.308 168 gr. TMK's Problem

[Sargesniper]

http://www.longrangehunting.com/for...ent.php?attachmentid=54295&stc=1&d=1448666788

 

[DMP25-06]

To Sargesniper ,
The explanation given to me by the man at Sierra was that the cartridge O.A.L. would be longer if the TMK were seated at the same distance from the lands as the SMK . If I wanted the O.A.L. to be the same with both bullets , then the TMK would have to be seated deeper into the cartridge case , thus resulting in slightly diminished case capacity , resulting in higher pressures , if the powder volume remained the same as with the SMK.
Thank You ,
DMP25-06

 

[Sargesniper]

To Sargesniper ,
The explanation given to me by the man at Sierra was that the cartridge O.A.L. would be longer if the TMK were seated at the same distance from the lands as the SMK . If I wanted the O.A.L. to be the same with both bullets , then the TMK would have to be seated deeper into the cartridge case , thus resulting in slightly diminished case capacity , resulting in higher pressures , if the powder volume remained the same as with the SMK.
Thank You ,
DMP25-06

Was not in disagreement with what you stated, you were quoting what someone said to you. I disagree with his statement. Yes you will lessen case capacity but the bullet will have to travel further before it slams the lands. Thus the pressure will have lessened before it contacts the lands. Then the pressure will start to rise. There are others on the forum that have tested this and found the opposite of what he stated. I personally have not tested it. It makes sense to me though. If jammed from the start then you will see pressure with close to Max. I load for accuracy not speed anyway. If I get really good speed then I consider it a bonus. My .308's shoot fine with lower speeds and lower powder charges. Accuracy is my doing, the speed takes care of itself.

 

[DMP25-06]

Was not in disagreement with what you stated, you were quoting what someone said to you. I disagree with his statement. Yes you will lessen case capacity but the bullet will have to travel further before it slams the lands. Thus the pressure will have lessened before it contacts the lands. Then the pressure will start to rise. There are others on the forum that have tested this and found the opposite of what he stated. I personally have not tested it. It makes sense to me though. If jammed from the start then you will see pressure with close to Max. I load for accuracy not speed anyway. If I get really good speed then I consider it a bonus. My .308's shoot fine with lower speeds and lower powder charges. Accuracy is my doing, the speed takes care of itself.

What you are saying makes sense to me . I never did try seating the TMK at magazine length , maybe I will try and see if I experience any different results .
I hope that you had a good Thanksgiving and wish you a MERRY CHRISTMAS .
DMP25-06

 

[Sargesniper]

What you are saying makes sense to me . I never did try seating the TMK at magazine length , maybe I will try and see if I experience any different results .
I hope that you had a good Thanksgiving and wish you a MERRY CHRISTMAS .
DMP25-06

I single load mine so I can't say what Mag. Length is. I have two Factory Rem Varmint barrels and one has the notorious long throat and the other is a little better. They both shoot very well in their own respect.
They aren't benchrest accurate but will stay below 1/2" if I do my part.

It was stated in a discussion that the pressure and speed will drop when the bullet moves away from the lands. Kind of like when your throat wears on some rifles and the bullet has to jump further to the lands.

I too hope you had a good Thanksgiving and also wish you a Merry Christmas. I'm glad this didn't turn into a hot discussion with you and others. I don't care much for that stuff. I have been reloading more than 50 yrs. and still like to learn from others. I'm not as technical as some seem to be and no longer shoot competition. I am in it for sheer pleasure.

Thanks for you input. SEMPER FI

 

[BountyHunter]

There are formulas and real pressure testing with strain guage that clearly show seating deeper changes the case volume and powder density which raises pressures not lowers it. Yes there is a pressure spike seating into the lands versus even slightly off of it. The key here is how much deeper are you seating for the same coal versus an untipped.

If everything is the same as you just stated except the seating depth then you just proved it whether you want to believe it or not.

Measure the oal and base to ogive between the two bullets. You will find the cause there.

 

[Sargesniper]

There are formulas and real pressure testing with strain guage that clearly show seating deeper changes the case volume and powder density which raises pressures not lowers it. Yes there is a pressure spike seating into the lands versus even slightly off of it. The key here is how much deeper are you seating for the same coal versus an untipped.

If everything is the same as you just stated except the seating depth then you just proved it whether you want to believe it or not.

Measure the oal and base to ogive between the two bullets. You will find the cause there.

Yes, the difference in the bearing surface could be the cause if it were the other way around. The bullet I am having trouble with has a shorter bearing surface though. My powder charge is well under max, in fact it is barely the minimum for the powder and bullet weight.

More measuring on the loaded rounds showed I was actually right at the lands. So what would your guess be as to what's going on? The bolt was hard to lift and extract the fired case.

 

[misterc01]

Data I have seen is 2.800COL. Same load data as original Match King.