300 win mag accuracy

[Jon MB]

Hi
Having accuracy issues with this caliber
Been using 180g noslers
My other barrels all shoot very well
Very surprised
Any thoughts very welcome

[Rick - Mauser M03 Blog author]

Hi Jon. Thanks for posting. It sounds like you're an experienced reloader, with this Mauser M03 rifle system too. I've had a similar inaccuracy problem, with a particular factory load. My 30-06 barrel just didn't like the pressure profile from the factory's recipe. This was with Remington's 180gn Core Lokt load. However, when I developed hand loads using exactly the same projectiles I started getting hole-in-hole groups. So, nothing wrong with the bullet and the barrel. For the moment I think you can assume there's nothing wrong with your barrel and those Noslers. Ballistic Tips? I've always had good results with those, once dialled in. Keep in mind though, some barrels are easier to tune by using flat base bullets with boring looking noses, i.e. nothing fancy. Such as spire points like Partitions.

What powder(s) have you tried? Does varying powder charge influence accuracy? Seating depth? I'm sure you've got the basics like case length and headspace under control.

In a situation like this my first step is to try different powders. If the barrel looks gritty with unburnt residue I try a faster powder.

You might have to cart your reloading gear to the range or a farm on a calm morning and spend a morning working up loads to try. A 300 Win Mag barrel is on my wish list so I'm keen to see you get to a successful outcome.

Regards, Rick.

[Rick - Mauser M03 Blog author]

Jon. Another thought, beyond trying different powders, is to try a 185gn Berger Classic Hunter bullet. There's no particular reason why these should work better than an equivalent Nosler Ballistic Tip or Accubond bullet. It's simpy that I've had excellent results with all of the Berger bullets I've tried, in terms of accuracy and on-game performance. Further, the lack of plastic tip with these bullets makes them so much more durable in a magazine. Some of my Ballistic Tips end up with flat tips from banging into the front wall of a magazine, under recoil. I suggest the Classic Hunter bullets (there's also a 168gn in 30 cal) as their ogive is not as pointy as the VLD (Very Low Drag) bullets Berger also make. These VLDs are quite specialised and take a lot of tuning in terms of seating depth to get the best accuracy. They also tend to deliver their best grouping at long distances, moreso than at short distances like 100 or 200 meters. The Classic Hunters are just easier to deal with, including being less prone to jamming while feeding, or indeed, simply fitting into a magazine if seated right out there to be close to the lands. I'm not sure what country you're in (your original post's time of 12.31am (my time) suggests you're not in Australia!) but here in Oz the best (only?) source is BRT Shooters Supply.

Regards, Rick.

[Rick - Mauser M03 Blog author]

Here is the rest of the conversation, which slipped over to email halfway through. Posted here with Jon’s consent. :-) Slightly edited for clarity. Summary - Jon started getting better accuracy from his 300 Win Mag once the barrel screws were done up a bit tighter than before. Rick.

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Hi Rick.

Great suggestions and will look at 

I have used RL 17, 19, 22 and H1000

All with average performance

Bullets tried so far:

150 & 168g A max hornady - poor 2-4 inch MOA

180 g nosler accubond and partition - average 1.5-2 inch groups 

200 g lapua mega - working on!

Disappointing - my 270WSM and 308 shoot 0.5-0.75 MOA easily

Jon

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Hi Jon.

In some respects I envy you. Your laws on long arms sometimes look more sensible than ours. We can’t use sound moderators, for example. They’re thought of as ‘silencers’, which are only ever used by assassins! 

Wow, you’ve certainly tried a few combinations. I’ll be honest and say that I’ve not had results from handloads in the 2 to 4 MOA category. Always better than that. The Remington Core Lokt factory loads I mentioned were getting close to 2 MOA and I decided not to buy any more of those. :-|

A friend recently mentioned that his first shot after a barrel change was always about 4 to 5 inches higher than the subsequent shots. Like your 2 to 4 MOA, that was also outside of my experience so we compared notes on our barrel change procedures. He was tightening his just like the Mauser guys do on the videos, that is, not particularly tight. I said that I was tightening my barrel screws as hard as I could, though only using the Mauser tool, which obviously limits the torque that weak ol’ me can apply. But it was working for me. My friend decided to give my method a try and he saw better results from his first shots straight away. So this leads to the question - are you cranking down on those torx screws enough? I’m sure you’re doing the same with this barrel as your others, but perhaps the 300 Win Mag is the most powerful and is rattling slightly in the receiver? I reckon I’m putting about 6Nm onto my barrel screws. I know other M03 shooters who use torque screwdrivers to do them up to 9Nm. I think that could almost be too tight, but it’s working for them. I wouldn’t be able to get those undone with just the Mauser tool. As it is, I struggle to get my hand tightened screws undone. By the way, a good thing about the Mauser tool is that it sits nice and deeply in the screw heads, so is less likely to slip out compared with other torx drivers I’ve used.

Give this screw tightness idea some thought. Perhaps you have or could borrow a good torque driver, to run some tests.

Slight change of subject, on figuring out how the discussion forum software is working. Was your response done as a reply to the email you got from the forum? I see it was from your iPhone. Because, while I received an email with info on your testing, I can’t see these words on the forum. It looks like replying to the notification email results in a ‘private message’. I’m fine with proceeding that way, though I also see value for others to be able to follow or find our conversation. At some point I’ll ask if you’re OK with me copying our direct messages onto the forum. All the better for the chaps out there to learn from.

Regards, Rick.

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Be delighted Rick

I think the MO3 is a cracking gun and capable of superb accuracy but it can also be a little quirky !

Some of the twist rates are a little unusual 

Whatever I will continue trying to improve the load and will place on blog

Well done and please keep it going

My experience is with 308 win and 270 WSM and now 300 WM

Kind Regards

Jon

Hi Rick.

Good news 

Finally shot some decent groups (0.6-0.8 MOA) today with my 300 win mag:)

What made the difference?

Tightening barrel locks

Better brass (Norma)

....and 75g of RL 22

180g nosler

Thank you all for your advice

Jon