Headspacing a mini 14 bolt

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Bearcat
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So I'm a new guy on this form. I've posted a couple of questions not much in response. I like things that go bang. A month ago I bought a new Ruger ranch rifle mini 14 .556 black stock, blue barrel and receiver. In a short time frame I've run a 1000 rounds down the pipe and ordered sights, rails, rings, slings ,scope, changed the stock then changed it back. and gun tools. I thought it would look different to change out my blue bolt to stainless kinda two tone. I had read that Ruger would sell just about every part of the mini except the bolt and the receiver. I started looking for parts I wanted to have spares of a number of the small springs and workings of the action and the bolt. Midway had most of what I wanted 14 items, no bolt offered. Looked a little more I found the factory replacement stainless bolt . Disassembled with the notice that the bolt would have to be headspace to the rifle, and the firing pin protrusion would have to be checked. I went ahead and ordered the bolt and all the assorted parts associated with the bolt. I know what the hell are you doing to that new gun? Would you gunsmiths out there help a guy out and explain the process to this 70 year old grasshopper
 

NikA

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Headspace: buy headspace gages; you may be able to get away with a GO gage and shim stock/tape to increase the datum dimension to NO GO gage size. Using your new stripped bolt (so as to minimize possible measurement effects), check that a GO dimension gage allows the bolt to lock up completely and a NO GO gage does not. It's generally too complicated to bother with adjusting headspace on a semi-auto rifle, so if the bolt does not headspace correctly, you'll likely be looking for a new bolt that does. Fortunately, most bolts will be within tolerances with most receivers.

Firing pin protrusion: measure the depth of the case head recess on your bolt face using a depth micrometer, caliper end, etc. Then measure the same dimension to the tip of the firing pin when it is pushed as far forward as possible. The difference between the two measurements is firing pin protrusion. I seem to recall for a Mini-14 this should be ~.025-.030", though you should definitely verify that number with a web search. More protrusion is better for setting off hard primers (think cheap steel case ammo) but increases the likelihood of a primer rupture on softer primers. You can lower the protrusion with fine (320+ grit) sand paper and the firing pin held in a rotary tool.
 

Mobuck

Hawkeye
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OR, you can just pull the bullets from 5-10 factory loaded cartridges, re-assemble the rifle with the new bolt, and see if it FULLY closes on the cases. If so, then run the cases through and snap the primers to see if the FP is working good or too good(too much protrusion). If this looks suitable, take that puppy to the range and see what happens.
I assemble AR platform rifles frequently and have NEVER checked any with headspace or FP protrusion gauges w/o any issues what-so-ever. Consider that if the company is requiring fitting, their parts are more likely to err on the tight side because it's darned difficult to 'fit' something that's already too loose.
 

Tailout

Bearcat
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Thanks a very common sense approach mobuck even I can understand that process. I get the removing material from the fp if hitting the primer to hard/deep but what would you do if the bolt fit tight? Where would you remove material?
I'm not talking about changing out the barrel just swapping out a factory bolt with another factory bolt. The only difference is one is stainless one blued steel. I only use factory loaded brass cased ammo, no Russian steel case for my mini. I found the bolt at Accuracy systems, they are a Licensed Ruger gunsmith. If a bolt was too tight would removing material from where the lugs lock/set into the receiver be an option? I'm going to preform the empty case primer test and go from there. I know of a good local gunsmith, I'll see if I can get his opinion? Thanks,
 

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Bearcat
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Well I ordered a set of headspace gauges from Brownell's part #GON5.56 $66.00 .
Go 1.4363- no go 1.4696. the gauge for .223 was the same go dimensions and 1.4666 for the no go. A little wiggle room for the NATO round .0030. the gauge is notched so you don't have to remove the extractor and plunger/spring. Anybody use this set?
 

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Bearcat
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So to edit what I previously wrote, I flipped the go number. The go number is 1.4636 for both calibers.
 

NikA

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Well I ordered a set of headspace gauges from Brownell's part #GON5.56 $66.00 .
Go 1.4363- no go 1.4696. the gauge for .223 was the same go dimensions and 1.4666 for the no go. A little wiggle room for the NATO round .0030. the gauge is notched so you don't have to remove the extractor and plunger/spring. Anybody use this set?
A gage is a gage provided it is properly manufactured. Good on you for getting a set that is notched for the extractor, it will make life easier.

