So how important is it? I have an FN SPR that I suspect doesnt have equal lug engagement. I tested it with a sharpie, a spent case, and a cleaning rod. It seemed to only remove the sharpie from one lug. It still seems to shoot better than I can, but the question is, is there anything that can be done to an assembled rifle to correct it? Or should I just shoot the piss out of it and fix it when the chrome barrel finally shoots out?
Gunsmithing equal lug engagement
- Thread starter WesP
- Start date
Re: equal lug engagement
If it works, why worry? I have had the same problem, which is really not a problem at all. You have a rifle that shoots well, so why bother with fixing a "problem" that is not impeding accuracy.
It has been noted more knowledgable shooters than me that some rifles bearing on only one lug shoot like hammers. If you go to lapping the lugs, you will increase headspace and leave yourself open to the associated problems with that.
Shoot it; shoot it; shoot it!
If it works, why worry? I have had the same problem, which is really not a problem at all. You have a rifle that shoots well, so why bother with fixing a "problem" that is not impeding accuracy.
It has been noted more knowledgable shooters than me that some rifles bearing on only one lug shoot like hammers. If you go to lapping the lugs, you will increase headspace and leave yourself open to the associated problems with that.
Shoot it; shoot it; shoot it!
Re: equal lug engagement
well I would only do something about it if there was no negatives associated with the process. I was just wondering what the hide-mind thought.
well I would only do something about it if there was no negatives associated with the process. I was just wondering what the hide-mind thought.
Re: equal lug engagement
Lapping them will increase the headspace. You might increase it by 0.0005" and you might increase it by 0.010" to get total lockup.
Repeatability is the key to a precision rifle. If the rifle shoots very well already it's because everything going on is repeatable. The single lug lockup is deflecting to dual lockup in a repeatable manner and everything else going on it likewise, happening similarly each time.
The easiest way to make sure things are repeatable is to make any biased loadpath go away, anything with geometric symmetry maintains load symmetry, etc. This is why guys blueprint actions and lap lugs.
I have a Model 7 that I lapped the lugs in, but it had a reasonably tight headspace to start (for a factory gun) and it already made partial contact on both lugs. It helped the rifle a little bit, the accuracy went from a just barely sub MOA rifle to about 3/4 MOA.
Lapping them will increase the headspace. You might increase it by 0.0005" and you might increase it by 0.010" to get total lockup.
Repeatability is the key to a precision rifle. If the rifle shoots very well already it's because everything going on is repeatable. The single lug lockup is deflecting to dual lockup in a repeatable manner and everything else going on it likewise, happening similarly each time.
The easiest way to make sure things are repeatable is to make any biased loadpath go away, anything with geometric symmetry maintains load symmetry, etc. This is why guys blueprint actions and lap lugs.
I have a Model 7 that I lapped the lugs in, but it had a reasonably tight headspace to start (for a factory gun) and it already made partial contact on both lugs. It helped the rifle a little bit, the accuracy went from a just barely sub MOA rifle to about 3/4 MOA.
Re: equal lug engagement
When you were checking this did you remove the firing pin assembly? If not you could have been getting a false reading.
The way you are going about it you would also have to assume the barrel chamber is perfect. In a factory chamber this is almost never the case.
If the rifle is working for you don't try and fix something that isn't broken. Worry about it when it's time to re-barrel.
When you were checking this did you remove the firing pin assembly? If not you could have been getting a false reading.
The way you are going about it you would also have to assume the barrel chamber is perfect. In a factory chamber this is almost never the case.
If the rifle is working for you don't try and fix something that isn't broken. Worry about it when it's time to re-barrel.
Re: equal lug engagement
How would the firing pin assembly cause things to be off and give false readings?
I would think that any tension that the firing pin assembly might put on the bolt and everything should be there when checking since when assembled and ready to fire it will be there as well.
This is just my thoughts, but I admit that I dont know anything.
How would the firing pin assembly cause things to be off and give false readings?
I would think that any tension that the firing pin assembly might put on the bolt and everything should be there when checking since when assembled and ready to fire it will be there as well.
