Ruger MK IV bolt headspace question

[Riomouse911]

Hey all,

I picked up a 5.5” Ruger Mk IV upper from Volquartsen for $40.00. I guess they buy the guns, pop off the upper and use the frame and bolt for their products, then they sell the original factory uppers and the case they come in. These come unfired with the factory sights, but with no bolt.

I found a new Mk IV bolt and ordered it for the upper. Will this need any fitting or head spacing, or is it just plug and play?

Oh, on a side note I learned the upper is the serialized part of the Ruger, not the frame. This means the MK IV uppers (which are interchangeable) must go through the FFL process and will be sold as the “firearm” rather than the frame like other handguns/AR rifles.

Stay safe.

 

[wiscoaster]

Plug it & play it.

(I'm assuming you do the usual stuff to function-check it)

 

[DerMerchant]

Is headspace a huge concern on .22s?

 

[wiscoaster]

No.

(Never heard of it mentioned in connection w/ .22s but I'm no gunsmith or even any kind of a gun expert)

Actually, after a moment's thought ... since it's a rimmed cartridge: No.

 

[wiscoaster]

But, I have a short story that sorta falls into a .22 LR "headspace" topic. Back when I was still really stupid about guns in general, I bought a revolver with swappable cylinders - one for .22 LR and one for .22 WMR, and you guessed it: one day I shot .22 LR's through the .22 WMR cylinder. I couldn't hit the target for beans. Bullets were flying all over the place downrange. Upon ejecting the cases from the cylinder I noticed they were all badly bulged. I thought that was pretty weird, so I took them out to show to my pistol instructor. He was wide-eyed but had no ready explanation. (He didn't know about the gun with the swappable cylinders). It took a few minutes, but eventually it dawned on me what I had done.

 

[Riomouse911]

Good deal.
The bolt is brand new and unmarked. It’ll be a couple of weeks before I can get the upper to shoot, it’s in the regulatory penalty box for 10 days after my FFL receives it and I fill out the paperwork... for the children, of course!


Once I get it together I’ll check function and then check accuracy .

Thanks again!

Stay safe.

 

[BBBBill]

I found a new Mk IV bolt and ordered it for the upper. Will this need any fitting or head spacing, or is it just plug and play?

Generally plug and play. It is always possible to get a badly machined bolt, usually with too much headspace for good accuracy, but not usually a problem for safe function. Spec dimension for 22LR rim thickness is .043". Many if not most rounds you measure will be less than that if nothing has changed in the last couple years. I've found .041" to be quite common. I've found the recess in the bolt face to be .046" - .049" on many bolts. Note that I don't see a recess on thet Mk4 bolt face. Might just be the fuzzy photo. I have no experience with the Mk4 so the following might not apply if it does not have the recess like the previous genrations.

A round with a thin rim and a deep bolt face will definitely inhibit accuracy and may induce failures to fire in the worst cases, depending on how much firing pin protrusion and firing pin tip shape/condition. It is simple enough to measure the depth of the bolt face recess and reduce it to a reasonable figure if it is far enough off spec to cause your gun to underperform. As simple as using a new sharp flat file and a square. Be careful to set it up properly and go S L O W. I've seem dramatic improvement in accuracy from that alone. First things first - try it. If it does what you want you're golden. If not then you have some simple options for improvement.

Is headspace a huge concern on .22s?

See above.

 

[SGW Gunsmith]

Actually, no, Volquartsen does not use the Ruger bolts, they sell those on ebay. What they use for bolts are only the versions they make and sell.

 

[SGW Gunsmith]

Yes, the Ruger Mark IV bolt faces are indeed recessed:



A fella named C. E. Harris wrote an excellent article in the 1988 Gun Digest concerning headspace involved with .22 rimfire firearms. His partner and him tested several .22 rimfire firearms and found that bolt face headspace can vary from 0.044 to 0.051 and it did not affect accuracy involved with their test guns.
If headspace is shorter than the rim thickness, or around 0.042, yes, then there could be a "slam-fire" condition, which might cause too much excitement for aging men.

 

[Project355]

Just gonna add ..DONT over think this! It will work. The "slop" is built into the design/manufacture of Ruger bolts.

This is a BR design, he designed what was easy to build and stay within spec.

 

[Riomouse911]

Thanks for the info. I didn’t think this would need much, if any, fitting...certainly nothing like a revolver cylinder sometimes requires.

I just wanted to check with those who know far more than I about these guns.

