No pressure sign with virgin brass, but significant pressure+slower MV in 2nd firing..reason?

[harry_x1]

Hi All,

Currently developing a load for 33xc in 30 inch bartlein for my AXMC. 299 Grain DTACs, H1000 110 grain, 0.001 neck tension, shoulder bumbed 0.002, 0.015 off lands.

When I fired virgin brass with same load (without body sizing) I did not get any pressure signs (except one odd ejector marks on some pieces) and velocity was ~3150. However in very next firing I am getting punctured primers, cratering, ejecter marks etc with same powder, neck tension and seating depth. The MV has also dropped to 3050. I bumped shoulder by 0.002 before reloading and the round chambered perfectly into my chamber without bolt handle freely falling.

I am trying to understand what might be going on here. If anyone has any hypothesis that they can share, will be great.

thanks

 

[KnowNothing256]

When you say "blown primers," are we talking punctured, or just leaking? I'm not really familiar with heavy magnums, but one thing I've heard of people doing is running mild loads for the first firing to work-harden the primer pockets. Apparently running full-strength loads in magnum cartridges can prematurely expand primer pockets, which would lead to primer leakage and slipping (and slipping might cause excess cratering or possibly even punctures), and the leakage might result in lower MV if it dropped pressure enough.

This is all raw speculation on my end, but one theoretically possible explanation. When seating the primers in the once-fired brass, did they go in too easily by any chance?

 

[harry_x1]

When you say "blown primers," are we talking punctured, or just leaking? I'm not really familiar with heavy magnums, but one thing I've heard of people doing is running mild loads for the first firing to work-harden the primer pockets. Apparently running full-strength loads in magnum cartridges can prematurely expand primer pockets, which would lead to primer leakage and slipping (and slipping might cause excess cratering or possibly even punctures), and the leakage might result in lower MV if it dropped pressure enough.

This is all raw speculation on my end, but one theoretically possible explanation. When seating the primers in the once-fired brass, did they go in too easily by any chance?

thanks for the inputs. Attached image of the primers after firing. I think they fall in category of "punctured"/cratering?....Dont think primer pockets got loose as I hand load and could still feel the pressure while seating primers. However I did notice that I hit the primer multiple times for it be slightly under flush.

 

[Huskydriver]

Too hot. How did you measure your speeds? I would back that back down to 108 gr and try 10.

 

[harry_x1]

ok...one additional piece of information. I use imperial dry case neck lube on inside of the necks before expanding. However I did not clean the inside of the neck before seating the bullet. Can that play a role here?

 

[Huskydriver]

ok...one additional piece of information. I use imperial dry case neck lube on inside of the necks before expanding. However I did not clean the inside of the neck before seating the bullet. Can that play a role here?

Not really

 

[rustyinbend]

Is it just me, or does a 3150 velocity sound crazy-high?

 

[Huskydriver]

Is it just me, or does a 3150 velocity sound crazy-high?

Not really... It's a 33xc.... 110 gr of powder behind that 299....30" tube.


I am curious how you are getting your speed @harry_x1 ?

 

[rustyinbend]

I am curious how you are getting your speed ?

I buy it on the street corner ... just like everyone else.

 

[harry_x1]

Not really... It's a 33xc.... 110 gr of powder behind that 299....30" tube.


I am curious how you are getting your speed @harry_x1 ?

while each barrell is diff, from the loads I have read about 110 should be on lower end...most people to my knowledge are 110.5+.

 

[hafejd30]

Assuming your running the same .001” neck tension

I’m just going to guess that pressure was initially higher which accounted for the velocity increase. The brass had more room to expand as it was virgin brass. Which is why the pressure signs weren’t there as it had some “give” in the brass/chamber relationship

Now your over pressure in a brass casing which has slightly more capacity in the case but less room to expand. So it’s pushing out where it can which is your ejector and primer cratering marks

 

[Huskydriver]

while each barrell is diff, from the loads I have read about 110 should be on lower end...most people to my knowledge are 110.5+.

How are you getting your speeds?

 

[KnowNothing256]

ok...one additional piece of information. I use imperial dry case neck lube on inside of the necks before expanding. However I did not clean the inside of the neck before seating the bullet. Can that play a role here?

