G29 chrono numbers

[45BBH]

Not sure if I should put this here or in the handloaded ammo section, but I'll put it here for now.

Ran some handloads and a few factory loads through the Gen4 29 today, with some kind of interesting results.  I'll post up the data first:

***All loads used new Starline brass and CCI LP primers, Beta Mater Chrony leveled on tripod***

Temp around 60 degrees, very low humidity.

Handloads:

(Stock barrel)
180gr Gold Dot, 8.5gr Power Pistol @ 1.250": 1,088 AVG - 16.74 ES - 11.31 SD
180gr Gold Dot, 9.2gr Longshot @ 1.250": 1,178 AVG - 48.41 ES - 33.94 SD
200gr Nosler JHP, 8.5gr Longshot @ 1.250": 1,104 AVG - .60 ES - 1.0 SD

(KKM barrel)
180gr Gold Dot, 8.5gr Power Pistol @ 1.250": 1,194 AVG - 24.03 ES - 16.97 SD
180gr Gold Dot, 9.0gr Power Pistol @ 1.250": 1,231 AVG - 12.77 ES - 9.21 SD
180gr Gold Dot, 9.5gr Longshot @ 1.250": 1,248 AVG - 89.53 ES - 63.63 SD
180gr Gold Dot, 10.0gr Longshot @ 1.250": 1,303 AVG - 27.22 ES - 19.10 SD
180gr XTP, 11.2gr VV 3N38 @ 1.250": 1,294 AVG - 9.27 ES - 6.40 SD
200gr Nosler JHP, 8.5gr Longshot @ 1.250": 1,173 AVG - 4.32 ES - 3.60 SD

Factory:

Factory Hornady 180gr XTP: 1,081 AVG - 47.20 ES - 23.51 SD
(KKM) Factory Hornady 180gr XTP:  1,151 AVG - 15.44 ES - 11.31 SD
Factory Hornady 155gr XTP: 1,248 AVG - 1.29 ES - 1.0 SD
(KKM) Factory Hornady 155gr XTP: 1,383 AVG - 11.70 ES - 8.48 SD

I had to run a few over once I noticed the velocity differences, notice how with the KKM comped barrel, the velocities are quite a bit faster...in two instances over 100 fps over the stock barrel.  That's not coming from the extra .4" of barrel either, can't be.   The stock barrel is 3.77" and the KKM threaded comes in right around 4.17". 

Any idea as to why the KKM was posting considerably higher numbers despite only having .4" more barrel (and in some cases only a little bit more powder)?

I've got a lot of 10mm data from over the years and will post up more as I run them through the 29, but this got me scratching my head.

[cwlongshot]

Interesting, Thanks for posting.

I just bought a 29sf Saturday.

I have a KKM for my G20 and love it. Did not plan on another for the G29...but who knows.

CW

[Intercooler]

  Would either one have Polygonal rifling?

[suncoastarmory]

  Would either one have Polygonal rifling?

Wouldn't the Glock barrel have it?

[The_Shadow]

Two things about the Glock factory barrels have a higher twist rate of 1:250mm/9.84" polygonal rifling but the bore tends to be slightly larger (0.4005" - 0.4010") than that the broach cut rifled barrels. 
This is also why the alloy bullets need to be bigger and harder, to allow them to conform to the polygonal rifling instead of skipping/sliding past the rounded rifling.
The amount of blowby is is why you may see differences and yes the extra bit of barrel length of you KKM does make a difference!

KKM's and other barrels usually run a 1:16" twist rate and the bores can run 0.3990" - 0.4000" depending on the maker.

These tighter tolerances barrels tend to seal better, translating into more energy behind the projectile...

[45BBH]

Thanks for the replies, it all shot great but the velocity difference was a bit unusual I thought!  Loving the 29, thinking about a 20 now...geeesh.

[cwlongshot]

Thanks for the replies, it all shot great but the velocity difference was a bit unusual I thought!  Loving the 29, thinking about a 20 now...geeesh.

Haha, I went the OTHER WAY!  Bought the G20 (Early 1st gen gun) and then the 29sf. Had Deltas (Reg blued and a sts gold cup) since they where offered. LOVE the 10!

[45BBH]

I understand! Typically I always went with the 20, an outstanding 10mm no doubt, but the 29 is a much better option for carry use.  Congrats on your 29SF   

[cwlongshot]

I understand! Typically I always went with the 20, an outstanding 10mm no doubt, but the 29 is a much better option for carry use.  Congrats on your 29SF   

I am beginning to see that!!

Put almost 150 threw mine tonight, form hot stuff to medium factory stuff. I had a couple boxes of Solver tips and Hydra shocks and five or six different hand loads. ALL shot well! HOT 135g Nosler HPs has a 2" fire ball at he muzzle!! 200G XTP's shot small groups and 155XTP did just as well! When it gets warm, I'll chrony it. I did experience a start of the dreaded glock smile on some loadings.