M&P 10 Muzzle Velocities

[SAWMAN]

Could people please list their ammunition preferences with what velocity they are getting from their guns. I'm curious how much velocity loss occurs from the MP10 barrel.

[BW460]

I load my own. BTW, I don't have issues with this riffle. I can drop 20 rounds inside a two inch circle at a 100 yards all day. And- I'm a ****** shot with these trifocals. Velocity compared to what? A 20" barrel, a 24" barrel? In general, you can count on a loss of somewhere around 50 fps per inch of barrel. Figure that in this 18" barrel, your bullets are going to come out at about 200 to 300 fps slower than what it says on the box of factory ammo.

[vfin]

SouthWest Ammunition's 308 Winchester, 155 OTM Scenar - L

I get 2,800 fps all day long out of my M&P10, but it's somewhat costly ammo; but worth every penny if extreme accuracy dominates your mindset.

And might I add, "IF" your loaded flush with cash, their 308 Match, 155 Lapua Scenar Premium Ammo rocks the competition (for near 42 smackerooz per 20 rd, not including s/h)

vfin

[Ltorote]

The following are my chrono'd velocities out of my M&P 10:

Factory:

Winchester X-S 150 gr 2671fps (vs. 2820 fps on box)
PRVI 145 gr FMJ 2684fps (vs. 2838)
Twin Cities M80 Ball 147gr 2717fps (vs 2790)

Handloads:
165 gr Hornady SST w/43.5gr RL-15, 2600fps
165 gr Sierra GK SPBT w/43.6gr RL-15, 2555fps

[rgsealsjr2]

Take a look at this article:

SWAT Article BARREL LENGTH

According to it, the velocity loss is insignificant for practical purposes.

[rojodiablo]

Originally Posted by Ltorote

The following are my chrono'd velocities out of my M&P 10:

Factory:

Winchester X-S 150 gr 2671fps (vs. 2820 fps on box)
PRVI 145 gr FMJ 2684fps (vs. 2838)
Twin Cities M80 Ball 147gr 2717fps (vs 2790)

Handloads:
165 gr Hornady SST w/43.5gr RL-15, 2600fps
165 gr Sierra GK SPBT w/43.6gr RL-15, 2555fps

These mirror my chrono'd speeds seen from various ammo types (Federal, Winchester, NATO, Wolf/WPA) It's the barrel length itself, not so much rifle specific. A 16" barrel gives up about 2700FPS. in ideal conditions.

[MistWolf]

Originally Posted by rgsealsjr2

Take a look at this article:

SWAT Article BARREL LENGTH

According to it, the velocity loss is insignificant for practical purposes.

They only tested a single load which is tailored for use in shorter barrels and only compared velocities of the 20 inch barrel to an 18 inch barrel

[rgsealsjr2]

Originally Posted by MistWolf

They only tested a single load which is tailored for use in shorter barrels and only compared velocities of the 20 inch barrel to an 18 inch barrel

They also stated that there was no significant velocity difference from 26" down to 20" for the given load.

From the article:
"During the development of the Tango 51, Tac Ops took a standard 26-inch barrel and cut it down to 18 inches in one-inch increments. Between 10 to 20 rounds were fired at each invrement. They found that a 20-inch barrel provides for a complete propellant burn and no velocity loss when using Federal Match 168-grain BTHP, a cartridge that has become something of a law enforcement standard. Going to an 18-inch barrel only resulted in a loss of 32 feet per second (fps).

The main difference I see is that the barrels they were testing were heavier contours unlike the S&W barrel's last 6" or so.

Regarding the load tested, it was used because it is one of the more commonly used factory loads for precision shooters. While it may not hold true for every possible load, one might draw the conclusion that loads using a powder with a similar burn rate will react similarly.

[MistWolf]

Police departments were switching to short barreled sniper rifles back in the 80s and the Federal Match 168-grain BTHP load was developed to meet the need for ammo to give efficient performance in 20 inch tubes. The 308 is capable of giving velocities of 2800 fps or more with loads developed for barrels of 22 inches or more. That's a greater than 32 fps difference from the 2670 fps from a 20 inch barrel reported in the article

[rgsealsjr2]

That's why I indicated this applied to the load referenced. Of course you can exceed 2800 fps with a 155 grain bullet or less. If you want to argue that the difference is greater, then provide some statistics for a given load rather than just making a random statement.

It doesn't make sense to compare the velocities of a lighter weight bullet with a heavier one, as you have done, you're talking apples and oranges.

I do not see a load in any of my references for a 168 grain bullet that will reach 2,800 fps safely and consistently. I'm sure one could work up to that for a given load, but doing so would be at your own risk and, in my opinion, unnecessary.

[MistWolf]

Blame it on CRS. Giving the books a quick look, it's a bit harder to break 2800 fps with a 168 SMKBT than I remembered. Always look up your data rather than rely on memory. However, it's quite easy to break 2700 fps using a 168 gr Sierra and there is one load that does exceed 2800 fps in a 24 inch barrel.

The point isn't that one must load for such velocities, but that the claim there is only a 32 fps difference between a 20 inch barrel and a 26 inch barrel only applies to the 168 gr Federal load in particular, not the 168 gr bullet in general. It also does not apply to lighter weight bullets. Longer barrel lengths in the 308 still have their place.

Take Aim at Rifle Reloading Data | Hodgdon Reloading
http://www.imrpowder.com/data/rifle/...-2005apr03.php
Sierra data shows 2700 fps in a 26 inch barrel, however they round off their velocities
http://www.6mmbr.citymaker.com/f/sierra308Win.pdf

[Ltorote]

Originally Posted by Ltorote

The following are my chrono'd velocities out of my M&P 10:

Factory:

Winchester X-S 150 gr 2671fps (vs. 2820 fps on box)
PRVI 145 gr FMJ 2684fps (vs. 2838)
Twin Cities M80 Ball 147gr 2717fps (vs 2790)

Handloads:
165 gr Hornady SST w/43.5gr RL-15, 2600fps
165 gr Sierra GK SPBT w/43.6gr RL-15, 2555fps

Ok I just got back to the range yesterday and have some updated velocity numbers.

I decided to push the 165 SGK to the 2600 level. Sierra book max is 43.1 gr RL-15 @ 2700 FPS with a 26" bbl test rifle. Since I was pushing Hornady 165 SSTs @ 2600 w/43.5gr RL-15 (Hornady book max 44.3, Speer 47 gr for 165) without issue it seemed safe to ladder higher. Below are the Chrono Results:

COAL 2.75 (mag length) 85 deg, 5250 altitude

1) Sierra GK 165, 43.8gr RL-15, 2628 fps avg, 2638 hi, 2589 lo
2) Hornady SST 165, 43.6gr RL-15, 2657 fps, 2663 hi, 2638 lo

Interesting that I only loaded .1 grain higher for the hornadys, but got 57 fps faster velocity. Since the highest velocity I got last time at 44 gr RL-15 was 2639 fps average. I stopped at 44 because I got a slightly flattened primer.

In conclusion, my hand loads are coming in at or close to book velocities with a 18" barrel vs 22" test barrel for the Hornady, and 26" test barrel for the Sierra. Both of which are conservative loads vs. the Speer book at 47gr (compressed) @2812 fps.

If not for the flattened primers (every other at 44), I would have taken the Hornadys at least to the book max to see if I got closer to 2700 fps.

[Fourth Horseman]

I'm not a reloader. Can you explain flattened primer for me? Is this the internal case pressure flattening the primer against the bolt face?