Home Forums Reloading Big Game Rifles 300 WinMag - Seating Depth/magazine length question

Not sure if this has been hashed over or not.

Anyhow, what is the deal with the contradicting lengths of the magazine OCL vs. the throated chambering of the 300 WinMag?

New to this round for reloading I'm coming into a dilemma where the max OCL for the magazine is .224 shorter than what I'm guaging with the Lock 'n' Load guage. Hence my bullets are having to make an (almost) 1/4" jump to get to the lands.

Is this normal behavior for rifle companies (mine, Ruger 77) to throat this round way out there, while restricted ultimately from the magazine well?

I'm going to dinker around with making .020 off the lands initial loads for first shot accuracy. (by the way, accuracy for this given rifle is minute of barn). Do any of you make a first round load development based off the lands measurements rather than books' OCL?

Thanks for any insight you may offer.


kcTbear

I load to the magazine limit. My rifle seems to be accurate enough without adding another troublesome variable like ammo of 2 diff lengths.
I believe the throating differential you are seeing to be pretty common. I have seen it in a Colt & a Rem 700.
On some hunts I am tickled to have remembered my hankie, knife & some bullets.

My Winchester model 70 .300 win mag is the same way. Long throated. It's not uncommon in magnums. Just load to a COAL about .010" to .015" less than max magazine length. If it's not shooting well then different powders and bullet weights are the way to find accuracy.

The one big thing to remember is it doesn't have to be loaded to however much off the lands for a load to be accurate. Weatherbys are long throated and can be extremely accurate. Same goes for other long throated magnums.

Don't get caught up in worrying about distance to the lands.

Agreeing with the 'fishes'...I've been able to get most rifles to shoot well within the magazine limits. That said, a couple of rifles seemed to shoot better with bullets close to the lands - different bullets will change the distance to the lands (while keeping same COAL) based on ogive shape. Speer Magtip or GrandSlams have blunt points compared to a TTSX or Accubond thus allowing the part of the bullet that engages the rifling to be closer to the rifling and reducing the 'jump'.

I have a BAR MKII safari. Dad has a Ruger M77. He got his rifle before i got mine. The loads we worked up for him wouldnt fit in my mag. I seated them deeper and they worked well. The velocities werent that different but the variances in velocity were more in my BAR than in his M77. Maybe comparing a bolt to an auto is like apples and oranges but I dont have any issues with hitting and killing game.

Going to sight in 2 in the morning.1 a browning single shot and the other a win bolt gun.I made some loads with what the nosler book said it should be,I'll let you know if it is a problem.
The load is 72.0grs of rl-17 with a 150gr accu-bond.If it will not shoot a group I will try next with the nosler part.

I have a ruger m77 MKII 300 win mag and seat most bullets off the lands by .020" and have no problem with the magazine length being too short. You've got me puzzled. Maybe I should measure my magazine length and see what it is. I'll post again after I do this.

My magazine length is 3.435" which is almost .100" longer than SAAMI maximum cartridge length. Seems odd that yours should be any different.If I loaded to just under or .015" less (as some have suggested) than the magazine length I'd have a bullet stuck in the lands and probably not even be able to close the bolt. Sounds like your freebore is a little too much.

Not that it matters, dads rifle is the stainless/synthetic. I do remember the COAL being quite long. I just called him and he said they were tight but not too long for magazine. We are shooting thursday so ill check them and measure his mag. Whats crazy is the mag on my BAR measures 3.360 and the loads, like i said before, wouldnt fit my mag but fit his rifle close but ok.

Whoa,

Every rifle is different. You will never find a post that I've made where I've said to just load to .010 or .015 less than magazine length for just any rifle. The OP said he couldn't reach the lands in HIS RIFLE. I've even made the point and argued the fact to measure the distance to the lands in YOUR rifle with each bullet to ensure that it doesn't contact the lands contrary to those that say don't worry about it.

Thanks for clarifying fishhead. The magazine length should be the same as my rifle though if it is a ruger m77 mkII. I'm still thinking the throat is way long, what do you think. I've also dealt with a 300 weatherby as some have suggested they are long throated and have ran into problems with a short magazine. I agree that you don't have to be right on the lands to get the best accuracy because my 300 wby was extremely accurate even with the bullet off the lands by .060" with some bullets.

Good point.
So far my experience has been 4"+ groups, hence my investigation and posting. I have only shot 2 loads with the experimental 1st shot loads that are .020 off the lands and groups have come down to a better, but still disappointing 2" grouping at 100yds.

