the magazine will most likely be your limiting factor. It is for me in my Ruger M77 300WM.

[Pighunter]

SAAMI spec oal is 3.34. Don't know what you mean by headspace here.

A way to determine seating depth is to seat a bullet out until it touches the lands and then reduce that oal by 0.020". Some magazines will not allow bullets to be seated that long. Book load data won't be accurate at that point either. The increase in case volume will decrease pressure and muzzle velocity.

When I use the Lyman OAL gauge to check my headspace on my rifle I'm getting 3.5770

[Pighunter]

I guess I'm confused. I thought with a rifle you measure your headspace so that your bullet sits as close to the rifling as possible? In my case with my rifle is3.570 so I was going to start with a C.O.L. at 3.55 But the Data I'm reading gives the O.A.L. shorter then that??

[Pighunter]

SAAMI spec oal is 3.34. Don't know what you mean by headspace here.
Some magazines will not allow bullets to be seated that long. Book load data won't be accurate at that point either. The increase in case volume will decrease pressure and muzzle velocity.

So then what do you do? Do you go with the OAL the book gives are do you go with the longer length that you measured in your rifle?

[charlie b]

It depends. Sometimes I load the longer length. If I do I might tweak the load and I might not (usually not). An example is my .223. Book oal is 2.25 and I load to 2.28 without changing the powder charge.

Headspace is usually defined as how to set the breech of the rifle, ie, how far to run the chamber reamer. It does not usually have anything to do with how far out a bullet is seated. Since I have no idea what a Lyman headspace tool does I am of no help there.

Do you mean overall length instead of headspace? If so your question makes more sense.

And yes, most of the time seating a bullet closer to the lands is better for accuracy. But, seating the bullet so it engages the lands can raise pressures significantly and should be avoided unless you know what you are doing.

PS FYI, if you seat as far out as possible, each bullet you use will have a different OAL based on the shape. So each time you change bullets you need to determine your oal all over again.

[Pighunter]

It depends. Sometimes I load the longer length. If I do I might tweak the load and I might not (usually not). An example is my .223. Book oal is 2.25 and I load to 2.28 without changing the powder charge.

Headspace is usually defined as how to set the breech of the rifle, ie, how far to run the chamber reamer. It does not usually have anything to do with how far out a bullet is seated. Since I have no idea what a Lyman headspace tool does I am of no help there.

Do you mean overall length instead of headspace? If so your question makes more sense.

And yes, most of the time seating a bullet closer to the lands is better for accuracy. But, seating the bullet so it engages the lands can raise pressures significantly and should be avoided unless you know what you are doing.

PS FYI, if you seat as far out as possible, each bullet you use will have a different OAL based on the shape. So each time you change bullets you need to determine your oal all over again.

Yes I mean OAL. Thank you
I've only loaded 41 mag. this is my first at loading rifle cartridges, I always made my revolver loads at the recommended OAL, with the rifle load I was confusing myself. I made 20 300wm rounds yesterday. 4 sets of 5 with different OAL and different powder and bullet weights. I loaded up 10 with OAL at 20 thousands short of my rifling and 10 at the suggested OAL. I'm going to the range tomorrow. Thank you for your help, I was confusing myself. I kept think I had to go by the OAL listed on the DATA sheets.

[charlie b]

You're welcome and glad I could help. The only caution...never load a cartridge shorter than the data sheet.

Good luck with your loading.

[Bazoo]

Personally, I'd try loading to suggested length first. That gets you sort of a base with a new cartridge and gun. Sometimes the best accuracy is found with a shorter length.

[charlie b]

He is doing both so he can see which is better.

I have done both and I get better accuracy seating closer to the lands. Not by much, and not significant for a hunting rifle.

That brings up another factor. If for hunting or other field use I would not seat that close to the lands. All it would take is one cartridge with a bullet not fully seated to jam up your rifle. I have had that happen at the range. I'd not want to have it happen in the field.

