High pressure with 107's.....

[Steve Ladino]

Had real high pressure today shooting my standard 6 BR load....30 grains Varget, 107 SMK's seated .010 off the lands in my .266 NK. chamber/.265 loaded neck size ammo, I thought. As it turned out I misinterpreted my written load data and ended up jamming the 107's .010". I wouldn't have thought that that would have caused me to have to beat out a fired case with a cleaning rod and a board but that's all I could find after coming home and re weighing and double checking everything including scale against scale. Same Lapua brass , clean barell to start and no gun changes except the install of the ejector which I haven't been using for years. Anybody experience high pressures with these combinations, especially jamming 107 SMK's ? ~ Steve

 

['Freak]

Just guessing; a .010” jump = at least some initial pressure leakage around past the bullet until it finally pretty much plugs the leak hole. A .010” jam = pressure leak hole already pretty much plugged from the git go.

 

[HTSmith]

My 6BR (fairly short throated) won't tolerate a full 30 Gr of Varget at any seating depth with Sierra 107's. My load is 29.7 Gr and when I tried them jammed I got high pressure (ejector hole smear and heavy bolt lift) even with this lighter load. I can go a full 30.0 of Varget with Berger 105's VLDH's with no pressure problems. Just my experience. Of course lots of Varget vary, chambers vary, barrels vary yada yada.

 

[geo.ulrich]

I don't know but .0005 per side neck clearance is kind of tight alittle carbon or misread mic and you will get high pressure

 

[ShootDots]

You have exactly 1 thousandths clearance in the neck! That is FAR less than what I believe is necessary. My personal opinion is that you need a MINIMUM of 3 thousandths and 4 is better! I believe the pressure you are experiencing is derived from not nearly enough neck clearance!

 

[Steve Ladino]

You have exactly 1 thousandths clearance in the neck! That is FAR less than what I believe is necessary. My personal opinion is that you need a MINIMUM of 3 thousandths and 4 is better! I believe the pressure you are experiencing is derived from not nearly enough neck clearance!

Maybe, but been shooting barell chambered with this tight neck reamer since 2007, mainly 105 VLD's ...no pressure problems.

 

[Steve Ladino]

I don't know but .0005 per side neck clearance is kind of tight alittle carbon or misread mic and you will get high pressure

Yes, along with the jamming I believe carbon build up added as the real trouble began with #4 shot and culminated with shot #6 on my sighter , which required the cleaning rod routine....Thanks

 

[Steve Ladino]

My 6BR (fairly short throated) won't tolerate a full 30 Gr of Varget at any seating depth with Sierra 107's. My load is 29.7 Gr and when I tried them jammed I got high pressure (ejector hole smear and heavy bolt lift) even with this lighter load. I can go a full 30.0 of Varget with Berger 105's VLDH's with no pressure problems. Just my experience. Of course lots of Varget vary, chambers vary, barrels vary yada yada.

Thanks Tim....me too with the vld's sometimes jammed but usually .010 " off never any over pressure signs.

 

[Steve Ladino]

Just guessing; a .010” jump = at least some initial pressure leakage around past the bullet until it finally pretty much plugs the leak hole. A .010” jam = pressure leak hole already pretty much plugged from the git go.

Absolutely, this is my conclusion as to this issue. Thanks

 

[dkhunt14]

I believe the 107 has a longer bearing surface, so that would make more pressure. They could also be fatter which would create more pressure and maybe too tight in the neck. I never run .001 clearence because it has proven no more accurate then .003. If the Bullet can't be released cleanly, accuracy can suffer. All it takes with .001 clearance is brass flow, a little carbon or necks not turned good enough to start with and pressures can rise to dangerous levels.

WHEN YOU REPLACE A COMPONENT YOU SHOULD START LOW AND WORK UP. Matt

 

[Laurie]

WHEN YOU REPLACE A COMPONENT YOU SHOULD START LOW AND WORK UP. Matt

Matt, the OP didn't change a component, he inadvertently went from 10 thou' jump to 10 thou' 'in' with the same combination.

To answer the OP's question: Yes, going from a jump to jam situation can have those over-pressure results if the original load was producing close to the limit pressures.

 

[johara1]

+1 on what Matt said. what free bore do you have? .001 per side is a minimum and you sure better know what the pressure ring is……. jim

 

[Laurie]

+1 on what Matt said. what free bore do you have? .001 per side is a minimum and you sure better know what the pressure ring is……. jim

Yes, + another on that. Far too small a clearance. Without looking it up, that sounds like the chamber designed for no-turn with the older thinner neck 'gold box' Lapua being used with current thicker-neck 'blue box' stuff.

 

[johara1]

It really doesn't matter what the reamer was to be used for. You had better measure things to the tenth and turn your necks to give the proper clearance. I had Blue box 6mm BR that had less than .011 necks……… jim

 

[joshb]

It should be mentioned that any change in seating depth should require a new work up. I encountered a problem with over pressure when I changed a "kiss the lands" warm 308 load to magazine length. Being a Newby, I naively assumed that moving back, away from the lands lowered pressure. Yes and no. Let's not forget the affects of reducing case volume with a shorter bullet seating. I did, with surprising results.

 

[jlow]

Yes, along with the jamming I believe carbon build up added as the real trouble began with #4 shot and culminated with shot #6 on my sighter , which required the cleaning rod routine....Thanks

I would do the carbon ring test which is to paint a dummy round with a sharpie, push it into the chamber by hand and see if it would fall free when you put your gun to vertical. If not, push it out with a cleaning rod and see if where the sharpie has been rubbed off to distinguish between jamming and a carbon ring.

 

[dkhunt14]

Matt, the OP didn't change a component, he inadvertently went from 10 thou' jump to 10 thou' 'in' with the same combination.

To answer the OP's question: Yes, going from a jump to jam situation can have those over-pressure results if the original load was producing close to the limit pressures.

In a farther down post the OP mentioned he shot mostly 105 VLD's. I thought he takes his VLD LOAD and put it in a 107 Sierra. I also asked if he switched lots of Powder. Some guys think they are really all the same and buy just one pounders. I have had lots of Varget that were really hot. Matt

 

[Steve Ladino]

Matt, the OP didn't change a component, he inadvertently went from 10 thou' jump to 10 thou' 'in' with the same combination.

To answer the OP's question: Yes, going from a jump to jam situation can have those over-pressure results if the original load was producing close to the limit pressures.

Yes I agree everything is on the edge and works good there in my gun, Thanks.

 

[Steve Ladino]

I would do the carbon ring test which is to paint a dummy round with a sharpie, push it into the chamber by hand and see if it would fall free when you put your gun to vertical. If not, push it out with a cleaning rod and see if where the sharpie has been rubbed off to distinguish between jamming and a carbon ring.

Thanks, haven't heard of this process before

 

[Steve Ladino]

In a farther down post the OP mentioned he shot mostly 105 VLD's. I thought he takes his VLD LOAD and put it in a 107 Sierra. I also asked if he switched lots of Powder. Some guys think they are really all the same and buy just one pounders. I have had lots of Varget that were really hot. Matt

Yes I did use my VLD load for the SMK's and did check the velocity of my new powder lot against my old expired powder lot to see if an adjustment was needed, Thanks