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Cronographed my 260imp 30 degree ??

I cronographed some of my loads last night and I am really unsure of the readings I am getting. My rifle has a 26" 1-8 twist, melonited barrel. My fire forming loads are 43grs of H4350 using 139s and 140s. This load ran 2917fps!!

I then shot a couple of loads in cases that were formed. The fist load was 43grs of H4350 with 139s and it was 2909fps.
The next load was 43.4grs of H4350 and it ran 2940fps. The last load was 42.6grs of H4350 with the 123 Lapuas and it ran 2934fps.

These loads seem to be way to fast for what I am loading in them. I would have figured them at around 2800fps not in the 2900s. I wasn't even sure I could reach 2900fps using H4350. The last time I used my cronograph it was pretty much dead on with a brand new one but now I am not sure about it. I hope I can borrow the new one and try these loads across it to see if they are right. They just seem to be crazy fast to me. Any thoughts or ideas from you guys who have cronograph numbers on your loads??? Thanks!!
 
Wow- I guess that bodes well for my loads being around the 2900-2950fps mark. One person has told me that about the 43.5gr mark should be over 2900fps. But Robert Whitleys work shows around the 2800fps mark. I guess it all depends on what cases and primers you use plus if you have a fast or slow barrel.

Maybe do a 300, 600 and 1000yd zero and type your details into JBM and slowly tweak velocity until it matches your come ups.
 
That was my thoughts too. Its suppose to be windy tomorrow but maybe sunday it will settle down some so I can get out and try some longer ranges.

Actually the 123 load would be close to being right because I was doing 2975+ with my old 260 with a 24" barrel with a load of 43.5grs of H4350 and the Lapua brass. That tracked really close to my JBM data. I guess one can only hope it will be that easy to get to 2900fps with one of these!!HA
 
Don't overlook your barrel for the extra speed along with the melonite coating.
Robert
 
You are probably running about right on your velocity. I have some Swede 96 Mausers with the 28" barrels in 6.5X55 but I am using AA 4350 which is just a bit slower than H4350 and with 46 gr and 120 gr ballistic tips and Sierras I get 3000 fps and with 45 grs AA 4350 with 140 Hornady and Sierras I get a 2850 fps. According to Accurate these are supposed to be under 46000 cup loads. I get good case life and show no sign of being higher pressure loads. Barrel length and type do make a big difference sometimes.
 
Thanks for the replys Guys!!

Robert,
Does the melonite process make the barrels faster?? I just never thought that it would be so easy to reach the 2900fps mark with the 140 class bullets esp with only 43+grs of powder!!

So far I am very pleased with the rifle. Its been averaging .6s fire forming with 4 of the rounds in under a .5 to a .3 (I suck shooting at 100yds) After my good scope took a dump I had to put my old 3.4x10 LR on it with the 1moa dials and it will not focus well at 100yds.

I had planned on using the 123 Lapuas again but if the 139s will shoot at 2900+ I may have to reconsider, I was using them in my 6.5x55.
 
What's the screen spacing on your chrono and what brand is it ? It's all very possible but you should be about 100-150fps less on your 140's . My Ackley does 3000fps+ out of a 24 inch barrel with 120's and N550 , it's a hunting rifle , and it's a hot load . Lapua cases show just a touch over .001" head expansion . What's your head expansion with 123's vs. 140's ? That should verify your velocities .
 
Shot some more loads today. We use electronic targets so we can see what the groups come up like. Most groups were one or two bullet holes high at 400m wind only wind taking it out of the x ring. 42.4gr of H4350 is a very good fireform load with berger 140VLD's jammed 15 thou. It shot same elevation as 43.8gr of H4350 and 140 hybrids jumped 15 thou.

Also tried 120gr sierras with 44.5gr H4350. They shot about two to three minutes higher and not as tight but more than acceptable for 300-500m target shooting on calm days.
 
I didn't get my friends cronograph until this morning so I hope I can get out this afternoon after work to get some "Good" numbers.

I did go out and shoot at 400, 600 and 800yds yesterday morning but it was a crappy day for shooting. It was between 34 and 40 degrees while I was shooting and I had a snakey headwind to shoot into.

I used 6moa for my 400yd dial and shot dead on with a few loads and about 3" low on some others. At 600yds I used 12moa for the 139s and 11moa for the 123s once again I was right on for a couple and low for some others.

The few loads I shot at 800 I used 19 for the 123s and 20moa for the 139s and most were between 6 to 14"s low with one 123 load being dead on.

I shot my 6BRX at 600 just before I left and it also shot low but I was running out of time so didn't have a chance to really check out why. I may have overlooked how cold it was and shooting through cold air may have put me on the low side too. With luck I should get a good idea of where I am at tonight. I will shoot through mine and his cronographs to see what I am actually doing for speeds.

lcazador,
My cronograph screens were about 1/2" short of 24"s but I had known this and had used a factor of .978 to come up with corrected numbers. I had shot it against other ones before and this factor seemed to be the answer but I did correct that this weekend and now its dead nuts on 24" between centers on the eyes. Like my original post states I too was very sceptical of the numbers that I got. But it had been good in the past.
 
Re: Cronographed my 260imp 30 degree ?? NEW UDATE

OK Guys, here are the cronograph figures from the new cronograph that has been checked with another for accuracy. I used my 6BRX as a standard. I know it shoots right at 3000fps on two different cronographs and it matches up with JBM out to 1000yds.

