Perfect Union banner

1 - 19 of 19 Posts

·
Registered
Joined
·
128 Posts
Discussion Starter · #1 · (Edited)
So I had some time today and using the firing pin gauge I got from Brownells, I measured the protrusion on my Mini 14 original factory pin.
It came out as 0.040". I measured it twice to be sure.
Has anyone else measured their Mini 14's firing pin protrusion?

This measurement is noteworthy to me because the spare Glend Arms firing pin I have states on the package:

WITH FIRING PIN FULLY SEATED FORWAD
MINIMUM firing pin protrusion=0.028"
MAXIMUM firing pin protrusion=0.036"

Does anyone know what the Ruger factory specs are?
 

·
Banned
Joined
·
2,271 Posts
The measurements you have are the correct one's. Both of mine run .035"
You run the posibliity of piercing primers or breaking the firing pin if it's too long. .040 is a little on the long side.
Any good gunsmith should be able to shorten it. If you don't have a good gunsmith close by, call Scott at S&S Sporting @ 208-313-1570, he would do a perfect job of shortening it at a reasonable price, You would only need to send the bolt and firing pin.
Re check your measurements to be sure you didn' have the guage cocked to the side a little.
It will give you a false measurement. Take several measurements.
If you shorten it yourself, make sure the tip is perfectly round, if it has a point at all, it will pierce primers.
Scott has a pretty good turn around time and would get it back to you pretty fast.

Best Regards, John K
 

·
Registered
Joined
·
128 Posts
Discussion Starter · #3 ·
Re check your measurements to be sure you didn' have the guage cocked to the side a little.
It will give you a false measurement. Take several measurements.
If you shorten it yourself, make sure the tip is perfectly round, if it has a point at all, it will pierce primers.
Scott has a pretty good turn around time and would get it back to you pretty fast.

Best Regards, John K
When you say 'cocked to the side a little', do you mean like not pressing the gauge fully onto the face of the bolt?
 

·
Banned
Joined
·
2,271 Posts
When you say 'cocked to the side a little', do you mean like not pressing the gauge fully onto the face of the bolt?
Yes, I was talking about tilting the guage before locking it down. They can be a little bit of a bugger to use on the small bolt face of the 5.56 mini.
You did round the end of the Pin didn't you?
The aftermarket one I got as a spare has the end squared off and it needs to be shortened and rounded before use.

Best Regards, John K
 

·
Banned
Joined
·
2,271 Posts
Hi,

My 581 Mini-14 firing pin protrusion measures precisely .0295". OAL is 2.688"

Ed
Ed,
I have measured 3 Mini 14 FP's and they all have protruded around .035" give or take. I'm thinking that your Mini may have a shorter FP or else all mine are long :lol:
As long as they work and don't put little holes in the primers, I guess the length does not have to be too exact. I still would like to know what their spec calls for as FP protrusion is a safety issue and can in some cases affect accuracy.
In any case, I think .040 is a little on the long side. The measurements that I took were on the old and new series (I will have to check my new Tacticle again, I'm sure it was one that I checked, but could be talking out of my rear end. I know I checked it, but will give it a second look).
I did call Ruger and told them that I was a gunsmith and wanted to know what FP protrusion should be as I safety check all my guns before sending them out and wanted to know so that I could advise the owner to send it back if there were a problem.
I was transfered to engineering. They said it was classified information (Don't want the Chinese to get a hold of such important info, who knows what they might do with it).
No surprise there. One poor guy asked how many inch pounds to tighten the scope rings and was told the same thing, they told him "finger tight"
Great customer service.

Best regards, John K
 

·
Registered
Joined
·
638 Posts
Another measurement...this time of my Mini 30, one revolution of the gauge and a couple needle widths extra = .030" protrusion + a few ten thousandths... ( I used a different gauge so, not as precise as the Mini 14's measurement), and 2.690" OAL.

Ed





 

·
Banned
Joined
·
2,271 Posts
Good system and cheaper than going out to buy a guage especially for FP protrusion measurement.
I made mine as a project in Gunsmithing school from a set of plans they had.
It's jsut a copy of the commercial version.

My Best To You Ed,, John K
 

·
Registered
Joined
·
583 Posts
Did you zero the indicator on the flat of the bolt face, or in the firing pin recess?
Unless the tip is perfectly flush with the face when retracted, you're getting a false reading.

The pic is pretty hard to tell exactly, it almost looks like there's some protrusion in the top (zero) position.
 

·
Registered
Joined
·
638 Posts
Did you zero the indicator on the flat of the bolt face, or in the firing pin recess?
Unless the tip is perfectly flush with the face when retracted, you're getting a false reading.

