Coal gets longer and longer

[WahooYahoo]

Only time I ever had a round grow in length was with a compressed load.The other way it can happen is if it's jammed into the lands and it pulls the bullet out when extracting the round.

This ^^^^

 

[jumpmasterkolo]

What bullet?
Case?
Die? Neck sizing or bumping?

If you seat an empty case with this bullet, try and push the bullet with your hands. Don't chamber it.

I have had this with monos of the Barnes and Hammer type because neck tension was not enough.

I have had this problem with ADG cases in a 300 RUM with a 245 Berger. If neck tension is not tight enough, you can move the bullet. Measured neck tension tells me I am getting .002" and that matches the bushing, however, the bullet sliding in the neck when I push hard tells me I need more neck tension.

As mentioned dirty throat, or maybe jamming into the lands, but when you go to extract it, the lands have a tighter grip than neck tension.

Excellent reply/explanation

 

[TRexF16]

Very interesting problem. I haven't noticed in reading the whole thread if we diagnosed the actual source of the .005 COAL increase.
Need to find out if it's coming from the case growing or the bullet moving in the neck. Or both.
Since it sounds like you have a comparator for both taking CBTO as well as headspace, try the following:
Take a fresh case and use the headspace comparator attachment to carefully measure the headspace, cartridge base to shoulder. Then do the normal chambering that has been causing the problem. Then measure the headspace again and see if the base to shoulder measurement is the same or has grown. That might tell you a lot.
Also, repeat the process with a new test round, and this time measure very precisely from the case mouth to the ogive. You can do this by setting up your CBTO comparator, putting the round in the measuring position, then use the inside dimension jaws of your caliper to measure from the case neck to the face of the CBTO measuring insert.
Compare these measurements before and after chambering. That'll tell you if the bullet is moving in the neck. Put a mark on the case mouth so you measure at the same point both times. You could also very precisely scribe the bullet where it joins the case mouth with a needle and see if there is visible movement forward after the cambering.

BTW, does the SAME round, when chambered over and over, keep growing by .005 or does it only happen the first time to each round, then stop? I didn't note that yet in the thread either.

I think the answer to the above will help at least a little with this mystery.

Cheers,
Rex

 

[RedsideMT]

BTW, does the SAME round, when chambered over and over, keep growing by .005 or does it only happen the first time to each round, then stop? I didn't note that yet in the thread either.

I was wondering the same thing, good question.

 

[RUFFIAN R - NY]

have you done a chamber cast ? Waiting for answer on the RedsideMT post ! TRexF16 Post

 

[RUFFIAN R - NY]

I don't use Peterson nor Lapua brass on the 300 WM use only Winchester what's the neck thickness on the two mentioned above and what does the loaded round neck thickness measure ?

 

[Chesterrose79]

Very interesting problem. I haven't noticed in reading the whole thread if we diagnosed the actual source of the .005 COAL increase.
Need to find out if it's coming from the case growing or the bullet moving in the neck. Or both.
Since it sounds like you have a comparator for both taking CBTO as well as headspace, try the following:
Take a fresh case and use the headspace comparator attachment to carefully measure the headspace, cartridge base to shoulder. Then do the normal chambering that has been causing the problem. Then measure the headspace again and see if the base to shoulder measurement is the same or has grown. That might tell you a lot.
Also, repeat the process with a new test round, and this time measure very precisely from the case mouth to the ogive. You can do this by setting up your CBTO comparator, putting the round in the measuring position, then use the inside dimension jaws of your caliper to measure from the case neck to the face of the CBTO measuring insert.
Compare these measurements before and after chambering. That'll tell you if the bullet is moving in the neck. Put a mark on the case mouth so you measure at the same point both times. You could also very precisely scribe the bullet where it joins the case mouth with a needle and see if there is visible movement forward after the cambering.

BTW, does the SAME round, when chambered over and over, keep growing by .005 or does it only happen the first time to each round, then stop? I didn't note that yet in the thread either.

I think the answer to the above will help at least a little with this mystery.

Cheers,
Rex

The rounds keep growing to about .005 growth. Sometimes it will grow .001 on first try but sometimes it will grow .005 on first. I have noticed that sometimes it won't go the full .005 as well. I'm going to try chambering the round without using the magazine. I am going to try measuring as you suggested as well.

 

[Chesterrose79]

I don't use Peterson nor Lapua brass on the 300 WM use only Winchester what's the neck thickness on the two mentioned above and what does the loaded round neck thickness measure ?

Lapua was around .014 and Peter sons and ADG. 0145 in spots and thinner in other spots

 

[Chesterrose79]

have you done a chamber cast ? Waiting for answer on the RedsideMT post ! TRexF16 Post

No chamber cast yet

 

[spladi]

I need help from the wealth of knowledge in this community. I have a friend who has 3 tikka t-3x's 300win mag that all have the same problem. I have quite a bit of experience with reloading and am bamboozled with this one.

I load a round with the bullet seated quite far into the case and we'll bow magazine length. Measure the base to ojive, rack it into the chamber to mimic a hunting scenario and then carefully eject the round and then measure the base to ojive and it always grows up to .005". Sometimes less. I've tried everything from using a bushing that gives it an ungodly amount of neck tention and it still moves.
I've taken the loaded round and it drops into the chamber with ease and falls out so it's not catching on anything. I took a marker and marked up the bullet to see if there is any scratch marks and nothing. I don't know what it could be. Also tried 3 different types of bullets and 3 different weights.
Could be tight chamber but would the bullet not fall into the chamber and out of the chamber if that was the case?

when you drop the loaded round into the chamber by hand and then just angle the rifle in order to let the round slide out of the chamber does the coal then grow also? or not?

 

[Chas1]

Try a factory round as a baseline.

+1

 

[Huntsman66]

I wonder if the reason this is so strange is that no one checks this, I can't think of a time where I have ever measured a loaded round after the loading process. and definitely not after chambering it in a gun, unless there was a problem why would you?

 

[Ol' Red]

I wonder if the reason this is so strange is that no one checks this, I can't think of a time where I have ever measured a loaded round after the loading process. and definitely not after chambering it in a gun, unless there was a problem why would you?

I measure almost every rifle load. Revolver rounds are dropped into the cylinder.

 

[Huntsman66]

I measure almost every rifle load. Revolver rounds are dropped into the cylinder.

RIght! I measure the hell out of everything as im loading it, but unless there was a reason to measure it after simply putting it into a rifle with no indication that there was a problem. It just never crossed my mind. After seating depth is set and you know you are not jamming it and it shoots well, why would you?