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338 lapua pressure? HELP PLEASE

 
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Old 06-09-2011, 08:09 PM
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338 lapua pressure? HELP PLEASE

I just got a 338 lapua with the tac 338 action, 28 inch rock barrel and ive been working up loads for it and every load i try i get a ejector mark. I cant figure it out. Im using fed 215 and started out with 87 gr of retumbo and went up to 93 with the same ejector mark. primers are not flat, and no hard bolt lift either. ive also tried h1000 and started with 87 gr and went to 90 and got the same mark. I just bought another 100 brass thinking maybe the lapua brass that i had was soft but got the same result. Im shooting the 300gr SMK and seated them from 20 thousanths off to just touching the lans. I dont no what the heck is the problem. Has anyone else had this issue with the stiller action or could it be something else. Any help would be appreciated and thanks in advance
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Old 06-09-2011, 08:43 PM
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Re: 338 lapua pressure? HELP PLEASE

Quote:
Originally Posted by MTDOGGER View Post
I just got a 338 lapua with the tac 338 action, 28 inch rock barrel and ive been working up loads for it and every load i try i get a ejector mark. I cant figure it out. Im using fed 215 and started out with 87 gr of retumbo and went up to 93 with the same ejector mark. primers are not flat, and no hard bolt lift either. ive also tried h1000 and started with 87 gr and went to 90 and got the same mark. I just bought another 100 brass thinking maybe the lapua brass that i had was soft but got the same result. Im shooting the 300gr SMK and seated them from 20 thousanths off to just touching the lans. I dont no what the heck is the problem. Has anyone else had this issue with the stiller action or could it be something else. Any help would be appreciated and thanks in advance
When seating close to or touching the lands pressure will go dramatically.

Check a fired case and see if a bullet will go in the neck,(It should have 2 or 3 thousandths
clearance. If not, The necks need to be trimed.(They are longer than the neck chamber)

I would recomend backing off a minimum of 20 0r 30 thousandths and working up to max loads
slowly.

I dont think it is Head space but it should be checked.

Let us know what you find.

J E CUSTOM
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Old 06-09-2011, 09:01 PM
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Re: 338 lapua pressure? HELP PLEASE

I just tried that and the bullet did go into the fired case. I called the guy that built the rifle and he told me that stiller actions do that and it's nothing to worry about, in fact thats how he counts how many times he's fired the brass. now im not a no it all when it comes to reloading but its always been my assumption when i see ejector marks then theirs pressure and it isint right. This is driving me crazy its a new gun that i waited for to be built and bought the best equipment i could afford and now ive already got this @$^#$^$ problem.
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Old 06-09-2011, 11:29 PM
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Re: 338 lapua pressure? HELP PLEASE

Might the chamber be too slick and/or the cases too clean and/or some lube left on them or in the chamber?
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Old 06-09-2011, 11:55 PM
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Re: 338 lapua pressure? HELP PLEASE

is the ejector too long?

i once had this issue with a savage in 6.5-284....

Joe from mexico.
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Old 06-10-2011, 05:26 AM
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Re: 338 lapua pressure? HELP PLEASE

Tests done years ago at the H.P. White Laboratory and the NRA showed peak pressure increased only about 3 to 5 percent when bullet jump to the lands went from 20 thousandths or so down to zero. Same thing was observed by folks using Oehler's strain gage pressure system. That means it goes from 50,000 CUP (or 58,000 PSI) up to a max of 52,500 CUP (60,900 PSI). That's not a dramatic pressure increase. My own crude tests measuring pressure ring diameters show about the same difference. And no brass extruded back into bolt face holes.

Most cartridge brass starts to extrude back into the bolt face cutouts at around 65,000 CUP (80,600 PSI). It only happens when pressure inside the case gets above those numbers.

I've asked several powder companies about brass starting to extrude back into bolt face ejector cutouts and they all say the same thing. The load's too high in peak pressure for safety. One's gone way past the normal and SAAMI limits for safety. The brass case is the weakest link in containing pressure and is the best indicator of pressure signs in the unsafe range.

Too much bullet extraction force to get the bullet out of the case typicaly causes much higher pressure increases than zero bullet jump to the lands. I'd measure how much force it takes to pull a seated bullet from a reloaded case. If it's more than 40 to 50 pounds, I'd be suspect of that being the reason for brass extruding into bolt face holes. I've seen this happen with sizing dies make fired case mouths too small for the bullet diameter.
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Old 06-10-2011, 07:01 AM
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Re: 338 lapua pressure? HELP PLEASE

Quote:
Originally Posted by Bart B View Post
Too much bullet extraction force to get the bullet out of the case typicaly causes much higher pressure increases than zero bullet jump to the lands. I'd measure how much force it takes to pull a seated bullet from a reloaded case. If it's more than 40 to 50 pounds, I'd be suspect of that being the reason for brass extruding into bolt face holes. I've seen this happen with sizing dies make fired case mouths too small for the bullet diameter.
I'd be interested in seeing some data showing that the tension from a .015" inch ring of brass gripping the bullet can dramatically raise the pressure.
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