Underwood 220gr Hardcast (New Load)

[Intercooler]

Here is my experience with the UW 220gr HC 10mm load.

Pistol: gen3 Glock 20, factory recoil spring, KKM 5.3" barrel.  I chose this barrel length to line up with the end of the SureFire X300U light mounted on the gun, which gives more holstering options.

Test 1: UW 220gr Hard Cast, bought in October 2013, shot in mid December 2013; temp = 55 degF

1264
1244
1263
1256
1256

avg = 1257, sd = 7.14; can't recall if this brass showed overpressure signs

Test 2: UW 220gr Hard Cast, bought in October 2013, shot in mid January 2014; temp = 53 degF

1296
1271
1273
1272
1274

avg = 1277, sd = 9.45

Some of these rounds had mild smilies (even with the KKM barrel) and one blew out a primer.  I called Kevin about it in February 2014.  He replaced it all with ammo from newer batches, and sent me a shipping label to return the unfired rounds from what I had bought in October 2013.

Test 3: UW 220gr Hard Cast, lot #B0901-003 received in February 2014, shot on March 9, 2014; temp = 68 degF

1177
1215
1179
1189
1195

avg = 1191, sd = 13.68; brass looks good with no apparent signs of overpressure

So it looks like the UW 220gr HC load has certainly been toned down, especially since the higher velocities were recorded in weather that was 15 degF colder.  I put this gun together for use out West against large animals when I have no other option.  I'm now unsure if the load is powerful enough for that, though it's no good for the gun to blow up, of course.

In bold is your issue with the numbers.

[Intercooler]

According to the 4949shooter full-power 10mm calculator... that's still full-power   

[4949shooter]

Haha! 

It's actually from Shadow's chart.

[DarnSkippy]

In bold is your issue with the numbers.

Can you clarify?  Are you referring to the velocities themselves, the SD, both?

When putting together this G20, I read this forum and others regarding G20 recoil springs.  There just didn't seem to be a consensus.  Some insisted you need heavy aftermarket, some said stick with factory, others said it didn't matter.  Would love to get clarification if it yields improvement.

Forgot to mention, I've never had a malfunction of any type with UW ammo and the factory recoil spring, either with the OEM or KKM barrels.

[4949shooter]

From Buffalo Bore's (Tim Sundles) website:

If you are firing this 10mm ammo from an autoloader and experience high extreme spreads in velocity, it is not the ammo. Here is why and how to remedy the situation.

Full power 10mm ammo has always generated enough recoil and pressure to require a pretty stiff recoil spring in your handgun - this of course depends on several variables such as your slide weight, etc. When the cartridge fires, it generates enough pressure/recoil to prematurely open your breech face in some guns. When this happens, the opening breech face has an effect on the burn rate of the powder. This can result in some fairly high extreme spreads in velocity. If you are experiencing extreme velocity spreads of more than 50 fps, simply install a stiffer recoil spring. For example, I have an original Colt Delta Elite. This gun with the factory spring runs extreme spreads of about 35fps with both of these 10mm loads. I am happy with 35 fps, so I leave the Delta Elite as is. I also have a custom built Para Ordinance with a Nowlin barrel. It runs extreme spreads of about 70 fps with its original recoil spring. When I install a spring that is 4 lbs stiffer, the extreme spread drops to about 35 fps. The new Glock model 20 comes with a recoil spring that allows the breech face to open too soon and my new Glock model 20 will get extreme spreads of about 100fps with the factory spring installed. When I go to a stiffer recoil spring, the extreme spreads drop to about 50 fps in my new Glock model 20. Of course none of this will be an issue in a revolver. None of this will be an issue in real life either, as these high extreme spreads don't hurt accuracy or function. However, I mention this because if you are like me and want things to be as correct as possible, I have outlined the problem and the solution. The industry fixed all these problems initially, by watering down the 10mm ammo over the last several years. The watered down 10mm ammo does not generate the pressure/recoil to open the breech face early. If you want the full powered 10mm ammo we make, you simply need to tweak your pistol. Or just realize that you are getting some fairly high extreme spreads and ignore it or live with it. It's not hurting any thing in reality.

https://www.buffalobore.com/index.php?l=product_detail&p=114

Intercooler is referring to the standard deviation. I do find it interesting though, you had the greatest deviation with the newer load.

[Intercooler]

Old original stock spring? I change my 20 and 22lb springs out pretty often when shooting the hard stuff.

[TheOtherMike]

In bold is your issue with the numbers.

Can you clarify?  Are you referring to the velocities themselves, the SD, both?