The pic is pretty hard to tell exactly, it almost looks like there's some protrusion in the top (zero) position.
The ball was flush with the face of the bolt as best I could manage. I will admit there could be a slight error but not enough to make a real difference in my opinion. The angle of the camera gives the impression that it is actually in the hole a bit. It wasn't. There actually is a bit of a "crater" around the pin hole so, using a surface plate wasn't an option. In my previous measurement of the Mini-14, I used a pin point depth gauge with .0001" divisions and measured depth from the bolt "lips" to the face near the hole, slid over and measured the depth to the pin tip. That measurement was .0295" with a higher degree of confidence. I do think that all this "hair-splitting" is a little bit moot with an inertia firing pin. Hammer weight, hammer spring tension and pin mass will have much more to do with setting off various primers than a couple thousandths here or there. I just like "tinkering" with stuff....Right John?? :)

Ed
 

·
Banned
Joined
·
2,271 Posts
Yes Ed, we are addicted to tinkering. Keeps me somewhat sane.
I think the range of .028" to .038" is about right. I like it to be .035" to .036", but that would be just for a good hard impact on the primer. I want that primer to be set off positivitly every time, not just getting it to go off.
I jut set mine to .038". I'm going to have to take a hard look at the primers. The military primers are harder, the CCI take less of a hit.
I shoot both types of ammo, so I need to find a happy:Dmedium.
I just want 100% firing unless I get a bad primer in which case I'm not too happy:angry:
I could go to a stronger main spring, but I fear FP breakage if you are hitting the FP harder than necessary.
I measured the protrusion with the FP back against the hammer and if I remember right it was .021". The FP floats some in the bolt, having no spring.
I like the design myself.
I might have to take .002 off, I'll see. I'm not going to have the rifle too close just in case it pierces the primer. I have the end nice and round.

Best Regards, John K
 

·
Registered
Joined
·
583 Posts
Here's a primer chart. CCI's are actually some of the thickest primers, which is why I use them in semi-autos (ARs have a floating firing pin, and thisk cups lessen the risk of slam-fires).



If that will help you out any. ;)
 

·
Banned
Joined
·
2,271 Posts
Good chart, thank you. I understand that CCI has just changed their primer compound and made it more sensitive.
For some reason I thought that CCI had the thinnest cups.
Looks like most of the small rifle primers vary a lot. I used the CCI 200's with my last group of loads. At the time, they were the only primers that I could get.
Large rile primers are all the same.
Good info to have. That's why I like this site, someone always has info on just about anything that you want to know.
I don't know if this is true, but it comes from a reliable source that more ammo was sold last year than was used in WWII.
Looks like Obama was the best guns and ammo salesman ever.
Behind every blade of grass.

Happy Fathers Day, John K
 

·
Registered
Joined
·
583 Posts
*right click* *save* ;)

CCI also makes a #41 "arsenal" primer, but from everything I've seen it's identical to the #450 SR mag.

I use #450s with spherical/ball in my loads, just to get the benefit of the thicker cup.

Here's something else that you may find useful:



 

·
Banned
Joined
·
2,271 Posts
Thanks, but I know that Ruger has more freebore than commercial reamers.
I'll just have to make a chamber casting.
I'm going to talk with the barrel maunfacturer before I have a barrrel made. Maybe a reamer without a throat cutter in 5.56, then cut the throat with a throat cutter leaving about .010" freebore being a semi auto.
I'm also going to talk with a couple of reamer manufacturers.
I should be able to figure out the minimum safe amount of freebore which should help accuracy.

Best Regards, John K
 

·
Registered
Joined
·
583 Posts
That Wylde chambering is very popular in ARs because it has enough freebore to shoot 5.56 NATO and still groups well. Rock River Arms uses it on all their match barrels.
You wouldn't want to chamber a Mini with any of the commercial .223 Rem. reamers if you intended to shoot 5.56 through the rifle, I wouldn't imagine.

My AR is chambered with the 223 Rem Match reamer, and 5.56 is a big no-no with that tight chamber. It sure shoots .223 nice, though. ;)
 

·
Registered
Joined
·
2 Posts
Mini-20 Firing Pin Protrusion for Wolf Ammo

I have a 581 series, (post 2008) mini-30 with Wolf springs that missfired at least 3 - 5 rounds per 10 round clip. The Wolf springs helped a little, but th eproblem remained.

So, looking at all the measurements I could find regarding FP protrusion on AK's and this rifle, I decided the problem was with the protrusion.

Stock, my FP protrusion was .026" which yielded a recess on the rear of the FP of .007"

I modified the FP, very carefully so that I got .041" protrusion and ground the back of the bolt so that I have .013" recess.

So far, I have had only 2 rounds out of 50 that failed to fire on the first hit, so I know I am going in the right direction. My next step is to take the rear recess down a bit more and run some more tests. My understanding is that the recess is necessary as this is a momentum FP design so that the life of the FP is extended over the full hit type where the hammer slams the FP completely into the primer (i.e. Zero, or negative, recess on the rear of the FP in the bolt).

I will post my results after I grind another .005 off the back of the bolt, leaving .008" of recess and run some tests.

It would be great if any of you ruger mini owners could post what your FP protrusion (and rear recess) is and the reliability to fire the Wolf ammo you experience. There must be a sweet spot there, and I think I am getting close.

I have been surprised how little information is available for these FP mods, which are absolutely required to reliably fire the Wolf ammo. I hope this helps some of the mini-14 and mini-30 owners to have hope in handling the wolf ammo.
 
1 - 19 of 19 Posts
Top