This is just my thoughts, but I admit that I dont know anything.
Re: equal lug engagement
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Outsydlooknin75</div><div class="ubbcode-body">How would the firing pin assembly cause things to be off and give false readings?
I would think that any tension that the firing pin assembly might put on the bolt and everything should be there when checking since when assembled and ready to fire it will be there as well.
This is just my thoughts, but I admit that I dont know anything. </div></div>
Because the sear and firing pin assembly would be putting pressure on the bolt and could cause it to move into a position not desired, then if you have an untrue chamber and an untrue bolt face this would compound the issue.
When one barrels a rifle the bolt is stripped to set headspace and to be sure there is no unwanted pressure influencing bolt lug contact and headspace. It's actually more important how the bolt lugs and the receiver lugs match up when the round goes off. You want even pressure to the rear during firing. This is not to say that one wouldn't want even pressure when the round is just sitting in the chamber but then one would need to check bolt and raceway tolerances and possible sleeve that bolt and a whole lot of other things, to include how well the chamber is cut, whether or not the bolt face is true, and so on.
Simply "checking" lug contact on a factory rifle with all the other possiable issues isn't going to tell you much.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Outsydlooknin75</div><div class="ubbcode-body">How would the firing pin assembly cause things to be off and give false readings?
I would think that any tension that the firing pin assembly might put on the bolt and everything should be there when checking since when assembled and ready to fire it will be there as well.
This is just my thoughts, but I admit that I dont know anything. </div></div>
Because the sear and firing pin assembly would be putting pressure on the bolt and could cause it to move into a position not desired, then if you have an untrue chamber and an untrue bolt face this would compound the issue.
When one barrels a rifle the bolt is stripped to set headspace and to be sure there is no unwanted pressure influencing bolt lug contact and headspace. It's actually more important how the bolt lugs and the receiver lugs match up when the round goes off. You want even pressure to the rear during firing. This is not to say that one wouldn't want even pressure when the round is just sitting in the chamber but then one would need to check bolt and raceway tolerances and possible sleeve that bolt and a whole lot of other things, to include how well the chamber is cut, whether or not the bolt face is true, and so on.
Simply "checking" lug contact on a factory rifle with all the other possiable issues isn't going to tell you much.
Re: equal lug engagement
Harold Vaughn analytically investigated this issue (and others) and documented his findings in the book titled "Rifle Accuracy Facts." It is well worth the read, as it tests and verifies hypothesis using the scientific method in-lieu of anecdote...
Harold Vaughn analytically investigated this issue (and others) and documented his findings in the book titled "Rifle Accuracy Facts." It is well worth the read, as it tests and verifies hypothesis using the scientific method in-lieu of anecdote...
Re: equal lug engagement
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: HateCA</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Outsydlooknin75</div><div class="ubbcode-body">How would the firing pin assembly cause things to be off and give false readings?
I would think that any tension that the firing pin assembly might put on the bolt and everything should be there when checking since when assembled and ready to fire it will be there as well.
This is just my thoughts, but I admit that I dont know anything. </div></div>
Because the sear and firing pin assembly would be putting pressure on the bolt and could cause it to move into a position not desired, then if you have an untrue chamber and an untrue bolt face this would compound the issue.
When one barrels a rifle the bolt is stripped to set headspace and to be sure there is no unwanted pressure influencing bolt lug contact and headspace. <span style="font-weight: bold">It's actually more important how the bolt lugs and the receiver lugs match up when the round goes off.</span> You want even pressure to the rear during firing. This is not to say that one wouldn't want even pressure when the round is just sitting in the chamber but then one would need to check bolt and raceway tolerances and possible sleeve that bolt and a whole lot of other things, to include how well the chamber is cut, whether or not the bolt face is true, and so on.
Simply "checking" lug contact on a factory rifle with all the other possiable issues isn't going to tell you much.
</div></div>
Are you saying that there is a difference in the position of the bolt (long enough to make a difference) when the rifle is loaded and cocked and when the rifle fires?
