Bullet weight question

[mdmp5]

Hey guys,

I am by no means an expert with ammo, but I am not quite a green rookie either. In any case, I have a rookie question about something I had not really thought about much until recently.

Using the Sierra manual, .308 Win and RE-15 powder as an example:
Why is it that in order to get 2500 ft/sec, for 168 grain SMKs it takes 40.4 grains, while for 190 gr SMKs, it takes the same 40.4 grains? I would think that the heavier bullet would require more of a charge to get it to the same velocity. I am sure someone has a simple answer that is gonna make me smack myself in the head.

 

[Wil]

Re: Bullet weight question

190 takes up more space in the cartridge... creating more pressure...creating velocity

 

[mdmp5]

Re: Bullet weight question

Yeah, I guess that makes sense. So in other words, the bullet has a slightly longer time to exit the case, allowing for more pressure to build up, right?

 

[Victor N TN]

Re: Bullet weight question

One of my powder loads is the same for 168SMKs and 175SMKs. Go figger...

 

[BLAWTON]

Re: Bullet weight question

The heavier the bullet will cause more pressure. You also have to figure in bearing surfaces and od of the bullets. It comes down to alot of different things that cann effect the pressures in the gun.

 

[Sig685]

Re: Bullet weight question

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mikepal</div><div class="ubbcode-body">Hey guys,

I am by no means an expert with ammo, but I am not quite a green rookie either. In any case, I have a rookie question about something I had not really thought about much until recently.

Using the Sierra manual, .308 Win and RE-15 powder as an example:
Why is it that in order to get 2500 ft/sec, for 168 grain SMKs it takes 40.4 grains, while for 190 gr SMKs, it takes the same 40.4 grains? I would think that the heavier bullet would require more of a charge to get it to the same velocity. I am sure someone has a simple answer that is gonna make me smack myself in the head.

</div></div>

If you use bullet manufacturers' load data, you are leaving a lot of performance on the table. I suggest you check the powder manufacturers' websites on how to use their product. The bullet manufacturers are VERY conservative in their loads; they do not control the powder.