Barrel Speeding Up

[eroksolfe]

How do you all observe barrel speed up when it happens:

Do you all find it is a gradual process over the course of the first 100-200 shots (or however long it takes)?

Or do you find that it'll happen 'all at once' between a small number of rounds?

For background I've got about 250 rounds down my 7 prc and just recently switched to shooting eld-x from federal factory ammo. My first 2 boxes of the federal stuff shot at right around 2900 for the first 25ish shots, then gradually moved up to ~2915 (the same lot). I then ran out of that lot and moved to a new lot of the federal eldx. Those first first shots were 2930ish and gradually worked up toward 2940-2960. My average seems to be 2935 from this new lot (25 rounds shot).

Clearly, I could just be seeing the result of a lot change but a 30 fps+ difference felt like more than I would have expected. I'll confirm if other ammo has sped up as well in the future but don't want to mess with anything at the moment as its dialed for hunting season starting on Saturday.

 

[JFK]

I’ve always observed it happening gradually. Then again, I don’t have a chrono with me most of the time. With a new gun I’ll typically just try to get 40-50 rounds through it without much concern for speed…just really more of a break in. Any ammo I have on hand. Develop a load and chrono it after that. At somewhere close to 200-300 rounds I’ll chrono it again and it’s sped up so I’ll rework whatever dope I have and it remains stable after that unless I introduce a variable like different brass, powder, primer.

30fps is not a lot of variation for factory ammo and could simply be attributed to a different lot. I wouldn’t mess with anything before season. Typically barrel speed up, if it’s going to happen, will be more significant…in the neighborhood of 75-100fps.

 

[TaperPin]

How do you all observe barrel speed up when it happens:

Do you all find it is a gradual process over the course of the first 100-200 shots (or however long it takes)?

Or do you find that it'll happen 'all at once' between a small number of rounds?

For background I've got about 250 rounds down my 7 prc and just recently switched to shooting eld-x from federal factory ammo. My first 2 boxes of the federal stuff shot at right around 2900 for the first 25ish shots, then gradually moved up to ~2915 (the same lot). I then ran out of that lot and moved to a new lot of the federal eldx. Those first first shots were 2930ish and gradually worked up toward 2940-2960. My average seems to be 2935 from this new lot (25 rounds shot).

Clearly, I could just be seeing the result of a lot change but a 30 fps+ difference felt like more than I would have expected. I'll confirm if other ammo has sped up as well in the future but don't want to mess with anything at the moment as its dialed for hunting season starting on Saturday.

Speeding up is a rather smooth thing. Average shooters never pay attention to lot to lot variances - it would be interesting to know if ten years ago lot to lot variances were as large as what you’ve been seeing, or if the current climate of shortages has encouraged somewhat looser standards.

 

[Vern400]

What you're describing is perfectly normal.
Yesterday I got a 20 fps shift simply due to temperature with a single lot number handloads.
It was supposed to be a temperature insensitive powder, and I didn't clean the rifle. SD was in the 10 range so I know nothing's wrong.

One of my buddies was running 50 FPS fast.