Can someone explain this velocity difference please

[warrenb]

Using Hodgeson online data I am comparing the produced velocity of varget and xbr 8208 with 3 different bullets. Please see table below. I currently shoot 69 and 80 grn smks over xbr 8208. My own measurments with the 69 smks and a charge 23.8 is pretty much agreeing with the published data at 2990 fps. Similarly my own tests with 80 smks and a charge of 21.0 8208 produces around 2600 fps on average.

My question is why are the produced velocities between the 2 powders so similar with 69 and 90 grain bullets and yet the 8208 loses significant speed with the 80 grainers.

I have zero pressure signs in either my 69 or 80 grain loads and am wondering if I can safely continue to work up the 80 grain load to try and achieve more fps. I am finding the 8208 very accurate and would like to continue with it. Or should I just switch over to Varget.

69 GR. SIE HPBT Varget .224" 2.235" 26.0C 3010 50,200 CUP

69 GR. SIE HPBT 8208 XBR .224" 2.235" 23.8 2959 52,900 PSI

80 GR. SIE MK Varget .224" 2.550" 25.0C 2869 51,500 CUP

80 GR. SIE MK 8208 XBR .224" 2.550" 21.0 2628 52,900 PSI

90 GR. SIE HPBT Varget .224" 2.380" 22.3C 2447 52,100 PSI

90 GR. SIE HPBT 8208 XBR .224" 2.380" 19.6 2419 52,800 PSI

 

[guntech]

All powders have individual characteristics... due to composition, coatings, etc. They react differently at different pressures and in different cartridges ... that is why published reloading data from a reliable source is very important.

 

[Mystic Precision]

Besides velocity, you should also consider load density which can really affect vertical dispersion at LR.

The best powder is the one that is nearly compressed at the max allowable pressure and speed with the best accuacy and the lowest amount of vertical.

In the 223/80gr, I have found Varget to be a very nice compromise for mag feed ammo.

In the 223/69gr for my semis, I am using a faster powder to suit both the recoil system and harmonics.

Let the rifles tell you what they want. Reloading manuals are only a reference. There are just too many quirks in rifles to make hard and fast rules.

Jerry

 

[DrXenon]

My experience is that the XBR is a faster powder in my 0.308 Rem 700 w/ 26" barrel with 155.5 gr Bergers. I was not able to achieve my goal of 2900 fps with Varget because there wasn't enough case volume for the necessary amount of it.

I am very pleased with the accuracy of 46.5 gr of XBR behind the Bergers. I shot at a 600m range on the weekend and got a significant number of V-bulls, which I was not expecting since it was my first time shooting at that distance.

 

[warrenb]

Jerry,
to get the 80s to shoot I am soft seating the bullet (Lee collet die) and then final seating when closing the bolt. The rounds are a little longer than mag length but no longer crushing/disturbing the powder when seating. This appears to have made a difference in accuracy. The throat on this chamber is more suited to the 69s but I'm trying to get the best of both worlds.

I have seen reports of guys using another 2.5 grains of this powder but their overall length was over 100 thou more than I am able to get. I think I will carefully go up another grain at a tenth at a time and see how it goes. I'l also switch back to Varget with this seating depth and see how she performs there with the 80s. I'l report back just in case anyone is interested.

DrXenon, thats cool that you actually got higher speed with the 8208. I really want to like this powder. But there are lots of unkowns where as with varget there is lots of info out there to filter. Good luck.

 

[guntech]

You have to be careful when approaching maximum loads and a bullet jammed in the lands and a small caliber... pressures can peak beyond what you want quite quickly.

 

[warrenb]

Dennis,
your warning is appreciated and noted. I will go up a tenth at a time and if I don't see results within one additional grain I'l either have the throat lengthened or stick to the 69 smks and buy another barrel for the heavies.

