Help! I've lost 500fps!

[Mr Fudd]

From your original load:

Are you using the same manufacturer brass?
Are you seating heads to same depth?
Are you using the same primers?
Are you using the same manufacturer heads?

Hi mate I've literally not changed anything!? I'm using the same fire formed brass which has been loaded once or twice at most, I'm neck sizing the brass the same as the first time round and did think it could be that as a couple of the heads I pulled off seem to come out more easily than the others but don't think that could equate to 500fps as any loss of built up pressure in the cartridge would be made up in the barrel??

Everything else is exactly the same, same powder, same brass, same head, same primer, checked the chronograph against another known speed load and came up with the right velocities?!

The hornady book states a velocity of 3500 fps for 33.7 grains so how can i be so far out, the barrel could probably do with a clean as I've put about 200-300 rounds through it since the first batch

[Fox121]

Have you checked for throat erosion? I had rifles lose velocity as the throat wears, although no where near 500fps!

[Mr Fudd]

it's a brand new rifle with stainless barrel so I'd be surprised if there was any throat erosion, it's only had the first batch and the new ones through it so far so not even had 500 rounds through it yet?

[Sako7mm]

Clean the tube for starters. Are you using a different batch of anything? Are the bullets definitely 50 grain, not 55?

[Mr Fudd]

Yeah will hopefully be able to get the barrel cleaned tonight, I originally bought two boxes of 250 50gr heads which I'm still using however will double check the actual weight of them later in case they have been mixed up, will hopefully get out later with a clean barrel and chrono again

[220AI]

Mr F,

If I've understood your comments correctly, then I think it's a chrony issue.

You say your bullets are striking 1" higher, yet have lost 500 fps?? Something doesn't sound right.

[Randy Bohannon]

Mr F,

If I've understood your comments correctly, then I think it's a chrony issue.

You say your bullets are striking 1" higher, yet have lost 500 fps?? Something doesn't sound right.

1" higher would make sense with a lower velocity load if he was measuring the maximum ordinate.

In other words if he zeroed at 200 yards he would then expect something like 1" high at 100 yards. If he found that it was in fact 2" high at 100 yards on shooting the lower velocity is indicated.

weird one, losing 500fps seems almost impossible without maybe having used a much slower powder in the second set of loads.

Soot on the cases?