Trigger pushing up on bolt

[lennyo3034]

I have a new action (Remington 40x Ti and PTG bolt) that seems to be having an issue once I install a trigger.

Bolt close seems extremely rough when the trigger is installed, and it appears the bolt is being pushed upwards significantly. The rough feel is probably the bottom bolt lug against the receiver abutement.

I tried two different triggers and both exhibit this issue, although one slightly worse than the other. While functional, bolt close is quite rough and my fear is galling between steel bolt and titanium receiver.

Does anyone know of a solution? Would removing material from trigger disconnector help?

 

[John Glidewell]

Are you installing it in a stock or chassis before testing it or is the action not mounted? I ask because if installing, the issue could be the front action screw is a bit too long and needs to be ground down so as not to infringe on bolt head.

 

[spife7980]

With no trigger installed what is the distance between the top of your trigger pin to the firing pin sear?

 

[lennyo3034]

With no trigger installed what is the distance between the top of your trigger pin to the firing pin sear?
View attachment 8004092

Thank you, I was looking for something like this exactly.

Mine measured consistently between 4.02mm and 4.04mm. Looks like I need a low sear. Does that make sense? The surface on my sear (Remington walker or 40x) is pretty easy to get to. Would it be worth trying to stone down that sear surface?

 

[ShtrRdy]

Are you lubing the bolt lugs?

The other suggestions are very good to have checked out.

 

[spife7980]

Seems like a pretty standard rem set up which rules that out, my two rem700s are right at the same.

https://bulletcentral.com/wp-content/uploads/2018/06/sear_compatibility_bix-Sheet1.pdf

And you’re sure it’s dragging over the compressed sear and not just a bunch of overcocking? The difference being mechanical interference vs just compressing the spring that much more.

 

[lennyo3034]

Seems like a pretty standard rem set up which rules that out, my two rem700s are right at the same.

https://bulletcentral.com/wp-content/uploads/2018/06/sear_compatibility_bix-Sheet1.pdf

And you’re sure it’s dragging over the compressed sear and not just a bunch of overcocking? The difference being mechanical interference vs just compressing the spring that much more.

I am not sure. How would I tell?

 

[spife7980]

First, put a pin through the trigger and see how tall the difference is in it vs the measurement you just took.

For over travel- measuring the back of the firing pin in its relationship to the bolt shroud.
When you close it with the trigger installed- how much does the firing pin protrude from the shroud vs its normal cocked position? And how far different is that from with the bolt uncocked with firing pin released?

 

[Evintos]

Thank you, I was looking for something like this exactly.

Mine measured consistently between 4.02mm and 4.04mm. Looks like I need a low sear. Does that make sense? The surface on my sear (Remington walker or 40x) is pretty easy to get to. Would it be worth trying to stone down that sear surface?

It's better to file down the easier to replace part. This would potentially be the cocking piece. Unless you can easily replace the trigger sear.

I am not sure. How would I tell?

You take a look at your bolt plug and cocking piece within the bolt plug. In the pic below, the cocking piece is the silver portion. The plug is the bell shaped portion that houses the cocking piece. When it's over cocking, as you close the bolt, the cocking piece is pressed against the corresponding trigger sear surface too early and as you close the bolt handle, it over compresses the firing pin spring.
In order to tell if you're over cocking, measure the firing pin fall. With empty gun and trigger installed, dry fire the action, measure the depth of cocking piece within the bolt plug . Cycle the action and then measure the position of the cocking piece. The difference between a fired state and cocked state should ideally be between 0.230" and 0.250" for an R700. If it's higher than about 0.250", you're over cocking.

If it's an over cocking issue, you can stone the slanted surface of the cocking piece in the pic below. Taking off very little at a time.

 

[lennyo3034]

Didn’t think I’d ever say this but I appear to be way over cocked.

Have .082” protrusion when cocked and .228” recess when uncocked for a .310” difference.

Still recommend working on cocking piece? Or is that difference too much?

 

[lennyo3034]

L

 

[Evintos]

Didn’t think I’d ever say this but I appear to be way over cocked.

Have .082” protrusion when cocked and .228” recess when uncocked for a .310” difference.

Still recommend working on cocking piece? Or is that difference too much?

.310" is too much fall. Stone the slanted portion of the cocking piece pointed by the arrow. You don't want to change the angle of it.

Remove in .010" to .020" increments. Checking for the bolt close feel every time. If it feels better and better as you reach the ideal range, then more than likely what you were feeling was the effects of over cocking.
If you're not comfortable with doing the work yourself, find a gunsmith that knows how to complete timing of a R700 trigger ("trigger timing").

If you aim for the lower end of the .230 to .250 range, you get better bolt close feel but theoretically less reliable (less than 0.250" that is) primer ignition under all (normal/adverse) conditions. If you aim for the upper portion of the range, you get more reliable primer ignition under all conditions. A balance between the two of course would be 0.240" total firing pin fall.

 

[lennyo3034]

I appreciate the help guys. Been a while since I messed with a Remington. Couple more questions:

1. How much of a problem is over cocking? Obviously bolt close sucks, but that something I can live with. I just don't want to be galling or damaging the bolt lugs/receiver abutments.

2. Since I'm pretty severely over cocked, can I just rotate the entire firing pin assembly out from bolt body one revolution?

 

[Evintos]

I appreciate the help guys. Been a while since I messed with a Remington. Couple more questions:

1. How much of a problem is over cocking? Obviously bolt close sucks, but that something I can live with. I just don't want to be galling or damaging the bolt lugs/receiver abutments.

2. Since I'm pretty severely over cocked, can I just rotate the entire firing pin assembly out from bolt body one revolution?

1. Benchrest shooters have found an adverse effect on accuracy due to weird primer ignition from excessive over cocking even at pin falls starting around 0.260". I don't think over cocking would damage the bolt lugs/receiver abutments anymore than firing a round would.

However, you would be placing excess pressure on the firing pin spring, the trigger sear and the cocking piece itself. If the cocking piece is an unthreaded type, then also excess pressure on the cross pin that holds the firing pin and cocking piece together. If and when any of those small parts fail, who knows?

2. Three potential issues off the top of my head with just backing off the firing pin assembly. First being just a safety aspect. second being you would potentially reduce the firing pin protrusion (should be around 0.055 to 0.060"). Third being the front of the cocking piece may be backed off from the cocking cam on your bolt body resulting in weird bolt, usual bolt lift feel. As a whole just seems sketchy from a safety perspective but someone else would know more about that than I do.

(Too little pin protrusion and you'd have a higher chance of light/shallow primer strikes. Too much pin protrusion and you run the risk of pierced primers.)

 

[lennyo3034]

Tried rotating to see. You’re right on all accounts. I will working on stoning the cocking piece down.