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> 7mm Rem Mag - 150gr NP - ADI AR2213SC - Low velocities
7mm Rem Mag - 150gr NP - ADI AR2213SC - Low velocities
@ 12:43 am (GMT) |
Erich KubaHi there,I'd really appreciate some help and/or advice. I recently bought a Remington 700 XCR II in 7mm Rem Mag. 24" tube, 3.6" mag. To date I have been breaking the barrel in (using factory ammo) and have just started reloading for it. The barrel has fired 120 rounds to date (excluding the tests below) My first effort was a 150gr Nosler Partition in a Hornady case on top of ADI AR2213SC powder and a Federal 215M primer. COAL was 3.280" (or 2.625" using a comparator), which gives me a seating depth 20 thous of the lands. Loaded rounds were then given a very light crimp with a Lee Factory Crimp die. Cases were FL sized to the point where the shoulder was bumped 2-3 thous and cases were trimmed to 2.490". I loaded 13 sets in 0.5gr increments from 59gr to 65gr. The powder charge was the only thing that was changed between all the sets. Each set consisted of 4 rounds. @59gr according to the ADI Manual should have produced 2775fps. I got 2572 avg. @61gr according to the Nosler reloading guide should have produced 2985 fps. I got 2765 avg. @62gr according to the ADI Manual should have produced 2956fps. I got 2718 avg. @63gr according to the Nosler reloading guide should have produced 3023 fps. I got 2817 avg. @66gr according to the Nosler reloading guide should have produced 3075 fps. I got 2925 avg. I got 3 loads of interest. One group of 1/4 inch @2633 fps. ES=63, SD=25.4. Good group, but way too slow and poor ES/SD. One group of 0.8 inch @2817 fps. ES=12.4, SD=5.4. Acceptable accuracy, but good ES/SD. Was hoping for more speed though. One group of 1 inch @2886 fps. ES=30.2, SD=13.6. Acceptable accuracy, but the pace is getting towards what I was expecting. I have another 50 of these projectiles and would really like to try and get more from them. I tend to feel that trying a different powder may be worth while as I really would like to get closer to the 3000fps mark, but I'm unsure which way to go. Do I try a faster powder such as AR2209, or a slower powder such as AR2217. I would prefer to only use temperature insensitive powders. Also, could anyone explain why I seemed to constantly get 200fps less than that the book said I should expect. I think that 200fps is quite a lot. Cheers Erich |
Replies
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@ 12:55 am (GMT) |
Erich KubaRe: 7mm Rem Mag - 150gr NP - ADI AR2213SC - Low velocities> @66gr according to the Nosler reloading guide should have produced 3075 fps. I got 2925 avg.That should have said: @65gr according to the Nosler reloading guide should have produced 3075 fps. I got 2925 avg. Also, one further point is that I did not run into signs of excessive pressure except for a bit of cratering on the primer, so perhaps I could try more powder, but I am reluctant to considering that I am 3gr over max (according to ADI) already. Cheers Erich |
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@ 02:31 am (GMT) |
Matt ReidRe: 7mm Rem Mag - 150gr NP - ADI AR2213SC - Low velocitiesHi Erich,This may not be your issue, but one experience I had was with a 'slow' batch of ADI 2208. In my .308 I was getting velocities around 100fps below what was stated and they were already at max and well compressed. There was plenty of head scratching involved until I finally ran out of powder, bought a new tin and all was back on track. Unfortunately this had the opposite effect of stuffing up another accurate load I had worked up with the bad powder. Another unique issue I had, was with a bit of cobweb getting up inside my powder scale near the balance beam. I ended up with loads going a lot faster than expected, and when I released and pulled the projectiles, I had been throwing nearly a grain extra into each case... Matt |
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@ 01:15 pm (GMT) |
Erich KubaRe: 7mm Rem Mag - 150gr NP - ADI AR2213SC - Low velocitiesAs a further point of interest, I chronied some 162gr Hornady Superformance Factory Ammo, and velocities were also 200 fps below what the ammo box claimed. Box claimed 3030fps, I got 2815fps as an average of 5 shots.I didn't think much of it at the time, but now I'm starting to wonder why there is a constant 200fps less in velocity. I've read on some forums that there is a phenomenon called a "slow barrel" ... I've never heard of that before. Can anyone explain it? I'm starting to think that maybe I should try some 160 Accubonds with AR2217 and see what velocities that produces. I suspect AR2225 would be too slow for my 24 inch tube. Cheers Erich |
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@ 05:42 pm (GMT) |
Nathan FosterRe: 7mm Rem Mag - 150gr NP - ADI AR2213SC - Low velocitiesHi Erich, those velocities are right on the money with those charge rates.Ok, here is what we have to keep in mind, I will use an example. One day a guy gives me a factory new Browning A-Bolt, wants me to sight it in and see how it goes out of the box. Its a .270, should be pretty straight forwards. Well, in this rifle, someone in Japan had cut the throat short. I don't actually really know how this can be done, short of bluntening the reamer, then regrinding it or maybe using a throating reamer. Its not exactly a reamer mistake as reamers are CNC machined. So in goes the factory Winchester ammo and I can already feeling the projectile bumping up against the rifling. I give it a whirl anyway and sure enough, its a hot load, the extraction is stiff, made much worse by the 60 degree bolt lift. I try a few hand loads, I can get near to the max listed velocities in the ADI manual, I push it as far as I can to test the rifle thoroughly and it goes from looking like it might be close to max to where the hell did I put that fence batten, its time to give that 60 degree bolt some more loving. So the ADI manual is spot on for tight dimensioned rifles. Your Remington on the other hand is so loose that in the gun world, its probably the town bike. And thats just the way I like my Remington's. So, lets