Reducing Bullet Jump

Shynloco

New member
Question on setting bullet depth. My understanding is that "bullet jump" reduces accuracy. I have heard and been told, that in order to reduce bullet jump, the bullet can be set further out than the COL spec, so long as it isn't set immediately on the lands and grooves. With that in mind, I am loading 52 gr Sierra HPBT bullets into a 22-250 casing that has been trimmed to 1.90. The Sierra manual calls for a COL of 2.350. QUESTION - how many thousands do I dare increase the COL before I get into the danger zones of creating too much pressure and catastrophy?
 
You really need to measure the actual length of your chamber so you will have a starting point for a measurement...

Potentially not all rifle barrels, even from the same manufacturer are the exact same measurement since many of them have multiple chamber reamers and machines that run them..

You will be dealing in measurements of thousandths of an inch and each cutter wears at a different rate...

I have one custom cut chamber on my .204AR and it was originally cut for a .030" jump when using a 40gr Hornady V-Max,,,With a 39gr Sierra BlitzKing bullet, I get a .035" jump when measured at the ogive and the overall length is set just below the magazine length..and it's extremely accurate.

My Savage .204 (Factory) has a much longer jump, but the accuracy is not than much different from a cold barrel, as far as groups go..

From what I've read from others, the jump of .035" seems to generally produce good results, but consider that all barrels are different and if you are shooting max. loads, you may be inducing faster barrel wear..by reducing the jump factor..
 
shy & loco...handloading is highly subjective...some rifles/bullets/handloaders like a jump...some don't...some like seated into lands...some bullets require a "leap"...barnes X's...2.350" is a SAAMi standard...just watch magazine OAL.
hornady markets a seating depth tool originally sold by stoney point that works well for me.
 
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Thx for the responses guys. I kinda expected the answers I got. So I had a friend take a measurement using his Hornady unit and came up with .080" which I find incredibly huge. Old Turtle says .035 seems to work well from his readings. So, does that mean in my case, theoretically I can add up to .045 (to my bullet set point) to the standard OAL of .2350 that would get me down to .035 jump space? Oh and by the way, I also ordered the Hornady Lock n Load OAL Measuring tools today as well.
 
You just need to remember that my chamber was custom cut to my specs...A factory chamber may be excessively long and still shoot well..

I haven't tried to load longer cartridges in my bolt action due to the magazine length restriction and if I moved to a heavier/longer bullet, I'm not sure my 1/12 twist would handle the weight/length and still maintain the accuracy...

I would need to re-barrel to a 1/10 or 1/9 to adequately handle the heavier bullets..
 
Thx for the info. And I am now mindful about the size of the cartridges the magazine can hold. So you'll have complete picture, my rifle is a Ruger M77 MkII 22-250 Target Grey which I bought new a little over a month ago. The barrel twist is 1/14. I really probably shouldn't complain about the accuracy since I've found it likes 34.9 Grns of RL15 pushing a 52 Grn Sierra HPBT. I plan on sticking with this combo. Since breaking in the barrel, I've only shot somewhere around 300 rds through her. At 100 yds, my groups are consistently within 1 inch and when I take my time, my groups have been under 1/2". I do strictly target shooting and strive for 5 shot groups under 1/2". Yet I'd love to see groups within 1/8", but then I suppose people in [beeep] would like ice water on a regular basis. Thx again.
 
An old fashioned way of coming up with a seating depth for your rifle is to take a spent casing and resize it. Seat the bullet tip that you've chosen into the case leaving it plenty long. With a bolt action rifle only, you can lightly close the bolt until you feel resistance, keep adjusting your seater die until your bolt closes all the way. Take an over all measurement, write it down and there you have it. Keep in mind that this measurement is for that particular tip only as each brand will have a differant ojive. I would be lost if it were'nt for my $15 Sinclair bullet comparitor (you will need a caliper also). Because once you have that measurement you just found you can use the comparitor to simply adjust your seater die for any make or style of tip in a matter of seconds.

I hope this dosen't sound too complicated, because it's not.
 
Originally Posted By: Wyoming DrifterAn old fashioned way of coming up with a seating depth for your rifle is to take a spent casing and resize it. Seat the bullet tip that you've chosen into the case leaving it plenty long. With a bolt action rifle only, you can lightly close the bolt until you feel resistance, keep adjusting your seater die until your bolt closes all the way. Take an over all measurement, write it down and there you have it. Keep in mind that this measurement is for that particular tip only as each brand will have a differant ojive. I would be lost if it were'nt for my $15 Sinclair bullet comparitor (you will need a caliper also). Because once you have that measurement you just found you can use the comparitor to simply adjust your seater die for any make or style of tip in a matter of seconds.

I hope this dosen't sound too complicated, because it's not. +1 on this Alex.
 
Well thx. Looks like good OLD methods are still the simplest and cheapest for sure. It sure makes sense. Now we'll test it for accuracy as see if theres are "falloff" at some point on this rifle. I've already made up 20 rds for each ten- thousands increase in OAL started at what the Sierra Loading manual lists as OAL and increasing up to the max length the magazine can stand and still feed a round into the chamber. But thanks for the info.
 
Maybe its just me, but my thinking is that maybe a magazine in a rifle with an excessive chamber one may never realise the best Col unless he shot it as a single shot? Couldnt the possibility of a better load just be beyond what the Magazine allows? Im always askin dumb questions. lol
 
Originally Posted By: Orneryolfart357Maybe its just me, but my thinking is that maybe a magazine in a rifle with an excessive chamber one may never realise the best Col unless he shot it as a single shot? Couldnt the possibility of a better load just be beyond what the Magazine allows? Im always askin dumb questions. lol

Heck yes!!!!

I have had many rifles that had magazines that I shot as a single shot. Some brands of rifles always have long throats...makes you wonder.....

These long throated rifles are almost shot out when they are new...duhhh....Huggghhh....
 
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Thank you for confirming my thoughts Ackleyman. I have always wondered about that. In previous discussions with you on getting a custom barrel, the " freebore" always comes to mind. I may be learning despite what people think! lol
 
Originally Posted By: Wyoming DrifterAn old fashioned way of coming up with a seating depth for your rifle is to take a spent casing and resize it. Seat the bullet tip that you've chosen into the case leaving it plenty long. With a bolt action rifle only, you can lightly close the bolt until you feel resistance, keep adjusting your seater die until your bolt closes all the way...

Just one thing to keep in mind here, fellas, the lands applies tension in both directions, so you aren't get an exact COL measurement here. I see nothing wrong with this method whatsoever - if it works for you then more power to ya. Just want to make sure we're all on the same page as far as limitations of this method.

Also, FWIW, I shoot a couple .223 rifles with the bullets loaded so long that I can only get two rounds in the mag and one in the pipe (and these are 4 round mags).
 
I was shooting with a buddy yesterday he had an AR, I asked him how he loaded his bullets. He said his max length was 2.260 "to the tip" of the bullet. I asked if he could squeese all 10 into the mag. I have noticed that with the length of bullet they are tighter in the Mag. Good point Songdogslayer.
 
shy&loco...don't forget that the OAL of the BULLET will probably vary...measuring from bullet's heel to it's ogive will be FAR MORE accurate than measuring heel to tip...measure sum bullets OAL&WRITE the results down - then measure those same bullets heel to ogive and notice how consistent those numbers are...so setting up a seat'n die on just one bullet or even 2 will give you a false promise of consistent OAL when you measure base of case to seated bullet tip.
ALWAYS measure from base of case to seated bullet's ogive....the bullet nose is just sumwhere in the bore.
 
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