I shot 7rds across the newer one to see what it said on my BRX. It came back 2993fps so well within specs. I shot my fireforming load to see what it was doing. It came in at 2871fps. My next load in the formed cases was 43.4grs of H4350 with the 139 Lapuas and it colcked in at 2890fps. My next load was 43.8grs of H4350 and it came in at 2917fps. I had one more load at 44.2grs and it clocked a whopping 2946fps!!

I then went to the 123 Lapuas and my first load was 43.8grs of H4350 and it was 2981fps. The next load was 44.4grs of H4350 and it was 3013fps. My last load was 44.8grs of H4350 and it clocked in at 3053fps.

All these loads shot in the .6 to .5 range with most of them having 4 in .3 to .4s like I said I suck at shooting 100yd groups plus the rifle has a 3+lb tigger in it right now. So from what I can tell the 260Imp 30degree will flat lay down the numbers!! Like I posted earlier my barrel is a 26" Melonited and that may have something to do with it too. I have not had any pressure signs at all the primers are not even pitting bad yet and extraction is smooth as silk.
 
Try some Sierras with the same load and see if vel. drops a little. the Lapuas are faster in my Std. .260. If you want to make the 123's really go,try Superformance. I'm getting 3100 with no pressure signs from a 30" 8-1/2" Bartlein. and accuracy is excellent. My bullet is the 123 gr. A-Max. ..... LARRY
 
I have both Sierra 140 and 142s and I just got a box of 123 AMAXs to try too. I am trying to develope a load that works with what I have on hand right now. The 140 Sierras shot well in fire forming loads. I have shot HV100 in my old 260 and it shot well so I may try some of it too. I like the extreme powders the best because of the extremes in temps out here. It can be 110+ in the summer and - 30 in the winter. Thanks for the info!!
 
Raptor thanks for the info on your loads. I tested 4 different powders and 3 different primers. My speeds are close to yours. I tried Berger 140's both hybrids and VLD's, they shot well. 139 Scenars shot well and so did the 123 Scenars. I did load H4350 up to 46.5 grs this load went sour with 123's, but according to my chrono they were averaging 3258. And there was a slight mark on the face of the brass. I found that 44.5 to 45.5 produced the best consistency with the 123's for me.
On the primer tests that I did with Fed 210m's and br-2' and wolf lrp's, the cci's were were faster and spreads were low. Fed 210m's were on the avg 20-40fps slower but low es also, the wolfs were the slowest at an avg of 50+ and shot poorly. When I get back home I can post the speeds for you,if you wanted to know.

The powders I tested were Imr4350,H4350, Varget and H380. They all shot well. I had posted a pic of one of the shot groups, but then deleted it. I will take a few pics of all the shot groups with load data and post them, take care and good shooting...
 
That sounds consistent with my findings, the 120gr sierras shot fairly well with 44.5gr H4350. Not sure if your familiar with our F class scoring in Australia but I shot a double possible at 500 meters (120 from 120 points) on sunday with mine. First detail was 140VLD's fireforming brass with 42.4gr H4350 and second was 140 hybrids with 43.8gr H4350 in already formed cases. X count wasnt that high but groups were nice and tight. I was trying to shoot conservatively to not drop a point, rather than try and get the largest number of X's.

Im happy to settle on the hybrid as my bullet of choice, the only thing I need to do is test at 900 meters (pretty much 1000yds) for vertical and to have a play with seating depth to see if I can tweak results further. I havent got a chrony yet still, hoping to have a MS2 in about a month to confirm velocity, SD and ES. But so far vertical spread is very tight suggesting its pretty good.
 
by1983, I think you can get close by zeroing at 100yds. Then shooting 2 further distances say 300 and 500yds, keeping the same dope on your scope that you have for 100 and measuring the actual drop and plug those numbers in to a ballistic program and come up with a close figure for your speed. The name of the program I used at one time slipped my mind, but I am sure someone will chime in with it. If not, I will try to post it tomorrow night when i get in from work , at the hotel..
 
Not really an issue if I dont know the velocity, F class is known ranges and I only shoot whats accurate. More so want the chrony for SD and ES but the way I've set up my load development process, I shoot at 300, 500 and 900 meters so I can prove vertical at all ranges. It wouldnt be as long winded if I had a chrony but it works and helps me get used to the rifle Im shooting. It looks to be a very efficient and accurate caliber with hopefully more barrel life than a 6.5x284.
 
120/120!! That's great shooting BY1983!
Did you use the long or short throated reamer for your chamber?
With the short reamer (bullets are very deep in the case) I am getting 2950fps from 44.3gr AR2209 (H4350) and a 28" barrel. Vertical for 2x consecutive 5 shot groups @ 300m was less than 0.26moa. (First group with a naked barrel, second group with a MagnetoSpeed chrony attached)

Being a warm load, my barrel gets hot quickly. At the end of a string, I have to be mindful of cartridge dwell time in the chamber or the ES opens up.
 
daj
Thats intresting, my 44.2gr load was 2946fps with the 139s so were pretty close. It looks like a person will not have any problem getting a solid 2900+ fps out of the 260imp 30 degree without getting into pressure problems. My barrel is only 26" long but then its melonited and according to Robert they are faster.
 
Raptor
Since we are using very similar loads, I am interested to see how much more throat life you get with the melonite treatment.
Which reamer did you opt for and how are you seating the Scenars? With the short reamer, my COAL is 2.886" with the VLDs jammed 20T.
 

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