Home Forums Reloading Big Game Rifles Loading COAL to mag box length

As a complete newb to the reloading game, I have a million questions but here is one: my COAL is going to be limited by my magazine length on a couple rifles (for my tikka .308 I just happen to have a m+ as my spare mag). How much should I back off of max allowable magazine length in order to keep recoil and general hunting abuse from rubbing polymer tips raw? FYI I’m loading 270 and 300 win mag. Thanks!!

I would just make them fit the mag and go with it.

You need to find out what your Coal is with the bullet seated just touching your lands and grooves to make sure your not jammed when seating to mag length. If mag length is shorter than start at mag length. If mag length is not shorter start 20 thousands off the lands and grooves. Just make sure your bullet is NOT JAMMED

Sorry guess I should have given more detail. I found my max coal at the lands with a Hornady oal gauge. BTW those must take a terribly long time to get the hang of. Getting repeat measurements is a pain. On my M70 300wm, my mag box is a good bit shorter thus limiting my allowable length. I’m slightly concerned about loading them tight in the box and recoil either damaging the tip or slightly seating the bullets further. Is this worth worrying about or should I just load them so they feed well and forget about it?

Load them so they feed well and forget about it

First off, you need to know where your lands are in relation to your loads. You can't always go by mag box length and in a Tikka, that is especially true if you are running a M+. You will be jamming the bullet into the lands if you load to mag box length. My best suggestion is to open a load manual to the section that shows you how to find your lands. Back off the lands by .020", if it is a hunting rifle/load and start working up, find OCW and a good accurate load and rock on. The more consistent you keep things, the better your loads are going to be. Don't "just load them to fit the mag and go with it", like someone else said. That is very poor advice..

If you want a number, try .010" under mag capacity. Stuff the mag full of these and test their feeding by cycling the bolt rapidly with the rifle pointed in a safe direction as you feed and eject them all. If it isn't smooth or there's any binding, bump them in to .020 under. Repeat until reliable.

This^^^

.01 shy of absolute mag box length should work.

My tikka 308 has a long action bolt stop and I too use both my stock mag and the M Mag. When I load for mine, I load to 2.830", which is about .005" shorter than the original stock mag for the 308. When I load the 130 ttsx for my 308, I do this because my 2 sons have Rem 700 308 and the load shots great in there's also. So By going just under mag length, I'm able to load for 3 rifles.

Now when I load up some 155 lapua scenars, I load specifically for my tikka. Swap out the mag and load them longer. COAL on the 155 scenars are 2.888" on my Tikka. So the M mag allows me to get closer to the lands.

Also, on the 130 ttsx, which is a ballistic tip, I made 3 dummy rounds at 2.830". Put them in the mag and cycles them as fast as I could to see if they would hang up. Cycled fine. Don't get caught up is "rubbing" the tips off the bullets. If they don't cycle in the field when you need them, kinda makes it pointless.

If limited by the mag box length after establishing the length to lands, I usually go somewhere around 0.015 - 0.020" shorter than what touches the front of the box. Some bullets might have the occasional misshapen nose that could hang up if the tolerance is much tighter than that.

Has anyone used AA powders with 250gr .35 whelen?

Hope I'm posting in the right forum.

I usually seat about .060 short of mag box.I want to make sure I have no feeding problems.

There have been a lot of articles and studies that say deformed tips on bullets do not affect accuracy.Sorry I cannot remember the source, but I have never worried about in a hunting round.

If you want to check deform some tips and compare them to non defomed.

You're in the right forum, but you're better off starting a new thread for that question. That way more people with knowledge will see it and it won't distract from the original thread topic.