Thanks again

Stay safe.

 

[243winxb]

The firing pin/stop can be adjusted, if more travel is needed. Shaving the bolt face sounds like a great idea. But i tried to cut a MK1 bolt with a hack saw. Could not even mark it. Very hard.

 

[BreechFace]

I purchased another SS hunter upper from another vendor that like volquartsen buys or works on stock Rugers and pitches the Ruger upper and sells them on the side. Mine was completely plug and play.

I immediately went out and sold my mk3, the mk4 design is that much better IMHO. I’m sure they’ll be some that say, “But my MKII...”

The ability to swap uppers when one has really tuned and configured the lower how one likes is very nice. I can bounce back and forth between iron sights and optic uppers in seconds and cleaning after running 1,000 rounds suppressed is a breeze.

 

[SGW Gunsmith]

Ruger Mark pistol bolts are harder than Hades. The best way to square up a bolt face "needing" that to be done is on a surface grinder where 0.0001 of an inch can be removed cautiously.
We see these folks on ebay who claim they, will do headspace setting and face squaring at a certain price. One question I have, is how sure are they that the breech face is square with the bore line? If not, what can be done about that? I have seen many breech faces where they have bolt imprints that are not even, yet it doesn't affect function or cause any harm. To me, bolt face rework is not necessary and what it can, and will do, is move the bolt face further away from the extractor, if/when over-done. That will indeed cause problems,
Several years ago I was bound and determined to get a Ruger Mark pistol perform full function with feeding, firing and ejection of CCI Quiet rounds at 720 FPS. I even butchered up a bolt, using carbide tooling, to try and get the bolt light enough to do what I want, to no avail:



Changing springs alone did not help as the light springs I tried did not store enough energy to return the bolt, to pick up another round and chamber it. I wound up with a "prototype" bolt made from titanium. That gave me what I was looking for because the bolt weighs less than half of what a steel Ruger bolt weighs at 5 ounces, complete with all parts. The effort was worth it to me, but the cost involved is not.

 

[SGW Gunsmith]

The firing pin/stop can be adjusted, if more travel is needed. Shaving the bolt face sounds like a great idea. But i tried to cut a MK1 bolt with a hack saw. Could not even mark it. Very hard.

Yes, the slot in the firing pin for the bolt stop pin can be elongated on the back end of the radius for the bolt stop pin. Still though, the firing pins are also quite hard, so a carbide rotary bit in a moto-tool would be needed for that modification, or for a slower process a diamond impregnated round needle file. That can be a slippery slope though, as you might wind up with a chamber mouth ding:



Those are a real PITB to fix properly.

BTW, check out the flame erosion on the left side of the breech face. So, what's out of square? The breech face or the bolt face?

 

[Project355]

This conversation has devolved from functioning to "accuracy".

Trust me.... The bolts can be interchanged.

 

[SGW Gunsmith]

Thanks for the info. I didn’t think this would need much, if any, fitting...certainly nothing like a revolver cylinder sometimes requires.

I just wanted to check with those who know far more than I about these guns.

Thanks again

Stay safe.

I don't understand why Ruger claims that bolts need "fitting" either. Fitting to what? I've tried the various model Ruger Mark pistol bolts in other versions they are not intended for, and they work just fine, as far as firing is concerned. Bolt hold open, that's a different feature all

 

[Project355]

Ruger has lawyer'd up significantly over the years. For instance - transfer bars now need "fitting" on SA (or at least the Bearcat). The LCR models... jeeze, the only factory part you can purchase is the screw for the grips! Every other part is "factory fit only".

Its my belief that they're being cautious. All of the tolerance is in two spots - the breech face to bolt face "recess" and the firing pin protrusion. I doubt that the former is any issue whatsoever. Ruger design parts - and the way they make parts - to be minimally fitted. That dimension would be very easy to hold accurately with even simplistic fixturing. Firing pin protrusion is more likely to be any concern, and really, its minimal concern. The "issue" being how far proud of the breech face the firing pin can go before it hits its "stop". While the firing is not so much a problem, dry firing is, whereas you'd dent the chamber mouth.

I've had plenty, literally scores and scores of Ruger 22 Automatic, Mk1, Mk2, MkIII, MkIV.....22/45... you name it, all of them apart, they are nothing precise when it comes to the bolt. I did that work for well over 10 years when working in the local range, and while I really didn't try to inter-fit all the pieces, you can tell there is nothing really to fit at all.