Measuring and experimentation

NE Newton 3 years ago

Greetings
For those that are curious , like measuring and checking things , and wonder about stuff

An Exercise - I have no idea what will happen or what the results will be - just curious

Lets take a popular rifle - HOWA 1500 and a popular cartridge - 308 Winchester

I am interested in how much cartridge brass expands and contracts and the effects of different reloading methods

We will need a box of twenty rounds of a well known good brand factory ammo
Ten rounds will be in one batch and the other ten rounds in a separate batch

Take a new factory round of the well known good brand

Carefully measure the cartridge plus bullet - head / web / body ( in a few places ) / neck /shoulder / length

Then ...

Once a round is fired - cartridge brass springback allows us to extract the round.
I assume one can then rechamber the fired cartridge ( doppie )

Now measure carefully the once-fired doppie in the same places that were measured before the round was fired.
Use a gauge to measure neck thickness

Neck Thickness Gauge

Use an accurate measuring tool to check neck inside dimensions - check with a pin gauge

Do this for ALL twenty rounds - which have been fire-formed to YOUR chamber.

Write this all down and notice which dimensions have changed
This will be a reflection of your rifles chamber

Not sure if HOWA follow SAAMi or CIP ?
Check your dimensions against a schematic from one of these organizations and see if anything matches

FL resize the doppie in a die where the decap pin and expander button rod has been removed
Setting the FL die to give 002 thou inches of neck setback ( bump )
Use a comparator to check this

Re-measure all dimensions again and write this down noting what has changed

Now replace the de-cap and expander button rod and re-size again
Measure again

This is your dies dimensions - check against your chambers dimensions

You are going to use the ten rounds of the one batch for this procedure
( Standard way one is taught how to reload )

For the other batch of ten rounds

Now - use ONLY a LEE Collet neck sizing die to resize ONLY the neck and not the body ( or shoulder )
Measure again - what has changed ?

What are the differences ?

Now fire all twenty rounds ten times using the same bullet and a well known accurate load below max

Using the above reloading procedures where Ten have been FL sized and Ten have been only neck sized
I do not know if firing / resizing five times would be significant or not ? I think ten is better
After each firing measure everything carefully

How do the respective rounds chamber after each firing ? Easy / slight resistance / heavy resistance / cannot chamber ?
How does this compare / relate to the changes in the dimensions and the reloading methods ?

An interesting exercise which if done carefully should produce some insightful and valuable data ...

One could of course use some fancy equipment to check bullet seating pressure ( tension ) but this would be too expensive for this exercise where we are only checking changes in actual physical dimensions.

Comments welcome

4

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TR Treeman

R1000 experiment ? Would be interesting, but the answers are out there on the web already.

NE Newton OP

R1000 experiment ? Would be interesting, but the answers are out there on the web already.

Reference please

JA janfred

Newton, how much reloading have you done?

NE Newton OP

Newton, how much reloading have you done?

Not enough
I try and learn from others more knowledgeable and experienced than I am
Those World class enthusiasts who are happy to share their knowledge.
Who are humble enough to state that they are still learning.

BTW ;
What is the news on the availability of SOMCHEM propellant ?

TR Treeman

BTW ;
What is the news on the availability of SOMCHEM propellant ?

*********************
I waS sent a photo yesterday of MP 200 on some shelf somewhere, with S365. The post implied that it was available again ?

JA janfred

Newton, how much reloading have you done?

Not enough
I try and learn from others more knowledgeable and experienced than I am
Those World class enthusiasts who are happy to share their knowledge.
Who are humble enough to state that they are still learning.
...

Can you please let me know which world class enthusiast actually uses neck-sizing in competition?

What those who have actually done neck-sizing found out. At the third use of your cases, the bolt closes with some resistance. By the 4th use you have to use quite a bit more force to get the bolt closed. 5th and up you basically need to travel with a hammer. A Palma shooter once broke the bolt handle off his Barnard P action during the WP open. He had to use a allen bolt and dishrag to keep shooting.

This is caused by the base-to-shoulder measurement of the case increasing with every shot. To avoid this, when neck-sizing, you should then use a body-die or full-length sizing die to bump the shoulder back 0.001"-0.003". That is when you realise that using a neck die then a body die, you might as well save a step and use the FL die from the start.

Unlike Mr Cortina, I won't say don't do neck-sizing. There are some cases where neck-sizing is preferred. Most notable if you have to load for an old battle rifle with oversize chamber. Like a Lee-Enfield circa 1920.

TR Treeman

I used to neck size for everything, now only for the .303 Lee.
The keeping track and then loading back to full length sizing just got too much.

NE Newton OP

Can you please let me know which world class enthusiast actually uses neck-sizing in competition?

What those who have actually done neck-sizing found out. At the third use of your cases, the bolt closes with some resistance.

This is caused by the base-to-shoulder measurement of the case increasing with every shot.

Thanks
What I was asking about in my post about measurement

Yes moving the shoulder affects the head-spacing on a center-fire rimless bottle nose cartridge

Something everyone worries about and why they do - stress-relief ( annealing ) on the shoulder and neck

However
One wonders about what happens with the rest of the body of the case and the web ?
This has to be sized to fit in the chamber but also expands upon firing ( and then "springs back")
One wonders if this part of the cartridge also "work-hardens" ?
Obviously if the web and area near the web is oversize the case will also not chamber - OR eject when fired !

Have you measured this portion of your cartridge - factory cartridge , and once fire cartridge ,and multiple fired cartridge
How much do these dimensions change ?

Have you measured your FL resizing die in the head / web area ?
In non-belted cartridges the case is sized all the way down to touching the shell holder
What are the differences between a factory round - and the fired rounds ?

Does this area "work-harden" ? IF so why is this not important ?

BTW;
Does HOWA use SAAMI or CIP specifications / dimensions ?

TR Treeman

the area's mentioned do work harden, but so much less and also under so much less work forces - if your chamber and die match and chamber is to spec that is. When your die and chamber do not match, your chamber is off spec, then you need only think .303 Lee to see the results of stretching and work hardening.

NE Newton OP

When your die and chamber do not match, your chamber is off spec, then you need only think .303 Lee to see the results of stretching and work hardening.

Do a careful accurate cast of your chamber
Take it to a CNC tool and die maker ( guru ) and get him to make you a "body-die"
Then just use a LEE universal decap die and a collet neck size die - and once in awhile FL size with the body die