Chambering issue.

[kenbro]

HI,
Most factory ammo except for the occasional PPU will chamber, cock and fire in my Bergara B13 break barrel .243.
Reloads are a different matter.....some chamber, cock and fire and others out of same batch need me to open and close the gun several times before the hammer will cock.
I've thought about whether I've loaded some too long and been jamming the bullet in the lands, shortening the coal makes no difference.
Empty case that have been fired in this gun won't allow the hammer to be cocked after insertion.
I've tried trimming cases to 20 thou shorter than minimum trim length and also run the shorter cases through a body die, I've tried those empty cases and still they won't allow the hammer to cock.
Beginning to think there's something wrong with the rifle.
It's fired less than 200 rounds.
Anybody got any ideas, please?
Thanks, Ken.
PS. I've nothing against Creedmoors but please don't suggest I change to one of those.

to cock

 

[Foxyboy43]

As a quick check measure the shoulder on a case that fits without issue then do the same with one that doesn’t fit - first thought is if they have all been fired in your gun and case/coal is correct I would be checking and if necessary bumping the shoulders back to specs….
If you have an issue trying to measure the shoulder try the old trick of placing another case - something like a 9mm or at worst .308 over the .243 case until it hits the shoulder then measuring the combined length.

 

[takbok]

As above, I think you need to adjust your resizing die so that the cartridges headspace better.

 

[Stalker62]

If you have an issue trying to measure the shoulder try the old trick of placing another case - something like a 9mm or at worst .308 over the .243 case until it hits the shoulder then measuring the combined length.

OK.

I'll take one for the team.





How does that work?

 

[Rory]

OK.

I'll take one for the team.


View attachment 297605


How does that work?

It's just a reliable way of measuring the shoulder (at a uniform circumference point dictated by the 9mm or other shell). Just measuring the case OAL will not tell you if the shoulder is being bumped back sufficiently to give you the correct headspace.
Obtain a reading from a factory round, then try a reading with a fired case - you will probably see that the fired case shoulder measurement is longer than the factory one, indicating that the fired case is not being sufficiently sized (assuming you are using a full length sizing die) and will need adjusting to bump the shoulder back more than it is.
If you are neck sizing only, and the shoulder is measuring a lot more than the factory shoulder, I would suggest investing in a full length sizing die.

 

[kenbro]

As I said, the cases have been in a body die, this should have bumped the shoulder back?
Thanks, Ken.

 

[Smellydog]

Needs more sizing Ken.
It may be a slight amount more. It could be a combination of a tight spec chamber and I little bit more sizing.
I recently had a similar issue and half a turn more of the die fixed it.

 

[Stalker62]

Obtain a reading from a factory round, then try a reading with a fired case...

Ahh, it was that bit which was missing.

Thank you.

I use the comparator thingy myself...

 

[kenbro]

Needs more sizing Ken.
It may be a slight amount more. It could be a combination of a tight spec chamber and I little bit more sizing.
I recently had a similar issue and half a turn more of the die fixed it.

While you were busy typing Smellydog, after reading the replies before my previous post I was back in the den.
I'd just assumed that as the cases had been in the body die with the die well (I thought) screwed down that should have bumped the necks. Some resized cases did work okay so it must have been a small amount but screwing the die in another 1/4 turn and I can feel the shoulder bump.
Done half a dozen cases and all are fine, so tomorrow I will start backing the body die out in small increments until I get somewhere near the minimum bump needed.
I didn't use the excellent method to compare shoulder position but that did give me the idea of checking the die position.
Another combination of members ideas solved my problem.
I thank you, Ken.

 

[Andy RV]

Bottom out the full length resizing die and don’t worry about this again!

 

[Smellydog]

While you were busy typing Smellydog, after reading the replies before my previous post I was back in the den.
I'd just assumed that as the cases had been in the body die with the die well (I thought) screwed down that should have bumped the necks. Some resized cases did work okay so it must have been a small amount but screwing the die in another 1/4 turn and I can feel the shoulder bump.
Done half a dozen cases and all are fine, so tomorrow I will start backing the body die out in small increments until I get somewhere near the minimum bump needed.
I didn't use the excellent method to compare shoulder position but that did give me the idea of checking the die position.
Another combination of members ideas solved my problem.
I thank you, Ken.

Good stuff.
When I was younger I use to think a tighter fitting cartridge would make for more accuracy. I've since learned it's not necessary and certainly not worth losing reliability.

 

[kenbro]

Bottom out the full length resizing die and don’t worry about this again!

I don't usually use a FL die.
Body die then Lee collet neck die.
Ken.

 

[Bavarianbrit]

There was a new item being added to the Forster range this year on show at the IWA trade show yesterday but my invention works much better than theirs but I am getting it up to manufacturing level before I show it here.
Here is their item to use to help measure the bump setback.

 

[Bavarianbrit]

Ahh, it was that bit which was missing.

Thank you.

I use the comparator thingy myself...

View attachment 297612

I had been using the 9mm trick until my set arrived this week, it was the only set I could find in the whole EU cost me 91 Euros.

 

[Foxyboy43]

I don't usually use a FL die.
Body die then Lee collet neck die.
Ken.

Hmmm.
If you load “stout” the shoulders move will faster (i.e. after fewer reloads) which of course the N/S die will not fix. I very, very rarely have to F/L resize as I long ago stopped using stout loads so chambering a (stretched) round will soon tell you whether the shoulders need a bump - as you have discovered. It is an interesting exercise to measure a few just to see the difference - I haven’t used a factory round as my “datum point” rather any round that chambers without issue is good enough for my humble needs.
If anyone wishes to avail of a 9mm brass and go down the cheap but very effective shoulder-check route just pm me - my friend has quite a few empties…..,
Other calibres are of course available.

 

[kenbro]

Body die definitely reduces case life but that's of no concern to me as I buy factory ammo every now and then.
Sako is the most accurate factory stuff for me, but no factory ammo comes near my load of 49 grains of Ranshot Hunter and 68 grain Barnes HP bullets.
Thanks, Ken.

 

[User00040]

Body die definitely reduces case life but that's of no concern to me as I buy factory ammo every now and then.
Sako is the most accurate factory stuff for me, but no factory ammo comes near my load of 49 grains of Ranshot Hunter and 68 grain Barnes HP bullets.
Thanks, Ken.

When you say 'body die' do you mean the Redding one?

That is just a shoulder bump die, sounds like you need a small base die.

RCBS do a good one (buy a 308 one as you are only sizing the bit above the case head).

 

[kenbro]

There was a new item being added to the Forster range this year on show at the IWA trade show yesterday but my invention works much better than theirs but I am getting it up to manufacturing level before I show it here.
Here is their item to use to help measure the bump setback.

I have some competition shell hders somewhere but I think I stopped using them because they didn't seem to work consistently for me.
Ken.

 

[kenbro]

When you say 'body die' do you mean the Redding one?

That is just a shoulder bump die, sounds like you need a small base die.

RCBS do a good one (buy a 308 one as you are only sizing the bit above the case head).

Yes the Redding one. It's not a small base die.
I think my problem is solved now, thanks.
Ken.
Ke.

 

[Foxyboy43]