When putting together this G20, I read this forum and others regarding G20 recoil springs.  There just didn't seem to be a consensus.  Some insisted you need heavy aftermarket, some said stick with factory, others said it didn't matter.  Would love to get clarification if it yields improvement.

Forgot to mention, I've never had a malfunction of any type with UW ammo and the factory recoil spring, either with the OEM or KKM barrels.

I am also not sure what Intercooler means, and frankly disagree with such a statement.

Rationale: We've all seen slow motion video of a pistol firing. In every example, the projectile has left the barrel quite some time prior to the slide starting to react and moving to the rear. Conclusion: RSA is not a factor in projectile velocity.

Additionally, assuming a very weak RSA would allow the barrel to begin rearward travel too soon, thus presumably decreasing barrel pressure and hence projectile velocity, then the weaker, stock RSA would yield lower velocities rather than higher velocities as DarnSkippy measured. If RSA strength is a factor in projectile velocity, I would expect results that contradict what Intercooler is implying.

So to me, such a statement is illogical. However, I may not fully understand all of the factors involved and, if so, I would really like to learn what all this means.

ETA: Ah, good. I just read what was posted above while I was typing. However, I still don't see evidence that the RSA strength is a factor. With an avg = 1191, an sd=14 is neglible and partially (mostly?) due to other factors like measurement error, powder loading, etc.

[Intercooler]

  Those Glock 5.3" barrel numbers are about what I got with a 4.75" barrel. What's different?


   I gave the comparison with my XD how quickly the slide moves back versus the hammer fired setup. The only thing I don't have is a Glock to run these tests to confirm things. If Tim Sundles already put it in print what kind of drop can be seen in his real world tests with a Glock it would be a waste.

DarnSkippy,

        Can you pull a bullet and weigh the charge comparing it with what we found?


  I doubt it is watered lower than the stuff I shot. I'm open to what others think is going on here.

[4949shooter]

Tim Sundles' explanation may or may not seem plausible. But what is more important is his observation of velocity effect when the different weight springs are used.

[Intercooler]

Mr.Redbull has done the test on video. Watch it and discuss:

[DarnSkippy]

That vid by RedBull was one of the things that led me to say "why bother with a heavier spring, as long as reliability is good?".  IIRC on the 155gr UW, the stock spring had an extreme spread of 60 fps while the 22# Brass Stacker had a spread of 44 fps.  Just doesn't seem like enough difference to me to drop $25 on another part.  Again, though, this is only if the gun has good reliability.  I just checked my records and my G20 has had 0 malfunctions in firing 330 rounds.  This has been a mix of loads by UW, DT, and Precision One.  I can certainly see experimenting with different RSAs if a pistol has been malfunctioning.

I pulled one of those new 220g UW rounds (lot #B0901-003, same as Test #3):

powder: 7.9gr; I think a few flakes were left in the puller
bullet: 217.1gr

All: reading through my few posts here I think I am coming across as argumentative.  Not intended, I assure you.  I have been lurking here a long time learning up on the 10mm and I appreciate all the great info you guys put out there.  I have shot over 100,000 rounds through Glocks since 1998 but just last year got into 10mm.

[The_Shadow]

When I was measuring the difference of the Glock 20SF factory spring and comparing it to the Wolff non-captive 22 lb I did notice a slight difference in the point to which the slide would start to move.  The data for that can be found here in this post...http://10mm-firearms.com/gunsmithing/wolff-gun-springs/

It is my understanding that the small amount of extra spring pressure, does keep the slide from moving by a few milliseconds to aid in maintaining lock up for that fraction of time.

The extra spring weight helps to also control slide speed and ejection distances with the higher impulse ammo like Buffalo Bore, Underwood, CorBon, Double Tap and especially my own handloads that match many of those being sold.

I would suggest that anyone who is running the higher impulse ammo, should experiment with various spring rates to see just how things work for their guns.  Now the kicker for you guys running the Glock gen 4's you don't have many options as of yet  when it comes to aftermarket RSA and spring rates...SORRY!  It will change I'm sure as the aftermarket companies study the dynamics involved and how to better control them.

[Intercooler]

  Your test was similar in every way to mine, except I did a hammer fired for comparison.  The striker fired style needs all the help it can get it appears.


   I checked the sheet and 8.0gr's was found in the pull-down. It looks like you are right there on the powder.

[Intercooler]

TheOtherMike,


                      Did you view the video? What's your thoughts?

[4949shooter]

Glockmeister now has the Gen 4 RSA with varying weights:

http://www.glockmeister.com/Glockmeister-Stainless-Steel-Recoil-Spring-Assembly-for-Gen-4-G20-G21-and-G41/productinfo/G4SS20CS/