Posted Feb. 26 2011 - 11:17 PM
Hot Rodding the Winchester 10mm Silvertip®
Or Building Cool Ammo in Anticipation of the Fortis Release by Vltor
The Winchester Silvertip® cartridge lineup holds an enviable position as one of the most respected series of bullet designs for self defense. In particular, the 10mm version is a slick feeding hollowpoint with a reputation of nearly 90% one shot stops. The 10mm Silvertip® is rated at 1290 fps from the factory with a 175gr bullet. Recently, there have been a few complaints about this round. Shooters are finding that the factory specs are not reflective of what they chronograph when they fire the round, especially out of a Glock 29. Also, Stopping Power, an area that Silvertips are rightfully famous for excelling in, is seen to “fall off”. Expansion in short barrels is not what should be expected of a Silvertip®. What gives?
History
Except for specialty manufactures like Cor-bon or Doubletap, most 10mm ammo manufacturers have downloaded the 10mm to a 40 S&W level, disparagingly referred to as “10mm lite”. This is in reverse of traditional revolver loads, where ammunition manufacturers were constantly seeking a higher velocity and power. The high power and pressure 10mm is hard on semi-auto guns, beating guns and accessories that are not designed for maximum endurance.
The 10mm performance was at its peak with the original Norma factory loads, driving a 200 grain JTC slug at a clocked 1200+ fps and a 170gr hollowpoint at 1300fps. When Winchester decided to come out with a 10mm Silvertip®, the designers choose for the 10mm a similar hollowpoint design as the 44/41 Magnum Silvertips® rather than the 45 ACP or the 44 Special Silvertip® designs, probably as the 10mm at full power has far more similarity in pressure and velocity to the revolver magnums. (See Photo’s #1 and #2)
Though it is difficult to tell without a caliper between the 10mm and the 44 Magnum Silvertips®, the 44 Special Silvertip® and the 45 ACP Silvertip® are radically different hollowpoint designs, reflecting their parent cartridges low pressure and velocity.
The .44 Magnum 210gr Silvertip® and the 170gr .41 Magnum Silvertip® are chronographed out of a 4” vented barrel to give similar results as a defense revolver with its barrel/cylinder gap. In a legal hunting handgun length for most states (6”) these bullets exit the barrel at or above their rated speed of 1250fps.
However, the 10mm Silvertip® was developed using a 5.5 inch non-vented barrel, a barrel length longer than has ever existed in Combat production guns. Combat barrel length for most Auto pistol barrels typically being 5 inches, with many a good deal less, such as 4.6” (Glock 20) or 3.78” (Glock 29). Further, numerous tests have shown that this is an optimistic muzzle velocity even in a full length gun, as the 10mm Silvertip® actual muzzle velocity exits in the lower 1200’s or even 1190’s out of a 5 inch gun in independent tests. The situation gets even worse with a short barrel like the Glock 29, with muzzle velocities posting an anemic (for the 10mm) 1129 fps. This is a total reduction in velocity of 161 fps from the printed specs! The irony is that this is also slower than the DoubleTap 40 S&W 180gr loads in the same barrel length. While the 40 S&W power is being increased by Ammo Manufactures to 10mm specs to get more stopping power and turn it into the 10mm, the 10mm has been downloaded to 40 S&W levels by some factories to make the gun more comfortable to shoot. We truly have come full circle.
Concentrating now on the 175gr 10mm silvertip bullet; in actual shootings it has been shown that recovered expansion diameters are smaller, penetration is increasing and stopping power is falling off in short barreled guns (See chart #1). If only one of these factors were documented, I would say that there is a likelihood that this is a statistical fluke given the size of the test sample, but the trend is coherent for all three factors simultaneously, with the only adjusting factor being barrel length. The velocity loss in any barrel length is consistent over several studies and the Author’s own test equipment.
In sum, what appears to be happening here is that the design for the Silvertip® bullet in 10mm was chosen from the magnum designs (.41 and .44 Magnum) and this design works beautifully as long as there is sufficient velocity for the bullet to open up. Combine the speed reduction with a shorter barrel and it appears that this bullet is on the ragged edge of not expanding.
10 mm Stopping Power Heavy bullet weights
Brand Bullet Shootings One Shot Stops Percent Diameter Penetration Notes
Winchester 175 gr ST 64 56 88% 0.76" 10.8"
Winchester 175 gr ST 28 24 86% 0.69" 12.4" 4" barrel or less
Federal 180 gr HS 57 49 86% 0.66" 12.9"
Federal 180 gr HS 19 16 84% 0.61" 13.2" 4" barrel or less
Federal 180 gr JHP 45 38 84% 0.68" 13.4"
Federal 180 gr JHP 11 9 82% 0.63" 13.9" 4" barrel or less
Winchester 180 gr JHP 59 48 82% 0.63" 14.6"
Remington 180 gr JHP 48 29 81% 0.67" 13.7"
The Handloading Cure!
