When you lap with the bolt assembled and the trigger installed, you have the firing pin spring holding the bolt lugs against the abutments. The bolt is also being pushed off center by the trigger. He stated he did that intentionally. If he had very much bolt to bore clearance, he only lapped one lug. If he lapped it enough to make them both contact, his bolt face in no longer true.
Truing an action.
- Thread starter J E Custom
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cahunter805
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I'm still new to a lot of this also just trying to learn as much as I can. LRH has been a great source of information for me.
mwkelso
Well-Known Member
@J E Custom
A couple days ago I was talking to a guy about accuracy who suggested applying a lapping compound to the bolt face and rotating the bolt open/close 70-80x to gain consistent contact. Without trueing the action, what purpose would this serve in accuracy or consistency in shot placement?
I know that might come across as a vague question, so let's assume that the reloading process is to tumble, neck brush, FL resize, trim, chamfer, prime, drop powder load and seat bullet. (This is my process as a novice reloader)
A couple days ago I was talking to a guy about accuracy who suggested applying a lapping compound to the bolt face and rotating the bolt open/close 70-80x to gain consistent contact. Without trueing the action, what purpose would this serve in accuracy or consistency in shot placement?
I know that might come across as a vague question, so let's assume that the reloading process is to tumble, neck brush, FL resize, trim, chamfer, prime, drop powder load and seat bullet. (This is my process as a novice reloader)
J E Custom
Well-Known Member
Lapping has it's place for surface preparation, But it will not correct miss aligned or uneven tolerances. the reason we face the bolt face and square the lugs and abutments is to make them perpindicular to the bore centerline. lapping, use to be a way of increasing the contact area of the bolt lugs. but it does nothing to square the lugs and abutments. They will just have better contact with each other and still be at different heights.
If the bolt face were convex or concave (Most of the time they are one of these) lapping would only resurface it and leave the same configuration as before. we machine all the surfaces that mate with other surfaces To square them and align them with the bore centerline. then we Lapp the heavily loaded parts to improve the fit and finish.
So if the part/surface is not true, lapping will not correct that.
J E CUSTOM
Alex Wheeler
Well-Known Member
Lapping has its place, its for removing a tenth or two (.0001-.0002). There is a thought that lapping with the trigger in is how it should be done because thats how the bolt is in the cocked position. Of course the bolt is not in the cocked position the second the trigger is pulled. If we back up a little, the issue with poor lug contact is the harmonic it adds due to uneven pressure on the seats. Well, if you lap a bolt in crooked you end up with a similar situation do to the case head now contacting first on one side of the bolt face. Not to mention you have created a situation where the lugs only seat in one exact position with no clearance. Of the top actions that are lapped in at the factory, none are lapped in with the trigger installed. The lugs are seated by the time the bullet enters the throat.
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Now I understand why it's so expensive to get the job done. Very good information.
Thank you
SC
Good post at a good time. I too was questioning the lapping with trigger installed. It didn't seem like the best. Seems to me that the amount that would need to be lapped would be dependent on how sloppy the bolt to raceway fit is. Tighter fit, less lapping. Then as has been pointed out, it wouldn't be square to the bolt face as cut. Not sure how you would get the bolt face lapped to match since pressure on the bolt face pushes back on the bolt axially which is not the same force as the trigger is acting at.
To me proper case sizing helps to center the case in chamber and counter act the trigger pressure on the bolt. Not to mention the ejector pressure.
To me proper case sizing helps to center the case in chamber and counter act the trigger pressure on the bolt. Not to mention the ejector pressure.
J E Custom
Well-Known Member
This is one of those differences that we talk about. Everyone has their way of doing things and there will always be differences. When I am lapping, I like to use a spring loaded tool that screws into the receiver and pushes on the bolt face to apply even loading of the bolt lugs.
The spring pushes on a plunger that apply's an even loading and allows me to push the bolt forward and redistribute's the compound while I am lapping for a smoother more uniform surface prep.
This is just the way "I" like to lap the bolt lugs and abutments. I can't tell anyone that It is better, it is just the most logical way I know. I also don't like anything that interferes with free movement of the bolt and that may become contaminated Like the trigger and ejector with lapping compound
Just Me
J E CUSTOM
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Like you, I have what looks like a short barrel tenon with a spring that threads onto the front of the receiver and puts pressure on the bolt face. Give forward pressure on the first sweep to keep the 600 grit paste from wiping off. I'm sure there are better ways...
J E Custom
Well-Known Member
Just A side note to why I lap with a striped bolt. I run little or no head space on all of my precision weapons so the bolt is held in battery where everything lines up square. And when the weapon is fired there is little or no movement of the bolt and everything remains square.
Brass cases can become distorted If proper alignment/square is not maintained during firing so I think all of this work to the action and the loading is well worth it.
This also seems to eliminate the disadvantage of bolt to raceway clearance extremes.
J E CUSTOM
Brass cases can become distorted If proper alignment/square is not maintained during firing so I think all of this work to the action and the loading is well worth it.
This also seems to eliminate the disadvantage of bolt to raceway clearance extremes.
J E CUSTOM
