Sticky bolt?

I fired my new to me model 70 today. And the bolt had a catch in it about 3/4 the way up. I can reinsert the fired case and it will still catch. It did this with one load but not the other. The load in question is 375 h&h 300 grain Sierra with 74 grains of IMR 4350. This is not near maximum and give about 2480. It was also six degrees today.
The primers are cratered a bit but not bad.
Is this a pressure problem or something else?

wyatt,
in my old 375 that load was pretty mild.
however it might have higher pressure if the bullet is jammed into the rifling.
it sounds like the bolt is "catching" at the extractor cam.
while it sounds like a pressure issue, it will be interesting to see what comes out in the wash.
bruce.

I was hoping to hear from you Bruce. It does not do it empty, but to me it seems mechanical. I guess I will try some lighter loads and determine if I have any “jump” to the lands. Then I will go from there.

wyatt,
if you push a projectile up to the lands, you can use a cleaning rod from the muzzle to touch the bullet nose, and mark it level with the muzzle.
then do the same chambering a live round and the firing pin removed.
the difference between the lines will be jump or jam.
while not exact like measuring from the ogive, it will be close.
also next time you shoot, try lubing the extractor and cocking cams with a good high pressure grease just for interest sake.
another thing, unlikely is that safe pressures are relative to the brass temper.
too soft brass will not hold the pressure of correctly tempered, and primer pockets will expand too quickly.
if your primer pockets will not hold a primer any more after 5 reloads, or even 3 is worse, there is too much pressure for that brass, and sticky extraction will be the first sign of this.
I used to use Winchester brass, and it took many loads of 76 gns h4350 (ar2209).
if the case expands beyond its elastic limit, pressure is too high, whatever the charge or speed.
another thing that can cause excess pressure is overlength cases.
they jam into the chamber/barrel transition, in effect crimping the bullet and refusing to let it release.
trimming will fix this.
bruce.

Thanks Bruce I will try that cleaning rod trick. I did trim the brass before I loaded them. The brass is Norma and once fired. What I can’t figure out is when I put the case back in the chamber and close the bolt. It sticks on the way back out.

it is obviously tight enough to grip the chamber wall, suggesting it has expanded.
if the first firing was norma factory, it might suggest some of norma's loads are true to suspicion of being too hot.
norma brass has also a reputation for being softer than American brass.
fclass shooters avoid it like the plague for this reason.
or were the first firings handloads.
bruce.

I’m sorry, this is the second loading. They once fired when I loaded them. I got them from a friend who doesn’t reload.

Suggest you get head space checked.

I just did doctor. It’s fine.

These are always hard to tackle without in-hand inspection. This is a difficult one as it has symptoms indicative of possibly more than one issue. Pressure related, ammo related or gun related.

One thing I do with belted mags is use a small base die or a collet die to resize the body just in front of the belt. If that area expands enough after a firing and many times a conventional sizing die won't re-size that area enough... sticky chambering/extraction can result. Since the 375 HH has quite a bit of body taper, it's usually not a big issue. But I have gotten into the habit of never saying never Just a possibility that popped into my head as I was thinking about this.

You said it seemed "mechanical". Something easy to inspect- close the bolt on empty chamber of course. Set safety to "mid" position (90' from bolt). Lift bolt and remove. Study the small tear drop shaped detent on the shroud opposite the safety lever. It should be popped out about 1/8" or so. It is called the "bolt sleeve lock". If you rotate the sleeve (shroud) you'll notice that if the bolt sleeve lock is depressed the shroud (sleeve) will rotate and the sleeve lock will pop into a slot on the boss of the bolt handle. If released, the bolt sleeve lock will lock the sleeve in that position to the bolt body. Slowly put the bolt back into the receiver and keep an eye on the detent action of the bolt sleeve lock as it contacts the rear receiver ring. Then rotate the bolt as per a normal cycle and watch the sleeve lock and sleeve (shroud) in relation to the bolt body.

