I have a new Montana 1999 375 H&H. I shot 14 rounds of factory ammo through it about a month ago then loaded some test rounds with three different powders. Yesterday I shot the 9 rounds of one powder then switched to another 9 rounds of a different powder. The first 6 rounds of the second powder did perfect then a misfire. I held for 10 seconds and no boom so I unloaded. The primer was dented but not as much as the ones that went off. I put another in and same result. I then unloaded the magazine and worked the bolt a few times and dry fired twice. I then put the third round of that load in and it fired. I then got the 6 rounds of factory ammo I had and fired all of them without a problem. On the last 6 I worked the bolt fast and easy and anything I could think that might replicate the problem.

I’m new to reloading. I’ve loaded maybe 200 rounds. Did I do something wrong or do I need to check something on the rifle?

Step 1, I think, would be to have the rifle ' s headspace checked. "Loose" headspace (this round headspace on the belt ) can cause what you experienced. Particularly with non belted rounds, over sizing the brass can induce a condition of excess or "loose" headspace which can and,will cause misfires. But if the headspace to the cartridge belt in your rifle is a bit long, this could be the cause.
Current wisdom regarding loading for belted rounds is to ignore the belt pretty much, and size the brass so that the round headspaces on the shoulder. Several discussions on this in this site and others.

Primers seated high?

Yes, if your primers are not dented as much as the factory ones then you have identified the issue but not the cause. It is one of three things; excessive headspace, . Weak mainspring, or too hard primers for that mainspring. It will be easy to isolate the root cause.
Working the bolt fast won't help. Belted mags have huge headspace allowances between ammo and chambers, so do what H47 said anyway.
You did nothing wrong.

Would neck sizing only on once fired brass solve the problem? This rifle will accompany me on a grizzly hunt next fall. I really don’t want this to happen in the field.

Don't over think it. It could be just a bad primer.

That would be one thing to try. I'm not too sure about the reliability of neck sized only brass for a grizzly hunt though....

If you get irregular primer indents on a belted magnum, it's the rifle. It headspaces on the belt and you can't alter that. Don't mess with it, send it back. If they argue on a DGR ring their necks.

Right; don't try to shotgun the symptoms with solutions until you know what the root problem is. Trouble shoot it systematically, one variable at a time, until you find out what is happening. As I said above; test those variables; don't just jump in and neck size, for example. You know that factory ammo works fine; how will neck sizing correct your hand loaded ammo?
Need to check the headspace first with gauges. Then use different primers.

Wes

Where are you going Grizzly hunting?

quote:

Originally posted by lindy2:
Wes

Where are you going Grizzly hunting?

Alaska. I’m going with Hurtle Creek Outfitters.

Don't know about your 1999 Kimber but 84M's have adjustable firing pin protrusion. You might check if all of your primers have slight indents and check the protrusion.
Also I had to replace the firing pin spring on my 84M. First rifle I have ever had to do that on. There are aftermarket springs available.
Good luck with the bear.

quote:

Originally posted by Blacktailer:
Don't know about your 1999 Kimber but 84M's have adjustable firing pin protrusion. You might check if all of your primers have slight indents and check the protrusion.
Also I had to replace the firing pin spring on my 84M. First rifle I have ever had to do that on. There are aftermarket springs available.
Good luck with the bear.

Wish it was a Kimber. This one is a Montana Rifle Company.

Wes

was the brass that you loaded yourself the same brass that you had fired in the gun as new brass or was it brass that came from someplace else.

Just trying to think of as many variables between the factory brass which has no problems and the reloaded brass which has problems. Can really be only one of two things. Problem with the brass or problem with the primers. And if the primers are being hit well on the factory stuff then I don't see how it could be a firing pin because you can seat a primer only so low. They only go so far. Seems like it has to be your reloaded brass moving around in that chamber.

quote:

Originally posted by lindy2:
Wes

was the brass that you loaded yourself the same brass that you had fired in the gun as new brass or was it brass that came from someplace else.

