How much jump is too much? Will it cause damage/throat erosion if too long?

rulellis

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I have a 300 WM that I was having trouble getting a good load out of. I thought I would try the Berger 215 gr Hybrid Targets, but for them to fit in my magazine I have to load them .05 off the lands (not .005). After first OCW it shot around 1/2 MOA which is satisfactory to me. However, my question is will this cause early throat erosion or other problems? Is there any problem with seating that far off?

Secondary question - if this is a problem, any alternative hunting bullet you would recommend? I tried ELD-X's but I could get nothing under 1
 

kriller134

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That’s not a lot of jump. If you listen to the last modern day sniper, Scott saterlee talks about reloading and how he jumps bullets. I think he said like almost 300 thou.
 

straightshooter1

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It's not going to cause any early throat erosion. In fact, that might be a good distance for accuracy. You just very well might find better accuracy at a longer distance . . . or a little shorter. You won't know till you experiment.

If you haven't read it already, you might find the following of interest:

 
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rulellis

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Thanks for the articles and the information - that definitely puts it into perspective for me.
 

chevy_man

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I have one rifle that I can't get to remotely touch the lands.

It responded to seating depth changes, however it also had swings and nodes in velocity. My theory is I ended up tuning the seating depth to a good spot in case volume. The velocity and groups have stayed steady over several hundred rounds so far.
 

DownhillFromHere

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Here's Berger's advice on finding the right amount of jump for their bullets - I use the same approach for my .223, which gets fed Sierra SMKs. For Berger 140 Hybrids in my 6.5CM, I actually found 0.070" off the lands to work best.
 

sierracharlie338

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When first loading for a 260 I bought years back, I went through Berger’s suggested load process for seating depth testing with the VLDs. Ended up at .090 off the lands because throat was too long for mag and had to back way out to find accuracy with that barrel.
 

Papamo

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My 260 with 140 hybrids are jumping .080 off the lands and mag feeds. Was doing load development on 210smk on a 300 WM and found that they liked to be jumped at .100 off the lands in my rifle. I see no downside to jumping bullets further, just less powder room in case.
 

DAMNKID

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Same here.. Thanks to guys like him for always testing and tweaking and sharing the info
 
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rulellis

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Whelp... now I feel like I need to try seating my bullets deeper to see what happens. If he tested .25 off the lands I have a lot of experimenting to do. It should be interesting...
 

Ryridesmotox

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It’s interesting how he finds his jump first with a generic load then tunes his charge weight. I’ve been doing it ass backwards hahaha.
Interesting. I came to ask that question, which to do first. The way this all works seems to be evolving rather rapidly recently for some reason
 

RescueRandyMD

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Interesting. I came to ask that question, which to do first. The way this all works seems to be evolving rather rapidly recently for some reason

There are a lot of variables that go into finding a "perfect" load. Taking the scientific R&D route, and with some data from a huge string of shots I did for a T3X Tac A1 workup, my dad and I did a DOE for all the factors that could most affect a cartridge. Some (CBTO, charge) are more important than brass, neck tension, bullet type, etc. We looked at 10 in total Specifically, independent variables that you can change will have the most influence.

The biggest factor to a cartridge that would vary the most independently was seating depth since it will have inter-variable effects (e.g. case pressure which is influenced by power charge, type). This likely is also why Berger suggest this as well and to then tune off a found seating depth.
 

Ryridesmotox

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There are a lot of variables that go into finding a "perfect" load. Taking the scientific R&D route, and with some data from a huge string of shots I did for a T3X Tac A1 workup, my dad and I did a DOE for all the factors that could most affect a cartridge. Some (CBTO, charge) are more important than brass, neck tension, bullet type, etc. We looked at 10 in total Specifically, independent variables that you can change will have the most influence.

The biggest factor to a cartridge that would vary the most independently was seating depth since it will have inter-variable effects (e.g. case pressure which is influenced by power charge, type). This likely is also why Berger suggest this as well and to then tune off a found seating depth.
Im mostly inclined to find something that shoots under 1 moa and send it. Usually I can find one that shoots half moa fairly easy. I dont particularly like fiddledicking around with shit. I know guys thay do, and they are playing with every aspect, I just don't have the patience.
 

kriller134

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Im mostly inclined to find something that shoots under 1 moa and send it. Usually I can find one that shoots half moa fairly easy. I dont particularly like fiddledicking around with shit. I know guys thay do, and they are playing with every aspect, I just don't have the patience.
Same here. I’m a lazy reloader and I’m not gonna chase the smallest group. My current load is .5 moa with good numbers. That’s good enough for me.
 

