Thread: Same load increased velocity 🤔

Hey all,

Been reloading for years now, and this is the first time I've come across this and can't find anything online to explain it.

Rifle is a howa 6.5creedmoor 24" with about 300 rounds through it.
I've settled on 143 eldx, 41.5gr of adi 2209, cci no.200 primers and hornady brass.

Velocity was 2704fps, but all of a sudden its had increased to 2855fps. Nothing has changed in the load. I use a rcbs lite and check on the little hornady scale every few rounds. I've even pulled bullets and checked the powder load 41.5gr. Still the same bottle of adi 2209.

What can cause this jump?

Bore fouled?


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Try another cronagraph

Sorry also forgot to add my impact has changed aswell, went from dialing 5.6moa @ 325m to 3moa.

Just had a similar thing.
Thought I'd sorted a load for my 7/08 with RL17 and ELD-X 150gr. Tested up to 47.5gr in new lapua brass and settled on 47gr with a COAL of 2.93", No signs of pressure (book max = 47.5gr)

Fast forward a few months. Went to the range to measure some drops to get a handle om MV and bugger me getting sticky bolt lift and extractor marks. 455yrd drop suggested MV of 2900fps!!! Way too hot!

It's been bugging me as to the cause as I'm reasonably pedantic when I load. Only thing I can think of is I used Oneshot case lube and didn't clean the cases after sizing. I wonder if the brass is still slightly lubricated and hasn't got enough friction to grip the chamber walls and is generating high bolt thrust? Be keen to hear others thoughts?

All cases where trimmed to spec
Confident charge weights were okay as checked scales regular throughout with reff weights.
Projectiles are still over 1mm away from the lands.
temperature was about 12 degrees (within 5degrees of when original load development done).

Originally Posted by mimms2

Warm weather... keeping shells in your pocket, or by heater vent in car...?

In a ammo case in a bag as usual

Amount of bolt thrust can have no discernable effect on muzzle velocity. The case / bolt are not moving backwards in any "equal & opposite" reaction, only the entire rifle is moving back.

That said, a thought on equal and opposite reactions.. if you support an all-metal rifle against a solid immovable back-stop (not even a soft recoil pad) vs a human shoulder, will the MV be significantly higher and/or more consistent from backstop-supported shots?

I’ve got the exact same rifle @jwightman. It’s also sped up a lot. A change of powder lot explains some of it, but even taking that and changes in altitude and atmospherics into account, it’s still getting faster. I adjusted the ballistic assumptions in November, again in January and once more in March. I noticed a jump in velocity around 350-400 rounds down the tube.

I don’t really trust el cheapo chronographs so tend not to base any assumptions on what they say, and drop test instead. I’ve noticed when the speed has picked up because I suddenly start shooting over the top of goats at 400-600m. Quick field adjustment then I’m back in business but last time out I thought this is nuts, so I drop tested it for the third time, and it’s running a full 100fps faster than when I reloaded the previous batch with the same powder. I started at 2720fps and have used the Strelok trajectory validation and am now at 2820fps, no changes whatsoever to the components.

I’ve got no technical understanding of what goes on inside a barrel as it wears, other than cooking the throat obviously. But it is interesting that your round count is very similar to mine and we are experiencing the exact same thing. One of the forum clever buggers will be better placed than me to offer an explanation if it is indeed barrel related.

EDIT. Just looked in my load notes and it’s not a change in powder lot because it was at a validated 2720fps when I first started using this same lot that I bought in bulk. So it is the same powder, same brass, same everything.

Greetings All,
I have heard a number of reports of velocity increases as a new rifle barrel wears in, generally about the 300 to 500 round mark. It makes sense. A bit like a new car being a bit stiff until a few thousand km are on the clock.. It could also be a carbon or copper build up so a good clean could be on the cards if not already taken care of. The increase would have been gradual and may still be continuing.
Regards Grandpamac.

I spoke to @Wingman about this after my post... his response was : wear. He has an anecdote about match rifle barrels and how the increase in velocity through wear is managed by the shooter. Interesting.

Yea Velocities on howas seem to get better after 3-400 rounds like @Flyblown pointed out

It's a well recognised (or spoken of) phenomenon in F Class shooting. 300 is the magic number and some report a step change although I cannot get my head around that. A ramped change would be more logical.

When I changed to a 284W ten years ago I was told to watch for the 300 round velocity jump which the 284 was recognised for. At the time I thought how does the barrel know it has a 284 cartridge pushing up its arse? Why 284. In reality calibre and cartridge shouldn't make a difference. Or maybe there is something to it in F Class at least where a lot of 284 owners try to get 7mm SAUM performance out of them.

I have shot well past 300 round count (in fact onward to barrel death) on a 6mmBR, a hot 6.5 Ackley and a 6.5x47L (not dead yet) and cannot say I noticed any significant the step change. That's not to say it doesn't happen. YMMV.

However strange things, or maybe not so strange, do happen. My 284 had a button rifled barrel that I considered to be "fast". By that I mean that compared to a mate's 284 with cut rifling of similar round count his velocities fell well short of mine for similar loads.

Red herring perhaps but can you confirm you seating distance is not jammed into the lands?

Originally Posted by Dead is better

Red herring perhaps but can you confirm you seating distance is not jammed into the lands?

Checked that aswell, Currently sitting 35tho of the lands like previous loads

Originally Posted by Flyblown

I spoke to @Wingman about this after my post... his response was : wear. He has an anecdote about match rifle barrels and how the increase in velocity through wear is managed by the shooter. Interesting.

I possible think that might be it, sounds to be a common thing. I would have never guessed it.
I did work up a 140gr ELD-M load at the start, I might load up a few a see if the velocity has changed aswell.