[Wayne Smith]

Yes I mean OAL. Thank you
I've only loaded 41 mag. this is my first at loading rifle cartridges, I always made my revolver loads at the recommended OAL, with the rifle load I was confusing myself. I made 20 300wm rounds yesterday. 4 sets of 5 with different OAL and different powder and bullet weights. I loaded up 10 with OAL at 20 thousands short of my rifling and 10 at the suggested OAL. I'm going to the range tomorrow. Thank you for your help, I was confusing myself. I kept think I had to go by the OAL listed on the DATA sheets.

You are still confusing yourself. If you have a different result you have no idea what caused it if you have different loads, different bullets, and different OAL's. Change only one thing at a time. Settle on a load, if you have accidentally stumbled on an accurate one, and then systematically start changing one thing at a time, powder charge, primer, bullet or OAL, but only one at a time. Shoot ten shot groups and see if the one change improved accuracy or made it worse. Then change one other thing, shoot ten shot groups, and see what happened. now you know the cause and can begin to draw some conclusions about your rifle.

Yes, it takes time, money and effort. It is worth it to most of us.

[Pighunter]

You are still confusing yourself. If you have a different result you have no idea what caused it if you have different loads, different bullets, and different OAL's. Change only one thing at a time. Settle on a load, if you have accidentally stumbled on an accurate one, and then systematically start changing one thing at a time, powder charge, primer, bullet or OAL, but only one at a time. Shoot ten shot groups and see if the one change improved accuracy or made it worse. Then change one other thing, shoot ten shot groups, and see what happened. now you know the cause and can begin to draw some conclusions about your rifle.

Yes, it takes time, money and effort. It is worth it to most of us.

I think your making a lot of sense. I'm going back to the drawing board. Yesterdays range trip was not exactly as I would have hoped. The last time I fired my 300wm was about 8 months ago. I was shooting 2" groups of 3 @ 100 yards with factory loads. Yesterday I brought 5 150g BT PMC factory loads to warm up my rifle, first shot was 3' low. I have no idea how it got so far off. It took the 5 factory loads to get on paper about 3" low of the bullseye. I left it there and tried my 20 reloads.

First group of 5 rounds
Nosler 150g Ballistic tips
69g H4350
O.A.L. 3.55" 20 thousands from rifling
4 rounds were .62" with one flyer 1.64"

Second group of 5
same bullet as above
74gn. H4350
O.A.L. 3.55"
2.57" group

Third group of 5
Nosler 180gn. BT
62.1gn. H4350 powder
O.A.L. 3.34 (Recommended O.A.L)
5 rounds at 1.87" with 3 @ 1.02"

4th group of 5
nosler 180gn. BT
66.8gn. H4350
O.A.L. 3.34
5 rounds @ 1.87" 3 rounds @ 1.10"
I'm going to make up some loads all @ the recommended length see where that takes me.

[popper]

It took the 5 factory loads to get on paper about 3" low of the bullseye Presume your sights/scope was off. Sight the rifle with THE (best?) brand of factory ammo and leave it there! Shoot your loads. Use the factory stuff to verify OK before each season.
HS is from a shoulder datum line to case head but usually spec'd go/no go about 5-10 thous. and is set by your sizer die. Too much, case stretches and primers look flat. Too short and bolt doesn't always close.
Seating depth varies accuracy and pressure. Into the lands increases pressure but may help accuracy. Too deep increases pressure (effectively increasing powder charge - fill). Some loads like jumping into the lands, some don't - that you get to determine. Start with the book recommendations and adjust from there. Find a good load and stick with it! Change components when MANDITORY!
edit: if your loads shoot different POI, so what - leave the scope alone (for hunters)! If POI is different, just remember it.

[white eagle]

O/A can be different for each rifle
I set up my o/a to be .010 off the lands of the barrel
or if thats not possible to fit the mag of the rifle
book dimensions I use as a guide

[Wayne Smith]

You have promise with your first load. Make up 20 of those and shoot two ten shot groups. See if the load holds up. For me a flier is almost always me, not the gun! If it holds up, then start changing one thing at a time if it needs improvement. If not, you have your first load.