Gunsmithing Headspacing Question on my .375 Chey Tac

zenbiker

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For the last few years i have been trying to cope with disability as a result of a spinal injury at the hands of a jiu-jitsu instructor by building, as I could afford, a .375 Chey Tac Rifle. I was originally going for a .408 CT, but Barney Lawton (that's how long ago it was) had just started the 375 program and I was hooked by his entusiasm. After some glitches along the way and having the whole project saved by Dave Kiff and Pacific Tool and Gauge who corrected a problem with the original Lawton cocking piece, I'm finally at the point of final checks, and today I'm checking the headspace.

The rifle is built on a Lawton 8000 action with a Lawton barrel. I had Lawton thread and chamber the barrel. I only have a GO gauge from PTG, and here is what I found

1) Bolt closes smoothly on GO gauge.

2) Bolt closes smoothly on GO gauge +.002" but with very slight drag

3) Bolt locks at 2o'clock position on Go Gauge +.006"

All checks made with fire controls removed.

At this point I took a round of DTC ammo loaded with a 352 grain Cutting Edge bullet. The action closed smoothly with slight drag. I used a Sharpie marker to mark the shoulder, neck, and bullet around the ogive; the round was inserted in the chamber and the bolt cycled 3 times and withdrawn; despite my attempts not to, I still dragged the bullet along the ejection port, so disregard any marks on the bullet, as I did not see any that looked like land marks, and circular marks are clearly evident on the shoulder.

4amy4e8y.jpg


At this point, I would appreciate any input on what I've presented regarding appropriateness of the headspace; thanks in advance.


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Straight Shooter

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According to your test the head space is in spec. + .004 is usually the "No Go". Super tight head space is not really that big of deal. Even if it was at .005" just load to accommodate whatever it is. Time to test fire. On new cases there is minimal danger and to get dangerous you can be many times your spec and not rupture a new case. This is why factory guns don't want anyone using reloads. The firearm can be way off and nothing will happen. With a reload the factory cannot control the history of the case and if resized too much then a rupture can occur.
 

zenbiker

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According to your test the head space is in spec. + .004 is usually the "No Go". Super tight head space is not really that big of deal. Even if it was at .005" just load to accommodate whatever it is. Time to test fire. On new cases there is minimal danger and to get dangerous you can be many times your spec and not rupture a new case. This is why factory guns don't want anyone using reloads. The firearm can be way off and nothing will happen. With a reload the factory cannot control the history of the case and if resized too much then a rupture can occur.

Thanks, appreciate it. This is virgin brass, too; my experience is that the brass will shorten .0005" to .001" as the case expands to fill the chamber on initial firing. Just never had anything this big drag on a "factory" load before, so I want to be safe rather than blow up this gun - me, I'm already wrecked. The ballistics guru from DTC is supposed to call me Monday, but I'm glad to hear your evaluation.

Wes



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zenbiker

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I tried to edit my original post but ran afoul of some sort of computer demon. In the picture you can clearly see marks on the shoulder of the round indicating where contact was being made.


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zenbiker

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Well, once you get this big pig figured out let that ninja have it that messed you up!!!!!

You know, everything seems to be working out well despite this (look at the leading edge of the cocking piece):

y2egyzu2.jpg


The metal work done at Lawton, probably one of the last pieces ever to be done before they shut their doors, is some of the best I've ever seen. I took the barreled action apart before I installed it in the chassis. Dave Kiff pulled my backside out of the fire from that cocking piece done by a secondary contractor for Lawton, the aforementioned "ninja", so I've got no gripes so far, just some tense moments. As for the "ninja", I'm afraid karma will get the better of him, because this botched cocking piece would allow the sear to release when the bolt handle was lifted. If I had put a live round in this thing in my enthusiasm, I could have hurt myself or someone else pretty badly, and as far as "ninja boy" goes, if he/she reads this forum, they know who they are and how close their cluster f*ck came to hurting somebody. Badly. No, I've got better things to do than chase down a world class loser like this. Life is too short.

Now, if he should die and be reincarnated as, say, a groundhog, and he appeared in my Nightforce crosshairs, well, all bets may be off ; )


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zenbiker

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I think he was talking about the ninja that hurt your spine. Build sounds great.

Ryan


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OK, I see what you're saying. Yes, that is an entirely different set of feelings altogether. I've called him out on it on Facebook; last I knew he was unemployed in Anchorage, AK. Very. very hard not to wish ill will on him, but in the end I don't see where it would bring me any satisfaction or improve my condition and only lower myself to his level.


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excaliber

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Actually the 375 Cheytac came out before the 408. Cheytac had Sierra to make around 500lbs of 350gr Matchkings for testing but since it lacked BC, the 375 was dropped. Then the 408 came out. Cheytac and Lost River combined to make the 408 bullet. The rest is history.
 

overspin67

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If the go - gauge dimensions are correct, than it's an ammo headspace issu, since the maximum ammo headspace should/must be always shorter than minimum chamber headspace. Unfortunately there are not SAAMI specs to check with as Cheytac calibers are not SAAMI certified.