Muzzle Velocity

higginsdj · Post by **higginsdj** » Mon Mar 19, 2012 5:49 pm

Obviously I will need a chrono for an exact value, but can anyone tell me what the muzzle velocity of the NRAA Palma Match 308 ammunition produces out of a 30" barrel. I'm just trying to guage what my 'starting' scope settings might be at each distance and whether I have enough adjustment to get to 1000 yds.

Cheers

David

Barry Davies · Post by **Barry Davies** » Mon Mar 19, 2012 6:18 pm

Had occasion to shoot some last weekend. Load was 43.8 of 2206h with HBC projectile. Barrel was 31" Border.
Speed was 2890 f/s which is not fast enough for 1000yds.
The batch of powder and make and type of barrel will give different speeds so what I say may not be same in your barrel. However I rather think that 43.8 gns of 2206h is light on in any barrel.
The other thing which did not impress me much is that the factory seating gave something like 50 thou jump in this rifle -- not conducive to super accuracy.
Better to load your own -particularly for F Class - much cheaper also.
Barry

Quick · Post by **Quick** » Mon Mar 19, 2012 6:23 pm

David,

Ideally you want over 2950fps and closer to 3000fps IMO to maintain velocity to 1000yds in all weather/tempreture conditions. My load is 2950.875fps at 6ft from muzzle with 46.2gr 2208 behind a 155gr HBC seated at 10thou of the lands. I have a 26" barrel though so I push my loads a tad more though. Most guys w/ 30" barrels are running around 44.5gr upto 46gr 2208 and I think around 44gr to 45gr 2206H IIRC.

Depends what powder you want to use. I like 2208 myself but havent tryed 2206H yet.

higginsdj · Post by **higginsdj** » Mon Mar 19, 2012 6:42 pm

Sorry, didn't mean the projectiles or custom loads - I meant the 'factory' ammo purchased through the NRAA. The factory ammo seemed to work fine for 900m as I shot it a couple of weeks ago through a fellow club members custom rifle with 30" barrel and equaled what he shot that day with his own loads.

Cheers

David

Barry Davies · Post by **Barry Davies** » Mon Mar 19, 2012 9:18 pm

David,
My post related to Factory Ammo.
Barry

Fireman_DJ · Post by **Fireman_DJ** » Tue Mar 20, 2012 5:21 am

I asked a very similar question on Sunday (only for a 26" barrel).
I was told around 2800-2900fps.

The reason I asked is I punched in known distances shot against known MOA drop into my ballistic calculator for it to produce a MV.
And it told me I was hitting 3100fps.

Now that sounded high to me, but I used it's figures based on that MV as my starting points for the next three ranges (800,900 and 1000) and I hit the paper every time first time. It needed some adjustment, but I didn't add in the correct temperature, humidity, air pressure etc. so I didn't expect a perfect hit on target.

higginsdj · Post by **higginsdj** » Tue Mar 20, 2012 6:58 am

Barry Davies wrote:David,
My post related to Factory Ammo.
Barry

Thanks Barry, nice to know what the factory load actually is.

Based on your figures, I should have about 4 MOA to spare at 1000 yds (and 5 MOA under 300m) based on my 600m sight-in. At the moment I just want to be sure my setup can aim and shoot at those distances - I'll worry about accuracy when I am a proficient shooter

Cheers

David

Barry Davies · Post by **Barry Davies** » Tue Mar 20, 2012 7:01 am

Factory loaded rounds tend to be conservative at best and far too light at worst. In addition they seat the projectile too far into the case.
All of this is done for a reason -- safety and functionability. The factory obviously care little about accuracy as a primary.
At best these type of loads would suit some TR shooters, but for F Class they are simply unsuitable -- moreso at long range.
26" barrels and factory ammo will definitely not give you the speed and accuracy for long range F Class - don't let anyone kid you it will.
28"barrel is absolute minimum coupled with a load of your favourite powder to give you 2930 minimum -- to accurately get to 1000yards. At sea level you will probably need to bump this up to 2960 minimum.
If you are shooting 900yd maximum then a 26" barrel with a speed of around 2810 is sufficient.
DJ your ballistic calculator is wrong because I can say with 100% certainty that with a 26" barrel and either 2208 or 2206h even at recommended maximum loads, you will not get anywhere near 3100 f/s.
Forget the ballistic calculator -- borrow a good chronograph and do it properly.
The best loads are the ones you make yourself, specific to your rifle with sufficient speed to get to 1000yds under all atmospheric conditions, and at the same time tuned to give you the smallest groups ( and not at 100 yards ) Start at 600 yds.