Actually it seems like it might, at least to me; if the bullet is slipping early, you might not generate the same peak pressure. 0.001” tension also sounds to be a bit on the low side to me, but if you sized your necks on the virgin brass to that tension, then it would just be the lube that was new.

Those primers don’t look bad to me, opinions may vary. They definitely aren’t punctured, you’re seeing mild cratering which could be just as much the fault of your firing pin hole on the bolt face as the load. Did the primers on the first firing look like that?

 

[Huskydriver]

Actually it seems like it might, at least to me; if the bullet is slipping early, you might not generate the same peak pressure. 0.001” tension also sounds to be a bit on the low side to me, but if you sized your necks on the virgin brass to that tension, then it would just be the lube that was new.

Those primers don’t look bad to me, opinions may vary. They definitely aren’t punctured, you’re seeing mild cratering which could be just as much the fault of your firing pin hole on the bolt face as the load. Did the primers on the first firing look like that?

Are you kidding me? Look at his one pick that primer is clearly punctured lol

 

[KnowNothing256]

Are you kidding me? Look at his one pick that primer is clearly punctured lol

You mean the blurry picture that may or may not be a shadow or smudge inside the pin mark? If we saw a clear photo of that one, maybe I would see that I’m wrong. But I certainly wouldn’t call that “clear” evidence. Happy to be wrong, but yeah was really only speaking to the primers of which we were given an in-focus photo.

 

[spife7980]

while each barrell is diff, from the loads I have read about 110 should be on lower end...most people to my knowledge are 110.5+.

A half grain isnt shit as far as a difference goes for something that large.

I also dont see much for people using h1000 in the 33xc with a 300gr bullet at all and those that are running that fast of a powder with that heavy of a bullet get into pressure at 3050(read as the only guy I could find who tried it). It sure seems like its too fast of a powder considering its an more appropriate burn rate for smaller chamberings such as a 338 lapua or 33 nosler on the large end but still with a lighter 250gr bullet. That powder is ideally suited for a lil 300wm.

And you yourself seem to have known h1000 wasnt an ideal powder for this application and too fast when you first were getting into it as shown by the first google result for "33xc h1000".

Hi all - David Tubb in his writeup recomends H50 or Vitavouri 20N29 for 33xc. However has anyone tried 33xc with H1000? The burn rate for H1000 is slightly higher than H50 so not sure if it will work as well...but checking if someone has actually tried H1000 for 33xc and what their experience has been. Thanks for the feedback/inputs.

The right powder is in stock and even "on sale".

Hodgdon H50BMG Smokeless Gun Powder | Powder Valley Outdoors 50 BMG Powder

Best Prices on Hodgdon H50BMG Powder. Hodgdon, IMR, Winchester, Alliant, Accurate, Shooters World, Vihtavuori, Ramshot Smokeless Powder at wholesale prices.

www.powdervalleyinc.com

 

[Long Range 338]

One item to consider is that a LOT of the test loads are using copper solids and the DTAC is a lead core bullet. The bearing surface is going to be much different between the two causing different pressure curves. The XC cartridges are fairly new and typically used by very experienced reloaders - not trying to offend here but experience teaches many lessons. I wouldn't be trying to reinvent with powders that aren't optimal in a case that large without some good data from reliable sources to help me keep my face intact. H50 and US869 have been faily available of late and should offer better burn rates. Pioneering in this arena without the proper background could be hazardous to your health.

Here's a link to Gordons reloading software that can give you rough estimates of pressure with given component combinations.

https://www.grtools.de/doku.php

 

[secondofangle2]

You guys are a bunch of unemployed retreads with no "real experience" in this reloading game and Harold isn't going to listen to you because he's smarter and wealthier than you so I suggest you all leave him to figure out himself the obvious things that he hasn't figured out yet.

[see any of his threads to understand this sarcasm or just wait till he comes out swinging.]

 

[harry_x1]

Not saying that the powder might not be the issue in my barrel… but just fyi, there are plenty of shooters using H1000 for 300 grain lead core .338 caliber. That list includes David Tubb, his daughter and some other top shooters.