Just trying to think of as many variables between the factory brass which has no problems and the reloaded brass which has problems. Can really be only one of two things. Problem with the brass or problem with the primers. And if the primers are being hit well on the factory stuff then I don't see how it could be a firing pin because you can seat a primer only so low. They only go so far. Seems like it has to be your reloaded brass moving around in that chamber.

This was once fired brass (fired in another rifle) then full length resized. I know that because I did all that. I’m taking it to a smith I trust Tuesday to check headspace. Then I’ll go from there. If it’s a headspace issue I may order a new shilen barrel and have my smith install it. He has built me several rifles that I’ve had zero issues with.

Could have been some crap got into the bolt either slowing the fin fall down or limiting the travel until it worked its way out. The first thing I'd be doing is pulling the pin assembly out of the bolt and degreasing, then a light oil. Sometimes the factory will put grease in there on the spring and that is not going to do you any favors.

Gunsmith said headspace was ideal. Firing pin protrusion was perfect and spring seemed strong. He suggested that the primers may not have been seated well enough.

I think I would want the mainspring strong enough to fire the primers, even if they were not seated deep enough.

But I'm kinda funny that way !

Hard primers; what brand were they? Since it fired factory ammo, we know the rifle is ok. Probably. Nothing is absolute except those two things about which we won't speak.

Remington magnum primers.

I only shoot Remington magnum primers in my Model 70 375 H&H, they're not hard.

I'm betting that you are not seating the primers deep enough and causing the misfires.

Wellll on any belted case its a good idea to set the die a bit at a time resizing until the bolt closes snug on round entry, then back off a very small tad until it feeds easy but snug... Now your head spacing on the shoulder..Too many folks size on the belt and that's always a mistake IMO, as the belts are never the same size. its fine for factory ammo as they have no other choice and it usually works, but in many cases folks have the problem you describe with all belted cases.

In your case the headspace of the belt is allowing the firing pin to hit the primer then it pushing the case forward to contact the belt, by working off the shoulder you can usually solve any headspace problem is you following me as the case cannot move forward. The ones that fired for you set the rifles headspace in other words they got fireformed so just neck size them until they are too tight then set the shoulder back a tad.

Y0ur now working off the shoulder not the belt just like on a 06 or a .270 or any non belted case..I think this will fix your problem.

If the headspace is good and the spring is good, I second the idea of crud or a burr inside the bolt, then primer depth.

I'm going to bet you didn't get the primer seated properly on the round or rounds that didn't fire. If you try them again, they will likely fire since the first firing pin strike probably seated the primer.
Phil

Did you have an over load on any of the test rounds that you fired? An overload can blank a primer and a small disk of primer metal the diameter of the firing pin can go inside the bolt body and interfere with the forward movement of the firing pin and give the kind of problems you describe.

I always seat primers with my press and seat them solid, doesn't hurt to sensitize them somewhat when seating hard so the three (or sometimes 2) anvil legs that protrude slightly from the bottom of the cup are seated solid to the bottom of the primer pocket.

Don't know what speerchucker is thinking but Jim is on the money, of course you can size belt magnum cases to seat on the shoulder, in fact it is a well known reloaders ploy to do so. This takes out the slop of the cartridge in the chamber, aligning the case in the chamber and bullet to the bore and lengthens case life by limiting stretching.

Belt cases are a manufacturers quick way of achieving headspace on their ammo which almost always is then sloppy in the chamber. Using belted headspace gauges to say the headspace is okay only just duplicates the factory slop.
Have loaded a lot of belted cases and always partially sized so the bolt has a faint hint of drag when closing the bolt. Case life is a whole lot better even with top pressure loads.

quote:

Originally posted by eagle27:

Don't know what speerchucker is thinking .

I'd just put in a heavier mainspring and the problem would go away. It's magic dontchaknow.

Assuming that the firing pin protrusion and headspace is correct:

Yes, you can endeavor to seat every primer fully and perfectly every time. But in regular loading you are always going to have the odd soft seated primer. Even in factory fodder. You need to have a firing system that will developed enough energy to not only fire the primers, but also enough energy to seat a soft seated primer and still have enough energy remaining to still fire it. Nearly all rifles are designed to work around this problem. Put in a heavier firing pin or increase your mainspring strength and make it work.

