Rifle barrel memory

[Mohamed]

Hi

Something I noticed, but not sure about. Does a rifle have memory of certain ammo used or is it that it just likes certain ammo? When I got my rifle, I used Federal Fusion 165gr for quite a while. I noticed that although it likes 165gr ammo, it shoots very good groups with Federal Fusion 165gr ammo compared to other ammo with the same grain, although it also shoots them well as well.

I read the following on the HOWA break in procedure recently, hence the memory question:
If the barrel is allowed to heat up during the break-in process, it will impede the steel's ability to develop memory or a home registration point. (https://www.habitatafrica.co.za/how-to-break-in-a-howa-rifle/)

In the attached image, from 2020, 2021 and 2023, grouping with 165gr Federal Fusion.

[223]

Interesting story about barrel memory.  I guess it has to do with stress relief in the steel.  Some of the better barrels are stress relieved in the factory, and some US firms once offered cryogenic stress relief services.

The reason why certain rifles like certain ammo has to do with barrel harmonics and the accurate nodes.  Reloaders can tune their ammo to optimize the harmonics. Factory ammo users have to select the load most liked by their particular rifle.

[Tripodmvr]

You did not perhaps measure speed on the Federal 165 ammo?

[Mohamed]

You did not perhaps measure speed on the Federal 165 ammo?

No, not recently, did a few years back but didn't record it. Will try and get a reading soon when I am at the range with a friend who has a chrony.

[Treeman]

I do believe that the different alloys used for different bullets can and often do mess with accuracy and grouping. Driepootz of Gunsite fame (Tripodmvr on this forum) once wrote an very informative piece regarding this matter. I for one believe this is the cause of good loads being called out as suddenly going inaccurate.
Some folk use, lets say Sierra Game Kings during the year for springbuck, warthog, practice and then revert to their costly Nosler AccuBonds for hunting season and kudu. When they go back to the Sierra's they find the load is no longer as fantastic as it was, there have been a few posts aking how? What? Happened.

I used to be a fanatical clean my rifle to bare metal after every use kinda guy, I never had this problem. Later in my shooting life I got lazy and started leaving the rifle till 30 -50 shots later before decoppering - deep clean. It was about this time that I started noticing some bullet, load combo's did perfectly well in a clean rifle, but behaved badly when sighting in after changing back to the particular brand.

If you wish to see this more clearly, just look at the first few shots after changing brand of ammo when using a .22

[223]

I do believe that the different alloys used for different bullets can and often do mess with accuracy and grouping. Driepootz of Gunsite fame (Tripodmvr on this forum) once wrote an very informative piece regarding this matter. I for one believe this is the cause of good loads being called out as suddenly going inaccurate.
Some folk use, lets say Sierra Game Kings during the year for springbuck, warthog, practice and then revert to their costly Nosler AccuBonds for hunting season and kudu. When they go back to the Sierra's they find the load is no longer as fantastic as it was, there have been a few posts aking how? What? Happened.

I used to be a fanatical clean my rifle to bare metal after every use kinda guy, I never had this problem. Later in my shooting life I got lazy and started leaving the rifle till 30 -50 shots later before decoppering - deep clean. It was about this time that I started noticing some bullet, load combo's did perfectly well in a clean rifle, but behaved badly when sighting in after changing back to the particular brand.

If you wish to see this more clearly, just look at the first few shots after changing brand of ammo when using a .22

A seasoned Bisley competitor once told me to check the hardness of the bullets or their jackets.  When going to a harder bullet, decoppering is not crucial, as the harder bullet will scrape out the softer fouling.  The other way round is problematic, as a softer bullet can not do much to some harder fouling sitting in the barrel, except to leave some more fouling on top of the hard fouling already in there.
Turned copper bullets are quite soft. Most imported copper jackets are harder. PMP jackets are harder than most others.  Then we have the brass bullets that are harder than copper.

.22LR lead bullets have a similar story w.r.t. lead fouling, but the specific lube also plays a role.

[Mohamed]

You did not perhaps measure speed on the Federal 165 ammo?

Did measurements last week, 2594 and 2569.

[Treeman]

Thats like 2.5 %? Is this really something that can be controlled at our level?
There are 4 components in a reload of which any can have many variances, there after there is also the environmental factors like humidity and temperature. All  these factors are then run through a rifle which has its own personality in regard to temperature number of shots fired and so forth.
I believe that a 2.5% spreads is pretty good for something which has no more than same brand components and a bench scale as contributors to achieve its goals.