Erratic velocities with older ammo

[ShooterB]

I have a 300 WM and load 180 gr Accubonds. This gun typically shoots low ES numbers, single digit to low teens. It's a hunting rifle so it doesn't get as much use as some of my other rifles. A few years ago, I loaded 100 rounds of this proven load and it has performed flawlessly. But now I seem to be getting some erratic velocities. ES is more around 35-40. I thought at one time I heard that ammo a few years old almost forms some sort of a bond between the case neck and the bullet. Any truth to this? Can anything be done to alleviate this?

 

[snert]

Yep it can. Simple solution is to reseat your bullets just a tad (scientific term) deeper.

 

[Pappy42]

Mr. snert is correct. The only thing that I would add is to "pop" (seat deeper) a few rounds per season, instead of all at once.

 

[ShooterB]

Yeah that makes sense. Thanks

 

[savagedasher]

40 FPS I wouldn't call it abnormal .
Many of hand loads isn't better .
Larry

 

[dmoran]

While it could definitely be a weldment of the bullet and case neck as stated, I've also seen where internal case fouling can cause the powder to get contaminated that can cause similar issues. The internal fouling is subject to oxidation aspects, which then can bleed off into the powder column over time. One attribute; media tumblers do a good job of cleaning and polishing the exterior of cases, they do a poor job internally.
Just my 2-Cents
Donovan

 

[Milo 2.0]

While it could definitely be a weldment of the bullet and case neck as stated, I've also seen where internal case fouling can cause the powder to get contaminated that can cause the same issues.
While media tumblers do a good job of cleaning and polishing the exterior of cases, they do a poor job internally. The internal fouling is subject to oxidation aspects, which then can bleed off into the powder column over time.
Just my 2-Cents
Donovan

Interesting point, I load as I go other than 223 and pistol blasting ammo. Ammo on hand is like beer in the fridge, just too easy to consume.

 

[ShooterB]

While it could definitely be a weldment of the bullet and case neck as stated, I've also seen where internal case fouling can cause the powder to get contaminated that can cause the similar issues. The internal fouling is subject to oxidation aspects, which then can bleed off into the powder column over time. One attribute; media tumblers do a good job of cleaning and polishing the exterior of cases, they do a poor job internally.
Just my 2-Cents
Donovan

Another good point! Coming up, I'll try to bump a few a little deeper and see how they do but won't rule this out as well.

 

[mikecr]

ShooterB, there is another potential issue.
How & how much were the necks sized & expanded when loaded & how long ago?

 

[Brians356]

FWIW bullets with moly (or a similar) coating should be immune from any "bonding" between the copper jacket and brass. (Assuming the case mouth was polished, e.g. with steel wool. and necks sized for minimal tension, so that little if any coating was scraped off during seating.)
-

 

[jlow]

Yeah that makes sense. Thanks

Just keep in mind that fine tuning a load requires proper seating depth and changes in seating depth sometimes as little as 3 thousands can put you out of an accuracy node. This of course is the worse case situation, and we don't know how it would affect your load this way. The point is don't go ahead and arbitrarily choose a new seating depth and re-seat all your rounds as this may not bring you to where you want to go. So since you don't know, I would start small and test before a full commit.

 

[Brians356]

Just keep in mind that fine tuning a load requires proper seating depth and changes in seating depth sometimes as little as 3 thousands can put you out of an accuracy node. This of course is the worse case situation, and we don't know how it would affect your load this way. The point is don't go ahead and arbitrarily choose a new seating depth and re-seat all your rounds as this may not bring you to where you want to go. So since you don't know, I would start small and test before a full commit.

If one wanted to retain the original seating depth, he could use an inertial bullet puller to draw the bullets out of the neck a bit, then run the rounds back through the seater die to put them back to the proper depth. I've done this before with old reloads. But by moving the bullets out and back in again, it may disrupt something (the original neck tension or ??) and they may not shoot quite the same as before, even at the original bullet jump.
-

 

[Eddie Harren]

40 FPS I wouldn't call it abnormal .
Many of hand loads isn't better .
Larry

C'mon Larry, we know you don't shoot loads with 40 fps variance and win all those matches.

 

[jlow]

If one wanted to retain the original seating depth, he could use an inertial bullet puller to draw the bullets out of the neck a bit, then run the rounds back through the seater die to put them back to the proper depth. I've done this before with old reloads. But by moving the bullets out and back in again, it may disrupt something (the original neck tension or ??) and they may not shoot quite the same as before, even at the original bullet jump.
-

Changing neck tension could indeed be a problem. The other is if the bullet is actually welded to the neck, not sure the inertial bullet puller will be able to dislodge it. OP may end up having to seat deeper first, pull out a bit with the inertial bullet puller, and reseat to initial seating depth. Not a great option but an option nevertheless.

 

[ireload2]

It is standard procedure when using an inertia puller to seat the bullets slightly deeper to break the bond to the neck.
This should be a clue that bullet pull can change over time.

Seat all your ammo .050 shallow and then seat it to the finished length just before you head to the range.

 

[Homerange]

If you search this forum for "case neck welding" there's a heap of further reading for you.
http://forum.accurateshooter.com/se...m=1&q=case+neck+welding&o=relevance&c[node]=2

 

[Dans40X]

Check for bullet to neck weldment by pulling & reseating.
Clean the barrel as if it had never been fired.
Shoot for group/SD/ES.

 

[Berger.Fan222]

While it could definitely be a weldment of the bullet and case neck as stated, I've also seen where internal case fouling can cause the powder to get contaminated that can cause similar issues. The internal fouling is subject to oxidation aspects, which then can bleed off into the powder column over time. One attribute; media tumblers do a good job of cleaning and polishing the exterior of cases, they do a poor job internally.
Just my 2-Cents
Donovan

I can see how this can be true of some media tumblers, but I have had excellent results with stainless tumbling media (water, dawn, and lemishine) getting the inside of cases clean also.

 

[mikecr]

Well a brass isn't going to cold weld to fouling or bullet coating. So taking necks to squeaky clean will not aid in reducing the phenomenon.
What can happen over time is creeping of spring back. Energy added releasing counter to last action, over time.

 

[ShooterB]

ShooterB, there is another potential issue.
How & how much were the necks sized & expanded when loaded & how long ago?

Sorry everyone that I haven't replied back to this post. I had no idea it had received so many more replies.

Mikecr, these were loaded about 3 years ago. The case mouth diameter of a loaded round is .336 with Norma brass. The die is a Forster FL that's been honed to .332, and the chamber is a no turn neck that measures .340. These are on there 3rd loading with 180 Accubonds.

Thanks again everyone for all the replies, I think I was able to take something from everyone on this.