Cases seems to grow too much

[QuietTexan]

A lot of the misconception comes from people that do not shoot thwm enough. And reload their brass 7-15+ times.

How does a misconception about trimming come about from the people who shoot the cases enough times to per you need to trim?

 

[Tac-O]

Sounds like a little to much guessing.
Remove the primer, don't do anything else when you measure. If your measuring with the primer in you can get some bad/wrong readings. Just went over this with a fellow the other day. What looks or feels like very little primer crater can be a lot more than one would think. He thought I was nuts until he did a few.
Also all the guts and ejector need to be out of the bolt to get a true feel.
Watch the video and it will show ya.

Yes I always deprime before I measure cases. I will work on gutting my bolt. I've had the firing pin assembly out but not the ejector and extractor. I'll see if my I can find a demo. I don't think I've seen any demos for those two parts being removed from a Tikka bolt.

So.... you physically put all the cases inside a sizing die that is set below the max length of the chamber.

I do size all cases, but I adjust the die so that it only bumps shoulders on the ones that are at max base to datum.

Let them be the length that they are (the only exception is for safety if they're too long for the chamber, which they shouldn't be in an AI after the first firing). It won't hurt anything. Cases that have different headspaces and different case lengths are absolutely, 100%, A-Ok to shoot. You might even be shocked at how well they shoot.

Yes by getting them the same base to datum I just mean getting them within 0.002ish of each other and don't trim unless I get to trim length. I am ok with some variance on these two metrics.

Strip your bolt down and put the cases in the chamber. You must take the firing control group and the ejector out of the bolt, there's no way around it. No tape on the cases, no marker, nada, zilch, nothing. Does the bolt close? Then size the neck only and shoot it again. Find an actual neck sizing die, or take the largest bushing die you have that won't touch this case at all and set it size about half the neck. Shoot and neck size until the cases don't fit. Don't worry that they're different lengths, don't size them and don't trim them until the cases don't fit anymore.

Then you can "bump" the shoulders. Do it only 0.001" if you have a die capable of that. Get a Whidden click ring if you aren't used to timing a die accurately.

Yes I'll work on getting the ejector out to measureax base to datum more accurately.

I only use a FL die, so I'd just have to adjust the die to only size the neck.

There are a few other parts to this - don't eject the cases and let them bang into concrete. Don't let them fall into the mud or get stepped on. Basically treat them so you don't have to clean them, other than to maybe wipe them down in a rag. You don't need them clean because they aren't going into a sizing die. Use a nylon brush on a drill to hit the carbon in the necks before charging and seating, that's all the lube you need.

Yes I always carefully eject cases and catch them in the hand. When I do brass prep, I deprime, take the carbon off the outer neck with 0000 steel wool, anneal, hit the inner neck with a nylon brush, then lube and size. Wipe lube off.

 

[lancetkenyon]

How does a misconception about trimming come about from the people who shoot the cases enough times to per you need to trim?

If you do not shoot them enough to get to the point of the cases finally growing back to max case length, you will never see that you need to trim them. I have found in many instances, that 6 to 7 firings is where you actually get back to that point. Once you have to trim for the first time, assuming you trim .010" from max case length, you will probably have to trim every 3rd or 4th firing again.

 

[QuietTexan]

15 times isn't enough?

 

[Tac-O]

I removed the ejector and firing pin from my bolt. Took a case that measured 1.810 with my Hornady headspace comparator and put some cellophane on it. Measured it again and it read 1.812 or maybe a touch more. Put the case with tape in my chamber and the handle fell halfway pretty much on its own, then had resistance.

Then I took a case that measured 1.809 and put tape on the base. Measured again and it was 1.811 or a touch more. Chambered it and there was still the tiniest bit of resistance closer to the bottom of the bolt handle drop.

Given that I've had fired cases from max pressure loads measure 1.812, I'll call that max headspace, which is what I'd figured using the tape method prior to removing the ejector and firing pin. But removing that sure does make it easier.

I had been targeting 1.809 for my measurement post sizing. I'd sometimes get 1.808 and occasionally a couple 1.807 or a touch less in a batch of 25, which I think was due to not letting the lube dry enough.

So for the most part, or at least what I'm targeting, I'm not sizing excessively. I'm wondering though if the shoulder dimensions of 0.486 chamber and 0.482 sizer could be causing extra growth. I also wonder if my brass happens to be "grabbing" the chamber walls upon firing really well and just stretching the web back to the case head hitting the bolt rather than the whole case moving back with ignition and then the shoulders of the case getting blown forward to fill the chamber.

Hmmm... Well, at least I know my max headspace measurements were accurate. I'll probably just start targeting 1.5-2 thousandths bump to give myself some room in the OK zone for bump error.

 

[Lefty7mmstw]

I'm shooting a 30-284AI and it seems I'm getting 0.004-0.005 of case length growth each firing. I'm not sure why. From what I've heard it should be almost nothing with an AI cartridge.

On the last round, I measured the brass before loading at 2.162. after firing, most were around 2.164-2.165. After sizing, they're 2.166-2.167.

This brass is on its 7th reload. I only bump the shoulder 0.003 when sizing. Chamber neck is 0.342 and loaded cartridge neck is 0.338. Sized shoulder diameter is 0.482 and fired is 0.486. My standard load is 1 grain under where I started seeing some ejector marks when pressure testing.