As far as adjusting headspace on the bolt, I wouldn't recommend that, especially not on a semi-auto like the Mini-14. The usual first point of adjustment is the depth of the chamber in the barrel, which is going to be impossible to adjust properly without pulling the barrel or using a pull-through reamer. The next point of adjustment would be the bolt face, and the final would be the locking lugs or corresponding recesses in the receiver. Just too much going on to recommend messing with unless you have a full setup for it.

If the bolt you have doesn't headspace properly, I'd be looking at trying again with another bolt or sending it off to someone. As I said before, there's a good chance it will be in tolerance from the factory and headspace fine.

Good luck!
 

Mobuck

Hawkeye
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"I'm not talking about changing out the barrel just swapping out a factory bolt with another factory bolt. "
The result is the same. Introducing a different bolt into the locking lugs changes whatever relationship there was between chamber/bolt face/locking lugs/locking recesses.
As NikA said, if the bolt is too tight, you'll need to find someone knowledgeable to cut/fit the bolt lugs.
The fitment of bolt lugs is different with a 2 lug system vs the multi-lug AR bolt. As far as I can tell, it's nearly impossible (short of a full-on lapping of the lugs) to get 100% contact with a multi-lug system. With a 2 lug bolt, most old-timers wanted to see nearly full contact on both lugs and their recesses. Considering the .223's smaller base diameter of .378", bolt thrust is much less than something like a .532" magnum cartridge base.
 

Tailout

Bearcat
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Thanks for all the great info. I started this bolt change out because I thought it would look good in stainless. Like I wrote, I bough this rifle new about six weeks ago and have fired a thousand rounds. The new bolt arrived and I fitted it in the gun, waiting for the headspace gauges. I've field stripped the rifle to clean it a couple of times, paying attention to the wear patterns and applying gun grease. The gun has preformed flawless, and with a scope old eyes I can shoot 2" groups at 100 yards. Well on closer inspection the back of my original bolt is getting the yugo beat out of it by the hammer. I inspected the trigger housing, everything is tight and the hammer strikes the back of the new bolt square. Has anyone else seen this? Can't be normal. If the new bolt headspaces ok I'm going to shoot it and keep an eye on the bolt and hammer. There's a little side to side play in the hammer, could my hammer need shims?
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Bearcat
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As you can see in the pictures the bolt is peened over and the firing pin is getting chewed on. Something ain't right. Seems like the bolt is out of alignment. The hammer is lined up, help!
 

NikA

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The wear/peening immediately under the firing pin is typical for a Mini-14/30 and can be addressed with light filing of the peened area to remove any raised areas.

The wear on the lug area probably indicates additional lubrication is necessary.
 

Tailout

Bearcat
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I checked the headspace, good to go. Took a stone to all the raised areas, on the original bolt
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and polished. At first I thought that the bolt was getting pinned by the face of the hammer. I surfed the web and found that this is a common problem with these Ruger rifles, 14 and 30. The bottom of the bolt is rounded at the rear on the port side which corresponds to a cured edge on the hammer. The bolt is getting pinned on the recoil stroke when it's cocking the hammer back. Interference fit, or lack of it. Some reference this as break in. This is a really fun rifle to shoot but Ruger could do better. The tolerances in the action are a barn door. The back of the bolt should be harden, or the design perhaps twerked. I put a Vortex Crossfire Il scope on her, zeroed in with a laser @ 25 yards. She's spot [email protected] 100yards, 2 inch groups. Fun gun to shoot, this is the Harley Davidson of Auto loaders. Ker chunk
 

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Bearcat
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California
Maybe the peening will harden up the steel in this area. I'm going to keep a eye on it, and grease the heck out of the action. I changed my recoil spring and bushing ordered a adjustable gas block to keep the brass from flying 50' and mellow out the recoil to save my scope from damage. What say you?
IMG_20220509_134124599.jpg
 

NikA

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I believe someone used to manufacture gas bushings with smaller bores to lessen the excessive gas in the Mini series rifles. If your ammo supply is consistent, that route seems less finicky to me than an adjustable gas block.

I shoot steel case in my 30, so I don't bother trying to find the cases. I think I have a recoil buffer on the spring assembly.
 

Tailout

Bearcat
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California
You can get sets with various sizes. The thing with the adjustable gas block you don't have to remove it to change the size of the bushing. You can even turn it off for single shot manual action. Accuracy systems Gen ,4 adjustable gas block. Has a knob in the front of the block for adjustments.
 

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