The "M" magazine is just the regular 308, 22-250, 243 win, 7mm-08 magazine. Basically the standard size for those cartridges. The "M" actually stands for medium (for medium length cartridges) according to Tikka. The OP has a "M+" magazine. I'd suggest he only uses that magazine and find out where those lands are for each bullet he will be loading up. Here's the OAL's for some bullets I use in my Tikka 308 Winchester:


In my rifle, it pays to use the M+ magazine because I load some quite a bit longer than what the M magazine will allow. The internal length of the M magazine is approx. 2.835", if I remember right. The internal length of the M+ magazine is right around 2.975", which is quite a difference. The M+ magazine is what comes from the factory for the 6.5 creedmoor rifles, but works very well with the 7mm08 and 308, if you need more length to get closer to the lands. Just be sure you don't need to modify your bolt stop. Sometimes you may have to. Especially on the older T3's. Today I was working on some loads with the 168 SMK bullets in my 308 win and I load those .020" off the lands:


That means I load them to 2.900" OAL, which is way too long for a factory 308 win mag medium (M) magazine. The op has the perfect magazine for his 308, if he needs to load long. I'd not worry about how long to load in relation to the magazine as much as I'd worry about where that bullet is in relation to the lands, as long as there is enough clearance in the magazine. In a hunting rifle, you always want clearance so your loads are reliable. I like .020" off the lands, typically with all of the C&C and controlled expansion hunting bullets I use. Even with most match grade bullets, I will load them at .020" off and find an accurate load. The group shape and dispersion will tell me if I need to load them shorter. Also, the OP is worried about the poly tip being damaged in the magazine. That is a non issue..

I screwed up BSA, it is M+

BSA I have found the lands and dropped back .020” on my loads. For my Tikka in 308 I had to swap to the m+ mag to accommodate my coal which was 2.888 using 165gr Sierra TGKs if I remember correctly. It fits great with plenty of room. My model 70s are where my mag length is a few hundredths less than my lands less .02” measurements. I can’t easily swap mag boxes on those like I can on my tikka, so I have to load short.

Lets address the issue one at a time. I know your mag box is a M+. Go back and read my previous post, if you have to. Furthermore, I will say this again. DO NOT load to that mag box length like someone else suggested. You'll be in your lands big time. As I would be with my 308 win. See picture of my OAL data. There may have been some miscommunication going on there? Also, good luck with that unnecessary Hornady tool. Those are unnecessary and cumbersome. Basically a waste of money. Like I said, go to the load manuals. Some will walk you through the steps needed for finding your lands. Soot the bullet and learn the proper way to do this. Doesn't require the use of any tools, just a piece of once fired brass from your rifle. Proper handloading does not have to be overcomplicated with unnecessary tools.

Now on to your next dilemma regarding your Winchester model 70 mag box:

You can very easily swap out your magazine box on a winchester model 70. Let me walk you through this with some pictures. Yours is s 300wm right? It uses the same magazine box as what my 7mm rem mag uses. If it has the hinged floorplate:


It has that little spacer in it to impede loading long. Now, what you need is a longer internal length, which a 300WBY magazine box has. The 375 H&H also uses this box, which measures approximately 3.600" on the inside:


To show the differences easier, I went with the stainless box on the 7mm Rem mag and the blued one is the H&H length box. This pic shows that the H&H box slips right into the stainless 7mm rem mag action and functions very well. No bolt stop mod was required either, so it is a win win. Your bolt stop may or may not need to be shortened. You won't know until you try it:


At roughly 3.600", you should have no issues getting closer to the lands. Problem solved and I'll bet you can wring a little more precision out of your model 70 300wm. That's what I'd do, if it were an issue.

BSA thanks for the detailed responses. You and I were communicating in the same page, I just added some responses/clarification for other replies to that same paragraph. Sorry for any confusion. And yes I agree - the Hornady gauge is a total waste of money. I have very little confidence in my coal measurements to date using that thing. I’ve seen reference to the soot method, but it’s not in any of my loading manuals (but I only have two). I’ll do some google/YouTube/24hc research and check that out before I go searching for potentially unnecessary mag boxes. Thanks again for your help.

Yes, starting with Dr. Mann over a century ago. Bases affect accuracy far more than tips.