 

[warrenb]

updated info - Anyone else shooting 8 twist shilen in 223

I thought I would update this just in case anyone is interested. I worked up to 22.5 grains of 8208 which produces 2775 fps. No big pressure indications but I can just see that the primers are losing their sharp edge and beggining to flatten.
22.4 gives me 2760. Not the 2850 - 2900 fps I was hoping for but I think I will just spend the summer getting trigger trigger time behind this load.

An interesting anecdote: when I was testing my loads yesterday the wind was pretty strong, even the chrony blew over twice. There was an older gentlemen also testing 82 grain Burgers in a 1/8 twist McClennan barrel. He shared some load information and it turned out the first competitions he shot in Ottawa was back in 1956. He did not say they were his first competitions mind you. Anyway his speeds were averaging just inside of 3,000 fps with varget. I offered to walk down to the 200 yard to collect his targets which were next to mine. Bearing in mind how windy it was. I was surprised when I got to his targets and found that he had had put his groups into one hole. While I don't expect to achieve his level of shooting skill/experience, its inspiring to see someone shoot like that and gives me something to work to. A very nice gentleman indeed.

 

[308BAR]

I'm shooting a 26" 1:8 Shilen SSM.

I've been trying to find a load using the 80gn VLDs. Similar to you I'm getting Vel. in the 2750 range with . No where near book value. I've loaded up to 25.0gn of Varget as per Hodgon reloading data hand haven't found anything that works right know. I've try 15-20 jam. Producing varied results so I'm thinking of trying a different powder. I'm using CCI 450. Just from my initial test I'm finding it hard to believe anyone could produce 3000 using the 80s and Varget.

I've found a load with 75 Amax that have produce a group in the twos at 200m. Which is my go to load right now for F-class. I still hope to find a load using the Berger 80s.

 

[warrenb]

Thanks for that info 308Bar. I can believe "some" guys are getting 3000 fps. As I mentioned the gentleman I was shooting next to on Friday was recording his speeds and they were up in the high 2900's. I saw at least one that was 3000 fps. He was shooting 82 grain Bergers that he had molyed.

I wonder if your Shilen has a similar length throat to mine. I am using the lands to seat the bullets. The COL is only 2.455 after closing the bolt with the 80 smks. So COL is about 100 thou shorter than some guys are using and I'm stuck well into the lands to boot.

I'm surprised I don't see more reports from guys shooting the 223 8 twist. I thought 223 was currently in vogue.

BTW, if I had a load that shot in the .2s at 200 I'd stick with it. But I don't compete so my oppinion may not count.

 

[Mystic Precision]

The higher speeds are with much longer throats which allow you to put in more powder. Also, higher pressures are used.

However, I have a 223 8 twist 22" shilen on my Savage tactical rifle and am getting 2800fps with 80gr Amx which are very similar to Berger VLD's I am loaded to mag OAL so the bullet is OFF the lands a litle bit. Varget and 450's in Win brass is used.

I am not a fan of jamming into the lands.

Most of the 223 use in F class is with 90gr VLD's and that use is still pretty new. I have a post elsewhere with lots of info.

3000fps in a standard 223 chamber with 80's is not going to happen. High 2700's to low 2800's is about right with the 80's. You can get into the 2900's with the 75's.

308BAR, I am glad that you have found a combo that is shooting in the 2's at 200m for you. That will be plenty accurate for the smaller ICFRA target.

Trying another type and brand of bullet may be what you need to get the heavier bullets to shoot the same.

Each barrel has its quirks so feed it what it likes.

Jerry

 

[warrenb]

Jerry, thanks for that info. It sounds like I am pretty close with the 2760 fps I am getting now with my barrel throated normally. Thats good to know. I am actually getting excited about this barrel/powder/bullet combo. I think its the first time I have had a rig where I understand the term "shoots better than I do".
I hear what you are saying about staying out of the lands. I have always seated 5 to 10 thou off and adjusted my powder charge to tune. Seems to be working in this instance though.