keep going with this. You were getting 100fps per 1 grain increase. You'll get about 40fps per grain from her on in I think- just a guess though. Its hard to say where optimum velocity will be, you just have to work through the loads and see. I want you to try and get the rifle to 3125fps atleast so that we can see a better picture so lets do that now (based on a 40fps assumption): 68gr 3045 68.5gr 3065 69gr 3085 69.5gr 3105 70gr 3125 70.5gr 3145 suspect near max. Now for anyone else reading this, don't try the above. The reason I am OK with Erich doing this is because he has supplied me with great detail including chamber dimensions. Because I have a lot of experience with rifles and reloading on a day to day basis, I know pretty much before I start out, the test range that is required. This is not based on what powder charge worked on the last few rifles and how silly those ADI people are- but what worked and did not work in the rifles based on the chamber dimensions. The primer cratering is simply from firing pin protrusion Erich, don't worry about it. Look for extractor marks (shiny scuff marks on the case head) for signs of pressure. The shiny marks occur when the brass attempts to flow into the plunger hole in the bolt face. During extraction, as the bolt is turned, the brass is scuffed as it is moved out of the plunger hole. If you go higher, you will begin to have difficult extraction (stiff bolt). Another grain over that and the case will rupture, venting gas into the mag well- getting ugly now. Another grain over that and the floor plate will rupture, starts getting real ugly now. Changing to 2217/H1000 won't make a difference if you once again follow the reloading manual with regard to this particular rifle. I do tend to use 2217 from the outset but I advise you to keep going with what you are doing, you are into it now so follow it through. If the rifle is unbedded, you may find that accuracy wanes at optimum velocities. This is not a reflection of hot loads but instead, a reflection of a poor platform, often combined with less than adequate shooting technique. You will have to read your cases to determine whether the loads are truly hot, or whether the platform and or yourself are not up to the task. |
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@ 01:35 am (GMT) |
Erich KubaRe: 7mm Rem Mag - 150gr NP - ADI AR2213SC - Low velocitiesHi Nathan,Thanks for your reply. I'm happy to continue along this process. I have checked all the brass and there are no shiny spots/scuffing on the case heads at all, and there was never any difficulty whatsoever in lifting the bolt handle (something I was concentrating on). I have also checked the dimensions between a fired case, and a previously fired case that has been partially FL sized (as described above), and there is very little difference between them. The shoulder has moved forward by the 3 thous that it had been bumped back by the FL die, the diameter of the case (just above the belt) increased by 1 thou, the diameter of the case at the base of the shoulder increased by 2.5 thous. The neck diameter increased by 3 thous. A further point of interest is that there are no dimensional differences between a fired case from this load and a fired case from the Hornady Superformance Ammunition. The only visible difference is that the cases from this load have a very slight sooting on the outside of the necks. I'll continue to load up in 1/2 grain increments and will post my results once done. I expect that this will be within the next month or so (weather dependant). Out of interest, Nathan, how did you deduce my chamber dimensions from the information that I supplied? Not questioning you, just want to know how you joined the dots. Cheers Erich |
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@ 05:36 pm (GMT) |
Nathan FosterRe: 7mm Rem Mag - 150gr NP - ADI AR2213SC - Low velocitiesHi Erich, throat length (your COAL) versus velocities was the key. Past experience with similar rifles producing similar velocities was a major factor also. Your description of the case head helped as well. Finally, past experience with Superformance ammo, it is usually within 20-40fps of advertised specs in tight tolerance rifles.Increases of 2.5 to 3 though signal fairly generous tolerances. The 7mm Practical reamer for example, keeps within 2 thou all over. That said, the throat area of the chamber tends to have a more profound effect on pressures. The longer the throat, the lower the pressures. The bore also has a pronounced effect, the looser the bore dimension, the lower the pressures which equates to low velocities- not the other way around where we would expect a loose bore to offer less friction and therefore higher velocities. Velocity is always relative to pressure. |
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@ 01:41 am (GMT) |
Erich KubaRe: 7mm Rem Mag - 150gr NP - ADI AR2213SC - Low velocitiesHi there,Just an update on this. I shot a further 5 groups (of 4 shots each) this weekend in 1/2 grain increments (into a reasonably strong headwind). The last group was 67.5 gr of powder (all other parameters remained the same) and produced an average velocity of 3093 fps and the best group size of all (the first 3 shots under 1/2 an inch ... I screwed up the 4th shot). There were no additional signs of pressure and I suspect that I can go a bit further ... and I'm tempted to as the previous 3 loads showed a contraction in group size, and I suspect that this contraction is not yet over. Also, the last load showed an SD of 12.5 and it would be very handy if this dropped under 10. I'll keep you posted as I go. Thanks for your help in this regard. Cheers Erich |
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@ 10:24 pm (GMT) |
Nathan FosterRe: 7mm Rem Mag - 150gr NP - ADI AR2213SC - Low velocitiesHi Erich, sounds very good. 3100fps is potent. If the rifle gives you more, so be it.It is a great thing when it all comes together. The Partition is an accurate bullet, just needs a bit of experimentation. Thanks for the update, much appreciated. |
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