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  #1  
Old 01-10-2020, 02:38 AM
mefizto mefizto is offline
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Default Cause for neck splitting?

Greetings all,

I have recently shot a Remington VLSS in .221 Fireball. All five rounds I fired split, not merely cracked, at the neck, all the way from the mouth of the case to the top of the shoulder.

I looked at the SAAMI specifications, which list the diameter of the neck of the chamber as 0.2550 and (max?) diameter of the neck as 0.2530.

The loaded round I was shooting, stamped R-P 221 Rem Fireball, measures at the neck on average 0.2470. The fired cases' necks were distorted out-of-round and measure at the largest dimension on average 0.2550.

I have also measured new cases (1) R-P 221 Rem Fireball with an average neck diameter of 0.2460 and (2) Lapua cases with an average neck diameter was 0.2470.

Could the difference of 0.008 (0.2550 - 0.2470) be the culprit?

Kindest regards,

M
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  #2  
Old 01-10-2020, 02:57 AM
SEM SEM is offline
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I have had this happen numerous times and with different cartridges, sometimes weak brass from deteriorated powder damaging the brass, to hot of a load, brittle brass and oversized chambers. 221 FB seems to be a real touchy case I am very religious about annealing frequently

forgot to mention get a chamber cast done
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  #3  
Old 01-10-2020, 03:30 AM
Bill K Bill K is offline
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Anneal those cases more often.
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Old 01-10-2020, 03:38 AM
mefizto mefizto is offline
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Hi SAM,

thank you for the reply. What is a chamber cast and how does making one help?

Hi Bill K,

How often?

So based on your comment, the difference is likely not the cause?

Kindest regards,

M
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  #5  
Old 01-10-2020, 03:49 AM
Oso Polaris Oso Polaris is offline
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Hey M,

Something to keep in mind is that the diameter of the necks on the fired brass is an approximation of your rifle's chamber, BUT the actual chamber is wider. Upon firing the case expands to fit/mirror your chamber. And then as it cools off the metal shrinks a bit.

Were these factory ammo or reloads?
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Old 01-10-2020, 04:28 AM
mefizto mefizto is offline
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Hi Oso Polaris,

thank you for the reply. If I understand your first paragraph, you are suggesting that the chamber may be out of SAAMI specification, correct? But is the shrinkage not only a thousand or two, in other words, would it make a difference? What about measuring the chamber with machinist's calibrated dowels?

I have to ask my acquaintance about the ammo.

Kindest regards,

M
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  #7  
Old 01-10-2020, 04:59 AM
Bill K Bill K is offline
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[

Hi Bill K,

How often?

With the way you say your cases are doing I would anneal them after three reloads. Just my thought.
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  #8  
Old 01-10-2020, 05:19 AM
georgeld georgeld is offline
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Sounds to me like you're using old brass, not new stuff.

Annealing should cure that. Take a propane torch and heat the
neck only til it barely starts to show a color change. Then drop it
in a container and let it air cool. DO NOT quench it! Regardless of what others
will be telling you.

My first annealing was with 7mm & 300 RUM used brass. I bought 500 at $1 each. Necking out to .35 cal. I split about 20 in a row. Then started annealing.
To compare, I heated 40. Quenched 20, air cooled 20.

The first 7 of the quenched split. I stopped to save brass. The air cooled I never split another one and did the rest of the 500. I sent the 47 split cases to BillK..

Far as chamber cast. Midway sells a half pound ingot of Cerrosafe Metal. It melts with just hot tap water heat. Plug the bore about 1/2-3/4" ahead of the chamber with paper or a patch. Pour the melted metal down into the chamber til full or a bit over. In the search line type: chamber casting, there's some demo vids there that show and tell etc.
In a few minutes the metal will shrink and fall out when tipped down. IF it don't, use a range rod or even a ram rod and push it out.

Then you can measure it with a micrometer or dial caliper. surely you have one or the other right? IF not, get a good one. I use both. A mic is more accurate than a caliper. MSC sells some good one's fairly cheap for such tools. Expect to pay $20 or more for quality. Top quality machinist tools can cost 5 times that easy. No need for those.

All a chamber cast does is show the actual chamber and lead of the rifling to the true size. Then compare your fired brass to it. IF the cast doesn't come out fully formed, remelt it and do it again til you get a good casting.
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Last edited by georgeld; 01-10-2020 at 05:25 AM. Reason: fixing
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  #9  
Old 01-10-2020, 01:28 PM
Gary in Illinois Gary in Illinois is offline
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Default Cerrosafe

Just to add a bit to George’s post - read the directions that come with the Cerrosafe. I seem to remember that the Cerrosafe comes out of the chamber slightly undersized (thus, it will come out of the chamber easily). I think the cast then expands over the next several hours until it is over-size. At a specific time after casting, it will be the exact size of the chamber; that is the time to measure the cast.

You will get a better cast if the receiver / chamber end of the barrel is heated slowly and evenly (with a hair dryer or similar) to a warm, but not hot, state before pouring the Cerrosafe cast.
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  #10  
Old 01-10-2020, 03:19 PM
Oso Polaris Oso Polaris is offline
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Quote:
Originally Posted by Gary in Illinois View Post
Just to add a bit to George’s post - read the directions that come with the Cerrosafe. I seem to remember that the Cerrosafe comes out of the chamber slightly undersized (thus, it will come out of the chamber easily). I think the cast then expands over the next several hours until it is over-size. At a specific time after casting, it will be the exact size of the chamber; that is the time to measure the cast.

You will get a better cast if the receiver / chamber end of the barrel is heated slowly and evenly (with a hair dryer or similar) to a warm, but not hot, state before pouring the Cerrosafe cast.
In addition to Gary's comment is that after the "Golden"mmoment to measure the chamber cast, the dimensions of the cast will continue to change. When it finally stabilizes (no more changes), the cast dimension will not be your chamber.

It all sounds a little spotty/iffy, but this process is actually well documented AND the growth/shrink rate of Cerrosafe is a known rate/factor. There are some other threads here or on Accurate Shooter forum that provides indepth detail to process for chamber casting.
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