Does lapping in the locking lugs on bolt increase head space

[JackF]

I want to lap in the locking lugs on my new Weatherby Vangard. Will this increase the head space or will the amount it does be negligible?.

Jack.

[hammermill]

depends if you polish the ramps on the lugs you may see little increase in head space, don't get carried away, i have seem several mauser and remington actions ruined by someone lapping the lugs while watching a tv show basically over lapping for a hour or so

every time you open and close the action you are removing metal


i dykem the bolt and with a few swipes know if one lug is farther back than the other and the mated surfaces are or arenot,. if it is the barrels will need to be removed and reset after the action is corrected


i would recommend renting or buying a set of guages if you are doing much action work on this rifle

of course by the time you buy a couple boxes of shells the price may break you

[GeorgeGaskill]

Yes, you will get an increase in headspace because you are removing metal from the locking surfaces. How much an increase depends on how good the contact is when you start. The first thing to establish is how well the lugs seat before you start. If there is a lot of contact, then you may decide not to proceed; if there is little contact, then you will be removing a lot of metal and make a significant change to the headspace.

Gauges are a good idea because otherwise you don't really know what's going on. As long as you can't close on the NO-GO you are all right but you will want to adjust your sizing die so you don't set the shoulder of the case back too much. Also, when you use the gauge, thoroughly clean the action and chamber of the lapping compound or your measurements will be wrong.

[JackF]

Hi George,

I did the Dichem test and one locking lug shows bright metal where the lug enters the closing (ramp?) and still shows rubbing (but no bright metal) for at least 75% OF THE ramp. The other lug doesn't show bright metal but does show rubbing (but no bright metal) for about 80% of the lug. I have only fired 16 rounds through the gun so will wait till I fire maybe 100 more and do the test again. The gun is the Weatherby Vangard 300 Win. Mag. listed in my sig. Weatherby guarantees sub MOA out of the box with premium ammo but I haven't the means to test that yet. Not sure I am capable of achieving this even with a "Lead Sled" but have read that balancing the lug contact can improve accuracy.

I will go out to the shop when time allows and make a head space gage to actually measure the space between the back of the cartridge case and the bolt face. It is difficult to find the actual head space specs (space between the back of the cartridge case and the bolt face) but the best I can decipher is ,001-.006. What are your thoughts on this?

Jack.

[hammermill]

With the exception of the .240 Weatherby Magnum, most belted, magnum cartridges are based on the .375 H&H Magnum case. Therefore, they all use the same headspace gauges. The following is a partial listing of those cartridges which use the same Belted Magnum Headspace Gauges: .257 Weatherby Mag., 6.5 Rem. Mag., .264 Win. Mag., .270 Weatherby Mag., 7mm Rem. Mag., 7mm Weatherby Mag., 7mm STW, .300 H&H Mag., .300 Weatherby Mag., .300 Win. Mag., .30-.338 Win. Mag., .308 Norma Mag., 8mm Rem., .338 Win. Mag., .340 Weatherby Mag., .350 Rem. Mag., .358 Norma Mag., .375 H&H Mag., .416 Rem. Mag., .458 Win. Mag.

so if i remenber right it headspaces off the rim and is a really straight foreward gauge



http://www.saami.org/specifications_and ... ad/206.pdf

look over page 61

[JackF]

Hammer, I understand the go and no go gages but they only tell you if you are in the range, not the exact head space. I plan to make a gage that registers off the belt and I will measure the belt to back of case from a once fired case, and refine that from there from twice fired and thrice fired cases. I want to know my exact head space before I mess with lapping in the lugs. I still cannot find exact head space tolerance specs. but near as I can figure is .001-.006. would still like an expert to verify.

Jack.

[redneckalbertan]

I still cannot find exact head space tolerance specs. but near as I can figure is .001-.006. would still like an expert to verify.

Jack.

Chamber tolerances are on page 61 of the document that hammermill posted, including headspace (belt dimensions). You can base the gage on those.

[GeorgeGaskill]

While the standard headspace for belted cases is measured between the breech face and the front of the belt, most accuracy wonks will eventually headspace off the shoulder as with normal bottleneck cases. Part of the problem is the belt is pretty narrow and the brass doesn't always fit it well. Another part is case life because most sizing dies set the shoulder back more than necessary and you get case stretching with each shot.

It sounds like you will pick up a couple of thousandths of headspace if you lap the lugs for a good fit. If you are reloading, that won't really matter much as you can adjust your case sizing for a good fit of the cartridge in the chamber. The only question for me would be what the current headspace is. If it is close to the GO gauge, a little increase wouldn't bother me. If it is close to the NOGO gauge, I would be less inclined to increase it unless I were planning to reset the barrel when finished. If I were going to do that, I would also check the bolt face for perpendicularity to the bore before making final adjustments.

[JackF]

Hi George,

Yes, my concern too is what the head space is now, actual physical head space, the space between the bolt face and the rear of the case. That's why I want to make a gage that measures the actual space between the bolt face and the rear of the case.

Jack.

[hammermill]

a trick is to add small thicknesses of scotch tape to the go guage head and test

the tape should be .001 in thick if my memory serve me.

you can then get a idea where you are, this is usually done with a striped bolt to give the best feel.

indexing off the shoulder with fired once brass is going to give i suspect also the best accuracy and brass life

[JackF]

Thanks Hammer,

I was thinking I would try to incorporate a once fired casing, drill out the primer pocket then locktite a plug with an adjustable counter sunk screw. Insert the cartridge and keep working the bolt until I feel added resistance. Take the cart. out and measure top of the screw to cart. base.

Jack.

[hammermill]

i doubt if you want things on the mark the brass case would do it, to soft,. also isnt the extractor holding the case to the bolt face by the rim???