It is true that some primers are slightly harder or thicker than others. When you build the machine to detonate these primers you want to build it powerful enough to detonate them all, RELIABLY. Blaming misfires on hard primers is simply admitting that the system that you built to detonate them is not strong enough. Nearly all rifles are designed to work around this problem. Put in a heavier firing pin or increase your mainspring strength and make it work.

Yes, you can work around any problem by modifying a system other than the problem system. Or you can simply correct the problem.

The problem with primers that are not seated fully is that despite good firing pin protrusion and a good spring (as it seems a gunsmith has said is the case with the OPs rifle) is that the primer will be dented but moves forward at the same time so the pin 'loses' protrusion. It is not as if the pin fully seats the primer first then fully dents it.
In most cases of primers that are not fully seated they fire the second time round as the pin has full protrusion to the anvil.

It is safe enough to decap live primers so this gives an idea of the general lack of sensitivity a primer has unless it is fully seated and sensitised. I seated one once that had half flipped and it just squashed up till I felt that something was wrong but it did not fire.

Absolutely no reason to not ever fully seat a primer if using a press with good firm pressure on the handle. I load Berdan primers too and use same technique to seat the primer 'cap' hard to the integral anvil in the primer pocket. Maybe with hand held primer seaters it is possible to tire. Need to get a grip

My bet is the mainspring. I have an MRC in 404 Jeffery and had the exact same issue. Factory ammo fired fine, handloads would misfire 75% of the time. My first thought was high primers. But I was seating them to the stops on my RCBS handprimer. I even switched shell holders a couple times but the problem persisted. I've been reloading a long time and have never had misfire due to a high primer so I didn't think that was the issue. And I miked the primers in my loads and factory and they were damn near identical.
Pin protrusion was good as well.
But when I dry fired the rifle and then dry fired another rifle right after, the "click" on the MRC was not as loud as on another, so I replaced the mainspring with a Wolff 32# and now it goes boom every time!

quote:

Originally posted by adamhunter:
My bet is the mainspring. I have an MRC in 404 Jeffery and had the exact same issue. Factory ammo fired fine, handloads would misfire 75% of the time. My first thought was high primers. But I was seating them to the stops on my RCBS handprimer. I even switched shell holders a couple times but the problem persisted. I've been reloading a long time and have never had misfire due to a high primer so I didn't think that was the issue. And I miked the primers in my loads and factory and they were damn near identical.
Pin protrusion was good as well.
But when I dry fired the rifle and then dry fired another rifle right after, the "click" on the MRC was not as loud as on another, so I replaced the mainspring with a Wolff 32# and now it goes boom every time!

Not much point in having a gun with a mainspring that is just barely powerful enough to fire certain ammo, when the moon is full, the stars are all in alignment and the dog is in heat, huh?

AMP that fawker up and go shoot the shit outta stuff ! ! ! ! !

quote:

Originally posted by speerchucker30x378:

quote:

Originally posted by adamhunter:
My bet is the mainspring. I have an MRC in 404 Jeffery and had the exact same issue. Factory ammo fired fine, handloads would misfire 75% of the time. My first thought was high primers. But I was seating them to the stops on my RCBS handprimer. I even switched shell holders a couple times but the problem persisted. I've been reloading a long time and have never had misfire due to a high primer so I didn't think that was the issue. And I miked the primers in my loads and factory and they were damn near identical.
Pin protrusion was good as well.
But when I dry fired the rifle and then dry fired another rifle right after, the "click" on the MRC was not as loud as on another, so I replaced the mainspring with a Wolff 32# and now it goes boom every time!

Not much point in having a gun with a mainspring that is just barely powerful enough to fire certain ammo, when the moon is full, the stars are all in alignment and the dog is in heat, huh?

AMP that fawker up and go shoot the shit outta stuff ! ! ! ! !

And by the way, I found your video of a Model 70 mainspring compression tool on Youtube. I don't have a mill but with a drill press, bench grinder and one of those round spark plug gap tools, I made my own version of yours. Worked well enough to change the spring that one time.