Powder weight changes between bullets

[MuleyFever]

I have been working on a load with a 142grn mono that is shooting ok at 59.5grn with no pressure signs. I actually took it to 60.5 and it was fine, just not as accurate. I am going to try some Barnes 139grn LRX and some 140grn TTSX and TSX for fun.

My question is where should I start with my charge weights? Would you back off any or just start where I am at with the 59.5? I am quite a bit off the lands at mag length so not sure if that has any significance.

 

[WeiserBucks]

Starting off with a new bullet I'd drop down a grain or two in the interest of safety. Even though the new bullet is a very similar weight there's no way to know how your rifle will react.

 

[tdot]

It isnt just bullet weight that changes. Bearing surface and metal density also seem to play a significant role. So personally I drop 5-10% and do a ladder test until if find pressure. I do it in 1 grain increments, so it's very quick. Usually 5 to 7 rounds will start at a conservative load and take me all the way to pressure.

But I like to know where a particular combo will show pressure signs. Then I have huge flexibility to play safely under that area.

 

[1shotgear]

Definitely drop down a few grains and conduct a ladder test to determine where you will hit pressure. Barnes typically have a longer bearing surface which can increase pressure.

 

[OXN939]

Definitely drop down a few grains and conduct a ladder test to determine where you will hit pressure. Barnes typically have a longer bearing surface which can increase pressure.

Spot on. You'll find that Barnes' recommended maxes for the LRX projectiles are significantly lower than projectiles of similar weights from other brands. I just did this same thing for 6.5 CM- trying to extrapolate powder charges for the 6.5 LRX based off another brand's reloading manual- and was consistently over by 1.5 grains. Found the Barnes manual, backed off to their recommended charges, and have now found several sub-MOA loads.

 

[MuleyFever]

Spot on. You'll find that Barnes' recommended maxes for the LRX projectiles are significantly lower than projectiles of similar weights from other brands. I just did this same thing for 6.5 CM- trying to extrapolate powder charges for the 6.5 LRX based off another brand's reloading manual- and was consistently over by 1.5 grains. Found the Barnes manual, backed off to their recommended charges, and have now found several sub-MOA loads.

Just looked up the Barnes data. I am surprised at the jump they recommend.

As far as charge weight I am using 4831sc and they start at 57 and list 63.3 as max for the 3 bullets I listed.

 

[OXN939]

Just looked up the Barnes data. I am surprised at the jump they recommend.

As far as charge weight I am using 4831sc and they start at 57 and list 63.3 as max for the 3 bullets I listed.

Jump appears to be spot on for me. Out of three loads I've tried, two are around MOA and one is right near .75MOA. I'll be using Barnes' recommended COALs as a starting point for load development in the future for sure.

 

[OXN939]

Just looked up the Barnes data. I am surprised at the jump they recommend.

As far as charge weight I am using 4831sc and they start at 57 and list 63.3 as max for the 3 bullets I listed.

Also, the more experienced reloading guys may be able to chime in with more on this, but I'd expect that the deeper seating depths Barnes recommends probably creates more pressure with the same volume of powder, thereby making a smaller powder charge recommended for equivalent performance. Anyone wanna spot check my thinking on that?

 

[MuleyFever]

If I found a good load with the TSX would it be safe to use that charge as a start for the TTSX? They appear to be the same bullet just one has the tip.

 

[PA Hunter]

There is so much load data out there for free no need to guess. I will say from my experience with Barnes they need a good jump don’t waste your time anywhere near the lands.

 

[MuleyFever]

There is so much load data out there for free no need to guess. I will say from my experience with Barnes they need a good jump don’t waste your time anywhere near the lands.

Thats what I am hoping for. Not much room in my mag.