Bolt not closing

[Gorgon]

I made up some rounds a couple weeks back and tested them last weekend. I was using Hornady brass (once fired, full length sized, trimmed to 2.044" with the Lee trimmer) and Pro Hunter 100gr and Vmax 75gr bullets. Accuracy is fine and I was setting the scopes up which all went fine.

The problem I had was some of the rounds would chamber but then I couldn't close the bolt. The Pro Hunters didn't have this problem but the Vmax did. I had to convince the bolt to close on some of the Vmax loads but five of them I couldn't close the bolt on. I saved two that I could close the bolt on so I could compare some dimensions but everything seems to be the same! The ogive distance, neck diameter, diameter just below the shoulder and the diameter just above the groove near the base are all the same. What is going on and what else should I check?

To determine which rounds were which I cycled them all through the magazine then put a marker pen dot on the ones I could close the bolt on, so I don't think it's a rifle issue. The photo isn't the best due to lighting but someone might spot something obvious!

 

[Will the chippy]

Your cartridge overall length is too long. Your bullet is seated too long and it's hitting into the lands. Be careful as this will cause pressures spikes.

 

[Gorgon]

Your cartridge overall length is too long. Your bullet is seated too long and it's hitting into the lands. Be careful as this will cause pressures spikes.

I've just measured and there is a bit of difference. They measure 2.632-2.638". I don't know if this is due to the tip being doinked when they ejected? Strangely the 2.638" one chambers and the bolt closes fine. The Lee manual says max length 2.710 so I'm well under.

 

[jb1]

See if Increased seating depth removes the problem. Just by 0.001 at time.
ONLY alter 1 thing at a time. What you will learn from this is that not all bullets ,even though same weight and calibre have slightly different Ogive's .
This is assuming that all your cases are resized to the same spec.

 

[Klenchblaize]

I see you are crimping, so if the bullets are seated too far out you will most certainly encounter greater resistance than were they of die neck tension only. I'm assuming you are full-length sizing?

K

 

[palo]

Take one of the rounds that the bolt won't close on and seat the bullet deeper and try again.
If the bolt still won't close the problem could be your sizing die is not set up correctly.
If the die doesn't touch the shoulder it could be pushing the shoulder forward on sizing .
Have you a way of measuring the case length to the shoulder ?

 

[paulst]

Your cartridge overall length is too long. Your bullet is seated too long and it's hitting into the lands. Be careful as this will cause pressures spikes.

Yes to this, the one on the left seems to have the ogive further forward, for want of a better term. This could be contacting the lands although I don’t see any marks.

 

[Gorgon]

See if Increased seating depth removes the problem. Just by 0.001 at time.
ONLY alter 1 thing at a time. What you will learn from this is that not all bullets ,even though same weight and calibre have slightly different Ogive's .
This is assuming that all your cases are resized to the same spec.

This makes sense. All the bullets are from the same box though and it's only the 75gr that seem to cause the problem. Would there be that much variation between bullets of the same batch? The bolt closes fine on some but not on others.

 

[Border]

Could also be primers not seated deep enough or seating die set too low??

 

[Gorgon]

I see you are crimping, so if the bullets are seated too far out you will most certainly encounter greater resistance than were they of die neck tension only. I'm assuming you are full-length sizing?

K

Does crimping push the bullet out the case slightly? All cases are full length sized and trimmed to 2.044".

 

[HonestJohn]

Looks a bit like the right one has a bit of a neck donut

 

[Bavarianbrit]

Use an old .38/357 pistol or 9mm fired case without a primer to use like a Hornady tool, I did until I upgraded.

 

[Gorgon]

Take one of the rounds that the bolt won't close on and seat the bullet deeper and try again.
If the bolt still won't close the problem could be your sizing die is not set up correctly.
If the die doesn't touch the shoulder it could be pushing the shoulder forward on sizing .
Have you a way of measuring the case length to the shoulder ?

I'll try and press one again in and see what happens. They are crimped though so they might not move! I don't think I can accurately measure from the bottom to the shoulder.

 

[Gorgon]

Yes to this, the one on the left seems to have the ogive further forward, for want of a better term. This could be contacting the lands although I don’t see any marks.

They're both the same! Both 2.203".

 

[Gorgon]

Could also be primers not seated deep enough or seating die set too low??

Is it wise to attempt to push the primers in on a loaded round?

 

[Heym SR20]

I have had this a few times. There will a few things going on.

