I have a pretty new Lilja barreled 280 Rem. 24"

When I first started loading and shooting I chronographed a 150gr ELDX at 2900 fps using IMR 4955 - this was at around 20 rounds through the barrel. I started shooting this load to explore different seating depths and found an accurate OAL. I then measured velocity again at around 90 rounds and it was about 75 fps higher, which seems too hot.

Does this change seem normal - perhaps due to barrel break in?

I clean after about every 20 rounds.

David

Your starting load and final are different. You changed the OAL. Pressure changes as does velocity.

Many barrels have a rough factory finish that is smoothed out after the barrel break in. It's not unusual to see a velocity increase in the first 100 rounds.

The changed OAL makes more sense to me than barrel break-in - unless, possibly, gilding-metal fouling was allowed to build up.

Not too hot if your brass extracts easily and the primer pockets stay tight.

Thank you for the replies.

Can a small (0.05" or so shorter) OAL change make that much difference?

No pressure signs that I can tell.

David

.05 is fifty thousandths; that is not a small change in OAL; it is a relatively large change.
So, yes.
Fire for effect. (That is what you tell the Artillery Battery when they are on target; no more adjusting; fire the allotted number of rounds, now)

Monometal bullets seem have a greater pressure/velocity reaction to OAL changes than do conventional cup-and-core bullets.

Relatively higher velocity indicates relatively higher pressure, but only the condition of the brass after several firings will tell you if your load is running sustainable pressures. If your bolt lift is not sticky and your primer pockets stay tight, then your pressure is, by definition, acceptable.

Tim North at Broughton barrels(also a buttoned barrel) told me that his barrels will likely gain 50-100 fps in the first hundred rounds of shooting. I have found this to be true on average.

Thank you for the replies.

I will stick with the current load, which hits around 2950-2975fps.

It's at 56grs. of IMR 4955, which is 0.5 grains more than the max listed on the Hodgdon website for 150 gr partitions @ 58,700 psi, although the velocity listed is 2776 fps (quite a bit slower).

From all that I can gather on the web, and the behavior of my rifle the load seems to be max or close to, but safe. Velocity spread is low and the load is accurate.

David

each barrel is a law unto itself --

you should NEVER use max loads from one to another --

and yes, i always expect vel differences, barrel to barrel, and OAL difference as well ...