 

[jbuck88]

I would definitely try a slower powder. Unless you are hung up on h1000 and cannot use anything else. I pressured out way too early with my 338lapua with 300gr and 285gr bullets. Not quite apples to apples, but it's pretty fast compared to h50

 

[harry_x1]

I would definitely try a slower powder. Unless you are hung up on h1000 and cannot use anything else. I pressured out way too early with my 338lapua with 300gr and 285gr bullets. Not quite apples to apples, but it's pretty fast compared to h50

Agreed. Experimenting with RL 50 and US 869 this week. However I will keep experimenting with H1000 as well to make sure I rule out all controllable factors. One other thing I suspect is the large carbon ring in chamber. I intend to clean the barrel fully with abrasives and then see if that makes a diff. That might explain why the barrel shot great on first day (50 shots) and showed no pressure signs even with 112 grains of H1000. Will share progress.

 

[Dave62677]

Did you bush your AXMC bolt? If not, send to LRI

 

[Dave62677]

Your firing pin is the issue. I had the same problem before. Now I’m at 3200fps (126gr H50bmg with 300gr Berger) without any issue.

 

[jbuck88]

Yeah I forgot about the axmc firing pin issue. I swapped mine large firing pin for the small one and it was night and day. I was getting craters like that with factory fgmm ammo.

 

[Dave62677]

I can tell from your primer , your firing pin is the bigger pin that AXMC had. All the new AI AXSR now use the small firing pin to handle more pressure load.

 

[jbuck88]

Accuracy International: AXMC Bolt Bodies, Small Firing Pin, RH

These Accuracy International bolt assemblies are only compatible with AXMC rifles and firing pin assemblies (27783BL).

www.milehighshooting.com

And

Accuracy International: AXMC Shroud & Small Firing Pin Assembly, RH

This firing pin and shroud assembly will only work with Accuracy International AXMC rifles.

www.milehighshooting.com

Should solve some of your problems. Assuming you have a right handed AXMC.

 

[harry_x1]

Did you bush your AXMC bolt? If not, send to LRI

What is LRI ? when you bush, does it mean getting the bolt pin head altered?

 

[Dave62677]

GUNSMITHING SERVICES: STRIKER PIN BUSHING: M7, M700, M70(PF AND CRF), ACCURACY INTERNATIONAL, BERGARA, HOWA 1500, & RUGER RPR

A relatively frequent complaint with M700 and Accuracy International actions (and others) are cratered primers with factory made ammunition. The root cause of this is from excessive clearance between the striker and the hole through the bolt face. When fired, the primer cup flows into the void...

www.longriflesinc.com

u are not hitting pressure , it is the AXMC firing pin issue.

Read the LRI explanation. Send your all your bolt and firing pin assembly to LRI, they will take care you.

Pretty much same issue as the old R700 308 action people rechamber with 65cm . Back then people were all screaming for pierces primer.

 

[KnowNothing256]

In fairness, let's not forget the original question: primer issues, but also low speeds. OP, what was your brass prep for the virgin brass when you loaded it up?

 

[Huskydriver]

Pull your firing pin out of your bolt @harry_x1 and post a pic of the firing pin tip

 

[BCX]

We ran the 299 Dtac up to 3180 w H50 BMB from 30 inch. I think H1000 is to fast. N570, RL33, H50 are the go to powders… Looking at your primers I also think it’s your firing pin. Chad @ LRI will get you back in the game.

 

[DownhillFromHere]

I'm going to toss this into the ring of "possibilities" simply because I was seeing same thing: pressure signs (heavy bolt lift, ejector swipe) on second loading of Alpha 6BR brass using same "standard" load - and brass lot - as buddies whose loads were fine. I have zero experience loading anything bigger than a .30-06 case so... there.

I got lazy and/or in a hurry and didn't do a very good job cleaning lube off resized cases.

Cleaned cases better, pressure signs disappeared.

That is all. Carry on.

 

[Dave62677]

Yea, I missed the part u using h1000, that’s too fast. Get some H50bmg.

 

[harry_x1]

thanks everyone for the inputs. I think it is a mixture of case lube, bolt and the powder being too fast. I cleaned up the case fully and changed powder to RL 50 (slower burn rate). I do not see punctured primers anymore however there is mild cratering. I feel that cratering is due to the bolt issue. Sending my bolt to LRI for bushing. I will report back once I get the bolt adjusted. Hopeful that this will help me go beyong 3100 fps. Currently choosing to remain at 3020 fps, untill I get adjusted bolt.