I am in need for some opinions. I have a brand new defiance action with a patriot valley barrel in 6mm br. My first time shooting it and it has a heavy bolt lift. The bolt face is leaving a rub mark on the back of the shell casing. It would be great if I could get some expert opinions on this as I’ve never had this happen before. Thank you
Heavy bolt lift
- Thread starter Pcaps
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Does the ammo feed normally?
Is the heavy bolt lift all the way up and through primary extraction?
Does the bolt, once open, extract the cases easily?
How do the cases measure before and after firing?
Are there any marks or signs of galling on the case sides?
The rub mark comes from the bolt face rotating against the base under tension.
So either the case jams on the way into battery and the bolt rubs against it then or the bolt face rubs against a case that is jammed hard against it after firing.
There are a variety of things that could lead to either of these outcomes.
Most relate to case sizing, chamber sizing/smoothness, or excess pressure.
Is the heavy bolt lift all the way up and through primary extraction?
Does the bolt, once open, extract the cases easily?
How do the cases measure before and after firing?
Are there any marks or signs of galling on the case sides?
The rub mark comes from the bolt face rotating against the base under tension.
So either the case jams on the way into battery and the bolt rubs against it then or the bolt face rubs against a case that is jammed hard against it after firing.
There are a variety of things that could lead to either of these outcomes.
Most relate to case sizing, chamber sizing/smoothness, or excess pressure.
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Best way to rule out headspace is using Go and No go gauges. I have read about improper headspaced prefits, doesn't seem to happen often, but snipershide has a few reports on them. And if you reload it might be reloading related, virgin brass etc.
That's excessive pressure. There's a handful of things that would cause this. most often it's just too high of a charge weight, if your far below max then it could be other things like carbon rings, seating depth, wet chamber/ammo... basically any that would spike the pressure on a normally safe load.
Ejector swipe is cause when the excessive pressure causes the brass to flow into the ejector cutout and then it's swiped off when extracted/ejected.
Also, Lapua and other high end brass often have slightly smaller case capacity/thicker brass so you will often get the top end velocity/pressure with a lower powder charge. (Eg. Starting charge is 32gr and max is 36gr, but you're getting 36gr velocity with the Lapua brass at 34gr because of this)
Ejector swipe is cause when the excessive pressure causes the brass to flow into the ejector cutout and then it's swiped off when extracted/ejected.
Also, Lapua and other high end brass often have slightly smaller case capacity/thicker brass so you will often get the top end velocity/pressure with a lower powder charge. (Eg. Starting charge is 32gr and max is 36gr, but you're getting 36gr velocity with the Lapua brass at 34gr because of this)
Sloped Roof Specialist
Regular
Good point, it's kinda blury but it definitely doesn't look super flat.
Possible bolt thrust causing the same brass flow into the ejector? But I don't think a case of bolt thrust could ever be accompanied by a heavy bolt lift? (case being thrown back into the bolt face with a running start would mean it's not expanding in the chamber beyond the brass' elastic deformation)
All I know is if I feel a heavy bolt lift it's certainly over pressure, especially if accompanied by an ejector swipe. IMO of course
Sloped Roof Specialist
Regular
That's what I've always thought too, but given that his action is brand new, is there some chance that his ejector is too proud by a wee bit?? If he didn't have wet/oily/greasy rounds or chamber, I dunno what else could do it.
SRS
That’s with 30grains of varget so I doubt it would be max charge weight. Maybe I’ll load some lighter stuff just to factor that out.
Sloped Roof Specialist
Regular
A quick google says that lots of guys are in the 30-31gr Varget range... that shouldn't be it, at least I don't think.
Something I learned from a podcast a couple weeks back is how detrimental oil/grease/lube on your case can be. It prevents the brass from "biting" on the chamber walls, and then the brass stretches, and overpressures the bolt head.
I've read that Defiance is very customer friendly, so maybe a call to them on Monday too??
SRS
Hmmm doesn't sound high, are your bullets jammed into the lands? And as a few others mentioned, water or other liquids on the brass/in the chamber is not a good thing either. (Good idea to clean out a brand new barrel cause it'll probably have some residual cutting lube from the chambering job)
Also I don't think the bolt having a proud or out of spec ejector would cause the heavy bolt lift?
Berger send me loaddata on 108EH's before. And their max charge in varget was 29gr. Start loading at 26gr and work your way up. And use starting weight to fireform brass to your chamber.
And as mentioned before make sure all sizing lube is cleaned off. I wipe every loaded case down with rubbing alcohol
270WSMXBolt
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Bullet seating depth on a case that size can have some significant impact on pressures but I don't think your powder charge is out of spec.
It looks like a funky ejector mark. It's not very flat contact. Should leave a round impression to start. I would contact your point of purchase for directions of what to do. Is it happening consistently or just at that charge weight. If so what bullet, weight and overall cartridge length ? Cheers
It looks like a funky ejector mark. It's not very flat contact. Should leave a round impression to start. I would contact your point of purchase for directions of what to do. Is it happening consistently or just at that charge weight. If so what bullet, weight and overall cartridge length ? Cheers
30gr of Varget in a plain BR is a high pressure load. Assuming you are using heavy bullets.
I agree that it appears to be high pressure...but as also mentioned, the headspace may be off just a bit...a tight a chamber...too much lube on the case...or a combination of one or more, or all of the above, that is enough to cause this.
I would have a gunsmith check over the firearm to be sure. If you have more of the same loads still, take them with you when having the gunsmith check over the rifle, along with some of these fireformed cases. May help determine the exact issue.
Just a thought on the primer not appearing to be flattened; some get a little aggressive with the primer pocket reamer and the primer may be seated just a tad deep so didn't flatten...or the priming tool is seating just a little deep...
In the end, too many variables to be able to determine fully from a photo.
I would have a gunsmith check over the firearm to be sure. If you have more of the same loads still, take them with you when having the gunsmith check over the rifle, along with some of these fireformed cases. May help determine the exact issue.
Just a thought on the primer not appearing to be flattened; some get a little aggressive with the primer pocket reamer and the primer may be seated just a tad deep so didn't flatten...or the priming tool is seating just a little deep...
In the end, too many variables to be able to determine fully from a photo.
