Hard Bolt Lift

[Jayhawker]

I am shooting a 6 BR Savage hybrid (Savage trued action with PacNor, three groove 1:8, 30" barrel). I load my own. Lapua brass, Federal Match primers and 30 gr. of Varget. The brass is shoulder bumped back .001"-.002" after each firing as well as partially neck sized with Redding comp dies. Bullet runout is.001" or less. No neck turn. The Berger bullets are 105 grain Berger BTs. The gun (and/or me) typically shoots in the .2s and .3s at 100 yards and .4-.6 MOA at 500 meters depending on conditions. Now (after all of that) the problem: Although the cartridges chamber easily, after firing lifting the bolt can be a real bear. Sometimes having to stand-up to get a purchase on it. No discernible marks on the fired brass except for a very slight flattening of the Federal primer. Any ideas about the tough bolt lift?

 

[Shynloco]

Jayhawker,
Two things I'd be checking...measure the shoulders of your casings and see if you have the same reading with each casing. I use an RCBS PRecision Mic on my Lapua brass after each firing. The second, is having some Gunsmith or person in the know, check the headspace and bolt face. Something doesn't sound right in that area. Just what I'd do if that happened to me. I doubt 30 grs of Varget would be a hot load as I've gone even higher with mine. Hope you find the cure. What you describe could also do some damage.

 

[gunsandgunsmithing]

Was the brass new, or had it ever been fired in another chamber?

 

[Jayhawker]

Shynloco: The brass does all measure the same after firing and you're right-I need to get this thing to the 'smith who built it. Been having too much fun with it.

G&G: The brass has been fired about 3x, all in this rifle. It appears to be in good shape but is due for annealing.

 

[racesnake]

I had this problem, once. Never did know for sure what was going on. I tried a different lot of brass and it went away. I figured that the brass was probably a little soft in the head area.
Are you FL resizing? If you are, mic the case web at the web before and after firing and see if you are getting expansion after firing.
D-

 

[BoydAllen]

Check your PMs.

 

[Rustystud]

Check and see if you have clearance in the web area of the case after firing. Also check the primary extraction cam for primary extraction. Check for loose bolt handle. Check for trash inside the bolt, and bolthead.
Nat Lambeth

 

[Jayhawker]

Two folks have mentioned checking the web area on the cases. Could you elaborate to this amateur exactly what you mean, please. Not sure what the "web" is.

 

[BoydAllen]

The web is the solid part of the head that is between the interior space that holds the powder and the back of the case. The primer pocket and flash hole go are in the center of the web. If hot loads are fired repeatedly, this portion of the case can become larger in diameter to the point that an interference fit may occur at the very back of the chamber. FL dies may not be able to reach quite far enough down the case to size this line thin area because of two potential conflicts, the shell holder , and the desired amount of shoulder bump. Even if the shell holder is ground down to allow the die to be adjusted lower, the shoulder of the case may be bumped back too far with the die in that position. The answer lies in reamer design. If the back of the chamber has enough clearance, the problem is unlikely to occur with any load that does not make primer pockets too loose for cases to be reused. To alleviate this problem in an existing chamber, the barrel may be set up in the lathe, and the back of the chamber polished out (carefully) to a very slightly larger diameter, taking care to make a smooth transition with the rest of the chamber.

There is one important detail that needs to accompany this. The problem that I have described shows up at the top of the bolt lift, when the bolt hits the primary extraction cam, which on a Savage is a separate piece that is part of the bolt. If your hard lift show up from the beginning of bolt lift, it is probably not being caused by expansion of the solid head of the case.

 

[Jayhawker]

It shows up at the beginning of the lift all the way through if lift motion.

 

[Jayhawker]

Here's a poor cellphone pic if it will tell anyone anything. Is the "clean" area underneath the web normal?

 

[BoydAllen]

At the back of your case, you can see where the chamber ends. If you measure the depth of the recess of the face of the bolt and add about .010 to that, you should come up with a total that corresponds to the length of what you are seeing on the case. The next thing that you need to do is to measure inside the case, from its mouth to the solid head. If you subtract this from the length of the case, you will have the approximate thickness of the solid head. Comparing these dimensions and totals, it may become apparent whether the solid head falls within the chamber. Let us know.

Because your problem is from the start of the bolt lift, it is unlikely that head expansion is the source of your problem. Another thing to look at is whether you have a ring of hard carbon in the throat of your chamber. If you have, this would give higher pressures and with that, harder bolt lift. One way to determine if you have a carbon ring is to draw a tight patch back toward the chamber, slowly and carefully, to see if it hangs up any at the throat, before passing into the chamber.

 

[Jayhawker]

Depth of the recess in the face of the bolt is .125" + .010" equals exactly (as good as 66 year old eyes can see) the clean area on the case up to the underside of the area that lives outside of the chamber.

Inside measurement of case: 1.395"

External case length: 1.557".
A difference of .162" if I'm doing this right

 

[Jayhawker]

After taking measurements again, it would appear that the measurement of the "clean " area is closer to .165" than the aforementioned .125" + .010". I hope I'm not confusing too many of you.

 

[BoydAllen]

If you subtract the depth of the case (inside) from its length, what do you get?

 

[Jayhawker]

.162"

 

[rain164845]

Does it occur during dry firing? If so, you just need to address your cocking mechanism. The savage bolts cock on raising the bolt handle. Just a possibility.
Joe

 

[Jayhawker]

I stripped the bolt down this afternoon and saw nothing amiss. Plenty of lube and no galling. Nonetheless, both of the Savage rifles I own have a hard lift after a dry fire. But with this particular one, after live firing, it can be really hard. I'm still picking around it. At one point, I marked the baffle that fits the groove in the receiver to see if there was binding but it came back unmarked.

 

[edlongrange]

From Lynn:

"If your bolt is hard on closing you need to push the shoulder back.If your bolt is hard on opening the area near the base is not sized enough.

If your die is making firm contact with the shellholder you can sand the shellholder with some 80 grit sanpaper in a figure "8" pattern to remove a couple thousanths off the top.This will allow your case to go deeper into the die thus reducing the size of the base more.

I have five 6 Dasher full length sizing dies and they are all a little bit different in how much they size the base of the cases.

Another thing that happens is if you use a high quality gunsmith/machinist to chamber your barrels they tend to run the reamer in extremely straight when compared to your ordinary gunsmith.This means you get a smaller chamber near the base of the case due to the fact the reamer wasn't allowed to wallow around.

For a fix you can sand the shellholder which allows the brass to go in deeper thus sizing the base area more.

You can polish the chamber which gives the brass more room to grow and creates a larger amount of sizing when using the same die.

Or you can order a small base die.

Lynn"

 

[BoydAllen]

I think that this will solve most of your problem. Note: the measurement that he shows is the wrong one. The difference in sleeve position with the mod installed is just the rim thickness plus the amount that the ball stick up above the rim. the rest of the thickness goes inside the sleeve. I have seen this fix on several web sites. Reduction in cocking effort is reported as high as 40%. I am going to do mine tomorrow.
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