Question on timing a new bolt

A

AdamZx3

Guest
I am in the planning stages of building up a tactical type rifle, planning on building from a Remington 700 action, chambered in 308 win. and throated for the 168gr Federal GMM, and would really like to bore out the receiver and install a PTG oversize bolt.

My main concern is timing the bolt correctly, I can't find any information at all on setting up the bolt handle so it has full cam. I'm prety sure I understand how the bolt and bolt handle cam, however I am not sure on how it is set up prior to welding/soldering.

Another question I just thought of, do the front and rear of the bolt lugs need to be trued on the PTG bolt or are they already trued?

My second concern is tig welding the bolt handle on, I have a friend who owns a machine shop (which is how I will blueprint it) so I will prob. have him do it. Is this a pretty easy job for an experienced welder?
 
I would send it to dans40x at accutig in alaska. he will turn it around fast and it will be done right.
 
Two things..

You might want to do 175gr GMM. Esp. in 1/12. 22"barrel

and talk to Mike Bryant re:the bolt.

:D:D:D
 
Dusty Stevens said:
I would send it to dans40x at accutig in alaska. he will turn it around fast and it will be done right.
Click to expand...

Dan has welded one handle on a PTG bolt for me, and has one now to do. his welding is top notch!!!!
Melvin Calliham
 
How can a new handle be positioned and timed without having the trigger and reciever to work with?
 
BR guy said:
How can a new handle be positioned and timed without having the trigger and reciever to work with?
Click to expand...

For my PTG bolt for a Rem XP100, Dan has an XP receiver he uses. I imagine he has other actions for such use.
Melvin
 
Wow thanks for all those reply's, I can see that the forum here will be a great resource. Great Idea on the vise grip clamps...I was pondering for the longest time how one would get it accurately clamped down while in the receiver :)

Stonewall and Chisolm, those links really helped! I will have to work on my searching keyword skills, "Remingon Bolt" did turn up quite a few hits :eek:

I will have to get a hold of dans40x to see if he can do an oversize PTG bolt, that way my first one is done right. (I sure can't do it, I can barely Mig cleanly lol)

Spott3R
You might want to do 175gr GMM. Esp. in 1/12. 22"barrel
Click to expand...

Being somewhat of a newbie to centerfire, what will the 175gr do better? Will it group better at extreme long ranges? I might shoot a bit at the Thunder Valley 308 challenge (1000yrds) but 600 is about max for most Ohio ranges.

The main reason I chose the 168gr GMM was the impressive accuracy that the Tac-Ops rifles shoot with them, under .25 MOA with 18-20" Krieger barrels. I am trying to mimic there tolerances and match chambering to get a real shooter....maybe not .25moa but I hope! *edit* I realize that Tac-Ops achieves it's performance by making an extremely true rifle, not the cartridges that they recommend :)

Tango-51 Article

X-Ray 51 (308)
103_0358.jpg
 
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Al Nyhus said:
Once you examine the variables, the answer is pretty clear. -Al
Click to expand...

Al
I understand how you would time the bolt to the action without the trigger but I don't understand how you would time the bolt handle without the reciever after the receiver lug abutments and bolt lugs have been trued, without having both of them together.
Maybe I am being more precise than necessary though.
James
 
Chisolm said:
Al
I understand how you would time the bolt to the action without the trigger but I don't understand how you would time the bolt handle without the reciever after the receiver lug abutments and bolt lugs have been trued, without having both of them together.
James
Click to expand...

James, you are correct. :) -Al
 
The bolt handle extraction cam timing can be done with bolt and receiver in hand--however --that is 1/3 of the job.

The actual trigger used in the rifle is needed to properly time the cocking and closing cams. Stan and Al have done a great job showing the extraction cam timing---it just has not addressed the cocking and closing cam timing.

There are some actions that you will struggle to get the timing correct on no matter what you do. there are some actions that do not use a true helix for the closing and extraction cams --and at times if they are both a helix, they have a different helical rate which reduces the extraction cycle to a point to point contact at one place in the extraction cycle. teh old Wichita 1375 is a good example of this
 
Adam,

Using 175gr's tightened up my groups on my LTR at 100-200yds.
If you are going longer distance the extra BC might help.
 
Thanks Spott3r,


So if I throated my barrel tightly for the matchking 168's would that mean I could not shoot factory 175's? What about reloads?

I haven't gotten into handloading just yet, but I do have some accuracy bases reloading dvd rentals on the way from smartflix :)
 
Jim Borden said:
The bolt handle extraction cam timing can be done with bolt and receiver in hand--however --that is 1/3 of the job.

The actual trigger used in the rifle is needed to properly time the cocking and closing cams. Stan and Al have done a great job showing the extraction cam timing---it just has not addressed the cocking and closing cam timing.
Click to expand...

Thanks for the kind words, Jim. You're so right...the extraction part of the puzzle only addesses part of what is commonly lumped under the heading of 'timing'.

Good shootin'. :) -Al
 
AdamZx3 said:
. . . . Being somewhat of a newbie to centerfire, what will the 175gr do better? Will it group better at extreme long ranges?
Click to expand...
Depending on your exact density altitude and initial velocity values, combined with your rifling twist, the 168s fired from a .308 will usually go trans-sonic before the 1k mark. They often become unstable during the transition to sub-sonic and, as a result, lose accuracy at best and turn sideways at worst.

My 20" LTR shoots 168s better at closer ranges, but won't take them past about 800 at the higher air densities. The 175s render slightly larger close-range groups and lower muzzle velocities, but retain their velocity better and will stay super-sonic and stable beyond 1k, which makes up for the bigger groups I get at closer ranges. Even a 26" barrel will not always impart enough initial velocity to a 168 to make up for the lesser BC, and we often see them sideways on the targets at 1k and beyond if current density altitude is near or below "sea level".

You might also consider trying Lapua 155 Scenars, which enjoy a high BC similar to the 175 SMK, but can be driven some 200 fps faster from the .308. This provides a shorter time of flight, resulting in substantially better drop/drift figures.
 
Thanks for the info :D

I will definitely go with 175gr Matchkings then. I am in Ohio about an hour south of lake Erie so the air's pretty thick around here. I will prob. be going up to Thunder Valley to their 1000 yard range. (well at least when i'm ready for that distance lol)

Would I still be able to push the 155 Scenars out enough to touch the lands if I chambered the throat tight for the 175 SMK ? (I need to start researching on rifle reloading!)
 
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