Herb Stoner

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I'm in a similar position as I'm getting good results but with a lot of jump that is mildly concerning. At what point does the jump become problematic in terms of throat erosion?
 

natdscott

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I've jumped a 77 Sierra Matchking about 1/4" and shot groups at ~ 1/2 Minute at 300.

Not a problem.

Don't forget: It is not engraving, etc. that causes throat erosion. It is HEAT and gas cutting the steel that causes it.
 

Old_Longhair

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I recently received some new Barnes 6.5mm 145gr bullets for my Creed, and since there isn't any load data available yet I picked a nominal charge weight I knew would be safe, and loaded a seating depth ladder from .010-.035 in .003 increments. I found that I got my highest velocities, smallest ES/SD numbers, and tightest groups with one particular seating depth. It all came together. Now I have a baseline, and I'll work on finding a higher velocity node to further tune.
 

trob_205

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I'm in a similar position as I'm getting good results but with a lot of jump that is mildly concerning. At what point does the jump become problematic in terms of throat erosion?
Will have no ill effect. If anything it would be better for it but that’s probably splitting hairs.

In the podcast Satterlee says he had a 6CM barrel do something like 2300 rounds before he replaced it and never changed seating depth. It was still shooting well but it repeatedly coppered up after 50ish rounds.
 

PhantomWorks

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I'm fresh into handloading myself and hence been reading everything/anything to gather as much info as possible, since you can never know 'to much'. Seen this exact question asked quite a few time in differently forums and might have a different way of looking at it from other experiences (been involved with misc. racing, machining, fabrication and such for many years)
If you think about it, will a rather soft bullet 'hurt' a steel barrel more because it hits it 'jumping' into the groves vs. launching already touching them? Not likely.
And there will never be any form of 'cutting effect' from burning gunpowder before the bullet entering either. For the latter to happen you have to have the bullet jump further then the lenght it's seated into the case!
(For the gasses to escape around the bullet and hit the throat of the barrel first right.)
 

MakeSawdust

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I had recently noticed a similar effect. My desire to shoot at long range came from calling coyotes. I put together a 243AI with an 8 twist Criterion. The first barrel I jumped bullets .040" plus and both the 115 DTAC load and the 105 AMAX load shot well and lost very little velocity before 2700 rounds. The barrel gave up and with the new barrel I played with seating close to and into the lands. The powder charges went way down to get the same velocities, but the load would stop shooting every 800 rounds or so. I was able to chase the lands and add powder and get good accuracy again. That barrel gave up at 2500 rounds. Now on the third barrel I decided to try to jump the DTACs .040 again and see if the laid would hold for longer.

Most of the matches I was planning on shooting have been cancelled and I started using a 223 to practice with. I don't have a ton of rounds on that barrel. I'm interested to see if the load holds for most of the life of the barrel.

I got the idea to jump bullets from Joe Hendricks that came up with the 6 Comp. Match. He stated in several posts that he started .040-.050" from the lands and just shot the same load until the barrel gave up with good success.

I will say there might not always be .25 moa accuracy at large jumps, but I feel half moa is good enough for what we do. If the load will hold longer at half moa it will be beneficial since it will save time and barrel life. If I had endless time and funds I would chase a quarter minute load as it makes those tiny 1/2 moa tyl/kyl twice as big.

In my experience, which is pretty limited compared to many here, it works best to test for the big seating depth window in .030" increments, test powder charge, then make minor changes in seating depth at .003-.005" increments if you still aren't happy with how the load shoots.

That said, I have gotten pretty lazy. I typically do a single ladder test in .1 grain increments at 800 yds with the bullet seated .040" off and call it good. Most of the time it works out.
 

TRyanOC

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Ankeny

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FWIW, some of the Accubond Long Range bullets respond very well to a long jump. I am using a 190 ABLR in my .300 WM, the 210 ABLR should work well for shooters that like heavies.
 

TRyanOC

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FWIW, some of the Accubond Long Range bullets respond very well to a long jump. I am using a 190 ABLR in my .300 WM, the 210 ABLR should work well for shooters that like heavies.
Nosler recommends starting at .050 jump. How much jump does your rifle like?