P-10F Recoil Spring and Tungsten Guide Rod Experiment

[earlan357]

TLDR:  I'm clearly insane

So it's common knowledge that the P-10C&F guide rods are nearly identical to Gen3 Glock guide rods except in length.  Since I wanted to optimize my recoil springs to my competition loads, I bought a CGW stainless guide rod and some flat-wire ISMI G17 springs.  The CGW rod weighs 0.7oz, the same as the OEM rod, but is uncaptured for easy spring changes.  Since I'd had good luck with 13# springs in my G34, I figured they'd be fine in the P-10F.  However, the P-10F's heavier slide was allowing the gun to return high.  I popped in a 15# spring to he same effect.  Even with a 17# spring the gun was flippy and returning high.  With the factory spring back in, the muzzle was dipping low.  It didn't make sense that the lighter springs were acting like they were heavier than OEM.

Annoyed, I decided to throw more money at the problem.  A while back I switched my Glocks over to round wire springs and larger diameter guide rods.  Round wire springs tend to cycle smoother and the larger guide rods adds more weight under the muzzle.  So I grabbed a Gen3 Extended G34 Tungsten Heavy guide rod from Jentra.  The Heavy version is thicker than standard at .275" and I wanted the extended version so I could cut the length down flush with the slide.  After facing the tip on a lathe, it ended up weighing 2.0oz, 1.3oz more than OEM.  I finished it off with a set of Sprinco G17 round-wire springs.  Surely all that extra weight would help.

Confident, I hit the range, popped in a 15# spring and...the dot was still returning just above the A-zone at 7 yards.  If anything, the muzzle flip was worse.  The 17# spring didn't help either.
 Back home, I tore into the gun again looking for the problem.  At that point, I realized I was an idiot.  I had completely forgotten to check the slide's travel with the new springs.  As it turns out, the coils were binding and preventing the last 2mm of slide travel.  The slide slamming into the frame early wasn't giving the recoil spring enough time to slow the slide's rearward velocity.  I had to cut about 2.5 coils off the springs to restore the lost travel.  But shortening the length reduces the preload while simultaneously increasing the spring's rate.  At that point I decided it would be easier to just use G19 length springs.  Browsing the web for springs, I saw that GlockStore had released a 2.8oz "Pure Tungsten" guide rod for Gen4/5 Glock17s.

Now at this point, a reasonable person would just be happy with the 2oz guide rod and call it a day.  But I'm not that person.  Knowing that the Glock guys could enjoy an extra 0.8oz would keep me up at night.  At least that's how I justified spending $120 on a part that I wasn't confident would even fit my gun.

I didn't know the diameter of the rod, nor did the customer service rep, just that they were larger and used special springs, but I figured I was in for a penny in for a pound at this point.  I ordered the Gen5 G17 rod and also bought 13#, 15#, and 17# G19 recoil springs from Sprinco.  The rod arrived yesterday.  Right off the bat it's not as nice as the CGW or Jentra rod.  The front wasn't cut very evenly, and the rod surface feels wavy, like it was cut with worn tooling or flexing a lot in the lathe.  Not that it matters because it also doesn't fit.  The guide rod hole in the P-10F's slide is .300".  The Glockstore Pure Tungsten Gen4/5 Rod is .310" and bulges slightly to .315" about 1/2" back from the muzzle end, before tapering back to .313" at the rear.  The diameter at the back is .503" compared to .415" for the Gen3 and P-10F, and won't seat in the frame.  Fortunately I have access to a machine shop.  Today I turned the back portion down to .415", and also took 0.040" off the front face.  This would give me an extra coil's width of travel.  I calculated that it wouldn't bind with the G19 springs, but figured I could use the insurance.  I also took .028" off the tip to clean it up and correct the length.  I left the bulge since it begins inside the slide's guide rod tunnel and won't effect the spring or slide movement.  After removing the material, the rod weighs 2.7oz.

I was going to just turn down the guide rod to .285'', but I calculated it would bring the weight down to 2.2oz.  Not really worth the money and time for a 0.2oz improvement over what I already had.  Then I thought, why not just make the slide hole larger?  I'll need to get it re-nitrided, but that gives me an excuse to get some additional front serrations and lightening cuts.  Unfortunately I didn't have the slide with me, so tomorrow, I'm going to ream the hole out to 8.5mm or .3346".  Hopefully I can figure out a way to fixture the slide in the mill and not burn up any tooling on the hard nitride finish.  Wish me luck.

Here's the CGW, Jentra, and GlockStore (after cutting) guide rods for reference.

[Earl Keese]

 Good grief, $120 for a guide rod. I think I'll wait for MCarbo to come out with their $35 version. 
 On a more serious note, thanks for sharing your experiments with the rest of us. Interesting stuff.

[earlan357]

Good grief, $120 for a guide rod. I think I'll wait for MCarbo to come out with their $35 version. 
 On a more serious note, thanks for sharing your experiments with the rest of us. Interesting stuff.

