High Pressure Signs? 300WM

[Lew Hodge]

Check headspace; if it's too much the backslap can do this to primers, and worse. Get your hands on a case gauge and a dial indicator with an adapter, like the one sold by Mike Bellm, Mike Bellm's T/C website. Measure a factory case and then a once fired case. If there ia a substantial difference, you have too much headspace, possibly from a cartridge that's shorter than SAAMI minimum. If the bolt closes OK on a fired cartridge, the size of that fired case is close to what it should be for your gun. Headspace is not a measurement of the gun, but is determined by the length of the case from the case head to the shoulder, that you are shootng at the moment. Some case manufacturers seem to make short cases, (Lapua among others), probably for some dumb safety issue, lawyers, liabilities etc.??? Starting with a case that is short and rersizing it all the way will ruin case life, often causing early head separation. Otherwise, it's hard to measure headspace in a bolt gun. You could try plastigage, but it is a little hard to work with. If you are reloading fired cases and the headspace was excessive from the factory, resize, neck size, shoulder bump, only until you reduce the headspace to a mil or two. Feeler gauges against the bottom of the die will give you the control you might need.

 

[Bio]

Throat is the period of barrel from the chamber rounds neck to the full engagement of the rifling. If the rifling is at full engagement to soon you could have a pressure spike as the bullet is leaving the case.

 

[GONE BAD]

@Lew Hodge the headspace ,as I stated earlier, from bolt face to where the belt engages in the chamber is .003 clearance from bolt face to cartridge base.
The overall length of case to a data line on the shoulder is around. 008 +/- on new brass.

When I resized the 1× fired brass , from another rifle witch did fit in my chamber, I bumped the shoulder back .002. In reality, after I fired it seemed to be .006.
To much headspace ? I don't think so.

@Bio I did look at the leads in the barrel with a borescope and they seemed to be pretty abrupt. I'll make a modified case from a fired case from my chamber and try different bullet profiles and see if I can tell anything. Probably not but I'll see.
I'll check again with the borescope and take some pics.
Might just send it back to the manufacturer and let them figure it out?
Thanks

 

[GONE BAD]

Well here are two images taken with the borescope. Kinda hard to figure out (lack of depth and perception) but looks as though the leads are more of a bullnose shape than normal leads with a rake at a certain angle of degrees?

 

[918v]

What Bio is referring to is jump length. If the bullet is close to the lands the start pressure will be higher than if the bullet is farther away.

 

[GONE BAD]

@918v oh. Well there is a lot of jump.
I seat only to mag length . I can't remember the actual length but it's long

 

[OkieMike]

A lot of the problem is the Hornady brass.

This was a brand new Hornady 300WM case with 66.4 gr of Alliant PP 4000 MR and a 225 ELDM. Max listed charge was 67.6 so I was well under max. I didn't know it had ruptured until I went to turn the bolt and it was a bit sticky... I examined the other 4 cases with that charge and they were fine. Likely just a bad one... But it spooked me a bit.

I measured capacity in grains of H2O and Hornady held more water... So in my mind I assume their brass is a tad thinner at the web than the Federal and Winchester I compared it to.

Makes me a bit hesitant to use it anymore.

Mike

 

[918v]

A lot of the problem is the Hornady brass.

BS

 

[918v]

This was a brand new Hornady 300WM case with 66.4 gr of Alliant PP 4000 MR and a 225 ELDM. Max listed charge was 67.6 so I was well under max. I didn't know it had ruptured until I went to turn the bolt and it was a bit sticky... I examined the other 4 cases with that charge and they were fine. Likely just a bad one... But it spooked me a bit.

I measured capacity in grains of H2O and Hornady held more water... So in my mind I assume their brass is a tad thinner at the web than the Federal and Winchester I compared it to.

Makes me a bit hesitant to use it anymore.

Mike

That kind of failure can happen with any brand. Don’t be a brassophobe. For the most part American big4 brands produce good brass. If you want the very best you have to go with premium brands. I have never had this kind of failure but I shoot mostly range pickup which is factory loaded 1x fired brass. I think the QC is better on those than the ones sold as reloading components. Ultimately it is on you to look the case over before you load it.

 

[GONE BAD]

Yep I've seen some "hot " whitetail hunter ammo ,too . I just got done looking at load data from Hodgdon .....yep middle load.......I'd strap on the magneto and see what the 73 and 73.5 gr. loads are running.......and go from there..

Okay, I didn't shoot 73 and 73.5 again but I started at 68.4 and went up to 72.8 in increments of .4

2705 was lowest. At 72.8 highest was 3002.
I didn't see anything in my books or doing a search that showed that high of a velocity with a 200gr bullet in a 24" barrel.
There are no signs of pressure on any of the loads other than primers being flat.
The 73 and 73.5 probably were in the 3015 to 3040 range?

 

[GONE BAD]

Okay, just bringing this up again.
I'm still thinking that something is not right.
I posted earlier that my headspace was .003 from casehead to the belt but redoing the measurements I have come up with this number .005 and possibly .006.
Now bare with me here.
I don't think I'm getting a true headspace off the shoulder on 1x or even 2x brass?

It seems that , I'm just guessing here, the ejector is pushing the case forward to engage with the belt face to chamber face . So when the round is fired the primer blows back to the bolt face, then the case follows ? So now the case really doesn't fireform at the shoulder.
Kinda like a rimmed case has play between bolt and base of case.

So now I think the case is blown out to fit the chamber and I bump the shoulder back .002 and now I have somewhere between .002 and .007 off the shoulder data.

I know I'm probably not explaining this clearly or it may not even be a fact but the only experience I've had with this, until now, was with a TC Contender I had in the early 80's.
The only way I could produce really good fireform brass was to leave the COAL long so that the bullet engaged the lands and pushed the base of the cartridge back against the block leaving only one way for the case to expand and that was to the shoulder.

To test this theory, I'm going to neck size only and probably remove the ejector to get the case to seat up against the bolt face and run a little hoter load.

Does any of this sound feasible?
I'm definitely open for comments

 

[918v]

What’s the problem again? Flat primers? That’s not a problem.

 

[NH4X]

Okay, I didn't shoot 73 and 73.5 again but I started at 68.4 and went up to 72.8 in increments of .4

2705 was lowest. At 72.8 highest was 3002.
I didn't see anything in my books or doing a search that showed that high of a velocity with a 200gr bullet in a 24" barrel.
There are no signs of pressure on any of the loads other than primers being flat.
The 73 and 73.5 probably were in the 3015 to 3040 range?

Seeing the speed for a 200 gr bullet is at 3000 fps.........."I'd " call that a max load and nor worry about what numbers are in any data / reloading book.......you have your data

 

[Slides]

All the Hornady American gunner and eldx hunter factory ammo I have shot in my 6.5cm has left primers like that, not evidence of printing in case head or heavy bolt lift, nothing changed with water on a case either.

 

[GONE BAD]

Seeing the speed for a 200 gr bullet is at 3000 fps.........."I'd " call that a max load and nor worry about what numbers are in any data / reloading book.......you have your data

Yeah, that was also one of my concerns.
Think I'll look for a charge in the 2850 range and work on seating to tune the rifle.
This rifle is for strictly hunting of elk at distance.

Funny thing is it shoots the factory Hornady .5 moa or less but they're not even close to what I need for this rifle.

Definitely not the time to be working on loads.
I was able to get 4 boxes of 200gn eldx.
But powder is tough to come by to say the least. Down to 1# of 7828, 1# H1000 and 2# ratumbo.
Not much to work with.
Thanks for the heads-up.

 

[yfz450guy]

update? how did you end up?