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).

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Originally Posted by mimms2

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

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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?

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Originally Posted by Dead is better

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

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

Quote:

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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.

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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.

What is your C.O.A.L.?

From memory we are internal mag length restricted on these rifles to ~2.875”. Mine are therefore 2.850” tip to primer. But my maximum possible overall length is 2.927” if I were single feeding, using the cartridge length tool.

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Originally Posted by Flyblown

What is your C.O.A.L.?

From memory we are internal mag length restricted on these rifles to ~2.875”. Mine are therefore 2.850” tip to primer. But my maximum possible overall length is 2.927” if I were single feeding, using the cartridge length tool.

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2.865" I am running ai mags with heaps of room left in the mag

Similar thing happened in my mates 6.5 was carbon ring build up. It was a prick to get it cleaned. Solvent and nylon brush in a battery drill. Finally worked it out by checking the distance to lands using the hornady gauge, was different from when new. After we cleaned it everything went back to how it was previously including the accuracy. He was very close to putting a new barrel on it. Can see the benefits of a bore scope after that.

Quote:

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Originally Posted by Plinky

Similar thing happened in my mates 6.5 was carbon ring build up. It was a prick to get it cleaned. Solvent and nylon brush in a battery drill. Finally worked it out by checking the distance to lands using the hornady gauge, was different from when new. After we cleaned it everything went back to how it was previously including the accuracy. He was very close to putting a new barrel on it. Can see the benefits of a bore scope after that.

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Had carbon rings in some big bangers that had lost accuracy and started showing pressure.
The best by far for removing the build up was the recommendation of using a foaming bore cleaner called wipe out and its precleaner called accelerator.
I just use patches and no scrubbing.
Unbeleivable stuff.
I keep going until the patch comes out as clean as when ya put it in.
I have got most solvents ever invented and this is by far the best of the lot.
Beware as it leaves nothing in the bore so I only use it for deep cleans when accuracy is falling off.
I will try find a photo of it.

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Quote:

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Originally Posted by andyanimal31

Had carbon rings in some big bangers that had lost accuracy and started showing pressure.
The best by far for removing the build up was the recommendation of using a foaming bore cleaner called wipe out and its precleaner called accelerator.
I just use patches and no scrubbing.
Unbeleivable stuff.
I keep going until the patch comes out as clean as when ya put it in.
I have got most solvents ever invented and this is by far the best of the lot.
Beware as it leaves nothing in the bore so I only use it for deep cleans when accuracy is falling off.
I will try find a photo of it.

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https://sharpshootr.com/wipe-out/

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https://sharpshootr.com/accelerator-for-wipe-out/

Quote:

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Originally Posted by andyanimal31

https://sharpshootr.com/wipe-out/

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https://sharpshootr.com/accelerator-for-wipe-out/

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I get it from guncity or deaddeye dicks

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Have you changed batches of powder? I have first hand experience of AR2209 producing significant velocity swings when using a new container of powder with a different lot#

Quote:

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Originally Posted by andyanimal31

Had carbon rings in some big bangers that had lost accuracy and started showing pressure.
The best by far for removing the build up was the recommendation of using a foaming bore cleaner called wipe out and its precleaner called accelerator.
I just use patches and no scrubbing.
Unbeleivable stuff.
I keep going until the patch comes out as clean as when ya put it in.
I have got most solvents ever invented and this is by far the best of the lot.
Beware as it leaves nothing in the bore so I only use it for deep cleans when accuracy is falling off.
I will try find a photo of it.

Sent from my SM-G950F using Tapatalk

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This is good stuff and what I use.
Save a whole lot of scrubbing which must be good for your bore.

Quote:

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Originally Posted by andyanimal31

Had carbon rings in some big bangers that had lost accuracy and started showing pressure.
The best by far for removing the build up was the recommendation of using a foaming bore cleaner called wipe out and its precleaner called accelerator.
I just use patches and no scrubbing.
Unbeleivable stuff.
I keep going until the patch comes out as clean as when ya put it in.
I have got most solvents ever invented and this is by far the best of the lot.
Beware as it leaves nothing in the bore so I only use it for deep cleans when accuracy is falling off.
I will try find a photo of it.

Sent from my SM-G950F using Tapatalk

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Quote:

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Originally Posted by winaa

This is good stuff and what I use.
Save a whole lot of scrubbing which must be good for your bore.

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Yep, same here. It's what Tony Boyer, one of USA's all time benchrest greats uses. Although he uses the liquid not the foam. They both do the same job. Got mine from DED.

