6.5x55 AI results

[acloco]

Just beginning load work on a 6.5x55 AI build in fireformed Winchester brass.

H4831
SHOT VELOCITY
1 2757.9 48.5
2 2830.6 49
3 2864.3 49.5
4 2883.7 50
5 2915.6 50.5
6 2937.3 51

H1K
SHOT VELOCITY
1 2766.1 51
2 2762.7 51.5
3 2821.9 52
4 2823.3 52.5
5 2842.2 53

H4350
SHOT VELOCITY
1 2840.7 15
2 2851 45.5
3 2904.9 46
4 2908.7 46.5
5 2938.9 47

RL 22
SHOT VELOCITY
1 2804.7 47
2 2788.5 47.5
3 2826.9 48
4 2857.6 48.5
5 2867.3 49
6 2941.2 49.5

 

[DukeDuke]

Which bullet?

 

[acloco]

140 Rem PSP's on the first three groups and 142 Sierra MK's on the last one.

 

[DJSBRS]

Why do you think there is minimal velocity gain after increase of powder on:

H 1000 shot 3,4
H 4350 Shot 3,4
RL 22 Shot 4,5

 

[acloco]

Why do you think there is minimal velocity gain after increase of powder on:

H 1000 shot 3,4
H 4350 Shot 3,4
RL 22 Shot 4,5

For the H1000 & H4350 - could be anything...or nothing at all. Could be at a point of barrel harmonics, the #4 bullet one or two nanoseconds smaller than the last, barrel warmth, or whatever.

The 4/5 RL22 is probably the same...or not having the ability to light that much RL22??

 

[flatlander]

I've finally gotten enough 6.5x55AI cases fireformed to try a few preliminary test loads. Have gotten decent accuracy & velocity with H4831, N165, & RL22 out of a 30" Krieger 8.5-twist on my BAT 3LL. So far, with Lapua 139, S142MK, and Berger 140 BT Match Thicks, best accuracy with .010" jump has been around 2960fps. Worked up to 3050fps with RL22 & the Bergers, but the accuracy wasn't there at that level.

The S142s have always shot best for me with .010" or less jump, and that's also the case in this bbl. Have just started shooting the Bergers, so there's more testing to be done in a wider range of seating depths with them. With the accuracy I'm seeing at 600 with FF loads, I'm wishing I'd have used this bbl. in a couple of 3x600 any/anys this past summer - at least I'd have enough cases formed to work with now.

 

[BHarvey]

Just beginning load work on a 6.5x55 AI build in fireformed Winchester brass.

H4831
SHOT VELOCITY
1 2757.9 48.5
2 2830.6 49
3 2864.3 49.5
4 2883.7 50
5 2915.6 50.5
6 2937.3 51

H1K
SHOT VELOCITY
1 2766.1 51
2 2762.7 51.5
3 2821.9 52
4 2823.3 52.5
5 2842.2 53

H4350
SHOT VELOCITY
1 2840.7 15
2 2851 45.5
3 2904.9 46
4 2908.7 46.5
5 2938.9 47

RL 22
SHOT VELOCITY
1 2804.7 47
2 2788.5 47.5
3 2826.9 48
4 2857.6 48.5
5 2867.3 49
6 2941.2 49.5

I always look for a 1 grain increment where I have little to no velocity gain. It looks like you have a slow barrel or a faulty chrono. My 260AI with 24" barrel gave 2930 fps with the 139's and 48 grains of H4831.

 

[savageboy]

My 260AI w/ Rem Brass and 48.2gr. H4831SC gives 2935fps consistantly too

 

[Tikkatoy]

Never chronoed mine but shoot 48 Rl 22 with 39 Lapuas in a straight 6.5x555 Original Swede. It's very accurate at 1000 giving high x count and forgiving of conditions. Was tempetd to AI it but doubt theres any point given excellent results with excellent Lapua components plus a long history of inherent accuracy as is. Pacnor 3 groove 31" 8 twist. Thanks for the chrono postings!

 

[243Mendoza]

Why do you think there is minimal velocity gain after increase of powder on:

H 1000 shot 3,4
H 4350 Shot 3,4
RL 22 Shot 4,5

Assuming one shot per load, there is not enough statistical data to make a judgment of velocity gain with load.

 

[acloco]

I will keep working on the loads. Most of the load development was done with cheap bullets. The 142 MK's are here now, so there will be some improvements across the board.

Mine might be a slow barrel, time will tell. The chrono has been close to everything I have seen tested with other calibers/bullets/powders/etc.

 

[acloco]

Between weather, work, and the holidays...and no time when I need time, we were able to sneak out to a 700 yard range.

Pic is the results of 50 gr of H4831, CCI LR magnum primer, Win cases previously fireformed, 142 gr Sierra MK's, and the resulting 5 shot group. I don't know how good this group could have been, I muffed shot 4 and did not care about shot #5,yes, lesson learned!!).

 

[Rust]

The lack of velocity increase in a certain range of powder increase is not uncommon in some cartridge/powder/bullet combinations. It is usually seen in larger capacity cartridges, ie larger than .308.

Many of the traditional single base stick powders disply this behavior of a "platue" in velocity while increasing powder charge and it has been well documented in the past, especially if you can law your hands on any of the old Dupont pressure charts that used to be available once upon a time. If the platue just happens to coincide with one of the barrel nodes then you have a sweet load indeed as it is fairly insensitive to small powder charge variations and helps with temperature sensitivity if loaded to the light end of the platue. What supposedly causes it is at some combination of case volume to charge weight the adiabetic compression heating is close to ideal for the powder combustion in a sort of "sweet spot". Sorry I can't explain it as well as the genius old timer who explained it to be with big scientific words and all, but that's the gist of it.

Couple of folks have played with the concept in recent years, using a variation of Audettes ladder firing test to determine if such a platued charge is really working well. One fella calls it an Optimum Charge Weight,OCW) load. He used to post a bit on the boards and then started his own site.

Doesn't work to the same degree with every chambering or load combination, but if it works in your rifle you'll have a nice dependable load that works well across a range of conditions.

So basically, the ideal load is one where the velocity platue occurs right at the barrels accuracy node,Varmint Al did a wonderful barrel vibration analysis about a year ago that describes what goes on with barrels) and this would be a best case condition.

The old Dupont ballisticians from forty or fifty years back knew this well.