Need some reloading help

[Bigeclipse]

Just got a 28nosler with 26in barrel. I put a magnetospeed on it and chrono'd some factory Hornady eld which I'm getting what factory states. Now here's where I'm confused. I went to Nosler a load data since I'm using all their components 160 accubonds with Nosler brass. This is once fired brass mined you that I have resized and trimmed etc. I typically take the min and max loads and start in the middle (have done this dozens of times). Well today I go to shoot and straight away I notice some of the brass is chambering slightly hard but not crazy. I immediately thought maybe I was getting some jam so I rechecked my distance to lands and validated my loads are .020 shorter. So I decide I'll shoot. The first Shot felt stout to the shoulder and the velocity was the same velocity as the book max charge but remember I'm only half way at 79 grains. Now here is the odd thing, that slightly hard to chamber brass is no longer hard to chamber after being fired. No signs of pressure. No hard bolt lift no ejector marks. This is the round that was initially slightly hard to chamber and now the brass is no longer hard to chamber. I move to the next shot which is .2 grains higher and boom hard bolt lift and ejector mark. Still well below book max but velocity is now above book max. What's going on? Could the bullet somehow be jamming? I've double and triple checked seating depth.

 

[L.Sherm]

My guess is your bump is not consistent on the some hard to chambering sometimes it takes 3 times fired sometimes not to fully form with the chamber case in point, yesterday I was fireforming some 22PPC Norma brass that i necked down to 20 cal for my 20 Blitz(20PPCAI) and after the first firing i had to bump my shoulders .003 to get them to keep from chambering hard.
If your not doing the stripped bolt method to check for jam that could very well be you are jamming into the lands.

 

[Bigeclipse]

My guess is your bump is not consistent on the some hard to chambering sometimes it takes 3 times fired sometimes not to fully form with the chamber case in point, yesterday I was fireforming some 22PPC Norma brass that i necked down to 20 cal for my 20 Blitz(20PPCAI) and after the first firing i had to bump my shoulders .003 to get them to keep from chambering hard.
If your not doing the stripped bolt method to check for jam that could very well be you are jamming into the lands.

I'm using Hornady tools to check for jam (comparator and such). As for bumping the shoulder, I set the die to full size the brass. I couldn't add more bump if I wanted to...

 

[L.Sherm]

If you arent using a comparator or something to measure your just guessing even if your against the shell holder, I've got a shell holder right know that has .010 ground off the top just so my die will bump the shoulder back .002 other wise it wouldnt bump at all

 

[Bigeclipse]

If you arent using a comparator or something to measure your just guessing even if your against the shell holder, I've got a shell holder right know that has .010 ground off the top just so my die will bump the shoulder back .002 other wise it wouldnt bump at all

Good point. I do use comparators but I didn't check this time since I figured I would full length size as far as the die would go. If it is the shell holder being too tall for my reloads what do I do? I don't feel comfortable trying to grind shell holders.

 

[Bigeclipse]

If you arent using a comparator or something to measure your just guessing even if your against the shell holder, I've got a shell holder right know that has .010 ground off the top just so my die will bump the shoulder back .002 other wise it wouldnt bump at all

So let's say the shoulders were not set back as far as they should, they still were able to chamber though with a slight more bolt pressure. Would that cause the pressure signs and increased velocities compared to the Nosler loan book though? I feel like it shouldn't.

 

[L.Sherm]

Probably not unless your right on the edge of your load, but I do know one thing when you have a round that's hard to chamber it will cause a flyer especially vertical.

 

[L.Sherm]

Remember though load manuals are guides I've seen manuals vary max loads as much as 2 grains for the exact same cartridge.

 

[jdyoung]

I'm using Hornady tools to check for jam (comparator and such). As for bumping the shoulder, I set the die to full size the brass. I couldn't add more bump if I wanted to...

Are you using a standard modified case or a fire formed modified case to check seating depth with your Hornady comparator ?

 

[Bigeclipse]

Are you using a standard modified case or a fire formed modified case to check seating depth with your Hornady comparator ?

Standard but I also confirmed with numerous rounds chambering and they were making no marks on the bullets so I doubt they are jamming but I can set them back further another .020 to see.

 

[Bang4theBuck]

I think that it is possible that your necks are just a touch longer than the chamber. This would account for the hard bolt close, and puts a slight crimp on the bolt. This would drive up pressure, which drives up velocity. Also, it is possible for the case to shrink in length if it is tight on headspace dimension. As the case expands it 'bulges' slightly, and reduces the overall length.

This is pretty easy to check by taking the outside dimension of a case right at the tip of the neck, and then chamber it, and then take the measurement again. Could be a brass length issue, or potentially even the neck portion of the chamber is cut a little short. I would say that there is a better chance that it is the former, and not the latter.

 

[Bigeclipse]

I think that it is possible that your necks are just a touch longer than the chamber. This would account for the hard bolt close, and puts a slight crimp on the bolt. This would drive up pressure, which drives up velocity. Also, it is possible for the case to shrink in length if it is tight on headspace dimension. As the case expands it 'bulges' slightly, and reduces the overall length.

This is pretty easy to check by taking the outside dimension of a case right at the tip of the neck, and then chamber it, and then take the measurement again. Could be a brass length issue, or potentially even the neck portion of the chamber is cut a little short. I would say that there is a better chance that it is the former, and not the latter.

Thanks. I will check this as well.

 

[Jester560]

It is possible that you need a small base die to size all of the case. You can measure the case to see if it is oversize.

 

[Tiny Tim]

Good point. I do use comparators but I didn't check this time since I figured I would full length size as far as the die would go. If it is the shell holder being too tall for my reloads what do I do? I don't feel comfortable trying to grind shell holders.

Redding makes a set of shell holders pre-ground to accomplish this. Sometimes if it only needs a little more setback, more cam-over will do it. Was fire forming for 243AI and one lot of brass needed this to properly chamber.