One point I must make before providing numbers is that this rifle was my late uncles and will never be sold or traded, but I think that if skim bedding, pillar adding and modifications were made I'm sure that he would give the blessing for some accuracy improving adjustments. I have to work with what I've got, and would like to see this thing shoot.

Working with 180 Nosler e-Tips I'm getting a OCL of 3.599
Magazine depth as book reads is 3.340, though I have seated and seated until I've found that a OCL round of 3.355 would still be functional in the magazine.

This is a Ruger 77, tang safety. The MKII must have had some adjustments if the two series didn't change during their respective runs.

I appreciate all the help.....so, no one's every used a bolt action as a single shot before, in order to obtain the optimum consistancy of group loading? This isn't my only intent of this post, and do appreciate any points of optimism that is offered.

The only two rifles I've dealt with that had extremely long throats, where no matter what, you couldn't get close to the lands are my model 70 .300 win mag and my buddy's Weatherby Vanguard .300 wtby mag. His rifle shot lights out 3/4" groups all day long. No exaggeration on that at all. My model 70 will only do 1" and then with fliers an 1 1/2" at best.

I was commenting based on my endless reading of what others have found in long throated magnums. It is common. The longer throats and freebore are made that way to reduce pressure in stout loads and allow for any factory loads to never hit the lands no matter what the COAL is. There are exceptions though. Rifles are different.

Good luck kctbear, keep us posted if you come up with anything that gets that thing shooting a little better. Sorry to hear your magazine is so short too, the mkII's must be a little different. I know that every rifle is different, but here are my O.A.L'S for the nosler bullets for my MKII: 165 solid base and ballistic tip 3.360", 180 grain partition 3.360", 200 grain partiton 3.355", 200 grain accubond 3.370". Since the throat or freebore on your rifle seems long you should be safe using this type of O.A.L for your rifle and see if they function through your mag. Start trying different powders too, mine likes IMR4350 near max book listings. Hope this helps a little. BSA

Fish head, your absolutely corect. My 300wby was made on the 1917 enfield action and it was like most true weatherby magnums: It had the throat of linda lovelace but boy could she shoot!! I know on some of my loads I was about .060-.100" off the lands, but with that heavy barrel and those loads stoked up it would shoot like your budies. I remember shooting some 1/4 inch groups and consistantly shooting 3/4 inch groups, one right after the other!!! Why did I get rid of that thing. Oh well live and learn.

KcTbear,

I'll give you a starting point on loads for your .300 win mag. The first powder to start with is REL 22. That's probably, of course it's debatable, THE powder for a .300 win mag and 180 grain bullets. 75 to 76 grains is most often THE most accurate load based on my endless reading on the subject.

My best load, in MY rifle, has been 75.5 grains with a 180 gr Nosler Partition, WW brass that's PFLR sized to fit my chamber and a COAL of 3.360".

You'll get many other opinions about THE load for a .300 win mag, but this is as close as it gets to a go to load.

Thanks for the encouragement.
Concerning pressures, I'm a bit ignorant on the philosophy of where pressures are applied. I understand that a load developed on the lands creates much more pressures. How about the depth of the bullet into the brass? If the E-Tip is a long bullet for the such short neck of the .300 WM brass, 2/3 or better 3/4 of the bullet is inside the case. It's down passed the shoulders quite a bit inside. Does this not create unusual pressures that the exhaust of the powder has no direct line of exit? Or am I just way too over thinking this?

As far as powders and bullets, it's true, I've used a combination of Hornady 165g Interbond and Nosler E-Tip with either RL-22 or VihtVouri 165. That's it. Looks like I have a long way to go.

fish head, looks like we doubled up on the post. I maxed at 75g with the RL-22, not much luck there.

BSA, who's linda lovelace? :0 yes, that's what I thought.

I've got a 338-06 that won't even seat a 250g round nose bullet, still working on that one as well. No such accuracy either. But dang if I'll give up.

Over thinking? YES.

Try some inexpensive 180 gr. Hornady spire points. They work as well as the Noslers in my rifle and they were the bullet I loaded for my buddy's .300 wtby that were very accurate in his rifle.

One thing worth saying is, the most accurate handloads are not a cure for rifle problems.

Here's a good question.

How did you determine that you maxed out at 75 grains of REL 22 and what was the load? Specifics needed.