When resizing is the shell holder coming into firm contact with base of the die. Sometimes it is easy enough to think you have full length resized but you are a couple of thou too short on the throw of the leaver. Often push the lever down, lift it and give it another push. A cartridge head spaces on the shoulder. If it it is not set back enough you can’t close the bolt.

If this is a consistent problem you will to remove a thou or two of the face of the shell holder. Use a piece of emery paper taped to a piece of glass (so its perfectly flat) and work the shell holder in a figure of 8 pattern. Check regularly the thickness with your calipers or micrometer. Remember that the case length is determined by both the die and the shell holder. Once you have a shell holder that works with a die make sure it is kept and used with that die.

And / or you have seated your bullets too long. Doesn’t really matter about the overall length to bullet tip, what matters is where the curve of the bullet touches the lands of the rifling. Colour up or smoke the bullet of a cartridge that doesn’t chamber - you will see the marks of the lands on the bullet. Seat it a bit deeper.

The neck at the mouth of the cartridge is too wide or not gripping the bullet tight enough, thus preventing it from fully chambering. Again use smoke and marks to test. Some get very particular about wall thickness at case mouth. I like to crimp my bullets in place, thus case mouth bites into the bullet.

Bolt and how you drive it. Many bolts have a spring loaded plunger to eject the cartridge. Often these are quite stiff springs and when you chamber the cartridge you have to compress this spring loaded plunger. You definitely need a positive forward pressure on the bolt handle as you close the bolt on a cartridge. You have a nice big fleshy bit at the base of your thumb. This was put there at birth to put positive forward pressure on a bolt handle.

These plungers can and do get gunked up with a mix of oil, greese, powder residue and rust along with any thing else that may be lurking. A good blast with de gunking fluid and then light oil may well help.

At the same time check the extractor claw as well to make sure that it snaps over the case.

(Note this last bit doesn’t apply to control round feed non plunger ejector type actions).

In any case with any hunting ammo, it is well worth, in a safe place cycling a batch of reloads through your magazine and into the chamber. Make sure that the ones you take hunting all feed well. Any that don’t use for practice. Last thing you want to need a fast reload and cartridge don’t chamber.

 

[Gorgon]

Looks a bit like the right one has a bit of a neck donut

There is a bit of variation. 0.271"-0.273". I'm getting 0.276"-0.280"for fired cases.

The two that fit measure 0.271". The other five that don't fit measure 0.272"-0.273". Is there a way I can squish the neck down a bit to see if this is the problem?

 

[Heym SR20]

I made up some rounds a couple weeks back and tested them last weekend. I was using Hornady brass (once fired, full length sized, trimmed to 2.044" with the Lee trimmer) and Pro Hunter 100gr and Vmax 75gr bullets. Accuracy is fine and I was setting the scopes up which all went fine.

The problem I had was some of the rounds would chamber but then I couldn't close the bolt. The Pro Hunters didn't have this problem but the Vmax did. I had to convince the bolt to close on some of the Vmax loads but five of them I couldn't close the bolt on. I saved two that I could close the bolt on so I could compare some dimensions but everything seems to be the same! The ogive distance, neck diameter, diameter just below the shoulder and the diameter just above the groove near the base are all the same. What is going on and what else should I check?

To determine which rounds were which I cycled them all through the magazine then put a marker pen dot on the ones I could close the bolt on, so I don't think it's a rifle issue. The photo isn't the best due to lighting but someone might spot something obvious!

Looking at the photo, the curve on the left bullet looks fatter than that on the right.

 

[Heym SR20]

This makes sense. All the bullets are from the same box though and it's only the 75gr that seem to cause the problem. Would there be that much variation between bullets of the same batch? The bolt closes fine on some but not on others.

There will of course be variation between the bullets in a box. If you are loading the bullets on the long side so they are close to the lands, chance are that some will be hitting the lands. This is just standard variation.

The difference between cheaper bullets and really expensive target bullets is the greater consistency and minimal variation from one to another. You pay for this greater consistency as there will be a greater rejection rate, production rate slower and more time taken in setup and quality control.

Bullets such as the VMAX are made in stamping dies, often with multiple dies making multiple bullets in the same stamp.

 

[Heym SR20]

There is a bit of variation. 0.271"-0.273". I'm getting 0.276"-0.280"for fired cases.

The two that fit measure 0.271". The other five that don't fit measure 0.272"-0.273". Is there a way I can squish the neck down a bit to see if this is the problem?

Use a crimp