Yeah it’s pretty steep.  I was gonna make my own, but 1/2” 99.5% tungsten rod is about $15/in.  It machines like cast iron so there are considerable tooling costs not to mention shop time.  Around here it’s $50-75/hr and the cutting bits alone are $20-30.  At that rate, I could ream the hole out to .350", then make a custom .336" guide rod and use 1911 springs.  That sucker would come in at about 3oz.

[Wobbly]

CGW will have it for $22 next week.  Thanks for the loan of your bank account.

 

[earlan357]

Well that was an ordeal.  At first I tried to open up the hole with a drill bit but the nitride finish is HARD and I only had HSS bits that couldn't break through it without getting smoked.  I did have a 5/16 carbide ball end mill though.  It left terrible tool marks inside the hole, but I was able to clean it up with a 21/64 reamer before opening it up with an 8.5mm reamer.  This puts the I.D. at .3446", 0.0296" over the thickest part of the .315" guide rod.  It also leaves me enough room should I ever want to use to try a 1911 guide rod/spring.

I chamfered the hole slightly but the nitride at the edges just won't cut, and instead rolls a lip around the hole.  I'll even it out when I send it off for slide cuts and nitriding over the winter.

I also cut back the front edge of the guide rod base to give me another .060" to prevent the spring from binding.  The slide cycles super smooth since the rod diameter closely matches the spring I.D.  My G19 springs are still in the clutches of the USPS  Right now I have a cut down Sprinco 15# G17 spring installed so I'm hoping this works out well when I test fire tomorrow.



Empty weight 32.3oz.

[Earl Keese]

Empty weight 32.3oz.

If nothing else, it looks cool!

[earlan357]

Shot 100 rounds this chilly morning.  No issues with my mags after setting them up to hold 22 instead of 23.  Had two Sprinco Gen3 G17 springs cut down to 22 coils.  The 13# was returning slightly high but on the target, and the 15# slightly low.  Target was half a sheet of paper(5.5 x 8.5" reduced A-zone) at 7 yards.  I think the 13# G19 spring (22.5 coils) I have on order will be perfect but I'll have to run the cut down 13# at my match tomorrow.

[earlan357]

Well the gun ran great until my 4th stage when I started getting erratic ejection and stovepipes.  I thought I was limp-wristing the gun which was odd since my splits were right around 0.20.  I discovered the problem when I removed the slide to clean it.  The ejector leg snapped off.



Fortunately I bought a bunch of spare parts from CZ including the rear insert.  I think the top round in the mag was hitting the ejector leg, and since I had previously setup the mag to take 23 rounds, there wasn't enough deadspace for the spring to compress and absorb the shock during reloads.  Some metal actually bulges down below the rest of the leg, so I'll fill it away.



I also ordered a foot of tungsten alloy rod.  The GlockStore rod is okay, but it just wasn't machined as well as I expect for a $120 part.  I'm gonna turn it in the lathe to .340", and open up my slide's spring tunnel to run with 1911 commander springs.  Should hit 3.1oz.  The guys in my shop tell me that tungsten alloys above 93% break when dropped on concrete and recommended a 90% tungsten, 6% nickel, 4% copper alloy.

I'm gonna turn the old rod down to .280", so someone here who owns a P10F can get it for a steep discount.

[earlan357]

I made my tungsten guide-rod today.  I turned it to .340", any larger and I wouldn't be able to get the 1911 spring on.  The coils just barely touch the rod, but they expand when compressed so the slide cycles smooth once installed on the gun.  The base is slightly over-sized at .437" over the OEM .420".  It still drops right in the frame, but I wanted it maximize the weight anywhere I could.  I reamed out the slide guide-rod hole to .359" with a 23/64" reamer and added a 60 degree chamfer.  The rod weighs 3.2oz, 4.5x heavier than the factory guide rod.  The extra weight at the muzzle counter balances the optic at the rear.  I prefer my guns to be heavy at the muzzle.  Currently I'm using a 14# 1911 Commander recoil spring because it's what I had on hand.  It seems a tad too heavy, but I have a 12# and 13# spring on order.  Total weight is 32.8oz with an empty mag.









.340" chonky guide rod vs .235" CGW SS rod.

[Joe L]

I agree with your first statement in the original post.   

And to think some of us make do with with a set of files and a Dremel, backed up with a credit card!!

(this is fun)

Joe

[cfrock]

Great write up.

[inthevalley]

Thank you for taking the time to write this!

I dont even own a P10 but I learned a lot about recoil spring tuning.

Interested to see how this progresses.

[Duke Nukem]

Very interesting to see what you are doing here, thanks for sharing.   

[armoredman]

Sir, that is definitely involved! Thanks for letting us follow along!

[earlan357]

Not totally CZ related, but since I had 6" of tungsten rod leftover, I made a .400" diameter rod for my Gen5 G34.    I had to narrow the front portion to .390" to get it in the slide, otherwise the base would hang on the barrel lugs.  I've got the large spring from the OEM RSA in as a place holder and I still need to polish out the tool marks.  The XD-M spring I plan to use will be here tomorrow.  Weight is 5.4oz.  An X300 with batteries is 4.3oz.  The factory frame alone weighs 5.2oz.