Longshot & HST chrono report

[Dieselman]

Perhaps.  Of course one of the other variables that we haven't discussed is the difference in rifling techniques.  Both posters here stated they can't achieve velocities like mine with Glocks.  So perhaps Glock's polygonal rifling vs my Kimber's traditional rifling has something to do with the discrepancies seen here.  I'm not sure, it's just a thought.

[fltbed]

You may be on to something Dieselman but I don't think Glock barrels are slower, in my experience, I think you just have a fast barrel. 
I've seen this in aftermarket "match grade" barrels.  The Bar-Sto barrel in my Para P16 spits out bullets almost 50 f.p.s. faster than the factory barrel did.

The 9mm handload I originally developed for my XD 4" is a 147 gr coated lead bullet fueled with 3.6 gr. of WST, chronoed 950 f.p.s.  When I switched to a M&P 9L 5", that started a now five year saga with two trips back to S&W, mostly searching for accuracy.
Springfield XD 4"            950 f.p.s.
S&W 9L 5"                     876 f.p.s.  8"-10" groups
1st replacement barrel    865 f.p.s.  80% key hole  (2 in 10 hit paper @ 50 yards)
2nd replacement barrel   922 f.p.s.  50% key hole
Storm Lake barrel           946 f.p.s.  6"-8" groups
Apex Barrel                    998 f.p.s.  3" groups

Sorry, I wandered off topic a bit, back to the 10mm & Longshot.
Hornady 180 gr XTP
9.0 gr Longshot
new Starline brass
CCI 300 primer
1.255 OAL

RIA  5"      1268 f.p.s.
Glock 40    1303 f.p.s.
Pro Match  1332 f.p.s.

I like this load.  I just wish my Glock 40 and my RIA 5" didn't group it like my shotgun.  The Pro Match doesn't care about them and shoots everything I've tested in it at least acceptably.

Jeff

[Dieselman]

Wow!  That is really horrible  what you had to go through to get the M&P running.     I haven't heard of any other factory barrel key holing problems like this before with the M&P.   

Kind of odd that only your Pro-match will shoot those XTP's good.  Wonder what's going on there?

[fltbed]

The accuracy issues with the full size (4.25" & 5" models) M&P 9mm Has been a well documented and on going since it was introduced.  S&W has quietly made two barrel redesigns with little improvement.  Thankfully, Randy Lee at Apex seemed to have solved the issue.

A few months ago, I posted my struggles with Longshot in my 5" Rock and my Glock 40.  http://10mm-firearms.com/reloading-10mm-ammo/powders-for-accuracy/  The only bullet I can get to group with Longshot in those two guns is the 220 gr. Xtreme.  It was only on a whim I tested the Longshot in the Match Pro because it shot everything else so well.  From the Federal 135 gr expanding FMJ's screaming out at 1600 f.p.s. to the Extreme 180, 200 and 220 gr bullets, XTP's, Gold Dots, cheap lead 155 & 180's loaded down...it just doesn't care. 
I swear, if I could figure out how to load gravel fueled with dog sh*t, it would probably shoot that well to.

Jeff

[Dieselman]

Well I guess that goes to show what I know, or rather don't know,  about M&P's.  Guess I won't be giving up Glock's anytime soon in favor of M&P's.

[Pctechdude]

One thing with the HST bullets, they have a fairly large cannelure, that is recessed into the bullet itself, so while a fairly long bullet compared to the Xtp, or nosler, the cannelure reduces the shank of the bullet, putting it's length closer to the nosler and Xtp bullets.

Sent from my XT1585 using Tapatalk

[Dieselman]

One thing with the HST bullets, they have a fairly large cannelure, that is recessed into the bullet itself, so while a fairly long bullet compared to the Xtp, or nosler, the cannelure reduces the shank of the bullet, putting it's length closer to the nosler and Xtp bullets.

Sent from my XT1585 using Tapatalk

I see your point when it comes to bearing surfaces within the barrel. But the length still reduces internal case capacity regardless

[ss30378]

Kimber barrels have always seemed to put up nice numbers.  I think its a combination between a smooth bore and a tight chamber that give it the good velocities.  In stock glock barrels the liberal chambers of the 10mm barrels seems to be the main area of velocity loss.  I've gained 80-100fps between a stock g20 and a storm lake 4.6" barrel then it was upped another 80-100fps by going up to the 6" version with heavy loads.  So 160-200fps over the stock barrel with the same loads with 1.4" extra of barrel and a much tighter chamber.   

[The_Shadow]

Yes this is why we say no two guns are alike when it  comes to ammo usage.  Some of the reason has to do with barrel and bore it self. 

Some guns had a bore that is cut at 0.3990" (Kimber possibly fits this) 1:16" twist rate left hand cut.
My Smith & Wesson are 0.4000" with a 1:16" twist rate left hand cut.
Glock factory barrels are 0.4015" - 0.4020" with a 1:9.84" twist rate right hand hexagonal.