CRF problem?

CarbonMTN said:

If you're single feeding a CRF (control round feed) is it prone to failure because the extractor has to go around the rim of the case instead of the case sliding up from the mag?

I have not seen much talk about this and if I am going to single load most of my bench shot would a push feed be better?

I only plan on using the Mag feed when I go varmint hunter, so a few times a year.

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I have a few CRF (ARC Nucleus and Bighorn Origin) I single round feed and they both work fine. You do feel little resistance when working the bolt slow as the extractor goes over the rim. My push feed are definitely smoother when working the bolt slow but when you run them fast I cant tell the difference.

Prone? No, some do it better than others though. That can have as much to do with the shape and exact diameter of the case head as it does with the extractor though. I would consider that a huge fail if i couldnt toss a round in the port and chamber it on any action.

It depends on the design and how large the extractor relief cut is. Some older CRF designs don't have a relief cut on them and would break the extractor if you single round feed. Modern CRF designs tend to allows for single round feeding.

Factory Win m70 after break in was in issue, brand new Win m70 that GAP built on was never a issue.

I will say that I did have issues with single feeding my Mausingfield with AICS mags. When I swapped to MDT mags (or ARC mags), I don't have that issue.

So there is a component to the mag geometry and how the round is presented to the bolt. I'm sure it's an easy fix, but someone who is more knowledgeable on it then I is better deserved to talk about it.

I have single fed thousands of rounds through my nucleus.

CarbonMTN said:

I will be using pmags (super budget rifle and Pmags are more than 1/2 the price less) could you see an issue with these?

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I honestly don't know enough to answer this question. There's certainly nuances to CRF, and I'm going to tag in someone who knows CRF much better then I do. You probably won't know until you try it, and if you do have issues, I'm sure some simple tweaking will sort it out.

@Ledzep

CarbonMTN said:

If you're single feeding a CRF (control round feed) is it prone to failure because the extractor has to go around the rim of the case instead of the case sliding up from the mag?

I have not seen much talk about this and if I am going to single load most of my bench shots, would a push feed be better?

I only plan on using the Mag feed when I go varmint hunter, so a few times a year.

Click to expand...

Years ago, long before the ARC stuff ever made it to the firing lines, Mausers and M70's were likely the dominant actions for CRF operating systems. It is widely accepted that they demand a bit more/different skillset(s) if they are going to function as intended. A wive's tale grew from that. It states that single feeding with a nonrotating claw extractor is a bad thing and it's both hard on case rims and the extractor.

That is false.

An extractor is little more than a ratcheting paw feature that grabs onto something. In the case of the CRF setup it's often coupled with a leaf spring arrangement as a means of exerting the shell pressure required to properly latch onto and retain the case rim. Automobiles have been cruising our highways for at least a century using leaf spring suspension systems. They last almost indefinitely. There's no reason to expect any less from a bolt gun.

If the extractor claw has the appropriate chamfer geometry it should slip over the rim of the case with very minimal effort and with no damage to the brass rim feature. A slight audible "click" will likely be heard as it does this. If it does not do that, then the fitting of the claw feature is wrong. (that skillset thing. . .) The line in the sand between pass/fail is pretty small with these things so I would encourage anyone messing with them to make very, very small moves.

Dremel stays in the drawer. Period! Use a good needle file to fit and polish with a hard felt wheel once you're done.

Hope this helps.

C.

What he said ^.

If you can't throw a round completely in the chamber and have the extractor easily snap over the rim, you (or a GS) need to change the geometry of the extractor until it does.

Most of the time I find that tossing a round on top of an empty AICS magazine allows the rim to drop low enough that it slides up under the extractor anyways, but in the instances where it doesn't, you can feel an hear the extractor clip over the rim on the case. Lots of experience with ARC Nucleus and Mausingfield, and Bighorn/Zermatt TL-3's & Origins and that's been true for all of them.

A non-related issue that happens whether you have CRF or push feed is if the length of the bullet ogive and neck is long enough, and the case body is the right shape/diameter, single feeding can become problematic because the meplat hits the breech face before the shoulder hits the feed ramp. You push the bolt forward to a hard stop where the bullet tip hits the breech face. It's dependent on action, bullet, case, and seating depth and sometimes doesn't have a concise fix, if any at all.

Sounds like I need to grab my files and stop ignoring my M70's problem. Feeds fine from the mag, but trying to run the bolt on a single round dropped into the action? The amount of force required to send it home is not dissimilar to what I would use if I wanted to break someone's nose. My M70 has been far more temperamental and decidedly less forgiving than my other actions...

DJL2 said:

Sounds like I need to grab my files and stop ignoring my M70's problem. Feeds fine from the mag, but trying to run the bolt on a single round dropped into the action? The amount of force required to send it home is not dissimilar to what I would use if I wanted to break someone's nose. My M70 has been far more temperamental and decidedly less forgiving than my other actions...

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The "sharpie" trick will likely help you out here. Mark up the extractor with one and cycle the bolt once or twice with a sample case. It should wipe away the ink where the contact is and if it's right on/at the edge of the transition from the flat face of the extractor to the chamfer feature, that is where I'd start. Accentuate the chamfer slightly to try and encourage the outward movement more.

LongRifles Inc. said:

The "sharpie" trick will likely help you out here. Mark up the extractor with one and cycle the bolt once or twice with a sample case. It should wipe away the ink where the contact is and if it's right on/at the edge of the transition from the flat face of the extractor to the chamfer feature, that is where I'd start. Accentuate the chamfer slightly to try and encourage the outward movement more.

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Thanks! Will do.

@CarbonMTN I've run TL3/SR3/Origins, an M7 Mausingfield, an Archimedes, and an FN SPR. None of them has exhibited any single feeding issues.
Like Dom mentioned above, I've used a variety of cartridges as well, .223 Rem, .220 Thunderbolt, 6XC, .243 Win, 6mm Comp Match, 6.5 PRC, .308win.

I will say that for NRA High Power comps I usually use a single feed sled, like a BobSled. I do this mostly because my magazines are already loaded for the rapid fire stages. The BobSled presents the case in the same relative position as a round that is loaded into the magazine.

https://www.midwayusa.com/product/1006294916

They also make a AICS .223 specific sled that I use for .223 and .220 Thunderbolt.
If you are not happy with how it feels when just setting the round on top of the magazine, try one of these Bobsleds.

Regards,
Ross

Some controlled round feed actions, like Wincherster's CRPF, have the same exact extractor that's used in many push feed designs and are designed to slide radially to pop over the rim of a chambered cartridge.

The original design of controlled round feed on Mauser 98 required that the round be inserted into the magazine and then cycled with the bolt or else the extractor would be damaged. Modern CRF designed actions do allow some amount of control in the feed and extraction but not to the degree of the original Mauser design. As stated above, the newer Win M70 CRF full length extractor design was changed so it could be used as a push feed with the full length extractor being able to snap over the cartridge rim without sustaining damage. I like the newer CRF designs that use the push feed style small plate extractors, they work well.

Edit: good pic above by 308pirate.

For giggles, here's a picture I took...still need to actually do the filing bit. This reminds me that I have a spare extractor hanging around because I do this thing where I drop rifle bolts on concrete (accidentally). I bent the extractor and popped it off the bolt body a few months back doing that. I grabbed a multi-tool, approximated what seemed "right" and put it back on while I waited for the spare. If anything, that slightly improved the situation. The 1911 similarity failed to impress/endear. I suppose in the name of science I should hunt that spare down...

https://photos.app.g

Holy crap!
That extractor looks like a tiger claw!
Trim kitty’s nail down would you!