Barry

higginsdj · Post by **higginsdj** » Tue Mar 20, 2012 7:08 am

Quick wrote:David,

Ideally you want over 2950fps and closer to 3000fps IMO to maintain velocity to 1000yds in all weather/tempreture conditions. My load is 2950.875fps at 6ft from muzzle with 46.2gr 2208 behind a 155gr HBC seated at 10thou of the lands. I have a 26" barrel though so I push my loads a tad more though. Most guys w/ 30" barrels are running around 44.5gr upto 46gr 2208 and I think around 44gr to 45gr 2206H IIRC.

Depends what powder you want to use. I like 2208 myself but havent tryed 2206H yet.

What does 10thou of the lands mean and how do I measure it?

Cheers

David

Barry Davies · Post by **Barry Davies** » Tue Mar 20, 2012 7:27 am

David.
Seating Depth is a term used to define the relativity of a projectile in a loaded round to the rifling of the barrel.
10 thou off the lands means that when chambered and the bolt closed the seating length of the loaded round is such that the projectile has 10 thou to jump before it contacts the rifling.
This is a variable in reloading and can be any amount of jump say up to 50, 60, more or less OR can also be set to give interference -- ie a minus figure.
This variation in seating length can ( and does ) affect accuracy.
An ogive gauge attached to a vernier caliper is used to measure and set this " seating depth/ length" -- this is a gauge that measures the distance from the case base ( bolt head ) to a point on the ogive of the projectile.
Having measured just where this point is in the barrel, you can then vary the seating length of the loaded round to give " jump " or " interference "
There are instruments available to measure the seating depth of your barrel.
Barry

bobeager · Post by **bobeager** » Tue Mar 20, 2012 7:35 am

David, I will be at the SSAA Majura Range (next door to Canberra Rifle Club) on Thursday from about 9.30 on testing my Kit for the upcomming F Class Teams in Mackay.
Will have all my loading gear and chrono. Happy to meet you and give you a rundown on reloading.
I shoot bot F Std and Open.

Rob Eager

Barry Davies · Post by **Barry Davies** » Tue Mar 20, 2012 8:14 am

David,
Bob's offer is too good to refuse.
Barry

higginsdj · Post by **higginsdj** » Tue Mar 20, 2012 8:52 am

Many thanks for the offer - but I still work (in the City) and Thursday is too critical a day for me to try to wangle time off (I'm hosting a multi government department meeting in town for most of the day).

I am a member of SSAA (though never actually used it for anything) and have my own Chrono gear (used for pistol - I'll have to check if it will cope with rifle speeds). I already reload pistol (Dillon 650) so know most of the process but it will be some months before I "bother" to reload (I'll spend that time buying the necessary gear - see my other thread)

Cheers

David

higginsdj · Post by **higginsdj** » Wed Mar 21, 2012 7:18 am

Barry Davies wrote:David.
This is a variable in reloading and can be any amount of jump say up to 50, 60, more or less OR can also be set to give interference -- ie a minus figure.
This variation in seating length can ( and does ) affect accuracy.

I assume this will be different for every barrel - where does one start? Obviously variables (for standard) will inlcude Powder type, charge weight, brand of brass, brand of primer, OAL, projectile seating depth and 'crimp' or tighness of projectile in the neck (is there any crimping of rifle projectiles?) One could spend years varying the combinations and by then the barrel will need replacing so you have to start over again!

If one does not strive for International representation, does one even need to bother? I'm competitive but not that competitive - ie I'm likely to only participate in the ACT Queens as a competition but I woudl still like my scores to be in the ballpark.

Cheers

David

Barry Davies · Post by **Barry Davies** » Wed Mar 21, 2012 7:32 am

HI David,
You are starting to come to terms with all that is required for accuracy, and you do need to bother because the local scene is just as competitive as the international scene.
The variables are many but it is not as bad as it seems.
Of all the variables finding the correct load is probably the biggest problem. Case, and primer choice are personal. You only have two choices of powder for the 308 -- 2206h and 2208 and either will do the job.
Seating depth does not vary dramatically rifle to rifle ( or should I say barrel to barrel ) Measuring it precisely is the key.
You need to spend some time with a competent reloader and learn what is good and what is bad -- for somebody as obviously keen as you are it won't be difficult.
Barry