A question about bullet effects on a round.

[Kuyong_Chuin]

I pulled a bullet from a 7.62x54R surplus round. I weighed the powder and I am logging each rounds powder of the ones I pull to check to see if the powder levels are the same. I wanted to replace a few of the steel cored FMJ bullets with the soft point boat-tails I have, and I was wondering if anyone knows what effect the new bullet would have on not only pressures but accuracy?

The bullet on the left is the original bullet and it weighed in at 147.8 grains.
The bullet on the right is a PPU 150 grain soft point boat-tail that weighed 149.2 grains. I lined up the channels for the picture. As you can see the SPBT has a shorter base as well as over all length but it is slightly heavier than the steel core bullet. I am figuring that the SPBT is going to have a lower pressure because it will not be seated as deep as the FMJ round.

By the way the powder that was in this first round I pulled is a stick powder that weighed 49.5 grains total if that helps.

 

[notaglockfanboy]

With the weight difference in the two bullets, I doubt you will see any pressure differences. If I were you and were "Mexican matching" as I have always heard it called, I would at least neck size the brass after pulling the bullets.

 

[Kuyong_Chuin]

With the weight difference in the two bullets, I doubt you will see any pressure differences. If I were you and were "Mexican matching" as I have always heard it called, I would at least neck size the brass after pulling the bullets.

I was going to do that anyway. Just wondering what effect the shorter seating depth was going to do to the round.

 

[rhinoh]

I could be wrong but I think the shorter seating depths will lower pressures a bit.
How much actual difference in velocity that makes I can't say.

 

[notaglockfanboy]

I wouldn't think you would see any noticeable affects, at least I have not. Maybe some of the others will weigh in on this.

 

[rcmodel]

The orginial boat-tail bullet will likely give less pressure because there is less bearing surface being engraved by the rifling.

The soft-point bullet has a shorter boat-tail, and a more abrupt ogive, so it appears to have more bearing surface, and pressure will be slightly higher.

But it will most likely be off-set by the lighter weight.

I'd Gofer it!!!

rc

 

[Kuyong_Chuin]

The orginial boat-tail bullet will likely give less pressure because there is less bearing surface being engraved by the rifling.

The soft-point bullet has a shorter boat-tail, and a more abrupt ogive, so it appears to have more bearing surface, and pressure will be slightly higher.

But it will most likely be off-set by the lighter weight.

I'd Gofer it!!!

rc

Thanks RC and and all the others that weighed in. I am going to make up 5 rounds (the 5 that I didn't have a clip for) and try them out as soon as I can get out and about better. Still somewhat recovering from the first total knee replacement surgery. Want to get as much shooting in I can before they do the other knee in June.

 

[rcmodel]

Then, good luck too'ya!

With both the shooting, and the knees!!

Let us know how both go.

rc

 

[Sport45]

The bullet with more bearing surface is also heavier. That said, they're close enough I wouldn't worry about it.

I'd just have my brother in law try them first.

 

[Kuyong_Chuin]

The bullet with more bearing surface is also heavier. That said, they're close enough I wouldn't worry about it.

I'd just have my brother in law try them first.

Would an ex-brother-in-law work? J/K I'll probably fire the first round by remote just in case because of the steel cases. Now if I could just find some H4895 or BLC2 powder around here I could load up the other 95 bullets that will be left after this loading. I am down to 1 pound of H4350 that I can't find any load data for a 7.62x54R using under a 165 grain bullet with that powder.

 

[Kuyong_Chuin]

Update: pulled the five test rounds bullets and weighed each charge. They were all over the place. Weighed each three time to make sure of the charge weight for each round. The high side was 49.5 grains with the low side being 47.8 grains. The average for the five came out to 48.5 grains exactly so that is charge I loaded each round with and then installed the new soft point bullets to the same O.A.L. as the P.P.U. factory rounds that have the same bullet. My O.A.L. is 2.895. As soon as I can get out to a range I'll update you all on the results.