Quote:

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Originally Posted by Dermastor

Have you changed batches of powder? I have first hand experience of AR2209 producing significant velocity swings when using a new container of powder with a different lot#

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Still the same bottle of powder. Was thinking about opening another bottle (from the same batch) and trying 5 test rounds.

Quote:

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Originally Posted by zimmer

Yep, same here. It's what Tony Boyer, one of USA's all time benchrest greats uses. Although he uses the liquid not the foam. They both do the same job. Got mine from DED.

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Might have to give it a try, wouldn't hurt.

Are you checking your brass length? Do you trim your cases?

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Originally Posted by canuck hunter

Are you checking your brass length? Do you trim your cases?

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Yip always check length, they sit around 1.914

Yep, in my experience it will be one or both of whats mentioned above, bore being run in and/or carbon fouling.

My Bartlein barrel (28 Nosler) had a big increase of speed at about 80-90 rounds down it, after it had run in i assume. The give away was when i started shooting over animals at distance, checked the velocity and it was much higher.

Also most people dont clean carbon out of a barrel properly with normal cleaning, i found this out the hard way a few years back with another rifle, velocity increase and accuracy blown out to about 3 inches at 100 yards, i checked everything and when just about ready to move it on, i got a tip from a target shooter about carbon build up, i polished it out with autosol and the problems went away like magic.

Ive since started using foaming bore cleaner and havnt really seen the problem again since. I do do regular carbon cleans on the 28 Nosler thou as the R33 carbon fouls pretty bad.

Quote:

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Originally Posted by Cordite

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?

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So, had to do some calculations on this. A 174grain (11.28gram) projectile at 2450 fps through a 4kg all-metal rifle.

Rifle will recoil at 7.14 fps into the shoulder by time the projectile is at the muzzle, as an opposite reaction to the accelerating bullet proportional to their relative mass difference. Additional recoil as gases exit does not affect muzzle velocity.

The same rifle supported against an immovable, non-giving back stop will launch the same projectile at 2457 fps, turning the rifle into an impressive, long-range shooter... (<:

Basically the more powerful the cartridge and the lighter the rifle is, the greater relative differences in MV between supported butt vs. unsupported butt.

Problem solved.
I thought I gave my rifles a really good clean, but apparently not.
Brought a can of foaming cleaner after cleaning, finally back down to 2704 fps

Standard clean won’t budge carbon ring. Good you got it sorted

Quote:

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Originally Posted by Hunty1

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).

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If you did your load development on virgin brass I’d expect the velocity to increase on subsequent firings as less energy is lost to fireforming the case. I got 100fps gain on second firing of Lapua brass for a 6.5 284

My .300 Win Mag increased mv by 80 fps from 2900 to 2980 with 208s over just a few rounds (chrono verified) at around 100 round count.

I clean my rifles with Autosol and a wire brush every 200 rounds, especially in the throat area. I think many shooters are too precious when cleaning their barrels and don’t get enough carbon out or polish the throat sufficiently to help slow erosion. Jags and plastic brushes are fine for normal cleaning but don’t really get into the grooves or prevent rings forming. Barrels are made from steel, not butter. That said, I use good bore guides (Lucas), Dewey rods, and don’t overdo it.

That’s my routine, but ask ten shooters and you will get ten different answers. Even barrel manufacturers don’t agree on cleaning routines.

$20 (but probably a rather long wait nowadays for freight) will put to rest any question over how much or how little to clean, and how effective your methods are on both carbon and copper. Would ID this sort of issue quick-smart.
https://www.nzhuntingandshooting.co....hawkeye-45930/

Quote:

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Originally Posted by Spitfire

My .300 Win Mag increased mv by 80 fps from 2900 to 2980 with 208s over just a few rounds (chrono verified) at around 100 round count.

I clean my rifles with Autosol and a wire brush every 200 rounds, especially in the throat area. I think many shooters are too precious when cleaning their barrels and don’t get enough carbon out or polish the throat sufficiently to help slow erosion. Jags and plastic brushes are fine for normal cleaning but don’t really get into the grooves or prevent rings forming. Barrels are made from steel, not butter. That said, I use good bore guides (Lucas), Dewey rods, and don’t overdo it.

That’s my routine, but ask ten shooters and you will get ten different answers. Even barrel manufacturers don’t agree on cleaning routines.

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The barrel makers will love you!
Try the wipe out foaming bore cleaner,
You will be amazed, no scrubbing just let it do its work.
It gets every thing out.

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Quote:

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Originally Posted by jwightman

Problem solved.
I thought I gave my rifles a really good clean, but apparently not.
Brought a can of foaming cleaner after cleaning, finally back down to 2704 fps

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Which cleaner preytell?


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