Shorter COAL Less Pressure???

[Zen Archery]

For my wildcat caliber Case Overall Length 1.690.
In working up the cases I trimmed some to 1.675.
As always I am running these loads really hot (5000fps HOT).

I noticed the cases at 1.690 had ejection mark, flat and pierced primer.
I noticed cases at 1.675 had ejection shine and flat primer.

Accuracy wise the bullets like to be loaded deep into the case. All the way to the shoulder. Big jump? (Wildcats are so unpredictable!)
There is about a .020 measurable difference with the longer cases showing better accuracy.

Question, why would a longer case produce more pressure signs on the case versus shorter case?
I can only presume the lack of wiggle room in the chamber causes the pressure on the cases versus having the .015 room to blow out.

Any thoughts or experience with this?

On a side note. I had to drill out the gas port. Talk about INTIMIDATING. But It's fully funtioning now. PDOGS in 1 month!!!

Cycle test for your viewing entertainment!

 

[Dmagna]

It could be a little less of a gas seal on the case that's shorter, letting a tiny little bit of gas escape before sealing tight.

 

[del2les]

Question, why would a longer case produce more pressure signs on the case versus shorter case?

It can be a few things:

1- Shorter case necks have less overall tension on the bullet due to reduced surface area.
2-If your longer cases were touching or entering the chamber leade area, especially in a shorter target chamber, they could have been "crimping" and increasing pressures.
3- If not properly adjusted, your longer cases could have been receiving a crimp from the seating die

Most of the higher pressure events I have seen in many peoples rifles/loads that were related to case length were #2, and tight target throats that needed neck turning.

 

[QuietTexan]

Did you get any more carbon shooting down the neck and body? Might be hard to tell if you're mag feeding because they probably come out pretty nasty already.

I'm putting a 6 Mongoose together, I'm kind of surprised you aren't catching those beautiful little cases in something with all the effort that goes into making them

 

[azshooter270]

For my wildcat caliber Case Overall Length 1.690.
In working up the cases I trimmed some to 1.675.
As always I am running these loads really hot (5000fps HOT).

I noticed the cases at 1.690 had ejection mark, flat and pierced primer.
I noticed cases at 1.675 had ejection shine and flat primer.

Accuracy wise the bullets like to be loaded deep into the case. All the way to the shoulder. Big jump? (Wildcats are so unpredictable!)
There is about a .020 measurable difference with the longer cases showing better accuracy.

Question, why would a longer case produce more pressure signs on the case versus shorter case?
I can only presume the lack of wiggle room in the chamber causes the pressure on the cases versus having the .015 room to blow out.

Any thoughts or experience with this?

On a side note. I had to drill out the gas port. Talk about INTIMIDATING. But It's fully funtioning now. PDOGS in 1 month!!!

Cycle test for your viewing entertainment!

What are you calling "ejection shine"? Do you mean extractor extrusion? Curious.

 

[RUFFIAN R - NY]

what you shooting at 5000 FPS ???

 

[Orange Dust]

Looking at the video it appears that the bolt is opening while the case is still under pressure. This can cause all sorts of marks on the cases that appear to be excess pressure. Looks like a lot is going on there.

 

[baggy270]

For my wildcat caliber Case Overall Length 1.690.
In working up the cases I trimmed some to 1.675.
As always I am running these loads really hot (5000fps HOT).

I noticed the cases at 1.690 had ejection mark, flat and pierced primer.
I noticed cases at 1.675 had ejection shine and flat primer.

Accuracy wise the bullets like to be loaded deep into the case. All the way to the shoulder. Big jump? (Wildcats are so unpredictable!)
There is about a .020 measurable difference with the longer cases showing better accuracy.

Question, why would a longer case produce more pressure signs on the case versus shorter case?
I can only presume the lack of wiggle room in the chamber causes the pressure on the cases versus having the .015 room to blow out.

Any thoughts or experience with this?

On a side note. I had to drill out the gas port. Talk about INTIMIDATING. But It's fully funtioning now. PDOGS in 1 month!!!

Cycle test for your viewing entertainment!

5000 FPS….me thinks not….

 

[QuietTexan]

5050 Max FPS, 17 Stinger, 18gr Deadblow Hammer

Ran load development through Quick Load (with weight factor, BA, and temperature adjustments - for you QL Nerds). LC Cases are failing right at 52,500k. Not bad considering 53K is listed max. This shooting system could produce faster velocities but case failure is where this project will end...

www.longrangehunting.com

 

[squeeeeze]

For my wildcat caliber Case Overall Length 1.690.
In working up the cases I trimmed some to 1.675.
As always I am running these loads really hot (5000fps HOT).

I noticed the cases at 1.690 had ejection mark, flat and pierced primer.
I noticed cases at 1.675 had ejection shine and flat primer.

Accuracy wise the bullets like to be loaded deep into the case. All the way to the shoulder. Big jump? (Wildcats are so unpredictable!)
There is about a .020 measurable difference with the longer cases showing better accuracy.

Question, why would a longer case produce more pressure signs on the case versus shorter case?
I can only presume the lack of wiggle room in the chamber causes the pressure on the cases versus having the .015 room to blow out.

Any thoughts or experience with this?

On a side note. I had to drill out the gas port. Talk about INTIMIDATING. But It's fully funtioning now. PDOGS in 1 month!!!

Cycle test for your viewing entertainment!

What wildcat is that? A .204 Bumblbee? Lol. Bullet weight?

I've seen what @del2les posted on #2 and #3 where trimming cases more equaled a lot less pressure. There is a lot more going on in a gas gun than in a bolt though. That is a smoking hot load. Should put them varmints down pretty fast! Looks fun for sure.

 

[squeeeeze]

5050 Max FPS, 17 Stinger, 18gr Deadblow Hammer

Ran load development through Quick Load (with weight factor, BA, and temperature adjustments - for you QL Nerds). LC Cases are failing right at 52,500k. Not bad considering 53K is listed max. This shooting system could produce faster velocities but case failure is where this project will end...

www.longrangehunting.com

You posted while I was typing lol. A .17 stinger? Paint scheme makes sense now haha.

 

[RidgeTop]

The case neck is being pinched by the lands.
What powder gives 5000fps in a case less than 2" ?