Any ideas?

I get less than that fl sizing regular cases unless the chamber is generous (like my 7stw)... one thing I do notice is the hotter the load, the more the case stretch. I wouldn't doubt your action is giving a bit of springing to your case length issue...

 

[Tac-O]

I get less than that fl sizing regular cases unless the chamber is generous (like my 7stw)... one thing I do notice is the hotter the load, the more the case stretch. I wouldn't doubt your action is giving a bit of springing to your case length issue...

Springing?

 

[Lefty7mmstw]

Springing?

There is always a certain amount of metal flex when you fire a rifle. You get the forces a bit too high with excessive pressure or too much push from a large case head and you will start to see more flex. You may even set the bolt back and damage the action.

Are your milder loads showing growth too, or just your full throttle stuff?

 

[Tac-O]

There is always a certain amount of metal flex when you fire a rifle. You get the forces a bit too high with excessive pressure or too much push from a large case head and you will start to see more flex. You may even set the bolt back and damage the action.

Are your milder loads showing growth too, or just your full throttle stuff?

I see. I had wondered if the hotter loads are contributing to it. When I have measured and tried to correlate the load to growth, it seemed inconsistent.

I had planned on the next outing to shoot half of them being low end loads and the other half my hunting load which was 1gr below where I started seeing ejector marks. It will be a bit before I get back out, but that's what I'll be doing next so I'll report back when that's done.

 

[lancetkenyon]

15 times isn't enough?

I am not sure what you are asking?

Is 15 times of firing/reloading enough times to lengthen your brass to max case length?

 

[QuietTexan]

I am not sure what you are asking?

You said this:

A lot of the misconception comes from people that do not shoot thwm enough. And reload their brass 7-15+ times.

You statement reads that people do not shoot AIs enough, yet still somehow reload their brass 7-15+ times.

I'm asking that since apparently reloading cases 7-15+ times isn't enough times to reload a case to qualify as "shoot[ing] them enough", then what is "enough" to you?

Do I need to have loaded my cases 25 times before I've shot my AIs enough to have an opinions on this apparent misconception?

Your statement basically doesn't make a lick of sense, not shooting enough while yet still reloading cases a significant number of times. If I reloaded all my cases 15 times I would have something like 6,000 rounds through a single barrel. Possible in 223AI, not possible in 243 AI.

 

[lancetkenyon]

You said this:

You statement reads that people do not shoot AIs enough, yet still somehow reload their brass 7-15+ times.

I'm asking that since apparently reloading cases 7-15+ times isn't enough times to reload a case to qualify as "shoot[ing] them enough", then what is "enough" to you?

Do I need to have loaded my cases 25 times before I've shot my AIs enough to have an opinions on this apparent misconception?

Your statement basically doesn't make a lick of sense, not shooting enough while yet still reloading cases a significant number of times. If I reloaded all my cases 15 times I would have something like 6,000 rounds through a single barrel. Possible in 223AI, not possible in 243 AI.

You misinterpreted my statement.

Most people do not shoot their AI brass enough, like 7-15+ times to realize that the cases, do in fact grow and will eventually need trimming.

Let's say you fire form 100 pieces of brass in 6.5PRC/SI (a 6.5PRC AI basically) originally. Since I have all that data saved on my phone, it is easy to pull it up. More than likely, during fire forming your brass has shrunk in OAL from 2.022" (crush fit) to 2.010" OAL. If your firing/FL sizing process grows .002" each firing, it will take you 6 more cycles to get back to max OAL and need to trim. I am testing with 20 pieces. I am on firing #7 and am trimming for the first time after #7 (total-1X FF and 6X on reloads). If you go through all 100 pieces before you FL size the batch, that is 600 rounds fired after initial fire forming. Some of us will fire that many rounds a year in a single rifle, and see that trimming will become necessary after that point. Some people might not shoot that many rounds in a lifetime, so never see the need to trim. Those are the people that say "You don't need to trim an AI".

My .260AI shrunk .015" from virgin (crush fit) to .260AI formed brass, and has grown .003" per cycle. So after 5 cycles from FF, I will probably need to trim. I formed 200 pieces, meaning about 1000-1200 rounds down before needing to trim brass. Since I will likely only shoot it 200-300 rounds a year, that brass could possibly outlive the barrel life before needing trimmed.

 

[QuietTexan]

People don't shoot them enough TO load their brass 7-15+ times. That makes more sense.

Using "and" isn't correct there, it makes the statement mean something entirely different.

 

[hitmancustoms]

I'm shooting a 30-284AI and it seems I'm getting 0.004-0.005 of case length growth each firing. I'm not sure why. From what I've heard it should be almost nothing with an AI cartridge.

On the last round, I measured the brass before loading at 2.162. after firing, most were around 2.164-2.165. After sizing, they're 2.166-2.167.

This brass is on its 7th reload. I only bump the shoulder 0.003 when sizing. Chamber neck is 0.342 and loaded cartridge neck is 0.338. Sized shoulder diameter is 0.482 and fired is 0.486. My standard load is 1 grain under where I started seeing some ejector marks when pressure testing.

Any ideas?

I had this problem in my 7 saum talked to gunsmith and he new exactly right away. Sometimes gunsmiths hand finish the reaming and can over ream. At least that is what happened to me. So measure and see if that is what happened.