Does bullet weight effect velocity and pressure?

[mnhunter2]

Am shooting a 300 WTBY with a 210 gr Berger VLD with 86.1  gr of H1000, I want to try the 205 gr Elite hunter bullets and was wonder if I should reduce my powder and how much the change would effect velocity and pressure.

[Grouchy]

Berger manual in hand says your 86.1 is almost 6 gr over their reccomended max. of H1000. Changing bullets would have me starting at the lowest charge and working up from there. 76.5 is the start load. BTW, that 86.1 has to be a seriously compressed load. 

[mnhunter2]

Don’t know what the Berger manual says but have shot this load in my 300 wtby for quite a few yrs, loads fine doesn’t seem to compress powder at all, no pressure signs and brass has been reloaded probably 10 times and seems fine, goes at 3000 muzzle velocity, originally started at like 80 gr and worked up to what the rifle liked.

[Grouchy]

Why ask if the manual means nothing? Their max load says 99 % of capacitiy. 6 grains over 99%  is not compressed? LOL!

[canadian reloader]

mnhunter2
Do you know your fired brass case capacity and your OAL. If I had them then I could run your #'s through Quickload and give you an idea of the pressure you may be running.

[Dino82520]

All bullets are different, even bullets of the same weight. Flat base bullets tend to have more bearing surface than boat tails. Type of construction, Nosler Partitions and Swift A-Frames have a solid shank of jacket material that can cause pressure differences. Jacket materials differ in composition meaning hardness. Any time you switch components of any kind, even primers, reduce powder charges by 10% and start load development all over.

If you have been exceeding max recommended powder charges with no pressure signs i recommend you have your scale verified and if you are using the old Lee scoops for powder measurements, I suggest you buy a quality powder scale.

Trust me, you don't want to go through what I have in the last two weeks.

[mnhunter2]

My OAL is 3.65, don’t know my cartridge capacity, the brass is 25-30 yr old Weatherby brass, it has been reloaded many times, I trim the cases after being shot 2-3 times down to 2.82 and never had any problems with the brass.

[canadian reloader]

Using your OAL of 3.65 and giving you a case cap of 100 gr ( average for 300 WeaM case) your pressure with 86.1 grs  of H-1000 with the 210 VLD would be 64464 psi. This puts you slightly over the max of 63817 psi although I can't figure out why the 300 WeaM would not be rated at 65000, for example the 270 Win max pressure is 65000 psi. Now your actual capacity would make a difference. It would take your pressure either way. Oh yes your case fill is 106.4 %. Keep in mind that these are only figures from a program and don't replace working up a load while looking for pressure signs.