Annealing causing pressure increase

[SDHNTR]

did you shoot the 20 rounds in a round robin or shoot all the not annealed first and the annealed second?

The latter, but the gun sat and cooled for about 20 minutes in between the not annealed vs annealed.

 

[ddowning]

How many rounds since last cleaning? What was sd and es of both 10 shot strings? Honestly, that's not much of a difference unless you are a top end reloader. Does this phenomenon repeat, or was it just random velocity dispersion that created it?

My opinion, there are too many variables and too much noise to know if it was caused by annealing or not.

 

[SDHNTR]

How many rounds since last cleaning? What was sd and es of both 10 shot strings? Honestly, that's not much of a difference unless you are a top end reloader. Does this phenomenon repeat, or was it just random velocity dispersion that created it?

My opinion, there are too many variables and too much noise to know if it was caused by annealing or not.

Es and SD were comparable between both groups. 25 ish ES and 6-8 SD. Yes, not much of a difference and I normally wouldn’t worry about it except for the pressure signs present in the annealed group. There was probably 50 rounds since last cleaning. It’s not a carbon ring. I thought of that.

I need to do the experiment again and re test.

 

[HighUintas]

Es and SD were comparable between both groups. 25 ish ES and 6-8 SD. Yes, not much of a difference and I normally wouldn’t worry about it except for the pressure signs present in the annealed group. There was probably 50 rounds since last cleaning. It’s not a carbon ring. I thought of that.

I need to do the experiment again and re test.

Did you happen to measure the overall length of your empty case after sizing, both the annealed and non-anield?

 

[HighUintas]

I'm just asking that because if they started out as the same length and ended up the same length after sizing, then it's very likely that all the dimensions of the cases of both groups after sizing were the same. In that case, the only difference is between the annealed cases and the non-annealed cases would be the oxidation layer on the outside of the case that got hot and the bearing surface inside the neck.

I think it's possible that the oxidation layer on the annealed cases could have not provided as much grip on the chamber interior, allowing the case to ram back into the bolt face harder. But I don't think that would explain the difference in velocity that you saw

 

[Bluefish]

Only a guess, but different neck tension due to the annealing? Did you check neck od before bullet seating?

 

[SDHNTR]

Did you happen to measure the overall length of your empty case after sizing, both the annealed and non-anield?

Yes, same same.

 

[SDHNTR]

Only a guess, but different neck tension due to the annealing? Did you check neck od before bullet seating?

I did check OD, but I don’t remember which group I checked, or if I checked both. The thought did not occur to me, as I don’t see how annealing could change the measurement, but I suppose stranger things have happened.

 

[Lawnboi]

I did check OD, but I don’t remember which group I checked, or if I checked both. The thought did not occur to me, as I don’t see how annealing could change the measurement, but I suppose stranger things have happened.

The whole point of annealing is to soften the neck and reduce/eliminate spring back as brass goes through its life. Both in shoulder bump and neck diameter.

Example wood be, before annealing it was not uncommon for me to need to change bushing size or deal with different size necks. Same goes for headspace. Annealing essentially resets the neck hardness and makes so the operations are the same on firing 2 as they are on firing 10.

 

[SDHNTR]

The whole point of annealing is to soften the neck and reduce/eliminate spring back as brass goes through its life. Both in shoulder bump and neck diameter.

Example wood be, before annealing it was not uncommon for me to need to change bushing size or deal with different size necks. Same goes for headspace. Annealing essentially resets the neck hardness and makes so the operations are the same on firing 2 as they are on firing 10.

Right, totally understand all that. But I also didn’t think of it changing interference fit. But I sure suppose it could, changing spring back.

 

[rayporter]

i have a nagging feeling that it is just heat.

if you perform the test again in a round robin i bet it will equal out.

 

[SDHNTR]

Out of curiosity I just grabbed 2 pieces of brass. Annealed one, not the other. Resized both. Zero difference in measurements, headspace nor neck OD.

 

[SDHNTR]

i have a nagging feeling that it is just heat.

if you perform the test again in a round robin i bet it will equal out.

I understand where you are going with this, but I was very mindful of additional heat. I brought two other rifles to the range to shoot in between. It was completely cool between groups. And I shot very slowly. In fact the first shot in that annealed string of 10 was faster than the last.

 

[TaperPin]

When brass isn’t annealed there is a layer of slippery carbon left inside the neck. Annealing burns out the carbon so it’s stickier unless a lubricant is used inside the neck prior to seating the bullet.

 

[rayporter]

there is more to consider than just cooling off the rifle. while you waited on the barrel to cool did the clouds dissipate and the sun come out? did the temperature rise during the day? temperature rises and humidity falls and sometimes bullets speed up.

not knocking the likely possibility of the annealing being the culprit, either.

strange things show up when testing. last month i was testing 2 rifles and one was shooting at 3404fps and the other was shooting at 3421fps with the same load. i switched bolts in the rifles and the first rifle now shot 3424fps and the second rifle now shot at 3411fps. just how is one bolt is faster? i am going change out the springs in the bolts and retest.

 

[SDHNTR]

there is more to consider than just cooling off the rifle. while you waited on the barrel to cool did the clouds dissipate and the sun come out? did the temperature rise during the day? temperature rises and humidity falls and sometimes bullets speed up.

not knocking the likely possibility of the annealing being the culprit, either.

strange things show up when testing. last month i was testing 2 rifles and one was shooting at 3404fps and the other was shooting at 3421fps with the same load. i switched bolts in the rifles and the first rifle now shot 3424fps and the second rifle now shot at 3411fps. just how is one bolt is faster? i am going change out the springs in the bolts and retest.

No to anything in Your first paragraph, consistent 60-65 degrees

 

[HighUintas]

More testing is necessary

 

[NevadaMike]

Wet tumbling with stainless steel? Probably totally irrelevant to your situation but I wet tumbled too long (and annealed) and I had increased seating effort and pressure signs. I had no idea what was going on until I happened to watch an area 419 reloading video where they talked about no longer wet tumbling and why.

 

[ResearchinStuff]

Out of curiosity I just grabbed 2 pieces of brass. Annealed one, not the other. Resized both. Zero difference in measurements, headspace nor neck OD.

Are you actually changing dimensions compared to a fired, unsized case?

 

[ddowning]

Right, totally understand all that. But I also didn’t think of it changing interference fit. But I sure suppose it could, changing spring back.

I'm too lazy to anneal every time, plus I don't want to buy an Amp and get best groups on second firing with flame annealing. I have whidden click rings on my fl dies to deal with the different # of firings since annealing (springback variation) I anneal every 3 firings for case longevity.

That said, I have shot strings over the chrono and groups with 1x, 2x, and 3x brass mixed on purpose and the sd/es and group size have been so close to shooting the same # of firings since annealing that I could not definitively say there was a difference. The guy that spins my barrels is good and most all of my 6 Dasher barrels will easily do 10 shots under 1/2" even when I call a pulled shot from a bipod and rear bag. The reason I throw that in is to iterate the fact that it is easy to see subtle differences in things with that gun that I could never identify with a gun that shot less precisely than that.

I have never loaded for a 300wsm, so I have no idea of the tendencies with springback or other idiosyncrasies. With the cartridges I load for it is definitely a thing to get different neck tension and shoulder bump with the same die set-up on annealed vs not annealed. That said, the difference is not enough to be noticeable downrange on the target even with very precise gun systems.