If so are you suggesting that the rear of the bolt may be tilted up forcing the top lug to break contact, but when the trigger is pulled and the trigger connector moves down the back of the bolt body is lowered, allowing the top lug to again gain contact before/during the firing process?
I was thinking about this all last night.............haha
Mark
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: HateCA</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Outsydlooknin75</div><div class="ubbcode-body">How would the firing pin assembly cause things to be off and give false readings?
I would think that any tension that the firing pin assembly might put on the bolt and everything should be there when checking since when assembled and ready to fire it will be there as well.
This is just my thoughts, but I admit that I dont know anything. </div></div>
Because the sear and firing pin assembly would be putting pressure on the bolt and could cause it to move into a position not desired, then if you have an untrue chamber and an untrue bolt face this would compound the issue.
When one barrels a rifle the bolt is stripped to set headspace and to be sure there is no unwanted pressure influencing bolt lug contact and headspace. <span style="font-weight: bold">It's actually more important how the bolt lugs and the receiver lugs match up when the round goes off.</span> You want even pressure to the rear during firing. This is not to say that one wouldn't want even pressure when the round is just sitting in the chamber but then one would need to check bolt and raceway tolerances and possible sleeve that bolt and a whole lot of other things, to include how well the chamber is cut, whether or not the bolt face is true, and so on.
Simply "checking" lug contact on a factory rifle with all the other possiable issues isn't going to tell you much.
</div></div>
Are you saying that there is a difference in the position of the bolt (long enough to make a difference) when the rifle is loaded and cocked and when the rifle fires?
If so are you suggesting that the rear of the bolt may be tilted up forcing the top lug to break contact, but when the trigger is pulled and the trigger connector moves down the back of the bolt body is lowered, allowing the top lug to again gain contact before/during the firing process?
I was thinking about this all last night.............haha
Mark
Re: equal lug engagement
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: brokefromguns</div><div class="ubbcode-body">...is there anything that can be done to an assembled rifle to correct it?</div></div>
Replace it with an assembled rifle with a floating bolt head? HAHAHA!
I'm actually wondering about removing the firing pin assembly myself. In the interest of not (potentially) contradicting Harold Vaughn, I won't go into how lapping the lugs of my CZ (with Remington 40X bore cleaner, aka diatomaceous earth) that was having trouble tightened things up noticeably.
Seriously, though, if the rifle shoots that well, I advise following the old saying: If it ain't broke, don't fix it!
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: brokefromguns</div><div class="ubbcode-body">...is there anything that can be done to an assembled rifle to correct it?</div></div>
Replace it with an assembled rifle with a floating bolt head? HAHAHA!
I'm actually wondering about removing the firing pin assembly myself. In the interest of not (potentially) contradicting Harold Vaughn, I won't go into how lapping the lugs of my CZ (with Remington 40X bore cleaner, aka diatomaceous earth) that was having trouble tightened things up noticeably.
Seriously, though, if the rifle shoots that well, I advise following the old saying: If it ain't broke, don't fix it!
Re: equal lug engagement
I actually checked it with the safety in the middle position. Dont get me wrong the rifle shoots better than I do. Im just curious of the importance of lapping this and trueing that...
I actually checked it with the safety in the middle position. Dont get me wrong the rifle shoots better than I do. Im just curious of the importance of lapping this and trueing that...
Re: equal lug engagement
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: brokefromguns</div><div class="ubbcode-body">I actually checked it with the safety in the middle position. Dont get me wrong the rifle shoots better than I do. Im just curious of the importance of lapping this and trueing that... </div></div>
Sometimes stacked tolerances can work in your favor. Even though things might be out of spec or not true for some reason or another it can still shoot. By truing things up and making sure its concentric you can greatly increase the chances of things going the way they should.
Mark
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: brokefromguns</div><div class="ubbcode-body">I actually checked it with the safety in the middle position. Dont get me wrong the rifle shoots better than I do. Im just curious of the importance of lapping this and trueing that... </div></div>
Sometimes stacked tolerances can work in your favor. Even though things might be out of spec or not true for some reason or another it can still shoot. By truing things up and making sure its concentric you can greatly increase the chances of things going the way they should.
Mark