I think everyone has given good advice about headspace, pressure and brass, so obviously those issues should be looked at first. Then maybe do an easy inspection of the bolt sleeve lock. If it doesn't depress properly and doesn't slip freely into the slot in the boss of the handle (part of the bolt body) it could have a slight "catch" during regular bolt cycle and operation. Won't hurt to look at it and won't take any time. The next mechanical thing to check may be the safety itself as it interacts directly with a boss on the striker. These parts can wear or even chip and cause issues. But probably best to do one thing at a time If it is a mechanical problem and not a brass or pressure issue, at some point, if not corrected or identified, it may require a visit to a competent Win 70 gunsmith- but hopefully not! Good luck on finding and correcting the issue.

1st pic shows pen pointing at bolt sleeve lock on sleeve (shroud) and the slot it fits into when depressed by the rear receiver ring on this post 64 Win 70 bolt.

2nd pic shows pen pointing to area on 375 HH brass for sizing concern.

Thanks @fourfive8 I learn an awful lot from you guys.

If you haven't already I would make sure the lugs are good and clean. Sometimes they get build up from cleaning. Put an oversized patch on a cleaning rod and spray it with gun scrubber. Twirl it in the lug area and see what it looks like. You gain bend q tips sprayed with gun scrubber and a flashlight and get in there the best you can to get the rest. Clean thebolt and lugs as well. Put a very small dab of gun grease on the back side of the lugs and work the bolt a couple times to spread the grease. If it still does it I would get some new brass and try that.

at the moment my money is on the need for more elastic brass than norma that has never been overloaded.
bruce.

One thing to try that I didn't see already mentioned is: with the rifle unloaded push the bolt forward, then while turning down press the trigger so that the firing pin will follow the cam down, basically putting the firing pin in fired position. So now you have a rifle with the firing pin forward on an empty chamber but without the dry-firing stresses. Now lift the bolt handle as you would if you had fired the rifle. If it has the same catching then the problem is somewhere in the mechanics of the rifle (possibly in addition to ammunition problems).

If this issue is from high pressure and the area just in front of the belt is suspected of not sizing correctly, there’s an easy way to tell.

Get some new brass and load up a couple rounds to same load. And also a couple of once fired pieces. Shoot them and compare the extractions.

Suggest gunsmith check the action. Maybe the cases need to be fully resized.
Maybe the reloads are hot because the wrong powder has been used.

Wyatt Smith said:

I fired my new to me model 70 today. And the bolt had a catch in it about 3/4 the way up. I can reinsert the fired case and it will still catch. It did this with one load but not the other. The load in question is 375 h&h 300 grain Sierra with 74 grains of IMR 4350. This is not near maximum and give about 2480. It was also six degrees today.
The primers are cratered a bit but not bad.
Is this a pressure problem or something else?

Click to expand...

Wyatt, just want to make sure I understand, and maybe you can check for me.
Once you fire a round, the bolt sticks about 3/4 up. If you cycle the bolt with or without a round, and keep cycling it without releasing the trigger, it doesn't stick?

I didn't see this suggestion previously but if it has already posted please forgive me. Have you tried using new factory ammo to see if there is an issue with it as well?

For you other posters, I was of the opinion that Norma brass is about the best you can buy. Am I totally off base?

bruce moulds said:

at the moment my money is on the need for more elastic brass than norma that has never been overloaded.
bruce.

Click to expand...

Could be. No argument from me on this. If this brass was fired first in another chamber- that chamber could be a little larger than this one. Given the fact that a conventional sizer doesn't touch that area just ahead of the belt plus the possibility of being oversized from the get go after firing in the first chamber.... maybe the culprit? Whether or not the Norma brand has anything to do with it? different or third question

There are plusses and minuses with nickel plated brass, but investing in a new box of it may shed some light on whether or not it's a brass/brand/sizing issue.

I'm still wondering about the overall length of the bullets. A little too long and Wham! a big pressure spike and a sticky bolt.