Extraction

[mike a]

Trying to understand extraction. Here a lot about primary extaction. So if there's primary is there secondary? My understanding is primary is the cam shape at the back of the reciever that the bolt handle rides across. I.e. My Bighorn or a Rem700. My Bighorn doesn't engage this cam until the bolt handle is way up there. So here's the deal, I get smears marks on my case heads even with mild loads. It seems to me that if the case is even slightly stuck in the camber and the bolt turns without moving back the case will stay stuck and your gonna get smears. So IS the bolt moving back at the start of lift? I realize the case should spring back away from the camber walls after pressure is gone. And if it does spring back why do we need that big ass cam anyway? 40 grains h4350 87 vmax 6 creed. 3150 fps. Smear marks!!!Do make it to complicated as I'll have to throw brain data away to make new space. Mike

 

[okie]

how hard is it to close bolt on same loaded round?

 

[mike a]

how hard is it to close bolt on same loaded round?

Easy, .002 bump.

 

[mike a]

Maybe I should say, is there Initial extraction Before the primary extraction?

 

[gunsandgunsmithing]

Maybe I should say, is there Initial extraction Before the primary extraction?

Primary extraction is the initial extraction. The bolt rotates without rearward movement until the primary cams make contact, then begins rearward. This is to break cases free that do not contract far enough for effortless extraction at all areas of the case. Virgin brass and relatively mild loads, and the primary cams don't do much, in a perfect world. But realistically, whether it's on the first load or the 5th, you'll need that primary extraction to aid breaking the tapered case free of the chamber as the brass loses its ability to constrict enough. Brass has a tendency to want to remain at its largest point. When you pull the trigger, the barrel swells a tad and that's where the brass wants to stay.

 

[mike a]

Primary extraction is the initial extraction. The bolt rotates without rearward movement until the primary cams make contact, then begins rearward. This is to break cases free that do not contract far enough for effortless extraction at all areas of the case. Virgin brass and relatively mild loads, and the primary cams don't do much, in a perfect world. But realistically, whether it's on the first load or the 5th, you'll need that primary extraction to aid breaking the tapered case free of the chamber as the brass loses its ability to constrict enough. Brass has a tendency to want to remain at its largest point. When you pull the trigger, the barrel swells a tad and that's where the brass wants to stay.

Very good. Still learning. For me it helps to understand how extraction works to better understand pressure signs. Thanx

 

[okie]

Easy, .002 bump.

ok --I think tight chambers quite often get blamed for extraction problems...my 2 cents

 

[gunsandgunsmithing]

ok --I think tight chambers quite often get blamed for extraction problems...my 2 cents

I agree to a point. I think it's about two things, mainly. First is chamber size to virgin brass relationship and 2nd, die to chamber relationship. The less you move the brass, the better. JMHO

 

[Tim s]

There is another point which often applies.
There are a lot of actions where the extraction camming is fairly progressive and there are some that are less so and right at the top of bolt lift you may encounter a hard “click” often with BR chambers, brass, pressures, etc.
This, largely is what lead to a BR variation of a FL die that does not really size the whole case, it sizes the neck, bumps the shoulder, and sizes the base only which is where the “extraction click “ originates.

 

[tmwinds]

Aside from a poorly designed and manufactured action and bolt that has no primary extraction, most extraction problems are self inflicted. In a quest for more speed and accuracy we have designed case bodies with little to no taper, use minimum clearance chambers and dies, tight necks, 40 degree shoulders, and load to pressures in the 70,000 psi range. We then wonder why we have extraction problems.

 

[mikecr]

Well, improved cases have less body taper and higher shoulder angles so that they grow less(in length). You understand that growth leads to harder bolt lift, regardless of extraction, right?
gunsandgunsmithing is also right about cases wanting to return to their largest dimensions. So the best way to mitigate cases defaulting to problem dimensions is to prevent them from ever getting there. That's where tighter clearances, custom dies, sound action design, and rational pressures come in. Minimal sizing, nothing wrong with that, and everything good about it.

Mike a is wiping the case head because the case head is hard against the boltface. And while concerned about bolt timing, he didn't actually declare extraction as difficult.
This issue may have nothing to do with 'extraction'. I don't know

 

[Nightraider]

 

[okie]

Aside from a poorly designed and manufactured action and bolt that has no primary extraction, most extraction problems are self inflicted. In a quest for more speed and accuracy we have designed case bodies with little to no taper, use minimum clearance chambers and dies, tight necks, 40 degree shoulders, and load to pressures in the 70,000 psi range. We then wonder why we have extraction problems.

yes

 

[rardoin]

Mike a is wiping the case head because the case head is hard against the boltface. And while concerned about bolt timing, he didn't actually declare extraction as difficult.
This issue may have nothing to do with 'extraction'. I don't know

Case in point... I had changed my method of lubricating my case necks prior to running an expander mandrel to set my 'neck tension'. This allowed lubricant to creep down the the case wall a bit. I did not clean off the lube as it seemed inconsequential to me. I showed up at nationals with these loads and was experiencing hard bolt lift from the beginning of the extraction sequence; not a heavy 'click' once the bolt engaged the extraction cam. The case face had galling from the bolt face appearing as 'swipe' arcs on the brass and deposition of brass on the bolt face (Borden BRMXD action/no ejector). These were not heavy loads; 184 Bergers run at 2805 fps in a straight .284. I really did not think I had enough lube to be a problem but, once I got home, I wiped down a few extras from Raton with a solvent wetted rag and fired them. No bolt lift issues and no galling of the case head. My cases were thrusting hard against the bolt face by growing in length more so than growing diametrically at the base leading to the bolt lift being very heavy.

 

[JFrank]

Nice’
Is this a video of your personal R700 action?

 

[Nightraider]

Nice’
Is this a video of your personal R700 action?

No, a customer's. I've been doing them for a few years, but the bolt handles always sucked from PTG. Andrew Delikat of AD Arms did a big run for us and they're literally perfect on the PE cam angle so now it's pretty much standard on all of the builds minus ones that want PTG 1 piece bolts.

 

[Ledd Slinger]

It would be a big help if you could post pics of the smear marks on the cases...

If by "smear Mark's on the case head" you mean getting marks on the cartridge stamping of the rim...Its probably your ejector.

You can remove the ejector and make sure there are no sharp edges on the edge of the ejector plunger or the hole housing the ejector plunger in the bolt face. Use 400 grit sand paper to knock down any sharp edges and clean debris away thoroughly when done.

You can also reduce the pressure of the ejector plunger on the case by cutting out 1 or 2 coils out of the spring before re-inserting and fastening the plunger to the bolt face. I always reduce the ejector power on my rifles by cutting a couple coils on the spring so they dont fling brass into the next county. I usually set them up with just enough power where they gently lay empty cases a few inches from the ejection port.

____________________________

If by "smear marks on the case head" you mean smear marks on the case body just below the .200" body line, then there's probably something wrong with your chamber cut.

 

[Alex Wheeler]

I have not had trouble with the PTG handles. You can't use them as they come, but thats normal for just about everything.

 

[Ledd Slinger]

I have not had trouble with the PTG handles. You can't use them as they come, but thats normal for just about everything.

I've got a full PTG one piece bolt on a Rem 722 with custom diameter I spec'd for the factory raceway. No issues. Dropped it in and extraction timing was good.