why the massive improvement in velocity?

Offroad Gary

Well-Known Member
Been running 55 gn ballistic tips over 35gn H4895 in my 22-250, getting 3700 fps, quite respectable and excellent accuracy. I just tried some ammo I made for my old R93 22-250 which was giving 3600 fps in that rifle(41gn H380, same col) and I got 3850 fps from the custom Tooley. fantastic improvement on velocity – well over book speeds, can I put this down to the tight neck? Barrel is only 24.5”.
 
Gary, I don't know why, but I have seen it and it seems to relate to certain bullets and powders in certain barrels.

My 260 has a LW match barrel, 1450 weight, Saami min spec chamber and a really short throat. I spec'd it to shoot 120gr BT's. Bullet is in the lands at about 2.5mm short of magazine OAL. When cleaning the barrel bore, it seems very smooth.

It won't shoot for s**t with H4831. With Varget I get very good accuracy, but velocity is not so good, 100 - 150FPS short of the book.

However, change the powder to Benchmark, or Reloder 17, it is a different beast.

With Benchmark and the 120gr BT's, it is hitting book max velocity (2900FPS) at about 1.5gr short of book max. It is badly over pressure at book max powder loads, flattened primers, extractor marks etc. Reloader 17 gives almost identical results with an extra 1.5gr's of powder.

Load a 100gr BT over Benchmark or Reloder 17, it turns into a pure animal. In excess 3300FPS, again with 1.5gr short of book max loads, again this is max load in this rifle. As you approach max powder charge, pressure goes mad. That is kicking the tripe out of a 25/06 with an '08 case. I am actually backing this load off, as I think it is too fast for deer. Confirming trajectory, I found a 2cm high zero at 100m gave a 2cm low POI at 200m. That is seriously flat shooting.

I should say all this is with a 20" barrel. I had 2" knocked of the barrel a few months ago for the net loss of about 40fps per load.

My conclusion is that this is as a result of a good quality barrel, combined with a tight chamber, short throat and fast for cartridge powders.
 
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forgot to add, the same load in a 26" vssf2 made 3700 fps - theory says longer the barrell means more beans!:cuckoo:
 
Well! If there was ever an argument for working up loads from scratch for a new rifle (or batch of components, for that matter) you made it with this post, Gary. The only way you got extra speed was from extra pressure; if you got that losing an inch and a half of barrel, then you can add that to the equation. It's all physics. More speed requires more push. I wouldn't be so giddy. Something is wrong someplace. Since H-4895 usually tops out around 3700 fps with max loads @ 62K pressure, your extra speed should be a cause for concern. :-| Don't put your eye out, Amigo.~Muir
 
:eek:

Gary -

Next time you shoot it can you do so somewhere far away...... like Sussex? I have no wish to become a cinder in a scorched hole that once was West Berkshire

Thank you.:D
 
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i still dont get it...

h4895 gives me 3700
h380 gives me 3850

why does h4895 behave as expected yet h380 give massive "over velocity" with NO pressure signs??

can anyone explain?

ps. with regard to trying the h380 loads in my new gun, a bloke who has dsc1, dsc2 and is an AW told me that it would be ok!
 
i still dont get it...

h4895 gives me 3700
h380 gives me 3850

why does h4895 behave as expected yet h380 give massive "over velocity" with NO pressure signs??

can anyone explain?

ps. with regard to trying the h380 loads in my new gun, a bloke who has dsc1, dsc2 and is an AW told me that it would be ok!

There's just a chance that a "massive over velocity" reading is a pressure sign in itself.
I really hope you were taking the Mick with your last line.
 
Gary,
Heed Muir's advise!
The increase in velocity is the result of increased pressure.
The pressure signs may not be immediately visible on your brass but your brass life will be short and the barrel life on your beautiful rifle will be considerably reduced.
The difference in trajectory between 3700fps and 3850fps is negligable and Mr Fox will never know the difference.
 
cheers Andy-advice will be heeded, i'm going to stick with the 4895 for hunting but concentrate on the 380 for the future for a real accuracy load (one that shoots better than 1/2" at 200Y). ps, i really am looking forward to burning the bugger out, i think a 6mm barrell would be ideal on the rifle, just incase i get the urge to shoot something a bit bigger than a fox! might even try some lapua brass now they make it for the 250.
 
Hmmm now I don't know Gary nor anything about him, or even if Gary is a him or just a pen name on the forums? but would just like to point out that just because someone buys all the tools for the job. It does not mean they know what they're doing or even how to use the tools. If it did there would be no need to people such as mechanics and fitters and we could go buy the spanners and voila all be skilled at it.

So Gary just having the measuring thingy actaully means diddly squat. Just like me having this here puter. Oh I can click on things and open things even post piccies on the web ;) but in fact I really know diddly squat how to use 90% of it's capabilities :oops:.

Now I have a feeling that your just in a mickey taking mood, at least I do hope that's it. On never knows on the web :rolleyes:.
 
This is probably the same fellow who advises him to stay away from starting loads and just use maximum. Old Gary is probably just jerking our chain but if not, he should realize that such dithery comments can get him tossed off of some web-sites. Too many people get too many ideas from the WEB and unsafe practices voiced in print are usually frowned upon by Moderators.~Muir
 
gents, i have just ordered my own measuring things - the quest for the perfect round will now commence from the bottom up! used up the last of the hot ones last night and found that they were not as good at 200y as the slower ones, 1.5" is just not acceptable!!. now going to experiment with seating depth. the chap that sold me the rifle said it will work best "kissing the rifleing", i think i will start 20 thou off with 38gn h380 and work in - any thoughts?
 
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