Happily the Winchester 10mm Silvertip® is available for reloaders in two bullet weights, one is in 155g intended for the 40 S&W and the 175 grain for 10mm. Though the 155 grain bullet is tempting, for this experiment I am sticking to the 175 grain bullet intended for the 10mm as the sectional density is better.
Dusting off my reloading manuals, I find quite a few loads for 180grain and 170 grain bullets that will work for the Silvertip®. I have to reference the closest common bullet weights due to the fact that even Winchester does not have a recommended reloading chart for their own 175 grain bullet in 10mm!
Looking at both Bren-Ten.com and Glock talk for powder advice plus a variety of reloading manuals, I see that the three powders that stand out for pushing heavy bullets is Accurate Arms powders #7 and #9 and IMR 800-X. Also these powders are either close to or at a compressed case fill, thus helping protect against bullet setback.
As I wanted to get the maximum burn and as little flash as possible out of this loading plus protection from recoil bullet pull, I rolled a cannelure onto the 10mm Silvertip with a Corbin cannelure tool. This would allow me to use the StarCrimp® crimp I have invented. See photo #3. First the AA #7 Published Results from Glock talk.
G20 with 5" KKM barrel, Doubletap Nickel cases, CCI standard primers, 180 gr Win FMJ, COL @ 1.25"
1) 12.0gr AA#7, Avg: 1288 Std Dev: 10 Hi: 1305 Lo: 1277
2) 12.3gr AA#7, Avg: 1324, Std Dev: 11, Hi: 1334, Lo: 1308 (Perfect Load)
3) 12.6gr AA#7, Avg: 1365, Std Dev: 16, Hi: 1395, Lo: 1346
This looks like a dang perfect loads, with 12.6gr being a bit too much. The 12.3 AA #7 is right on the edge of losing the low standard deviation variance that signals an inherently accurate load and is a MAX pressure load. The same load with 175 grain bullet rather than the 180 might give us 1300 average out of 12gr even. Perfect!
The Accurate Arms Reloading Manual Lists the following loads:
AA #7 powder using the Nosler 170gr Hollowpoint 12gr for 1305fps out of a 5” barrel. This load is listed as MAX, so start 2gr lower.
For AA #9 the 170 grain Nosler is pushed with 15 grains of powder MAX for 1341 fps and 180 grain Speer the AA#9 load is 14.5 grains MAX for 1290. I would start using the starting loads for the 180gr bullet and work up to 1300fps or 14.5gr Max for the 175 Silvertip. This represents a great powder for those who want to prevent bullet setback, as the powder is compressed, no setback is possible. AA#9 may represent the best powder for reloading on a progressive press as it meters so well.
Moving to 800-X, Mike McNutt of DoubleTap has this load published on Glock 10mm Forums:
Nosler Jacketed HP 170 800-X 10.6g (Comp) 1.250" 1350fps Avg 688fpe avg.
He advises that you start 2grs lower than his loads and work up watching out for pressure signs and a fully supported barrel. Different barrels and different brass will show different reactions and pressure levels. Please note this is much faster than we are looking for! For a short barrel he publishes the 10.6gr load for a Hornady 180XTP bullet. 10.8grs of 800X gives 1263fps out of an AFTERMARKET 3.78 Glock 29 barrel. The Silvertip might give 1300 flat! Please note that these are all OVER max loads recommended for experts by experts. Use the reloading manual data if you are unsure what you are doing or see signs of high pressure!
IMR data recommends a lower charge of 9.7grs MAX for 800-X for 1320fps and low pressure of 34,200PSI for a 180gr bullet from a 5” barrel, so this charge seems to combine speed, fill, and low relative pressure like AA #9. Unhappily, each load must be hand weighed as 800x meters very poorly and you risk very high pressures if you try to use a powder measure, which removes it from ease of mass production. Astonishingly, IMR does not list a starting load, but I feel that a range of 9.5gr to 10.0gr of 800-X will give me 1300fps for the Silvertip. I might even back down a little if less than 10.0grs gives me 1300fps.
Overall, AA #9 appears to be the best powder for 10mm. With its 100% fill to prevent bullet setback, its ease and consistent metering, the impossibility of overcharging the cartridge, the cleanliness of the powder, low terminal pressure and the high velocity achieved, this powder may represent the perfect blend of characteristics. Using the Starcrimp® to prevent bullet pull due to recoil a totally rugged cartridge is produced with high velocity. Remember, the goal is not to build the most screamingly hot, brass destroying, primer busting, gun breaking load possible, the goal is to bring back the 10mm Silvertip into its operating envelop within a 5 inch barrel.
so better late than never.
to the forum! You have summed this up pretty well, and as a handloader of over 35 years, I know all to well the stated claims sometimes don't match the real world facts...Like you I have studied every bit of data to learn what others have done. The barrel length will be a determining factor for powder performance overall. FBI's reduction of the loadings was detrimental to the original 10mm specifications to say the least!
