RustyRick
Well-Known Member
I know what lapping a scope is, but what is lapping an action?
Lapping action
- Thread starter RustyRick
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Lapping the bolt lugs to the lug abutments to improve surface contact
RustyRick
Well-Known Member
Thanks for the come back. Is there any way to ascertain how bad it's needed if at all?
J E Custom
Well-Known Member
I lap the bolt lugs to the receiver abutments after I have machined them perfectly flat and true
because it makes them fit/contact each other 100%.
If they are lapped with fine compound the bolt lift will be easier with high pressure loads.
Lapping, even if the surfaces are not machined true will improve the contact % and improve the bolt lift but it will not assure bolt alignment during firing.
Either way it is considered to be an improvement.
Lapping the bolt to the action (Some think it will smooth the bolt operation)can be very risky and I don't recommend doing it. polishing the bolt will produce better results at less risk.
J E CUSTOM
RustyRick
Well-Known Member
Awesome thanks as always. LRH better than Google 
RustyRick
Well-Known Member
oH My WORD - I tried the felt pen trick, and one lug doesn't loose any black and another about half the ink and the 3rd looses most of it.
It's an X-Bolt. And I have been blowing primers without even approaching max book loads. I'm grey haired and loaded since High School and never blown primers before.
Could this be the cause for blown primers not a flat tight seal?
By lapping the lugs one must be increasing the head space right?
It's an X-Bolt. And I have been blowing primers without even approaching max book loads. I'm grey haired and loaded since High School and never blown primers before.
Could this be the cause for blown primers not a flat tight seal?
By lapping the lugs one must be increasing the head space right?
J E Custom
Well-Known Member
The partial contact of the recoil lugs should not cause the primer to blow. This is due to other problems with the ammo or the chamber. It will just deform the brass making it hard to chamber
a fired case unless it is in the exact same position.
This condition does load the lug in contact more than the others (The reason we true/blue print
the actions and bolts) to distribute the load and improve accuracy.
And yes it does increase headspace and it normally done before final head spacing is done.
Un even contact of the bolt lugs, is not uncommon with factory rifles and is not dangerous, just undesirable.
J E CUSTOM
wbm
Well-Known Member
Might consider a Savage action.
gohring3006
Well-Known Member
Hi JE
First let me say I'm sorry for the highjacked thread but it seemed like a good place to finally ask a question that's been on my mind. Does neck sizing only and letting the rounds get a little hard to chamber gall the bolt lugs or am I just paranoid? And if it does can it cause some headspace problems? Thanks
Ps . Sorry for the highjack
Hired Gun
Well-Known Member
All the lugs will never touch when held up by the cocked sear nor should they. Neither will a 2 lug action. The top side will be out of contact until the sear releases. If they do then it really is out of square. I would be surprised if your X Bolt is out of square by much. The bolt is once piece with the lugs machined in place. It would be hard for the lath to cut one shorter than the rest. 3 lugs actions are known to very stable under firing pressure. Even after all that, having the bolt face out of square by a little bit isn't going to have about zero affect on accuracy.
The bolt face is just a cap on the end of the chamber. During firing the brass might as well be made of rubber. It inflates and is only a bladder that seals in combustion gasses before the bullet begins to move and contracts after the bullet has left. The neck and it's alignment to the bore is the most critical part of accuracy on this end of the barrel.
The entire round is held in alignment by the chamber. This is why when building a precision rifle it is absolutely critical to get the chamber aligned with the path of the bore to get the bullet as straight and square into the throat as possible.
Even the most crooked bolt face fit of all time will not cause blown primers. Across the width of a primer I doubt that most crooked rifle of all time would be out of square by a couple tenths of a thousandth. You will usually head separate a brass before you blow a primer from excessive head space.
Blown primers are a sign of way too much pressure. Possible causes, a defective chronograph, (I was 500 fps slow and still blowing primers) misread scale, wrong powder, different lot of powder, different brand of brass has different case capacity, pistol primers in a rifle round, carbon build up in throat, too long of seating depth has bullet jammed in the lands or throat, seated too deep reduces case capacity, Out of spec bullets.
The bolt face is just a cap on the end of the chamber. During firing the brass might as well be made of rubber. It inflates and is only a bladder that seals in combustion gasses before the bullet begins to move and contracts after the bullet has left. The neck and it's alignment to the bore is the most critical part of accuracy on this end of the barrel.
The entire round is held in alignment by the chamber. This is why when building a precision rifle it is absolutely critical to get the chamber aligned with the path of the bore to get the bullet as straight and square into the throat as possible.
Even the most crooked bolt face fit of all time will not cause blown primers. Across the width of a primer I doubt that most crooked rifle of all time would be out of square by a couple tenths of a thousandth. You will usually head separate a brass before you blow a primer from excessive head space.
Blown primers are a sign of way too much pressure. Possible causes, a defective chronograph, (I was 500 fps slow and still blowing primers) misread scale, wrong powder, different lot of powder, different brand of brass has different case capacity, pistol primers in a rifle round, carbon build up in throat, too long of seating depth has bullet jammed in the lands or throat, seated too deep reduces case capacity, Out of spec bullets.
J E Custom
Well-Known Member
It is not a Hijack, Just a discussion.
It takes many, many chambering's to wear the recoil surfaces any unless there is no lubricant at all
present. So over many thousand's of rounds you might remove/wear .0001 to .0003 from the lugs.
As Hired Gun said, the bolt surfaces will not line up perfectly in the ready to fire/shoot condition because the ejector, current head space, bullet follower and any other outside influence on the bolt.
When a bolt and action are trued/blue printed the bolt and action are stripped completely and
then machined true. Head space is also set in this condition.
Another problem with most bolts, is the bolt face, rarely are they flat. They need to be squared
to remove the concavity that is normally present to improve the fit and make the head space very consistent. (It also improves brass life).
This makes the system true during firing. Neck sizing forces the action into this true state and will
hold all alignment as true as it can be in spite of the ejector or other outside influences.
The brass can be sized just enough to ease chambering, with out over sizing and losing the best
fit/head space.
If the brass is not sized enough and is difficult to chamber, it will make extraction more difficult.
There is a lot that should go into setting everything up correctly and if done right, the results will
show in the performance of the rifle.
Hope this helps.
J E CUSTOM
gohring3006
Well-Known Member
thank you. I just neck size for a while and sometimes get a little lazy when they need the shoulders bumped. Its not like I have to use excessive force but it gets where you know its well past due on the shoulder bump and was wondering if I was doing damage..
Thanks again.
Bill Gohring.
